CA1194856A - Method of installing subsea templates - Google Patents
Method of installing subsea templatesInfo
- Publication number
- CA1194856A CA1194856A CA000420391A CA420391A CA1194856A CA 1194856 A CA1194856 A CA 1194856A CA 000420391 A CA000420391 A CA 000420391A CA 420391 A CA420391 A CA 420391A CA 1194856 A CA1194856 A CA 1194856A
- Authority
- CA
- Canada
- Prior art keywords
- template
- vessel
- hoisting apparatus
- foundation
- deck
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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- Earth Drilling (AREA)
- Placing Or Removing Of Piles Or Sheet Piles, Or Accessories Thereof (AREA)
Abstract
METHOD OF INSTALLING SUBSEA TEMPLATES
ABSTRACT OF THE DISCLOSURE
A subsea template is installed by a method which includes the steps of securing the template in a position beneath the deck of a semi-submersible drilling vessel, moving the semi-submersible drilling vessel to an appropriate offshore site and subsequently lowering the template from the semi-submersible to the sea bed. In addition, at least three anchorage templates may be loaded onto one or both of the pontoons of the semi-submersible drilling vessel at its original position and are subsequently lowered from the pontoons to their respective locations on the sea bed after the semi-submersible has moved to the offshore site.
ABSTRACT OF THE DISCLOSURE
A subsea template is installed by a method which includes the steps of securing the template in a position beneath the deck of a semi-submersible drilling vessel, moving the semi-submersible drilling vessel to an appropriate offshore site and subsequently lowering the template from the semi-submersible to the sea bed. In addition, at least three anchorage templates may be loaded onto one or both of the pontoons of the semi-submersible drilling vessel at its original position and are subsequently lowered from the pontoons to their respective locations on the sea bed after the semi-submersible has moved to the offshore site.
Description
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The invention relates to the transpor~ation and installation of subsea templates.
The invention provides a method of installing a subsea template which comprises the steps of lifting the template to a position beneath the deck of a semi-submersible drilling vessel, moving the semi-submersible to an offshore site, and then lowering the template from the semi-submersible to the sea bed.
It is preferred that the templa~e is a drilling template, and is lowered to the sea bed from beneath a drilling table of the semi-submersible.
The invention may be applied to the installation of templates for a tension leg platform.
A tension leg platform ~T~P) comprises a buoyant body anchored to the sea bed at an offshore site by at least three anchorage (or foundation) templates, there being tension legs extending between the body and templates, the length of said legs being such that the buoyancy of the body keeps all the legs under tension in all anticipated sea states In accordance wi~h an aspect of ~he invention there is provided a method of installing a subsea template at a predetermined site on a seabed comprising the steps of providing a semi-submersible drilling vessel having a pair of spaced apart 5ubmersible hulls, a deck supported above said hulls and connected to said hulls by frame means of said vessel, and hoisting apparatus on said vessel including means extending through an opening in said deck ~ and between said hulls; providing at leas~ one subsea template of a configuration such that said templa~e cannot be lifted through or lowered through said opening in said
The invention relates to the transpor~ation and installation of subsea templates.
The invention provides a method of installing a subsea template which comprises the steps of lifting the template to a position beneath the deck of a semi-submersible drilling vessel, moving the semi-submersible to an offshore site, and then lowering the template from the semi-submersible to the sea bed.
It is preferred that the templa~e is a drilling template, and is lowered to the sea bed from beneath a drilling table of the semi-submersible.
The invention may be applied to the installation of templates for a tension leg platform.
A tension leg platform ~T~P) comprises a buoyant body anchored to the sea bed at an offshore site by at least three anchorage (or foundation) templates, there being tension legs extending between the body and templates, the length of said legs being such that the buoyancy of the body keeps all the legs under tension in all anticipated sea states In accordance wi~h an aspect of ~he invention there is provided a method of installing a subsea template at a predetermined site on a seabed comprising the steps of providing a semi-submersible drilling vessel having a pair of spaced apart 5ubmersible hulls, a deck supported above said hulls and connected to said hulls by frame means of said vessel, and hoisting apparatus on said vessel including means extending through an opening in said deck ~ and between said hulls; providing at leas~ one subsea template of a configuration such that said templa~e cannot be lifted through or lowered through said opening in said
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deck; positioning said templ~te with respect to said vessel beneath said deck and lifting said template to a transport position beneath said deck; securing said template to vessel; moving said vessel and said template to said site;
and lowering said template from said vessel to said seabed.
In a particular application the invention provides a method of installing foundations for a TLP (as hereinbefore defined) which comprises the steps of loadlng at least three anchorage templates onto one or both of the pontoons of a semi-10 submersible drilling vessel, moving the semi-submersible to the site for the TLP, and then lowering the templates from the semi-submersible to their respective locations on the sea bed.
In one preferred form of the invention a drilling template is moved out to the site using the semi-submersible at the same time as the anchorage templates are moved out to the site.
In this form the drilling template may be lifted beneath the drilliny table of the semi-submersible.
In a specific form the drilling template~ four foundation templates, subsea pile-driving hammers and a limited number of piles for the drilling templa~e are loaded out in one operation, with the templates loaded onto the semi-submersible in sheltered water~
The invention may include the additional step of piling the template or templates to the seabed using piling means operable from the semi-submersible.
According to a feature of the invention one or more of the templates may be levelled by means of a rotary drill string - 2a -dependent from a heave compens~tor mounted on the semi-submersible.
According to a feature of the invention one or more of the templates may be levelled by means of a rotary drill string dependen~ from a heave compensator mounted on the semi-submersible.
According to another feature of the invention a pin pile slip assembly may be used to handle piles which are .installed from the semi-submersible in order to secure one or more of the templates to the sea bed.
The invention also provides a method of levelling a subsea template which includes the step of using a heave compensator dependent from a semi-submersible to adjust the height of the template relative to a fixed pile.
The following procedures are proposed as an advantageous method to loadout, seafasten, transport and install a well drilling template and four six-pile foundation templates from sheltered water to an offshore site.
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A specific embodiment of the invention will now be described by way of example with refe~ence to the accompanylng drawlngs, in which:
Figure 1 is a diagramma~lc plan view of a fiemi-aubmer~ible drilling vessel ad~acent to a quay in sheltered water.
Figure 2 i8 a similar vlew of the ~emi-submerslble with a drilling template in a transportation position.
Figure 3 is a side view of the semi-submersible showing how the drilllng template ls llfted into the transportation position.
Flgure 4 is a diagrammatic plan view illustrating a foundatlon template being loaded onto the semi-submersible.
Figure 5 is a side view showing an intermedlate stage in the loading of the foundation te~plate onto the semi-submersible.
Figure 6 is a similar view to that of Figure 5 showing the foundation template being set onto a hull of the semi-submerslble.
Flgure 7 ls a cutaway plan vlew illustrating how a drilling tèmplate and four foundation templates can be loaded onto the semi-submers~ble and how the foundatlon templates are sea fastened.
Figure 8 is a sectional view on the line VIII in Figure 7 Figure ~ is a sectional view on the line IX in Figure 7.
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Figure 10 illustrates the semi-submersible about to depos~t the drilling template on the sea bed in unfavourable weather condltlons.
Flgure 11 shows a recovery chain about to be released following the deposit of the drilling templa~e on the sea bed.
Figure 12 is a diagrammatic plan view showing how the seml- submersible manoeuvres over the site for a tenslon leg platform ~TTP).
Figure 13 lllustrates the installatlon of the drilling template at the ~ite of the TLP.
Flgure 14 shows the formation of a hole for a grouted pile.
Figure 15 is a dlagram lndlcating how a heave co~pen6ator i8 used to level the drilling template.
Figure 16 shows how a foundatlon template is ~nshipped from the hull of the semi-submersible.
Figure 17 shows the installation of that template at the site of the TLP.
Figure lô indicates the levelling of the foundation template, and Figure 19 is a cross sectional view of a pin pile slip assembly, one half of which shows an engaged condition, and the other half of which shows a retracted condition.
..~ ,, Loading of the drilling template is shown in Figs. 1-3.
Prior to the load out, the templates will have been brought to the sheltered water on a 'dumb' transport barge 51 (having deck plan of 60m x 16m) which will be berthed alongside a ~uay 52 prior to the arrival of a vessel comprising a semi-submersible drilling rig 53 such as a type 700 series operated by Sedco, Inc., Dallas, Texas, U.S.A., and with all the li~ting slings and ancillaries preslung.
The templates are handled using a crane barge 54. The barge (size ~5 x 20 x 3.6m with 2m draft) has a 400 tons capacity barge mounted crane 55. It also has a 120 HP 3 speed bow thruster, not shown, for station keeping. The crane barge is berthed alongside the transport barge at a point where its reach can pick up the drilling template 56. Lifting slings and a recovery wire and inflatable recovery buoy are connected to the template.
After the rig 53 enters the sheltered water o~ a bay (near the inshore base) and has placed its anchors in proper positions, the erane barge picks up the template and manoeuvres to a preselected site in the bay to place the template on the sea bed at position 56'.
The crane barge 54 is then released and moored at a convenient berth out with the rlg anchor pattern to await ~urther use.
With the template resting on sea bed the rig 53 is positioned over the pick-up point on the template as shown in Fig. 2 (which is drawn at right angles to Fig. 1). Using the buoy and recovery wire, the slings are attached to the spiral riser running assembly 57.
The drilling template is then raised to it5 transportation position 58, qee Figure 3, under tha horizontal 6 ~t. dia. truss structure 59. Special stab guides and receivers will have been installed prior to raising the template.
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- 5a -Before being handed over to the rig 53, the template should have various items installed for use with the proposed positioning ~ystems, such as one gyro package, one inclinometer package, two.
Aquafix-3 transducers, four Aquafix-3 transponders (one for each corner), and four closed manometer tube loops with ~luid and calibrated sight~, one along each sideO
Loading of the foundation templates is illustrated in Figures 4~6.
As previously described it is intended to load out and seafasten all the templates prior to the rig departing for the offshore ~ield.
The loading of' the foundation templates contlnues a~ter the drilling template is loaded and secured ~or sea.
The four foundation templates 61 are located on a transport barge G2 (which may be the same barge which brought the drilling template to the sheltered water). The crane barge 54 is moved to a position over the li~t point o~ the first template 61A and i5 cornected to the lift sling assembly.
The template i8 rai~ed with 4 part 3" diaO slings in order to install guide ~tabs which are locked into place.
The guide stabs are placed temporarily into the pile guides on the - ~oundation template to allow the template to be properly aligned onto a transport frame 63 mounted on top of one of the hulls 64 o~ the semi-submersible rig 53. Once the template is in its stowed position the guide stabs are removed.
The first template 61A is positioned by crane over the transport frame 63 at a point midway between the two starboard 18 ft. dia. stability columns 65 and 66. Provision is made for alignment by two guide wires 67 ~rom the main deck 68 to the transport frame 63. A pull back tugger line 69 iq used to positlon the template.
