US 3722584 A
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United States Patent 1 Nelson 54] APPARATUS AND METHOD FOR DRILLING UNDERWATER  Inventor: Arthur John Nelson, 3304 Shasta Drive, San Mateo, Calif.
 Filed: Aug. 13, 1970  Appl. No.: 63,507
UNITED STATES PATENTS 2,606,003 8/l952 McNeill ..1 75/7 2,923,531 2/1960 Bauer et al. r ..l75/7 3.353.364 ll/l967 Blanding et al... l75/6 X 3,359,74l l2/l967 Nelson ..6l/46 3,491,842 l/l970 Delacour ..l75/6 Primary Examiner-Marvin A. Champion Assistant ExaminerRichard E. Favreau  ABSTRACT A system forming a well through the floor of a body of 1 Mar. 27, 1973 water obviating the conventional conductor pipe used to; encase the drill string, seal off the well from the water and convey slurry for return to a vessel at the water surface. lnstead to have an integral drill string uninterruptedly torqued by an immersed drilling station fixedly positioned adjacent the floor and adapted to provide continuous boring of the well hole corresponding to the full extent available of a lengthened string suspending above from an immersed support station controlling the bit pressure in the hole as that support descents with penetration. An independently supported articulative conduit in fluid communication between a fluid supply aboard the vessel and the hollow string, and an independently supported remote conduit in fluid communication between the vessel and a diverting assembly terminating the well annulus completes a fluid circuit by which hole borings are removed for processing. The diverting assembly accommodates sealed entry of the bared string, has a diverter directing flow from the well annulus to the remote conduit and has terminating means sealing off the annulus to a mitigated well condition at the seal. A system to line the bored hole concurrent with reassemblage of the string is conducive to furtherance of the expeditious penetration system.
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PATENTEDHARZ'IIHYS SHEET OSUF 10 INVENTOR Arthur JNelson APPARATUS AND METHOD FOR DRILLING UNDERWATER This application is a supplement to U.S. Pat. 3593808 dated 8-20-71. The initial application stressed the basic concept to bare to natural elements an extended drill string retained as an integral assembly to prolong drilling by an automatic and continuous method. Particular mode of operation was suggestive of an assembly together with inclusion by simple recitation of mandatory accessories to present a feasible apparatus. The present application discloses alternate ar rangement embodying the underlying principle, further discloses and importantly, detailed disclosure of apparatus and provisions previously deferred for this patent application.
BACKGROUND OF THE INVENTION The present invention relates to the art of off-shore drilling especially applicable to deep and rough seas.
Conventionally used conductor casings secured to the well to reach above water, sealing off the seas, are an anti-fouling means to provide an enclosure through which apparatus is extended and as a conveyance to entrain bore cuttings. Numerous difficulties and limitations are associated with the conductor pipe, though variously applied to avoid failures. A common arrangement provides an extended and enclosed string, hopefully coaxial with the conductor; so is subject to the abrading fluid in flow through the annulus defined. The string is subject to the full tension, torque and internal bursting stresses all localized at the top end of the string. Breakdown expenses and more serious public liabilities make such a conductor impractical in deep water.
The use of a Kelly bar to transmit torque to the string requires repeated retraction of the bit off the bottom to introduce a segmental length while contending with the full weight.
Accordingly it is a primary object to obviate the extended conductor by terminating the well with a diverter assembly immediate to the floor and beneath an immersed drilling station stabilized there to provide clearance for such appurtenances.
A prime object is to obtain prolonged effective penetration of the floor by automatic and uninterrupted application of torque to a maximum extended drill string bared to environmental conditions.
Another object is to provide a fluid transmission system which is alterable with continuous penetration of the bit.
Still another object is to provide sealing means at the diverter assembly in accommodation with descent of the drill string.
Another object is to sustain the fluid transmission system by monitoring and control means responsive to variations in the assembly during drilling.
Another object is to provide a method and system undertaking intermediate phases between boring operations.
The foregoing and other objects of the invention will become more apparent when viewed in light of the following description and accompanying drawings.