The template 61A is lowered until it is submerged to a floating position. Uslng ballaqt control lines the template 61A i5 ballasted until the guide stabs enter receiver cones 71 in the transport frame 63 as shown in Figures 8 and ~. Ballasting continues a~ter land-out until a maximum o~ 50?000 lbs. net negative bouyancy is obtained.
This is measured by uqe of the starboard deck crane 72 on the rig 53.
The ballast line and guide stabs are removed. The li~t sling is removed from the crane and stowed on sling carrier hooks mounted on hanging wires.
A second foundation template 61 i3 loaded by the same method as for template 61A but the second template 61 will be located between the 30 ft. column 73 and 18 ~t. column 66 a~t of the centre line.
A~ter the first two foundation templates 61A and 61 have been loaded and are securely sea~astened 9 the loading and sea ~astening o~ the third and fourth foundatlon template 61 proceeds as outlined above.
The semi-~ubmersible drilling rig 53 i5 IIOW loaded as sho~n in Figs.
7, 8 and 9. The departure of the rig is dependent upon a favourable weather forecast. However, ~hould environmental conditions develop that exceed the 20ft., 12 second wave it would be necessary to deposit the drilling template.
lS This could be accomplished prior to the development of these conditionq by the following procedure, as shown in Figures 10 and 11.
A riser running string 74 is set on the riser spider, not shown, and the riser is removed ~rom the special pup, also not shown. Using ~pecial chain elevators, suf~icient 3" chain 75 in lOOft. lengths is added to reach the seabed. The template is run to the seabed 76 and the chain is releaqed with a recovery wire 77 and buoy 73 attached.
The template can be recovered later in calmer weather.
A~suming ~avourable weather conditions, the rig carries all five templates out to the of~shore field.
When the ~inal position has been obtained, all riK anchors are tensioned up to test at 350,000 lbs. After all anchors have been tested, they are detensioned to 200,000 lbs. and the rig 53 is deballasted to 45ft. dra~t. At the ~5ft. draft auxiliary lines are installed for levelling services. If wave action is too great, 50~t.
dra~t iA maintained, and the installatlons are made by surface divers. The rig 53 is then ballasted to 80-90~t. dra~t.
In~tallation o~ the drilling template 56 is shown in Figures 12 to 14.
Figure 12 shows the rig 53 manoeuvring over the positions for the drilling template 5~ and the four foundation templates 61, using wind la~es and anchor chains, not shown.
With the rig 53 on the exact heading for template operation, the template 56 is lo~ered with the 21" riser string 81 to a depth of 100 ~t. using double stands of pre-made up riser. At this point the drilling rig hook and rotary table are unlocked and the template is rotated to the desired heading. With the hook and rotary table locked off, the template is lowered to lOft. above sea bed. At this elevation the heading of the template is checked for proper aligmDent. After any required corrections have been made, lowering is continued. When the template 56 reaches sea bed 82 the weight is slacked off in 50,000 lb. inorements until all the weight is o~f the string, then an additional 30ft is slacked o~f. When the template is level the lift j slings are released and recovered.
Guidance and verification of template positions is planned as a three-phase programme:
Phase 1. Guidance during initial set-down:
a) Acoustic system for plan location (hard line cannections~.
b) Incllnometer and gyro devices (hard line connections) for level and orientation.
Theoretically, the systems should be accurate to within 1/3 degree of angle and O.lm of location. However, experience has shown that in particular situations the acoustic system is susceptible to errors and malfunctions. On the other hand, the system is well suited to following progress o~ a template as it moves about on its way down, therefore, it can be used together with an inclinometer/gyro package , during inltial placementO
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-- Phase 2. Verification, after set-down:
a~ Inertlal Navlgation SysLem (INS) for - verification of plan locstlon and orientatio~.
The INS system requires a ~anned submerslble and a support vessel. The submersible carries an inertial navigatlon system, comprising a gyro package and a data-processing unit. From signals produced by the gyros, the INS system works out its posltion continuously based on continous integration of displacements over time.
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The submersible sets out from a fixed reference point such as the corner of a pre-set template. The support vessel has a tracking system which can be used to relate the submersible's location to the vessel location at any instant in time 1.
The submerslble then moves along to othPr points as required, an~ gives the new coordinates on demand. The coordinates should be accurate ~o within 30cm~
Plan orieneation of a template can be related to the submersible heading ~hich is accurate to within 0.1 degrees.
Experlence has shown the INS system to be very reliable. The cost can be Justified due to the varlous suppor~ services which the submersible can provlde while ', ln the tleld.
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- '~ 4Q~i6 b) Manometer tubes across corners for verificatlon of level.
Manometer tube6 can be attached to the templates to link three or four corners. Once filled with fluid and callbrated such tubes glve very good accuracy with no electrical or mechanlcal parts to fall.
Ideally, the tubes could be monitored from ~he surface vla TV, however slnce dlvers are llkely to be present anyway, they might be relled on the make of the readings. The TV surveillance is reco~nended ~n order to save time and avold communication problems.
Phase 3 Back-up: I
Divers can run out hard wire measurements, primarily to .¦
check plan locations.
Based o~ e~perience, thls may not be as accurate as the INS information. Also, the hard wire measurements ~ell only the distance from one component to another, but do _ l li~tle to describe accurately the plan orientations.
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Nevertheless~ as divers will he on the scene, ~he hard wire measurements are proposed as a third back-up ~yst~. ~
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When the drilling template 56 has been positioned on the sea bed 82, piles are inserted through pile guides 83 in the template to ~ecure that template to the sea bed.
` If the template is more than 2 degrees out o~ level, a 1.75" dia.
tensioner line is connected from a low point on the template to a tensioner assembly, deqcribed herein in con~unction with Figure 15, and the template is levelled to within the required accuracy.
A drilling assembly is made up for the ~irst pile hole, selecting a low point on the template for the fir~t pile.
A conventional drilling procedure can be used ~or 2 36" hole, as shown in Figure 14.
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~ 12 There are a number of ways that a template may be levelled. The preferred method of template levelling using a heave compensator is as follows:
The drilling template can be levelled with a heave compensator 85 by the method used when compensating for logging equipmentO (See Figure 15). This procedure starts after all the pin piles have been drilled, run and cemented (as illustrated in Figure 14) and the hydraulic pod guide lines have been established. The levelling procedure comprises the following ~teps:
Step 1 ~ Reposition the rig 53 over the centre 86 o~ the template 56 and let the rig mooring system normalize.
Step 2 - U~ing the 21" riser, run the sling assembly to the template and set the ri3er string on the spider after ensuring there is enough slack in the ~lings to compensate for rlg heave.
Step 3 - 3ump the diverq to attach the slings to the li~ting points on the template 56 and attach.
The underwater TV camera 87 can be run in Step 2 on the bottom of the riser with a telescoping frame, or two guide lines can be attached to the template in Step 3 by the divers to run the TV camera frame for guldance. The TV
camera will be focused on a levelling pile which will have white bench marks on it so that movement o~ thP template relative to the pile~ can be observed. A Decca system can be used to indicate that the template is in a level condition.
Step 4 - While the divers are attaching the li~ting slings remove the bails and elevator from the hook and attach an air tugger support assembly 88 to the hook with a bridle assembly which is attached to the top of a lifting frame ~or the air tugger assembly 88. Pick up the assembly with the travelling block and heave compen~ator.
Step 5 - Pin the bails and elevator to the lifting points on the bottom of the air tugger support assembly and latch the elevator back onto the riser string.
Step 6 - Unlock the locking bar o~ the heave compensator and with the air tugger support assembly and drilling string attached to the hook, raise the travelling block until there is approximately 8~. of slack in the li~ting slings.
Step 7 - Lower the sensing line 83, Figure 15, through the rotary table 89 to the moon pool 91 and shackle it to one of the pod guide lines, not shown, and run it on to the template;
divers then unshackle the sensing line ~rom the guide lines and attach the sensing line to a pre-selected levelling pile 92 to be used as a re~erence point. Retrieve divers.
The constant tension tugger air supply is set to support the weight o~ the sensing line.
Step 8 - Run the hydraulic control pod via the guide lines and latch the pod into a female pod receptacle which is mounted on the template. Observe procedure with the TV camera 87.
5 Step 9 - Pressurize the heave compensator 85 to about mid-stroke at which point it will take the template weight. Pressurize compensator until template 56 is in a level plane.
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Step 10 - Focu~ the TV cam~ra 87 on the reference plle 92 wlth the whlte bench marks and observe the movPment of the template 56 relaelve -to the pile. Ad~ust the alr 6upply to the on~tant tension t~gger 88 to lncrea6e the tension in the sensing line. Ob~erve the dampening effect on the relatlve movement between the template and the pile. Increase the sensing llne tension untll there is no ~elatlve movemen~ bétween ~he temp1ate and the pile, The template i~ now level and motlonles~.
lO Step 11 - Re-check level indicating instrument to ensure template level i~ within the allowable tolerance.
Step 12 - Activate pile slips from the drillers' pan~l via the hydraulio control pod. (The slips can be selectlvely activated) A sultable slip assPmblyis shown in Figure 19, and ls more fully described followiQg the desc~iption of this procedure.
Step 13 ~ Lo~er travelling blocks to set partlal weight of the template onto the slip segments to lock onto the pileO
Observe that the slips are set and holding.
20 S~ep 14 - Slack off total weight of template onto ~he levelling piles aod re-check level of template. If the template level is correct prepare to rlg down levelling equipment; lf template level is not withln the tolerance, plck up on travelling block to take weight of templa~e and retract the slip5. Repeat procedure lndlvidually until template is level.
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Step 15 - After template is level and locked to p~les, retrieve h~draulic control pod.
Step 16 - ~ump divers ~o dlsconnect liftlng slings and sensing ll~e. Dlvers shackle the sensing llne ~o guide line and the seosing line is retrleved to the moon pool. The sensing llne ls removed from ~he g~ide line and pulled ; back through the ro~ary table to the air tugger support ~ssembly. Retrieve divers at the same tlme.
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Step 17 - Recover riser ~unning assembly and sllngs.
Step 18 - If neces6ary re~positlon rig over plles and grout pile holes bnc~ to the top of the template wlth a cement ~tinger Figure 19 i8 a cros~-~ectional vlew of a pin pile flllp assembly. The left han(l ha1f shows the as~embly in an engaged condition, and the rlght ~and half il1~lstrates a retracted condltionO
The 61ip assembly is intended to surround 2 pila 100- There are upper and lower ~butment rings 101 and 103 respectlvely, which are secured to and spaced apart by a tubular wall 102. An annular piston assembly compriqes upper and lower plates 104 and 106l spaced apart by an outer tubular wall 105, and a tapered inner tubular wall 107~ The annular piston assembly fits loosely between the abutment rings 101 and 103.
The lower ring 103 is supported on a base plate 108 by a body tube 109 and mountinK ring 111. The base plate 108 is attached ~o a protector sleeve 120 and a locating flange 121 by eight gusset plates 122.
An outer tubular member 112 surrounds the abutment rlngs 101 and 103 and i8 fixed thereto by eight gusset plates 115. Guide cones 113 and 114 are dlsposed respectively above and below the tubular member 112.
Right case hardened slip segments 116 are arranged to engage the pile 100 as shown in Figure 19 (left hand side), but are normally biased outwardly against the tubular wall 107 by two retaining sp~ings li7;
An annular hydraulic cylinder 118~ mounted ~n four roller ball houslngs 119 ~upported on the base plate 108~ is arranged to act~ate a slider guide ring 110 vertically within the body tube 109.
In response to increased hydraulic pressure3~ the slider gulde ring 110 moves upwardly, and so movea the outer surfaces of the 31ip se~nents 116 again~t the tapered inner eubular wall 107. Thus the effect of lncreased hydraulic pressure is to force the slip segment9 116 inwardly against the resistance of the retaining springs 117, and into gripping en~agemen~ with the pile 1009 a~ ~he upper plate 104 comes into ellgagement ~ieh the upper ad~ustment ring 101.
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Foundation Template Handling and Installation is illustrated in Figs.
16-18.
The complete handling system ~or the foundation templates 61 will have been installed in sheltered water at the in~hore base whi.le the templates and other equipment were being loaded onto the rig 53.
Each template 61 will have its own handling system independent o~ the others to reduce rigging time at the of~shore ~ield, where succes~ive template handling systems wlll be rigged while pile installation operations are in progres3.
The drilling template 56, installation of which has already been de~cribed, is to be the index for placement of the ~oundation templates 61. Range and bearing for the foundation templates are derived from a Decca system (or equivalent). Orientation of the foundation template3 is e~fected u~ing the rotary equipment on the rig 53O The ~inal posi.tion fix and orientation is determined using a manned submersible with an onboard inertial navigation system (INS), and level is verified with pre-calibrated manometer tubes prior to pile installation.
When the drilling template 56 has been installed and the levelling operations are complete, installation o~ the Pirst ~oundation template 61A is commenced.
The rig 53 is ballasted to 35 ft. draft and moved on anchors to position number one. While the move i9 in progress a 1.5" dia~
snub-line 94 is installed ~rom the template 61A to the starboard deck crane 72. The snub-line 94 and a snatch block, not shown, are located in an opening in the main deck at the outboard perimeter girder. The ballast line is recovered and hooked up to vent ballast, and two guide wire tugger~ 92 are tensioned. The riser lifting/running tool is connected to the main lift line 95 which was tied o~f at the moon pool when the templates were loaded at the inshore base.
The template is positioned under the moon pool by venting template ballast until the template 61A floats free of the support ~rame guides (see Figs. 8 and 9), with the snub-line and lift lines held taut. The lift line 95 is taken up and the snub-line 94 is slackened of~ unt~l the template is in position under the moon pool 91. Transverse snub-lines may be required depending on sea and current conditions.
However, it i9 possible to hold the template in position by running a very tight lift assembly with 5 to 10 ft. seas and slack tide.
The running operation is commenced u~ing the riser as described ~or the drilling template installation.
When template is at 100 ~t. below sea level the orientation is checked ~or the required heading. I~ adjus~ent is necessary the table and hook are unlocked, the template 61A is rotated to the exact heading, then the running system is locked ofP and the template i run to the sea bed.
The template 61A is landed on the sea bed and the lift slings are slacked o~f 30 ~t. The manned submersible verifies position and orientation with the INS system, and can also report manometer level reading~ ad~ustment is required, the slack is taken up and the template shi~ted or rotated using li~ting gear.
The running assembly including the lift line 95 and slings 96 are reco~ered to commence rigging ~or the next template.
Re~erring to Figure 18, a riser or drill string 57 with screw jack stinger assembly and bumper sub is picked up with one drill collar below the sub. The drill string and assembly are tripped to the template on pre-installed guide lines and an of~set frame. The level instrument is consulted to select the low point, and the collar is stabbed in and rotated until the template is le~el. The sequence is repeated until template is within 0.5 deg. level.
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The drill string and screw jack stinger are recovered and rigging for a Hydra Block subsea type pile dri~ing hammer is started.
Handling for the two ~oundation templates qkowed towards the aPter end of the rig's hulls i3 slightly dif~erent.
The rigging and handling equipment is arranged to allow the aft templates, for exa~ple, the template 61B to be maneouvered into position between the two 18 ~t. dia. stability columns 65 and 66 by the use o~ a 20 ton "popeye" winch and a work boat (not sho~n) tied up alongside tha rig. The work-wire is passed ~rom the work boat to the rlg and attached to a snub-line installed on the template 61B.
A "popeye" winch on the rig is taken up until the snub-line is taut. Vsing the ballast method as on the previous template 61A, the template 61B is raised to the surrace holding tight on the work wire and tugger. As the template rises the popeye winch is slacked off to allow the template to move to the stern of the boatO
The work boat is shifted to a central mooring position. Using the deck crane 72 the snub-line is transferred to the boat anA the line i3 taken up until taut. The work wire from the boat to template is released. The handling lines ars taken up and the snub~line i3 slacked off (using the crane and 20 ton winch) until the template 61~ is in position under the moon pool 91.
Therea~ter the same procedure which was described for the ~orward stowed foundation templates, ror example, the template 61A can be u~ed.
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An outline will now be given of the pile driving hammer handling operations necessary to drive the 54" foundation piles.
It should be pointed out that no modifications are required on the rig 53, particularly i~ the rig is a Sedco 700 qemi-submersible series drilling vessel to handle an HBM 1500 type pile driving hammer. The addition of certain equipment is nece3sary, but no structural modifications are anticipated.
The power pack and reels should be on loaded flrst to allow maximum time to locate and check out. Cable and hose sheave~ are required to allow proper access o~ lines to the moon pool opening.
It is proposed that the primary hammer should be loaded on board in one piece. While the rig is at a dockside the hammer can be loaded with a dock crane with its transport skid on the starboard side. A
roller skate system is used to dolly the hammer into the spider deck area on channel type rails. The ha~er can then be hoisted upright in the spider area using the BOP bridge cranes.
Thiq method is pre~erred because it does not require the primary hammer to be disassembled. The hammer will have gone through a thorough test prior to the loadout. The back-up hammer could be kept in storage in a disassembled condition on the rig 53.
An alternate loadout procedure is to load the primary hammer in three parts and assemble it on the rig ln the spider area.
Hammer storage and assembly, if required, can take place in the spider deck area between the moon pool and BOP service pit on the starboard side. This is a convenient location to allow for sea fastening and required work.
~99~356 ~ 20 ~
The hammer can be moved about ln the 6pider area uslng the BOP brldge cranes. There are two cranes for BOP handllng and both are requ~red to llft and move the hammer. This l~ a common practice when movlng BOP's.
The only hammer modlficatlon required is a reduction ln height of the lower hammer sklrt. The height i8 reduced by approxlma~.ely 541mm. The maln functlon of ~he skirt is to align the ha~er wlth the follower.
A Regan bullseye ls ~ttached f or vl~ual level indication.
The ma~or equipment additions to facilitate u~e of the aforementioned h~mmer and its support equipment are as follows:
a~ Installation of power pack and rig services, such ascair and electrical power.
b) Instal1atlon of required sheaves ~o run hydraulic and elec~rial cables.
; 15 c) Skid beams and s~ate dolly for movlng hammer from starboard loadiog posltion.
The $4" piles each comprise upper and lower halves of approxlmately equal lengths. Each plle half is approximately 50 feet long. Towards one end of each pile, as near as practical to the end face3 there are two lifting pad eyes and combination landing dogs. A smaller pad eye i5 welded at the opposite end of the pl1e in between the two large -ones. The plles are marked with paint every foot and a full circumferentlal mark ls placed every-lQ feet The two halves can be attached elther by mechanical connector~ or by weldin~.
Loadout of the piles can be accomplished by either crane. However~ it may be preferred not to loadout all of the piles together, but rather to use the available deck load capacity to carry a combinatlon of piles and bulk stored drilling materials.
Each crane ha~ the llft and reach capacity to land one 50ft. pile length In the pipe rack area. The cranes do not have the capacity to place a 50ft. pile length on the center of the dragway. The crane csn load the piles on the outboard edge of the plpe raclc and the piles must then be rolled to the edge of the dragway using tuggers.
To land a pile on the false rotary, the following procedure is adopted:-, a~ With the lower pile half at the edge of the pipe rack next to the dragway~ both cranes are required to lift the pile and place it 1n the V-door and on the dragway.
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b) The tugger at the end of the dragway is used with a double sheave block to provide a multi-part line to the back of the pile half going into the V-door. This will allow a constant tension to be applied to the pile half while it ls going into the derrick. This addition wi-ll have its greatest value when the lower end ls ready to swing into the drill floor area, after it has been lifted off -the pipe ra~p.
c) Slings are attached from bail hooks to the lifting pad eyes on-the pile half. The pile half is eased into -the derrick while keeping 8 strong tension on the dragway tugger. As the lower end of the pile comes into the drill floor area all available ~uggers are used to keep it under control.
d) The pile half is lowered and landed on the false rotary beams provided. If guide lines are used they are attached to the pile half at this time.
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e) The cranes should have th~ upper plle half ready to be ralsed in the derrick by Lhe same procedure.
f) The upper pile half should be ralsed in the derrick using the same slln~s and procedure.
g) The upper plle half i8 carefully lowered over the lower pile half and the two halves are connected together.
h) i) If mechanical connectors are used the vendors make-up tools should be used to accomplish the connection and permanently locked using vendors instructions.
ii) If the two halves are to be welded together the~ are ~oined using an appropriate welding procedure~
i) After the two pile halves have been connected the complete pile assembly ls lifted and the support dogs on the lower pile half are removed.
J) The pile assembly is lowered and landed on the dogs on the upper pile.
To land a pile on the work platform the following steps are taken:-a) The slings are removed and replaced with slings whlch will reach to the work platform on the BOP guides below.
b~ The assembled pile is picked up and rotated through 45 degrees for the pile dogs to clear the false rotary beams. The pile is - lowered and landed on the dogs of the work platform on fixed BOP
guides.
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To attach the hammer to the pile the following procedure is used--a) Uqing the bridge crane on the rig 53 the hammer follower is picked up and attached to the pile using shear pins.
b) The pile is picked up using the rLg bridge cranes. and the support dogs on upper pile half are cut of~. The pile i~ landed smoothly on dogs located on the follower on the work platform.
c) The hammer is picked up with the bridge cranes and set on partially closed spid~r beams in approximately the well center.
d) The ha~ner running assembly ~from the bottom up) consists o~:
i) Universal joint with pin connection to hammer and 6 5/8 regular tool joint.
ii) Three bumper subs with minimum 5ft. stroke each with 6 5/8 regular tool ~oints.
iii) X-over from 8 inch drill collar to 5 inch drill pipe.
iv) 5" -135 drill pipe to blocks.
e) The insert i~ placed in false rotary beams to handle drill pipe. The running assembly is picked up and attached to the hammer with a pin on the U-joint.