SUMMARY OF THE INVENTION An apparatus and system for forming a well in subaqueous strata obviating the conventional conductor pipe. The basic concept is an apparatus devised for uninterrupted and continuous boring of a well sustained in operation by a fluid transmission system having an injector portion for introducing fluid at the well bottom to entrain formation cuttings with return as a slurry up the annulus defined by the injector portion in the well to a diverter assembly sealing off the annulus and directing flow through a remote branched conduit separately supported and extending to a surface vessel. The hollow drill string preassembled as an integral length borne by an immersed support station comprises the lower part of the injector portion. An articulatively assembled conduit with inlet connected to a fluid supply on the surface vessel is separately supported by a buoyant control station as the upper part of the injector portion. A universal fitting connects the two injector parts in accommodation with relative rotative and axial movement of the two rigid member parts. Monitoring and control means are adapted to adjust the member supports corresponding with progress in drilling and opposing disruptive forces to the stability of the apparatus. Upon completion of a well boring operation to the extent possible with the assembly, means are utilized for rapid retraction of the string for reassemblage to obtain greater depths, meanwhile a preassembled casing is introduced to the well and cemented in simultaneous with alterations to the string. Appurtenances are included to effect the intermediate phase conducive to a sustained high rate of well development.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational view diagrammatically illustrating the entire system of the invention in the condition it would assume during a drilling operation, with parts thereof broken away for purposes of compactness.
FIG. 2 is a plan view illustrating an example of the base composition of control station 34.
FIG. 3 is a partial elevational view diagrammatically illustrating the drilling station with the base 154 and superstructure portions 156 thereof separated as they might be during a servicing operation.
FIG. 4 is a sectional elevational view of the drilling station 150 in an assembled condition, with parts thereof broken away.
FIG. 5 is a plan view illustrating an example of the base portion 154 of the drilling station 150.
FIG. 6 is an elevational view, partially in section, of the support station 52.
FIG. 7 is a sectional view taken on the plane designated by lines 99 of FIG. 6 illustrating one of the elements of the tension equalizers 106a shown in FIG. 6.
FIG. 8 is an elevational view diagrammatically illustrating the support station 52 in a condition out of vertical alignment with the stations to either side thereof.
FIG. 9 is an elevational view illustrating the leveler monitor 301 for the tension equalizers 106.
FIG. 10 is a sectional view, in elevation with parts thereof broken away, showing the construction of the joint 50 between the drill string and the drilling fluid supply line 46 and the support arrangement 96 for the drill string on the support station 52.
FIG. 11 is a partial elevational view in section of the leveling device 47 monitoring the posture of control station 34.
FIG. 12 is an elevational view partially in section, illustrating the regulator 51 monitoring free-board of the control station 34.
FIG. 13 is a sectional view taken on the plane designated by lines l414 of FIG. 4 illustrating the shuttle type sealing mechanism 357 employed to establish a fluid-tight connection between the drill string and the casing of a hole being drilled thereby.
FIG. 14 is a sectional view taken on the plane designated by lines 15-15 of FIG. 13.
FIG. 15 is a schematic elevational view of a multistage adaption of the throttling system 363.
FIG. 16 is an elevational sectional view of a typical portion of the composite assembly of clamp 77 in support of the conduit coupling 48 with the coupling releaser 81 disposed above when viewed in the planes 24a and 24b of FIGS. 17 and 18 respectively.
FIG. 17 is a plan view of the clamp 77 taken from the plane 25-25 of FIG. 16.
FIG. 18 is a plan view of the coupling releaser 81 taken from the plane 2626 of FIG. 16.
FIG. 19 is an elevational view diagrammatically illustrating the arrangement of apparatus at the apex 37 of the control station 34.
FIG. 20 is an elevational sectional view of a typical portion of the composite assembly of coupling 48 with the coupling releaser 87 disposed above associated with the flexible joint 38.
FIG. 21 is an elevational view partially in section showing the diverter assembly 348 connecting the well to the drilling station and diagramatically illustrates some of the remote control associated.
FIG. 22 is an elevational sectional view of a typical half portion of the composite assembly of the throttle mechanism 363 incorporated in the diverter assembly 348.
FIG. 23 is an elevational sectional view of a typical portion of the automatic fastening and remote means to disengage flange 349 separating the diverter assembly 348.
FIG. 24 is a schematic diagram of the pneumatic and wiring system associating the vertical array of stations.
FIG. 25 is a sectional elevational view of the first baffle 217 sealing off the well during installation of the well lining.
FIG. 26 is a sectional elevational view of the second bafile 221 sealing ofi' the well during installation of the well lining.
FIG. 27 is a sectional elevational view of the grip 21 1 sacrificially parted with completion of lining installation.