The assembly is run to the sea bed as follows:-a) The hammer and pile assembly is picked up, the work plat~orm is retracted on the BOP guides and the bottom of the pile is to run to 50 ft. above the sea bed. The hose bundle is strapped to the drill pipe every 50 ft.
deck; positioning said templ~te with respect to said vessel beneath said deck and lifting said template to a transport position beneath said deck; securing said template to vessel; moving said vessel and said template to said site;
and lowering said template from said vessel to said seabed.
In a particular application the invention provides a method of installing foundations for a TLP (as hereinbefore defined) which comprises the steps of loadlng at least three anchorage templates onto one or both of the pontoons of a semi-10 submersible drilling vessel, moving the semi-submersible to the site for the TLP, and then lowering the templates from the semi-submersible to their respective locations on the sea bed.
In one preferred form of the invention a drilling template is moved out to the site using the semi-submersible at the same time as the anchorage templates are moved out to the site.
In this form the drilling template may be lifted beneath the drilliny table of the semi-submersible.
In a specific form the drilling template~ four foundation templates, subsea pile-driving hammers and a limited number of piles for the drilling templa~e are loaded out in one operation, with the templates loaded onto the semi-submersible in sheltered water~
The invention may include the additional step of piling the template or templates to the seabed using piling means operable from the semi-submersible.
According to a feature of the invention one or more of the templates may be levelled by means of a rotary drill string - 2a -dependent from a heave compens~tor mounted on the semi-submersible.
According to a feature of the invention one or more of the templates may be levelled by means of a rotary drill string dependen~ from a heave compensator mounted on the semi-submersible.
According to another feature of the invention a pin pile slip assembly may be used to handle piles which are .installed from the semi-submersible in order to secure one or more of the templates to the sea bed.
The invention also provides a method of levelling a subsea template which includes the step of using a heave compensator dependent from a semi-submersible to adjust the height of the template relative to a fixed pile.
The following procedures are proposed as an advantageous method to loadout, seafasten, transport and install a well drilling template and four six-pile foundation templates from sheltered water to an offshore site.
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A specific embodiment of the invention will now be described by way of example with refe~ence to the accompanylng drawlngs, in which:
Figure 1 is a diagramma~lc plan view of a fiemi-aubmer~ible drilling vessel ad~acent to a quay in sheltered water.
Figure 2 i8 a similar vlew of the ~emi-submerslble with a drilling template in a transportation position.
Figure 3 is a side view of the semi-submersible showing how the drilllng template ls llfted into the transportation position.
Flgure 4 is a diagrammatic plan view illustrating a foundatlon template being loaded onto the semi-submersible.
Figure 5 is a side view showing an intermedlate stage in the loading of the foundation te~plate onto the semi-submersible.
Figure 6 is a similar view to that of Figure 5 showing the foundation template being set onto a hull of the semi-submerslble.
Flgure 7 ls a cutaway plan vlew illustrating how a drilling tèmplate and four foundation templates can be loaded onto the semi-submers~ble and how the foundatlon templates are sea fastened.
Figure 8 is a sectional view on the line VIII in Figure 7 Figure ~ is a sectional view on the line IX in Figure 7.
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Figure 10 illustrates the semi-submersible about to depos~t the drilling template on the sea bed in unfavourable weather condltlons.
Flgure 11 shows a recovery chain about to be released following the deposit of the drilling templa~e on the sea bed.
Figure 12 is a diagrammatic plan view showing how the seml- submersible manoeuvres over the site for a tenslon leg platform ~TTP).
Figure 13 lllustrates the installatlon of the drilling template at the ~ite of the TLP.
Flgure 14 shows the formation of a hole for a grouted pile.
Figure 15 is a dlagram lndlcating how a heave co~pen6ator i8 used to level the drilling template.
Figure 16 shows how a foundatlon template is ~nshipped from the hull of the semi-submersible.
Figure 17 shows the installation of that template at the site of the TLP.
Figure lô indicates the levelling of the foundation template, and Figure 19 is a cross sectional view of a pin pile slip assembly, one half of which shows an engaged condition, and the other half of which shows a retracted condition.
..~ ,, Loading of the drilling template is shown in Figs. 1-3.
Prior to the load out, the templates will have been brought to the sheltered water on a 'dumb' transport barge 51 (having deck plan of 60m x 16m) which will be berthed alongside a ~uay 52 prior to the arrival of a vessel comprising a semi-submersible drilling rig 53 such as a type 700 series operated by Sedco, Inc., Dallas, Texas, U.S.A., and with all the li~ting slings and ancillaries preslung.
The templates are handled using a crane barge 54. The barge (size ~5 x 20 x 3.6m with 2m draft) has a 400 tons capacity barge mounted crane 55. It also has a 120 HP 3 speed bow thruster, not shown, for station keeping. The crane barge is berthed alongside the transport barge at a point where its reach can pick up the drilling template 56. Lifting slings and a recovery wire and inflatable recovery buoy are connected to the template.
After the rig 53 enters the sheltered water o~ a bay (near the inshore base) and has placed its anchors in proper positions, the erane barge picks up the template and manoeuvres to a preselected site in the bay to place the template on the sea bed at position 56'.
The crane barge 54 is then released and moored at a convenient berth out with the rlg anchor pattern to await ~urther use.
With the template resting on sea bed the rig 53 is positioned over the pick-up point on the template as shown in Fig. 2 (which is drawn at right angles to Fig. 1). Using the buoy and recovery wire, the slings are attached to the spiral riser running assembly 57.
The drilling template is then raised to it5 transportation position 58, qee Figure 3, under tha horizontal 6 ~t. dia. truss structure 59. Special stab guides and receivers will have been installed prior to raising the template.
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- 5a -Before being handed over to the rig 53, the template should have various items installed for use with the proposed positioning ~ystems, such as one gyro package, one inclinometer package, two.
Aquafix-3 transducers, four Aquafix-3 transponders (one for each corner), and four closed manometer tube loops with ~luid and calibrated sight~, one along each sideO
Loading of the foundation templates is illustrated in Figures 4~6.
As previously described it is intended to load out and seafasten all the templates prior to the rig departing for the offshore ~ield.
The loading of' the foundation templates contlnues a~ter the drilling template is loaded and secured ~or sea.
The four foundation templates 61 are located on a transport barge G2 (which may be the same barge which brought the drilling template to the sheltered water). The crane barge 54 is moved to a position over the li~t point o~ the first template 61A and i5 cornected to the lift sling assembly.
The template i8 rai~ed with 4 part 3" diaO slings in order to install guide ~tabs which are locked into place.
The guide stabs are placed temporarily into the pile guides on the - ~oundation template to allow the template to be properly aligned onto a transport frame 63 mounted on top of one of the hulls 64 o~ the semi-submersible rig 53. Once the template is in its stowed position the guide stabs are removed.
The first template 61A is positioned by crane over the transport frame 63 at a point midway between the two starboard 18 ft. dia. stability columns 65 and 66. Provision is made for alignment by two guide wires 67 ~rom the main deck 68 to the transport frame 63. A pull back tugger line 69 iq used to positlon the template.
The template 61A is lowered until it is submerged to a floating position. Uslng ballaqt control lines the template 61A i5 ballasted until the guide stabs enter receiver cones 71 in the transport frame 63 as shown in Figures 8 and ~. Ballasting continues a~ter land-out until a maximum o~ 50?000 lbs. net negative bouyancy is obtained.
This is measured by uqe of the starboard deck crane 72 on the rig 53.
The ballast line and guide stabs are removed. The li~t sling is removed from the crane and stowed on sling carrier hooks mounted on hanging wires.
A second foundation template 61 i3 loaded by the same method as for template 61A but the second template 61 will be located between the 30 ft. column 73 and 18 ~t. column 66 a~t of the centre line.
A~ter the first two foundation templates 61A and 61 have been loaded and are securely sea~astened 9 the loading and sea ~astening o~ the third and fourth foundatlon template 61 proceeds as outlined above.
The semi-~ubmersible drilling rig 53 i5 IIOW loaded as sho~n in Figs.
7, 8 and 9. The departure of the rig is dependent upon a favourable weather forecast. However, ~hould environmental conditions develop that exceed the 20ft., 12 second wave it would be necessary to deposit the drilling template.
lS This could be accomplished prior to the development of these conditionq by the following procedure, as shown in Figures 10 and 11.
A riser running string 74 is set on the riser spider, not shown, and the riser is removed ~rom the special pup, also not shown. Using ~pecial chain elevators, suf~icient 3" chain 75 in lOOft. lengths is added to reach the seabed. The template is run to the seabed 76 and the chain is releaqed with a recovery wire 77 and buoy 73 attached.
The template can be recovered later in calmer weather.
A~suming ~avourable weather conditions, the rig carries all five templates out to the of~shore field.
When the ~inal position has been obtained, all riK anchors are tensioned up to test at 350,000 lbs. After all anchors have been tested, they are detensioned to 200,000 lbs. and the rig 53 is deballasted to 45ft. dra~t. At the ~5ft. draft auxiliary lines are installed for levelling services. If wave action is too great, 50~t.
dra~t iA maintained, and the installatlons are made by surface divers. The rig 53 is then ballasted to 80-90~t. dra~t.
In~tallation o~ the drilling template 56 is shown in Figures 12 to 14.
Figure 12 shows the rig 53 manoeuvring over the positions for the drilling template 5~ and the four foundation templates 61, using wind la~es and anchor chains, not shown.
With the rig 53 on the exact heading for template operation, the template 56 is lo~ered with the 21" riser string 81 to a depth of 100 ~t. using double stands of pre-made up riser. At this point the drilling rig hook and rotary table are unlocked and the template is rotated to the desired heading. With the hook and rotary table locked off, the template is lowered to lOft. above sea bed. At this elevation the heading of the template is checked for proper aligmDent. After any required corrections have been made, lowering is continued. When the template 56 reaches sea bed 82 the weight is slacked off in 50,000 lb. inorements until all the weight is o~f the string, then an additional 30ft is slacked o~f. When the template is level the lift j slings are released and recovered.
Guidance and verification of template positions is planned as a three-phase programme:
Phase 1. Guidance during initial set-down:
a) Acoustic system for plan location (hard line cannections~.
b) Incllnometer and gyro devices (hard line connections) for level and orientation.
Theoretically, the systems should be accurate to within 1/3 degree of angle and O.lm of location. However, experience has shown that in particular situations the acoustic system is susceptible to errors and malfunctions. On the other hand, the system is well suited to following progress o~ a template as it moves about on its way down, therefore, it can be used together with an inclinometer/gyro package , during inltial placementO
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-- Phase 2. Verification, after set-down:
a~ Inertlal Navlgation SysLem (INS) for - verification of plan locstlon and orientatio~.
The INS system requires a ~anned submerslble and a support vessel. The submersible carries an inertial navigatlon system, comprising a gyro package and a data-processing unit. From signals produced by the gyros, the INS system works out its posltion continuously based on continous integration of displacements over time.
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The submersible sets out from a fixed reference point such as the corner of a pre-set template. The support vessel has a tracking system which can be used to relate the submersible's location to the vessel location at any instant in time 1.
The submerslble then moves along to othPr points as required, an~ gives the new coordinates on demand. The coordinates should be accurate ~o within 30cm~
Plan orieneation of a template can be related to the submersible heading ~hich is accurate to within 0.1 degrees.
Experlence has shown the INS system to be very reliable. The cost can be Justified due to the varlous suppor~ services which the submersible can provlde while ', ln the tleld.
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- '~ 4Q~i6 b) Manometer tubes across corners for verificatlon of level.
Manometer tube6 can be attached to the templates to link three or four corners. Once filled with fluid and callbrated such tubes glve very good accuracy with no electrical or mechanlcal parts to fall.
Ideally, the tubes could be monitored from ~he surface vla TV, however slnce dlvers are llkely to be present anyway, they might be relled on the make of the readings. The TV surveillance is reco~nended ~n order to save time and avold communication problems.
Phase 3 Back-up: I
Divers can run out hard wire measurements, primarily to .¦
check plan locations.
Based o~ e~perience, thls may not be as accurate as the INS information. Also, the hard wire measurements ~ell only the distance from one component to another, but do _ l li~tle to describe accurately the plan orientations.
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Nevertheless~ as divers will he on the scene, ~he hard wire measurements are proposed as a third back-up ~yst~. ~
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When the drilling template 56 has been positioned on the sea bed 82, piles are inserted through pile guides 83 in the template to ~ecure that template to the sea bed.
` If the template is more than 2 degrees out o~ level, a 1.75" dia.
tensioner line is connected from a low point on the template to a tensioner assembly, deqcribed herein in con~unction with Figure 15, and the template is levelled to within the required accuracy.
A drilling assembly is made up for the ~irst pile hole, selecting a low point on the template for the fir~t pile.
A conventional drilling procedure can be used ~or 2 36" hole, as shown in Figure 14.
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~ 12 There are a number of ways that a template may be levelled. The preferred method of template levelling using a heave compensator is as follows:
The drilling template can be levelled with a heave compensator 85 by the method used when compensating for logging equipmentO (See Figure 15). This procedure starts after all the pin piles have been drilled, run and cemented (as illustrated in Figure 14) and the hydraulic pod guide lines have been established. The levelling procedure comprises the following ~teps:
Step 1 ~ Reposition the rig 53 over the centre 86 o~ the template 56 and let the rig mooring system normalize.
Step 2 - U~ing the 21" riser, run the sling assembly to the template and set the ri3er string on the spider after ensuring there is enough slack in the ~lings to compensate for rlg heave.
Step 3 - 3ump the diverq to attach the slings to the li~ting points on the template 56 and attach.
The underwater TV camera 87 can be run in Step 2 on the bottom of the riser with a telescoping frame, or two guide lines can be attached to the template in Step 3 by the divers to run the TV camera frame for guldance. The TV
camera will be focused on a levelling pile which will have white bench marks on it so that movement o~ thP template relative to the pile~ can be observed. A Decca system can be used to indicate that the template is in a level condition.
Step 4 - While the divers are attaching the li~ting slings remove the bails and elevator from the hook and attach an air tugger support assembly 88 to the hook with a bridle assembly which is attached to the top of a lifting frame ~or the air tugger assembly 88. Pick up the assembly with the travelling block and heave compen~ator.
Step 5 - Pin the bails and elevator to the lifting points on the bottom of the air tugger support assembly and latch the elevator back onto the riser string.
Step 6 - Unlock the locking bar o~ the heave compensator and with the air tugger support assembly and drilling string attached to the hook, raise the travelling block until there is approximately 8~. of slack in the li~ting slings.
Step 7 - Lower the sensing line 83, Figure 15, through the rotary table 89 to the moon pool 91 and shackle it to one of the pod guide lines, not shown, and run it on to the template;
divers then unshackle the sensing line ~rom the guide lines and attach the sensing line to a pre-selected levelling pile 92 to be used as a re~erence point. Retrieve divers.
The constant tension tugger air supply is set to support the weight o~ the sensing line.
Step 8 - Run the hydraulic control pod via the guide lines and latch the pod into a female pod receptacle which is mounted on the template. Observe procedure with the TV camera 87.
5 Step 9 - Pressurize the heave compensator 85 to about mid-stroke at which point it will take the template weight. Pressurize compensator until template 56 is in a level plane.
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Step 10 - Focu~ the TV cam~ra 87 on the reference plle 92 wlth the whlte bench marks and observe the movPment of the template 56 relaelve -to the pile. Ad~ust the alr 6upply to the on~tant tension t~gger 88 to lncrea6e the tension in the sensing line. Ob~erve the dampening effect on the relatlve movement between the template and the pile. Increase the sensing llne tension untll there is no ~elatlve movemen~ bétween ~he temp1ate and the pile, The template i~ now level and motlonles~.
lO Step 11 - Re-check level indicating instrument to ensure template level i~ within the allowable tolerance.
Step 12 - Activate pile slips from the drillers' pan~l via the hydraulio control pod. (The slips can be selectlvely activated) A sultable slip assPmblyis shown in Figure 19, and ls more fully described followiQg the desc~iption of this procedure.
Step 13 ~ Lo~er travelling blocks to set partlal weight of the template onto the slip segments to lock onto the pileO
Observe that the slips are set and holding.
20 S~ep 14 - Slack off total weight of template onto ~he levelling piles aod re-check level of template. If the template level is correct prepare to rlg down levelling equipment; lf template level is not withln the tolerance, plck up on travelling block to take weight of templa~e and retract the slip5. Repeat procedure lndlvidually until template is level.
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Step 15 - After template is level and locked to p~les, retrieve h~draulic control pod.
Step 16 - ~ump divers ~o dlsconnect liftlng slings and sensing ll~e. Dlvers shackle the sensing llne ~o guide line and the seosing line is retrleved to the moon pool. The sensing llne ls removed from ~he g~ide line and pulled ; back through the ro~ary table to the air tugger support ~ssembly. Retrieve divers at the same tlme.
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Step 17 - Recover riser ~unning assembly and sllngs.
Step 18 - If neces6ary re~positlon rig over plles and grout pile holes bnc~ to the top of the template wlth a cement ~tinger Figure 19 i8 a cros~-~ectional vlew of a pin pile flllp assembly. The left han(l ha1f shows the as~embly in an engaged condition, and the rlght ~and half il1~lstrates a retracted condltionO
The 61ip assembly is intended to surround 2 pila 100- There are upper and lower ~butment rings 101 and 103 respectlvely, which are secured to and spaced apart by a tubular wall 102. An annular piston assembly compriqes upper and lower plates 104 and 106l spaced apart by an outer tubular wall 105, and a tapered inner tubular wall 107~ The annular piston assembly fits loosely between the abutment rings 101 and 103.
The lower ring 103 is supported on a base plate 108 by a body tube 109 and mountinK ring 111. The base plate 108 is attached ~o a protector sleeve 120 and a locating flange 121 by eight gusset plates 122.
An outer tubular member 112 surrounds the abutment rlngs 101 and 103 and i8 fixed thereto by eight gusset plates 115. Guide cones 113 and 114 are dlsposed respectively above and below the tubular member 112.
Right case hardened slip segments 116 are arranged to engage the pile 100 as shown in Figure 19 (left hand side), but are normally biased outwardly against the tubular wall 107 by two retaining sp~ings li7;
An annular hydraulic cylinder 118~ mounted ~n four roller ball houslngs 119 ~upported on the base plate 108~ is arranged to act~ate a slider guide ring 110 vertically within the body tube 109.
In response to increased hydraulic pressure3~ the slider gulde ring 110 moves upwardly, and so movea the outer surfaces of the 31ip se~nents 116 again~t the tapered inner eubular wall 107. Thus the effect of lncreased hydraulic pressure is to force the slip segment9 116 inwardly against the resistance of the retaining springs 117, and into gripping en~agemen~ with the pile 1009 a~ ~he upper plate 104 comes into ellgagement ~ieh the upper ad~ustment ring 101.
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Foundation Template Handling and Installation is illustrated in Figs.
16-18.
The complete handling system ~or the foundation templates 61 will have been installed in sheltered water at the in~hore base whi.le the templates and other equipment were being loaded onto the rig 53.
Each template 61 will have its own handling system independent o~ the others to reduce rigging time at the of~shore ~ield, where succes~ive template handling systems wlll be rigged while pile installation operations are in progres3.
The drilling template 56, installation of which has already been de~cribed, is to be the index for placement of the ~oundation templates 61. Range and bearing for the foundation templates are derived from a Decca system (or equivalent). Orientation of the foundation template3 is e~fected u~ing the rotary equipment on the rig 53O The ~inal posi.tion fix and orientation is determined using a manned submersible with an onboard inertial navigation system (INS), and level is verified with pre-calibrated manometer tubes prior to pile installation.
When the drilling template 56 has been installed and the levelling operations are complete, installation o~ the Pirst ~oundation template 61A is commenced.
The rig 53 is ballasted to 35 ft. draft and moved on anchors to position number one. While the move i9 in progress a 1.5" dia~
snub-line 94 is installed ~rom the template 61A to the starboard deck crane 72. The snub-line 94 and a snatch block, not shown, are located in an opening in the main deck at the outboard perimeter girder. The ballast line is recovered and hooked up to vent ballast, and two guide wire tugger~ 92 are tensioned. The riser lifting/running tool is connected to the main lift line 95 which was tied o~f at the moon pool when the templates were loaded at the inshore base.
The template is positioned under the moon pool by venting template ballast until the template 61A floats free of the support ~rame guides (see Figs. 8 and 9), with the snub-line and lift lines held taut. The lift line 95 is taken up and the snub-line 94 is slackened of~ unt~l the template is in position under the moon pool 91. Transverse snub-lines may be required depending on sea and current conditions.
However, it i9 possible to hold the template in position by running a very tight lift assembly with 5 to 10 ft. seas and slack tide.
The running operation is commenced u~ing the riser as described ~or the drilling template installation.
When template is at 100 ~t. below sea level the orientation is checked ~or the required heading. I~ adjus~ent is necessary the table and hook are unlocked, the template 61A is rotated to the exact heading, then the running system is locked ofP and the template i run to the sea bed.
The template 61A is landed on the sea bed and the lift slings are slacked o~f 30 ~t. The manned submersible verifies position and orientation with the INS system, and can also report manometer level reading~ ad~ustment is required, the slack is taken up and the template shi~ted or rotated using li~ting gear.
The running assembly including the lift line 95 and slings 96 are reco~ered to commence rigging ~or the next template.
Re~erring to Figure 18, a riser or drill string 57 with screw jack stinger assembly and bumper sub is picked up with one drill collar below the sub. The drill string and assembly are tripped to the template on pre-installed guide lines and an of~set frame. The level instrument is consulted to select the low point, and the collar is stabbed in and rotated until the template is le~el. The sequence is repeated until template is within 0.5 deg. level.