FIG. 28 is a sectional plan view of grip 211 taken in the plane 3737 of FIG. 27.
FIG. 29 is an elevational view diagrammatically illustrating a system to line the bored well in sequence with the drilling operation.
FIG. 30 is an elevational view with progress to the placement of the lining in the bored hole.
FIG. 31 is a sectional elevational view of the borable plug 227 employed as a sacrificial member of the assembly of FIG. 29.
LEGEND Symbol Reference Date Inventor Ref. A Patent application 3,593,808 8-20-71 A. Nelson Ref. B 3,570,815 3-l6-7l Ref.CPatent serial 3,359,74l 12-26-67 (The legend specifically identifies references each bearing a symbol used in the description to concisely and accurately signify the reference.)
CONTENTS OF DESCRIPTION Subject Identity fig. pg. General arrangement for drilling l 8 Intermediate phases l3 Conduit assembly and appurtenances l5 Coupling 48 20 15 Clamp 77 l7 l6 Coupling Releaser 8 l l 8 16 Upper Releaser 8 7 20 l 7 Universal Fitting 50 l0 l8 Diverter Assembly 348 21 20 Shuttle significance 357 13 2I Throttle 353 22 21 Appurtenances detailed Shuttle Detail 357 13 22 Throttle Detail 35 3 22 25 Establishing the Transition Chamber 359 2l 27 Remountable Flange 356a 23 30 Alternate Equalizer Arrangement 10Gb 6 31 Alternate alignment arrangement 296a 8 32 Pontoon details 5 2 7a 3 3 Pontoon detail Base portion 154 4 34 Leveling Device 47 l l 34 Regulator 5 l 1 2 35 Chamber volume controls 500 24 35 Support System 3 l 3 6 Lining bored well .29 40 Seals 2 l 7 25 221 26 42 Latch 21 l 27 44 Barrier 227 3l 47 GENERAL ARRANGEMENT A service station 20 floating on the surface 28 of a body of water provides transfer means, supplies and master control attending an array of objects stabilized and extending as a vertical arrangement for boring through the floor 152 of the body of water. The array, fixed to a site by an erect drilling station bearing on the floor, extends to include a control station 34 buoyantly supported by immersed pontoons 40 in vicinity of the surface 28 to define the extent of movement of a support station 52 functioning between as a buoyantly manipulated feeder. The array further includes; a drill string 146 preassembled to suspend from support station 52 as bared to the water in reach to the diverter assembly 348 fixed to the floor, and a conduit in fluid communication with the drill string extending therefrom upwardly with a vertical constituent 46 connected by a flexible joint 38 to a pivotal constituent 22 having the inlet end supported by axis 24 on the service station and adapted for connection to a source of fluid supply. (In FIG. 10) A universal fitting 50 effects union of the non-rotating conduit 46 to the drill string 146 with the latter automatically and continuously rotated by the drilling station to effect uninterrupted penetration of the strata below the floor by the terminally connected bit 284. (In FIG. 6) As part of the array, too, is a wire system comprising a lower portion 99a connecting the drilling station 150 to the support station 52 and an upper portion 99b connecting the control station 34 to the support station 52. In addition to the preliminary function to tie the array together when in an inoperative position, the wire system also in transmitting a tension load provides taut members serving as an element in the stabilization system 2960 of the array established by a hydraulic thruster system, as developed in Ref. A in which three wires 100a, 102a, 104a comprise the upper portion 990 and three wires 100b, 102b, 104!) comprise the upper portion 99b.
(In FIG. 19) The control station 34 includes a superstructure 36 transmitting the pontoon buoyant support to an apex assemblage 37 towering above the surface 28 to accommodate mounting of a crane 39 used to manipulate a frame 41 bearing; the flexible joint 38, unsupported end of pivotal constituent 22, all the vertical constituents 46 and other apparatus subsequently to be discussed.
(In FIG. 2) The superstructure 36 is constructed upon a base 43 supported by the pontoons 40 connected at the vertices of a polygonal configuration dimensional in excess of the height to the apex 37. One of the lateral sides provides passageway 45 for articulative pivotal constituent 22 and assemblage of the array as to be subsequently discussed. The superstructure is provided with a leveler 47 arranged to retain the structure erect or with a slight list towards the side with the passageway 45; so that the vertical projection of the apex 37 just clears the center connection of base members 43. Freeboard of the control station 34 is established by adjusting the-position of a regulator 51 mounted to the superstructure at the desired mean water line. The regulator monitors the variable gas chambers of the immersed pontoons 40 providing greater or less support capacity to retain the selected freeboard. The freeboard selected is dependent upon particular situations; whether for normal drilling, when drilling during changes to the array or when working on the inoperated assembly. For normal drilling the superstructure is positioned to accommodate allowable movement of axis end 24 attributed to the bearing service station 20. When changes are made to the vertical constituent 46 while drilling, the superstructure freeboard may be altered to better position for the assembly method to be subsequently discussed.
(In FIG. 6) The upper and lower portions of the wire system 99b, 99a are connected by equalizers 1066, 106a respectively to the top and bottom of support station 52 to provide balanced tension in the 3 wires of its portion and the other wire ends are secured to reels. Three similar reels 1 18b supported by frame 41 provide adjustment of each wire associated with equalizer 106k and are locked during normal drilling to transmit a deliberate deficiency in the support of the drill string to the control station by way of the loaded crane 39. Thus the support station is insufficiently buoyed to avoid the contingency of buckling the conduit 46 if excessively supporting. Reels 1 18b provides wire length adjustment corresponding with length changes to conduit 46 and the crane 39 sustains movement of the conduit 46 by paying out cable to lower its tail block 55 consistent with penetration of the drill bit 284 in the strata below floor 152. The frame 41 is hung by bails 57 connected to tail block 55 of the crane 39 itself complete with drum, gear reducer, motor, brakes, etc., corresponding in assembly to Ref. B.
(In FIG. 4) Three similar reels 118a at the drilling station periodically haul-in the lower wire portion 99a with accommodation means 274a to relate descent of the support station as progress in drilling to prescribe payout by the crane; so that the vertical conduit 46 descends accordingly to preserve a space relationship of its end within the fitting 50. The lower wires 100a, 102a, 104a are provided with a weighted means to establish taut lines essential to the stabilizer system 296a. The weighted means being sheaves 272 guided for vertical movement representing half the descent of the support station 52 to indicate progress in drilling. These sheaves provide a takeup means so that reels 118a need not be rotated except at periodic intervals when returning sheaves 272 from a lower limiting position to an upper limiting position with the limit switches touched-off communicating with the solenoid included in mechanism 208a transmitting power from the torque table to reels 1 18a. Ref. A covered this treatment of the lower wire portion.
(In FIG. 4) The means 274a relating hole penetration to the crane 39 is herewith interpreted to be a selsyn transmitter 61 clutched to a sprocket 63 engaging a chain 65 connected at one end to the guide bearing of one of the sheaves 272 and the other end weighted 67; so that when the transmitter is rotated with descent of the sheave it electrically activates a selsyn receiver 49 monitoring the motor powering crane 39 to provide movement of conduit 46 corresponding to movement of string 146. The clutch 69 becomes disengaged in opposite rotation of sprocket 63; so that crane 39 doesnt respond when re-establishing the upper position of sheave 272. A subsequent discussion will account for the effect and correction to maintain space relation of the two rigid members, conduit and string.
(In FIG. 1) In especially deep water drilling requiring an extended conduit 46, intermediate buoys 71 are sectionally included in the array to diminish the concentration of load of the aggregate mass that would have resulted from sole support by the control station 34. The drill string and lower wire portion are not sectionally supported; since the string is subject to maximum stress only at the time when fully extended below the drilling station when torque is then transmitted through its entire length and the lower wire portion is only tensioned sufficient to provide the taut lines for the stabilization system.
The flexible joint 38 connecting the conduit constituents 22, 46 moves vertically within the superstructure between a contracted position 73 of the tail block 55 and a lowermost clamped position 75 of the conduit 46 to the control station 34, whereupon when so clamped the joint 48 may be disconnected from the conduit 46. The clamp mechanism 77 is integral with the bridge 79 extending between pontoons 40 and in its normal inactivated position as shown in FIG. 16 provides clear passage through all of the pipe segments 46a of the conduit 46 but intercepts couplings 48 connecting adjacent segments 46a. With the coupling engaged to the normal intercepting position of the clamp the conduit can no longer lower except as will occur with lowering of the control station 34. Means are included to remotely activate the clamp to a non-interceptive position as shown by phantom view in FIG. 16 subsequently to be discussed when detailing the construction.