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The drill string and screw jack stinger are recovered and rigging for a Hydra Block subsea type pile dri~ing hammer is started.
Handling for the two ~oundation templates qkowed towards the aPter end of the rig's hulls i3 slightly dif~erent.
The rigging and handling equipment is arranged to allow the aft templates, for exa~ple, the template 61B to be maneouvered into position between the two 18 ~t. dia. stability columns 65 and 66 by the use o~ a 20 ton "popeye" winch and a work boat (not sho~n) tied up alongside tha rig. The work-wire is passed ~rom the work boat to the rlg and attached to a snub-line installed on the template 61B.
A "popeye" winch on the rig is taken up until the snub-line is taut. Vsing the ballast method as on the previous template 61A, the template 61B is raised to the surrace holding tight on the work wire and tugger. As the template rises the popeye winch is slacked off to allow the template to move to the stern of the boatO
The work boat is shifted to a central mooring position. Using the deck crane 72 the snub-line is transferred to the boat anA the line i3 taken up until taut. The work wire from the boat to template is released. The handling lines ars taken up and the snub~line i3 slacked off (using the crane and 20 ton winch) until the template 61~ is in position under the moon pool 91.
Therea~ter the same procedure which was described for the ~orward stowed foundation templates, ror example, the template 61A can be u~ed.
,~
An outline will now be given of the pile driving hammer handling operations necessary to drive the 54" foundation piles.
It should be pointed out that no modifications are required on the rig 53, particularly i~ the rig is a Sedco 700 qemi-submersible series drilling vessel to handle an HBM 1500 type pile driving hammer. The addition of certain equipment is nece3sary, but no structural modifications are anticipated.
The power pack and reels should be on loaded flrst to allow maximum time to locate and check out. Cable and hose sheave~ are required to allow proper access o~ lines to the moon pool opening.
It is proposed that the primary hammer should be loaded on board in one piece. While the rig is at a dockside the hammer can be loaded with a dock crane with its transport skid on the starboard side. A
roller skate system is used to dolly the hammer into the spider deck area on channel type rails. The ha~er can then be hoisted upright in the spider area using the BOP bridge cranes.
Thiq method is pre~erred because it does not require the primary hammer to be disassembled. The hammer will have gone through a thorough test prior to the loadout. The back-up hammer could be kept in storage in a disassembled condition on the rig 53.
An alternate loadout procedure is to load the primary hammer in three parts and assemble it on the rig ln the spider area.
Hammer storage and assembly, if required, can take place in the spider deck area between the moon pool and BOP service pit on the starboard side. This is a convenient location to allow for sea fastening and required work.
~99~356 ~ 20 ~
The hammer can be moved about ln the 6pider area uslng the BOP brldge cranes. There are two cranes for BOP handllng and both are requ~red to llft and move the hammer. This l~ a common practice when movlng BOP's.
The only hammer modlficatlon required is a reduction ln height of the lower hammer sklrt. The height i8 reduced by approxlma~.ely 541mm. The maln functlon of ~he skirt is to align the ha~er wlth the follower.
A Regan bullseye ls ~ttached f or vl~ual level indication.
The ma~or equipment additions to facilitate u~e of the aforementioned h~mmer and its support equipment are as follows:
a~ Installation of power pack and rig services, such ascair and electrical power.
b) Instal1atlon of required sheaves ~o run hydraulic and elec~rial cables.
; 15 c) Skid beams and s~ate dolly for movlng hammer from starboard loadiog posltion.
The $4" piles each comprise upper and lower halves of approxlmately equal lengths. Each plle half is approximately 50 feet long. Towards one end of each pile, as near as practical to the end face3 there are two lifting pad eyes and combination landing dogs. A smaller pad eye i5 welded at the opposite end of the pl1e in between the two large -ones. The plles are marked with paint every foot and a full circumferentlal mark ls placed every-lQ feet The two halves can be attached elther by mechanical connector~ or by weldin~.
Loadout of the piles can be accomplished by either crane. However~ it may be preferred not to loadout all of the piles together, but rather to use the available deck load capacity to carry a combinatlon of piles and bulk stored drilling materials.
Each crane ha~ the llft and reach capacity to land one 50ft. pile length In the pipe rack area. The cranes do not have the capacity to place a 50ft. pile length on the center of the dragway. The crane csn load the piles on the outboard edge of the plpe raclc and the piles must then be rolled to the edge of the dragway using tuggers.
To land a pile on the false rotary, the following procedure is adopted:-, a~ With the lower pile half at the edge of the pipe rack next to the dragway~ both cranes are required to lift the pile and place it 1n the V-door and on the dragway.
. I
b) The tugger at the end of the dragway is used with a double sheave block to provide a multi-part line to the back of the pile half going into the V-door. This will allow a constant tension to be applied to the pile half while it ls going into the derrick. This addition wi-ll have its greatest value when the lower end ls ready to swing into the drill floor area, after it has been lifted off -the pipe ra~p.
c) Slings are attached from bail hooks to the lifting pad eyes on-the pile half. The pile half is eased into -the derrick while keeping 8 strong tension on the dragway tugger. As the lower end of the pile comes into the drill floor area all available ~uggers are used to keep it under control.
d) The pile half is lowered and landed on the false rotary beams provided. If guide lines are used they are attached to the pile half at this time.
.
- 22 ~
e) The cranes should have th~ upper plle half ready to be ralsed in the derrick by Lhe same procedure.
f) The upper pile half should be ralsed in the derrick using the same slln~s and procedure.
g) The upper plle half i8 carefully lowered over the lower pile half and the two halves are connected together.
h) i) If mechanical connectors are used the vendors make-up tools should be used to accomplish the connection and permanently locked using vendors instructions.
ii) If the two halves are to be welded together the~ are ~oined using an appropriate welding procedure~
i) After the two pile halves have been connected the complete pile assembly ls lifted and the support dogs on the lower pile half are removed.
J) The pile assembly is lowered and landed on the dogs on the upper pile.
To land a pile on the work platform the following steps are taken:-a) The slings are removed and replaced with slings whlch will reach to the work platform on the BOP guides below.
b~ The assembled pile is picked up and rotated through 45 degrees for the pile dogs to clear the false rotary beams. The pile is - lowered and landed on the dogs of the work platform on fixed BOP
guides.
s~
To attach the hammer to the pile the following procedure is used--a) Uqing the bridge crane on the rig 53 the hammer follower is picked up and attached to the pile using shear pins.
b) The pile is picked up using the rLg bridge cranes. and the support dogs on upper pile half are cut of~. The pile i~ landed smoothly on dogs located on the follower on the work platform.
c) The hammer is picked up with the bridge cranes and set on partially closed spid~r beams in approximately the well center.
d) The ha~ner running assembly ~from the bottom up) consists o~:
i) Universal joint with pin connection to hammer and 6 5/8 regular tool joint.
ii) Three bumper subs with minimum 5ft. stroke each with 6 5/8 regular tool ~oints.
iii) X-over from 8 inch drill collar to 5 inch drill pipe.
iv) 5" -135 drill pipe to blocks.
e) The insert i~ placed in false rotary beams to handle drill pipe. The running assembly is picked up and attached to the hammer with a pin on the U-joint.
The assembly is run to the sea bed as follows:-a) The hammer and pile assembly is picked up, the work plat~orm is retracted on the BOP guides and the bottom of the pile is to run to 50 ft. above the sea bed. The hose bundle is strapped to the drill pipe every 50 ft.
3~
~ 24 -b) Move rlg over template and locate desired slot, lower a~sembly until TY vision indlcates plle has contacted mud llne. Raise TV
to watch Regan bubble on hammer. Continue to lower and aiternate po~itlon of TV from template to Regan bullseye. Continue to lower untll 60il reslstance beglns to plck up welght. At this point a constant watch must be kept on the bubble.
The plle is then driven as follows:-a) When the pile is self standing due to ies own weight penetratlon, ~he tension is slacked off and the lower two bumper subs are allowed to collapse. The upper sub is spaced out to atlow for vessel heave~
b) Low power blows are applied to the hammer, (approx. 25Z) and the bumper subs are spaced out while visual checks are made.
c) Driving is started, watching the bumper sub spacing, and occasionally checklng for penetrationO The shear pins between follower and pile will be sheared.
d~ For the last 5 to lOft. of driving, the bumper subs are spaced out and the pile is watched at the template. Driving ceases when the proper pile elevation is reached.
e) The hammer ls retrieYed and the same procedures are applied fo~
the next plle.
No rig modifications are required to handle the 54 inch diameter pile, but rig additions include additional tuggers in the plpe rack area to handle moving piles. ~ work platform on fixed BOP guides ls needed ln the moon pool, and addit~onal stiffeners are required to the tie back this platform to substructure. A false rotary with insert ls necessary to handle the drill plpe and drill collars.
- 25 ~
Template levelling is done according to the template manufactures incorporated system. It ~hould be noted that if the bottom conditions allow the template initially to be excessively out of level, the template will have to be levelled prlor to hammer drlvlng.
Cementlng the Annulus between the templat~ and each 54" dlameter pile ls accompli6hed wlth the use of a ~mall dlameter ~tinger run on the end of drill pipe.~ The stinger i8 inserted in the annulus and as much penetratlon as posslble obtained. A~ ce~ent is pu~ped into the annulus any over displacement will fall into the I.D. of the 54 inch pile.
Cleanlng the I~D~ of the 54 inch pile should be done prior to drilling the 20 inch diameter hole. This can be accomplished by two methods:
a) A 48 inch diameter jetting assemhly can be used in the 54 inch pile to jet the 100 feet required. The 48 inch O.D. stinger needs ~, to be only a f~w feet in length and can then be tapered to a smaller O~Do ~ e.g. 42 inch. The small annulus clearance should give a good washing action as the stinger ls jetted.
b) An underreamer with approximately 52 inch arms havlng large ~et no~zles could be used to open the I.D. The sizing of the jet noz~les would allow large volume~ of drilling fluid to pass but produce only a sufficient pressure drop to 'iJust keep the arms -extended" to prevent the tool bindingO A modiflcation would have to be made to the underreamer arms to prevent damage by the metal to metal contact with the 54 inch plle. Bearing pads could be -welded to the arms to give a low friction bearing surface. The ~5 underreamer arms can also be locked to approximately 48"
d~ameter.
~ - 26 ~ 5~
20'` pile drilling and install~tion 18 carried out ln the following manner. Drilling the 26 inch hole for the 20 inch plle is done in a manner similar to normal drllllng for 20 lnch caslng~ Entering the 54 inch pile I.D. can be accomplished with or without guide lines being established. If the cholce i8 made not to use guide lines, the funnel diameter on the template should be of sufflcient size to allow re-entry.
Drilling the 26 inch hole will require initial stabilizers to assure a vertical hole. It is proposed that an expendable type seabiliæer (8uch !;
as rubber or plastic) be used on the drill plle, to ensure initial verticallty. It would be necessary to have one spaced out near the bottom of the 54 inch pile and one near the top; this will give many feet of hole at zero degrees. Depending on the type of s~abilizer chosen, the drill pipe may have to be tripped out to remove the stabalizer lf the parts do not come apart when they meet the 26 inch diameter hole. J
If stabili2ers are not used, a potential angular discrepancy of approximately 1.15 degrees could exlst.
Speclal care must be glven to the initial portion of the hole to ensure verticality. Lo~ bit weight and sufficient RPM will be chosen to enhance the straight hole. The hole will be overdrilled by a - ~
- sufficient length to prevent any problems. I
Cementing the annulus between the 26" hole and 20" plle can be done~ I
with existing techniques used in offshore drilling of 20" casing. A
standard float shoe can be welded to the botto~ of the 20 inch pile and a stinger can be connected to the runnlng tool on the 20 inch pile at the top end.
Cementing the ID of the 20 lnch pile can be accomplished after cementing the annulus. When the running tool is disengaged from the pile the stinger can come out of the float shoe. As the stinger is slowly brought to the surface, cement can be pumped lnto the I.D. of the 20 lnch plle. When the ~tlnger has reached the surface any surplus cement can be washed away by pumping seawater through the s~inger.
~ 24 -b) Move rlg over template and locate desired slot, lower a~sembly until TY vision indlcates plle has contacted mud llne. Raise TV
to watch Regan bubble on hammer. Continue to lower and aiternate po~itlon of TV from template to Regan bullseye. Continue to lower untll 60il reslstance beglns to plck up welght. At this point a constant watch must be kept on the bubble.
The plle is then driven as follows:-a) When the pile is self standing due to ies own weight penetratlon, ~he tension is slacked off and the lower two bumper subs are allowed to collapse. The upper sub is spaced out to atlow for vessel heave~
b) Low power blows are applied to the hammer, (approx. 25Z) and the bumper subs are spaced out while visual checks are made.
c) Driving is started, watching the bumper sub spacing, and occasionally checklng for penetrationO The shear pins between follower and pile will be sheared.
d~ For the last 5 to lOft. of driving, the bumper subs are spaced out and the pile is watched at the template. Driving ceases when the proper pile elevation is reached.
e) The hammer ls retrieYed and the same procedures are applied fo~
the next plle.
No rig modifications are required to handle the 54 inch diameter pile, but rig additions include additional tuggers in the plpe rack area to handle moving piles. ~ work platform on fixed BOP guides ls needed ln the moon pool, and addit~onal stiffeners are required to the tie back this platform to substructure. A false rotary with insert ls necessary to handle the drill plpe and drill collars.
- 25 ~
Template levelling is done according to the template manufactures incorporated system. It ~hould be noted that if the bottom conditions allow the template initially to be excessively out of level, the template will have to be levelled prlor to hammer drlvlng.
Cementlng the Annulus between the templat~ and each 54" dlameter pile ls accompli6hed wlth the use of a ~mall dlameter ~tinger run on the end of drill pipe.~ The stinger i8 inserted in the annulus and as much penetratlon as posslble obtained. A~ ce~ent is pu~ped into the annulus any over displacement will fall into the I.D. of the 54 inch pile.
Cleanlng the I~D~ of the 54 inch pile should be done prior to drilling the 20 inch diameter hole. This can be accomplished by two methods:
a) A 48 inch diameter jetting assemhly can be used in the 54 inch pile to jet the 100 feet required. The 48 inch O.D. stinger needs ~, to be only a f~w feet in length and can then be tapered to a smaller O~Do ~ e.g. 42 inch. The small annulus clearance should give a good washing action as the stinger ls jetted.
b) An underreamer with approximately 52 inch arms havlng large ~et no~zles could be used to open the I.D. The sizing of the jet noz~les would allow large volume~ of drilling fluid to pass but produce only a sufficient pressure drop to 'iJust keep the arms -extended" to prevent the tool bindingO A modiflcation would have to be made to the underreamer arms to prevent damage by the metal to metal contact with the 54 inch plle. Bearing pads could be -welded to the arms to give a low friction bearing surface. The ~5 underreamer arms can also be locked to approximately 48"
d~ameter.
~ - 26 ~ 5~
20'` pile drilling and install~tion 18 carried out ln the following manner. Drilling the 26 inch hole for the 20 inch plle is done in a manner similar to normal drllllng for 20 lnch caslng~ Entering the 54 inch pile I.D. can be accomplished with or without guide lines being established. If the cholce i8 made not to use guide lines, the funnel diameter on the template should be of sufflcient size to allow re-entry.
Drilling the 26 inch hole will require initial stabilizers to assure a vertical hole. It is proposed that an expendable type seabiliæer (8uch !;
as rubber or plastic) be used on the drill plle, to ensure initial verticallty. It would be necessary to have one spaced out near the bottom of the 54 inch pile and one near the top; this will give many feet of hole at zero degrees. Depending on the type of s~abilizer chosen, the drill pipe may have to be tripped out to remove the stabalizer lf the parts do not come apart when they meet the 26 inch diameter hole. J
If stabili2ers are not used, a potential angular discrepancy of approximately 1.15 degrees could exlst.
Speclal care must be glven to the initial portion of the hole to ensure verticality. Lo~ bit weight and sufficient RPM will be chosen to enhance the straight hole. The hole will be overdrilled by a - ~
- sufficient length to prevent any problems. I
Cementing the annulus between the 26" hole and 20" plle can be done~ I
with existing techniques used in offshore drilling of 20" casing. A
standard float shoe can be welded to the botto~ of the 20 inch pile and a stinger can be connected to the runnlng tool on the 20 inch pile at the top end.
Cementing the ID of the 20 lnch pile can be accomplished after cementing the annulus. When the running tool is disengaged from the pile the stinger can come out of the float shoe. As the stinger is slowly brought to the surface, cement can be pumped lnto the I.D. of the 20 lnch plle. When the ~tlnger has reached the surface any surplus cement can be washed away by pumping seawater through the s~inger.
Claims (14)
1. A method of installing a subsea template at a predetermined site on a seabed comprising the steps of:
providing a semi-submersible drilling vessel having a pair of spaced apart submersible hulls, a deck supported above said hulls and connected to said hulls by frame means of said vessel, and hoisting apparatus on said vessel including means extending through an opening in said deck and between said hulls;
providing at least one subsea template of a configuration such that said template cannot be lifted through or lowered through said opening in said deck;
positioning said template with respect to said vessel beneath said deck and lifting said template to a transport position beneath said deck;
securing said template to vessel;
moving said vessel and said template to said site; and lowering said template from said vessel to said seabed.
providing a semi-submersible drilling vessel having a pair of spaced apart submersible hulls, a deck supported above said hulls and connected to said hulls by frame means of said vessel, and hoisting apparatus on said vessel including means extending through an opening in said deck and between said hulls;
providing at least one subsea template of a configuration such that said template cannot be lifted through or lowered through said opening in said deck;
positioning said template with respect to said vessel beneath said deck and lifting said template to a transport position beneath said deck;
securing said template to vessel;
moving said vessel and said template to said site; and lowering said template from said vessel to said seabed.
2. The method set forth in Claim 1 wherein:
said step of positioning said template with respect to said vessel comprises placing said template on the seabed in sheltered water, moving said vessel into a position over said template, connecting said hoisting apparatus to said template, and lifting said template to said transport position beneath said deck.
said step of positioning said template with respect to said vessel comprises placing said template on the seabed in sheltered water, moving said vessel into a position over said template, connecting said hoisting apparatus to said template, and lifting said template to said transport position beneath said deck.
3. The method set forth in Claims 1 or 2 wherein:
said vessel includes drill stem rotating means and said hoisting apparatus includes elongated riser means adapted to be rotated by said rotating means, and said method of installing said template at said site includes the steps of positioning said vessel on the sea at said site, lowering said template with said riser means, rotating said template with said riser means and said rotating means to a predetermined heading, and further lowering said template to setdown said template on said seabed.
said vessel includes drill stem rotating means and said hoisting apparatus includes elongated riser means adapted to be rotated by said rotating means, and said method of installing said template at said site includes the steps of positioning said vessel on the sea at said site, lowering said template with said riser means, rotating said template with said riser means and said rotating means to a predetermined heading, and further lowering said template to setdown said template on said seabed.
4. The method set forth in Claim 3 together with the step of:
verifying the position of said template on said seabed after setdown of said template.
verifying the position of said template on said seabed after setdown of said template.
5. The method set forth in Claim 3 together with the step of levelling said template on said seabed by:
providing tensioning means connected to a sensing line and supported by a heave compensator connected to said hoisting apparatus;
connecting said sensing line to a pile for securing said template to said seabed;
lifting said template and tensioning said sensing line to dampen the motion of said template with respect to said pile, and securing said template to said pile when said template is level and said template becomes substantially motionless with respect to said pile.
providing tensioning means connected to a sensing line and supported by a heave compensator connected to said hoisting apparatus;
connecting said sensing line to a pile for securing said template to said seabed;
lifting said template and tensioning said sensing line to dampen the motion of said template with respect to said pile, and securing said template to said pile when said template is level and said template becomes substantially motionless with respect to said pile.
6. The method set forth in Claim 5 including the step of providing said template with at least one pile slip assembly and engaging said pile with said slip assembly to secure said template to said pile.
7. The method set forth in Claim 1 including the steps of:
providing at least one other subsea template to be installed at a predetermined site on said seabed.
providing at least one of said hulls with frame means for supporting said other template;
placing said other template on said one hull and secured to said frame means before departing with said vessel to said sites;
repositioning said vessel at said predetermined site for said other template after installation of said one template;
removing said other template from said one hull with said hoisting apparatus and positioning said other template under said deck; and lowering said other template to its predetermined site on said seabed.
providing at least one other subsea template to be installed at a predetermined site on said seabed.
providing at least one of said hulls with frame means for supporting said other template;
placing said other template on said one hull and secured to said frame means before departing with said vessel to said sites;
repositioning said vessel at said predetermined site for said other template after installation of said one template;
removing said other template from said one hull with said hoisting apparatus and positioning said other template under said deck; and lowering said other template to its predetermined site on said seabed.
8. The method set forth in Claim 7 wherein:
said other template is adapted to be buoyant and is ballastable to rest on said one hull under its own weight when said one hull is submerged, and said method includes the steps of ballasting said other template upon placement on said frame means to a negative buoyancy condition;
deballasting said other template to a positive buoyancy condition after connecting said other template to said hoisting apparatus;
removing said other template from said one hull by floating said other template off of said frame means; and positioning said other template under said deck with said hoisting apparatus.
said other template is adapted to be buoyant and is ballastable to rest on said one hull under its own weight when said one hull is submerged, and said method includes the steps of ballasting said other template upon placement on said frame means to a negative buoyancy condition;
deballasting said other template to a positive buoyancy condition after connecting said other template to said hoisting apparatus;
removing said other template from said one hull by floating said other template off of said frame means; and positioning said other template under said deck with said hoisting apparatus.