Flushing fluid compounded at the service station is circuited through the system of the foregoing presentation and herewith summarized to exclude the concluding phase involving processing of the returned slurry.
The fluid compound is pumped through conduits 22, 46 and through fitting 50 where some mix occurswith flushing liquid injected to protect parts of fitting 50. The string then conveys the mix for jetting from the bit 284 at the well bottom; to cool and lubricate the bit, entrain all cuttings with return up the annulus 53 under pressure opposing all liberated fluids seeking escape into the hole bored and to plaster the walls of the well in passage through annulus 53. The exterior of the drill string is abraded only to the extent when defining the annulus 53 with the well. Thereafter a diverter assembly 348 at the floor 152 in fluid communication with the well directs flow via a remote conduit 362 to the service station 20. The destructive properties of the fluid to the system is further minimized by protective measures employed at the diverter assembly 348 and fitting 50 as will be subsequently discussed.
INTERMEDIATE PHASES Retracting the rotating bit from the well is performed by both the control and support stations depending primarily on excess buoyant support to load the upper wire portion to full allowable stress if necessary and as a last resort further stressing the drill string through the thrust surfaces 96 by increasing the buoyancy of the support station. The lower wire portion supports the freed structure position 156 of the drilling station as a mass suspended from the support station 52.
(In FIG. 29) During the drilling operation another preassembly is undertaken in anticipation of its completion prior to divesting the well of the string positioned then at its ultimate reach into the strata. Such another preassembly would ordinarily first be comprised of the surface casing 350, diverter 347, preventer 353 suspended from a suspension tube 213 transmitting the assembled load to a buoy 215. The remote conduit 362 independently supported as by Ref. C is an integral extension of the diverter 347 when lowering the first casing 350 for grouting into the hole bored by the drilling station then without the diverter assembly 348; since drilling then will be accompanied by flushing borings to waste with water pumped into fitting 50 without benefit of conduits 22, 46. conduit 362 is joined to diverter 347 by branch 358 connected between with flexible unions 360, 364 to accommodate moderate displacement of the joined members. The inclusion of valve 351 and pump 355 is optional to the situation. (In FIG. 4) Base portion 154 left at the hole site has a well 175 communicating both with conical flange 176 and alley 177 extending axially and radially from well 175 with profile conforming to outer wall 158. Well 175 and alley 177 cooperate with outer wall 158 to define the gas compartment 481 established with liquid level 179 and those openings 175, 177 ac commodate passage through of assembly 362 and branch 358 with the base portion 154 positioned to the well site.
(In FIG. 18) A coupling releaser 81 used in conjunction with the clamp mechanism 77 provides remote control to automatically release the snap-on type conduit couplings 48. With approach of the joint 38 to the clamp 77 certain advance preparations minimizes the time to add a pipe segment 46a to lengthen constituent 46 while penetrating the strata as a continuing operation. This anticipation principally includes transfer of a pipe segment 46a from the stock pile aboard the service station 20 to an erect posture immediate to its installed position as suspended by a hoist 83 fixed uppermost on the control station. A valve 85 is shut off just prior to disconnecting the joint 38; so that during the seconds time required to effect the lengthening, the inertia effect of the moving fluid column is depended upon to maintain the jet at the hole bottom.
Frame 41 bearing freed joint 38 is raised by haulingin on crane 39 and paying-out on reel 118b to provide space above the clamped coupling to add segment 46a. During this brief interchange, the crane 38 and reel 1 18b have influenced the control station 34 to descend with the support station so as to retain a spaced end relation of the two rigid members 46, 146 not then controlled by crane 38 as previously disclosed. With the conduit 46 lengthened crane 38 is powered to raise the assembly an increment sufficient to activate clamp 77 free of interference with the coupling; thereafter the crane is reinstated to respond in lowering the conduit 46 and the clamp deactivated to normal position for interception of the next coupling. To disassemble the conduit 46, as expeditiously, another upper releaser 87 assembled to the flexible joint 38 serves to disengage the adjacent upper coupling of the pipe segment 46a while releaser 81 disengages the lower coupling supported by clamp 77.