9. The method set forth in Claim 8 including the steps of:
providing said vessel with secondary hoisting apparatus above said one hull;
connecting a snub line from said secondary hoisting apparatus to said other template, and maintaining tension on said snub line while floating said other template off of said one hull and during the positioning of said other template under said deck.
providing said vessel with secondary hoisting apparatus above said one hull;
connecting a snub line from said secondary hoisting apparatus to said other template, and maintaining tension on said snub line while floating said other template off of said one hull and during the positioning of said other template under said deck.
10. The method set forth in Claim 7 together with:
providing at least four foundation templates including said other template;
placing two of said foundation templates on one of said hulls and two of said foundation templates on the other of said hulls, and repositioning said vessel prior to installing each of said foundation templates over respective installation sites on said seabed for each of said foundation templates.
providing at least four foundation templates including said other template;
placing two of said foundation templates on one of said hulls and two of said foundation templates on the other of said hulls, and repositioning said vessel prior to installing each of said foundation templates over respective installation sites on said seabed for each of said foundation templates.
11. The method set forth in Claim 1 including the steps of:
providing said template with lifting chain means, recovery wire and a buoy;
temporarily abandoning said template by lowering said template to the seabed with said chain means and said recovery wire connected to said chain means and said buoy, disconnecting said chain means from said vessel, and recovering said chain means and said template with said hoisting apparatus when sea conditions permit transportation of said template to said site.
providing said template with lifting chain means, recovery wire and a buoy;
temporarily abandoning said template by lowering said template to the seabed with said chain means and said recovery wire connected to said chain means and said buoy, disconnecting said chain means from said vessel, and recovering said chain means and said template with said hoisting apparatus when sea conditions permit transportation of said template to said site.
12. A method of installing one or more subsea templates at preselected sites on a seabed comprising the steps of:
providing a semi-submersible drilling vessel including spaced apart submersible hulls including means for supporting a template on at least one of said hulls, a deck supported above and by said hulls and connected to said hulls by frame means, primary hoisting apparatus on said vessel including means for raising and lowering a riser through an opening in said deck between said hulls and spaced laterally from said one hull, and secondary hoisting apparatus on said vessel including cable means adapted to be connected to said template;
providing at least one submersible template of a configuration such that said template cannot be lifted through or lowered through said opening in said deck, said template being adapted to have controllable positive and negative buoyancy;
loading said template on said support means on said one hull using a crane and at least one of said hoisting apparatus on said vessel to position said template beneath said deck and over said support means;
securing said template to said vessel by lowering said template onto said support means and ballasting said template to shift the weight of said template to said support means;
transporting said template to a predetermined site on said seabed with said vessel;
connecting said template to said primary and secondary hoisting apparatus;
venting ballast from said template to float said template free of said support means while controlling the position of said template with said hoisting apparatus;
positioning said template under said opening in said deck with said primary and secondary hoisting apparatus; and lowering said template to said seabed with said primary hoisting apparatus.
providing a semi-submersible drilling vessel including spaced apart submersible hulls including means for supporting a template on at least one of said hulls, a deck supported above and by said hulls and connected to said hulls by frame means, primary hoisting apparatus on said vessel including means for raising and lowering a riser through an opening in said deck between said hulls and spaced laterally from said one hull, and secondary hoisting apparatus on said vessel including cable means adapted to be connected to said template;
providing at least one submersible template of a configuration such that said template cannot be lifted through or lowered through said opening in said deck, said template being adapted to have controllable positive and negative buoyancy;
loading said template on said support means on said one hull using a crane and at least one of said hoisting apparatus on said vessel to position said template beneath said deck and over said support means;
securing said template to said vessel by lowering said template onto said support means and ballasting said template to shift the weight of said template to said support means;
transporting said template to a predetermined site on said seabed with said vessel;
connecting said template to said primary and secondary hoisting apparatus;
venting ballast from said template to float said template free of said support means while controlling the position of said template with said hoisting apparatus;
positioning said template under said opening in said deck with said primary and secondary hoisting apparatus; and lowering said template to said seabed with said primary hoisting apparatus.
13. The method set forth in Claim 12 together with:
providing at least four foundation templates including said one template;
placing two of said foundation templates on one of said hulls and two of said foundation templates on the other of said hulls, and repositioning said vessel prior to installing each of said foundation templates over respective installation sites on said seabed for each of said foundation templates.
providing at least four foundation templates including said one template;
placing two of said foundation templates on one of said hulls and two of said foundation templates on the other of said hulls, and repositioning said vessel prior to installing each of said foundation templates over respective installation sites on said seabed for each of said foundation templates.
14. A method of installing a plurality of subsea templates at preselected sites on a seabed comprising the steps of:
providing a semi-submersible drilling vessel including spaced apart submersible hulls, frame means for supporting a deck above and between said hulls, drill stem hoisting apparatus on said vessel including means for raising and lowering a riser through an opening in said deck spaced laterally from and between said hulls, and secondary hoisting apparatus on said vessel including cable means;
providing a drilling template of a configuration such that said drilling template cannot be raised through or lowered through said opening in said deck;
providing at least three submersible foundation templates adapted to have controllable positive and negative buoyancy;
positioning said drilling template on the seabed in relatively shallow sheltered water;
moving said vessel into position with said deck over said drilling template;
lifting said drilling template with said hoisting apparatus to a transport position beneath said deck and between said hulls;
securing said drilling template to said vessel;
loading said foundation template s on support means on at least one of said hulls using a crane and at least one of said hoisting apparatus on said vessel to position said foundation templates over said support means;
lowering said foundation templates onto said support means and ballasting said foundation templates to shift the weight of said foundation templates to said support means;
transporting said templates to a predetermined site on said seabed;
postioning said vessel at said site t lowering said drilling template to said seabed, and disconnecting said hoisting apparatus from said drilling template;
repositioning said vessel over a site for a foundation template;
connecting one of said foundation templates to said hoisting apparatus;
venting ballast from said one foundation template to float said one foundation template free of said support means while controlling the position of said one foundation template with said hoisting apparatus;
positioning said one foundation template under said opening in said deck with said hoisting apparatus;
lowering said one foundation template to said seabed with said drill stem hoisting apparatus and disconnecting said drill stem hoisting apparatus from said one foundation template;
and repeating the steps of repositioning said vessel, connecting another of said foundation templates to said hoisting apparatus, venting ballast, positioning said other foundation template under said opening in said deck, lowering said other foundation template and disconnecting said drill stem hoisting apparatus for each of the remaining foundation templates.
providing a semi-submersible drilling vessel including spaced apart submersible hulls, frame means for supporting a deck above and between said hulls, drill stem hoisting apparatus on said vessel including means for raising and lowering a riser through an opening in said deck spaced laterally from and between said hulls, and secondary hoisting apparatus on said vessel including cable means;
providing a drilling template of a configuration such that said drilling template cannot be raised through or lowered through said opening in said deck;
providing at least three submersible foundation templates adapted to have controllable positive and negative buoyancy;
positioning said drilling template on the seabed in relatively shallow sheltered water;
moving said vessel into position with said deck over said drilling template;
lifting said drilling template with said hoisting apparatus to a transport position beneath said deck and between said hulls;
securing said drilling template to said vessel;
loading said foundation template s on support means on at least one of said hulls using a crane and at least one of said hoisting apparatus on said vessel to position said foundation templates over said support means;
lowering said foundation templates onto said support means and ballasting said foundation templates to shift the weight of said foundation templates to said support means;
transporting said templates to a predetermined site on said seabed;
postioning said vessel at said site t lowering said drilling template to said seabed, and disconnecting said hoisting apparatus from said drilling template;
repositioning said vessel over a site for a foundation template;
connecting one of said foundation templates to said hoisting apparatus;
venting ballast from said one foundation template to float said one foundation template free of said support means while controlling the position of said one foundation template with said hoisting apparatus;
positioning said one foundation template under said opening in said deck with said hoisting apparatus;
lowering said one foundation template to said seabed with said drill stem hoisting apparatus and disconnecting said drill stem hoisting apparatus from said one foundation template;
and repeating the steps of repositioning said vessel, connecting another of said foundation templates to said hoisting apparatus, venting ballast, positioning said other foundation template under said opening in said deck, lowering said other foundation template and disconnecting said drill stem hoisting apparatus for each of the remaining foundation templates.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8202491A GB2094856B (en) | 1981-01-28 | 1982-01-28 | Slip assembly for subsea template |
| GB8202491 | 1982-01-28 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1194856A true CA1194856A (en) | 1985-10-08 |
Family
ID=10527945
Family Applications (3)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000420393A Expired CA1203228A (en) | 1982-01-28 | 1983-01-27 | Installation and levelling of subsea templates |
| CA000420392A Expired CA1215965A (en) | 1982-01-28 | 1983-01-27 | Slip assembly for subsea template |
| CA000420391A Expired CA1194856A (en) | 1982-01-28 | 1983-01-27 | Method of installing subsea templates |
Family Applications Before (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000420393A Expired CA1203228A (en) | 1982-01-28 | 1983-01-27 | Installation and levelling of subsea templates |
| CA000420392A Expired CA1215965A (en) | 1982-01-28 | 1983-01-27 | Slip assembly for subsea template |
Country Status (1)
| Country | Link |
|---|---|
| CA (3) | CA1203228A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6036404A (en) * | 1993-08-31 | 2000-03-14 | Petroleo Brasileiro S.A.-Petrobras | Foundation system for tension leg platforms |
| US6318933B1 (en) | 1993-08-31 | 2001-11-20 | Petroleo Brasileiro S.A. | Foundation system for tension leg platforms |
-
1983
- 1983-01-27 CA CA000420393A patent/CA1203228A/en not_active Expired
- 1983-01-27 CA CA000420392A patent/CA1215965A/en not_active Expired
- 1983-01-27 CA CA000420391A patent/CA1194856A/en not_active Expired
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6036404A (en) * | 1993-08-31 | 2000-03-14 | Petroleo Brasileiro S.A.-Petrobras | Foundation system for tension leg platforms |
| US6142709A (en) * | 1993-08-31 | 2000-11-07 | Petroleo Brasileiro S.A. - Petrobras | Foundation system for tension leg platforms |
| US6312195B1 (en) | 1993-08-31 | 2001-11-06 | Petroleo Brasileiro S.A. — Petrobras | Method of installing foundation for tension leg platform |
| US6318933B1 (en) | 1993-08-31 | 2001-11-20 | Petroleo Brasileiro S.A. | Foundation system for tension leg platforms |
| US6568880B2 (en) | 1993-08-31 | 2003-05-27 | Petroleo Brasileiro S.A. - Petrobras | Foundation system for tension leg platforms |
Also Published As
| Publication number | Publication date |
|---|---|
| CA1203228A (en) | 1986-04-15 |
| CA1215965A (en) | 1986-12-30 |
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| Date | Code | Title | Description |
|---|---|---|---|
| MKEC | Expiry (correction) | ||
| MKEX | Expiry |