CONDUIT ASSEMBLY AND APPURTENANCES (In FIG. 20) The vertical conduit constituent 46 comprises a series of conduit segments 46a joined by coupling 48. Each segment is a smooth pipe preferrably extending in length in excess of 150 feet, having a collar 93 formed to the upper end and a plug 95 formed to the lower end to provide the matching elements of adjacent segments which are locked in place by a (split) snap ring 97 partially occupying a groove 97a in the collar. The snap ring has a free diameter less than the shoulder of the plug to which it grips with spring action tending to close to the lesser diameter. The groove 97a has excessive depth which permits the ring to be expanded when a force is applied against prongs 101 formed to the ring and extending upward through accommodating slots in the top of the collar. 0 rings 103 provide fluid seal of the coupling. (In FIG. 16) The conduit 46 is temporarily secured to superstructure 34 by arranging the back of the collar 93 shaped to a frustum of a cone 119 to bear upon a clamp mechanism 77 mounted to a bridge 79 spanning the base 43 to permit changes he made as needed.
Bridge 79 provides rigid support of a peripheral bracket 105 formed with a series of stops 107 and drilled lugs 109 bearing pins 1 11 about which intercepters 113 pivot from a radial inward position 115 to an erect position 1 17. At least 3 interoepters are uniformly spaced from the peripheral bracket so that when in position 115 they will support the couplings 48 at the cone face 119. From position 115 the intercepters can only turn counter-clockwise because of a dog 121 projection of the intercepter engagement with stop 107. Accordingly, the intercepter does not interfere but is tripped out of place when a coupling 48 is raised past the clamp. In order to pass a coupling 48 down past the clamp however, the intercepter is rotated counterclockwise by activating a solenoid 123 which then pulls on a rack 125 in engagement with gear teeth 127 formed concentric with pin 111 in the hub 129 of the intercepter. The solenoid also pulls against a spring 131 inserted between an ear 133 projecting from the rack 125 and the bracket 105 used to assure retention of position 115 against inadvertent displacement. (In FIG. 18) The coupling releaser 81 comprises a guide frame 135 secured to superstructure 34 establishing vertical travel of a bracket 137 formed with a ringed stops 139 and drilled lugs 141 bearing pins 143 about which claws 145 pivot from a normal vertically depending position 147 to a horizontal position 149. Three claws are uniformly spaced around the bracket 137 so that when in position 149 present a full circular cylinder disposed above prongs 101. From position 149 the claws can only turn clockwise because of dogs 151 projection of the claw engage with stops 139. With the claws in position 147 the releaser 81 then provides both vertical passage through it of the coupling 48 and a sideways passage 153 of the conduit segment 46a. In order to establish the 3 claws in position 149 a solenoid 155 is activated to push on rack 157 in engagement with gear teeth 159 formed in the hub 161 concentric with pin 143. The solenoid also pushes in opposition to a tension spring 163 employed between an extension of the rack 157 and bracket 135.
Having established the full cylindrical aspect of claws 145 the bracket 137 is depressed by a power means preferrably a pneumatic jack 165 secured between frame 135-and bracket 137. At least 3 prongs 101 formed to split ring 97 are subject to the force of the descending claws and by virtue of their wedge configuration are displaced radially outward expanding the ring 97 in the process to occupy the depth of grooves 970. Thus the conduit segment 46a may be lifted out since hub 95 clears the releaser assembly. It is here noted that at assembly of the conduit segment 46a to the coupling 48 that the taper pointed hub 95 facilitates engagement past the free diameter ring 97 and that the tapered shoulder within collar 93 avoids accumulation of debris to that face.
(In FIG. The upper coupling releaser 87 comprises a guide frame 167 fixed to joint 38 establishes vertical travel of a depressor 169 disposed concentric above prongs 101 formed to the split ring 97 of the coupling 48 connecting the joint 38 to the uppermost conduit segment 46a. A tension spring 171 holds the depressor 169 to a normal position clear of the prongs 101. With the raise of frame 41 to lift uppermost segment 46a from the next lower coupling secured by clamp 77 the depressor 169 abuts a protruding stand 173 fixed to superstructure 34 halting rise of depressor 169 while crane 39 continues to raise frame 41 with a corresponding radial outward displacement upon contact with the prongs 101 then expanding the ring 97 in the process to occupy the depth of groove 97a. With the segment 46a previously secured to hoist 83 and also loosely to derrick 26 the segment then dislodges from joint 38 by gravitational effect whereupon derrick 26 assumes the load and transfers the removed segment to storage aboard vessel 20.
(In FIG. 10) Reference is now made to the detailed construction of the fitting 50. This fitting comprises, as its basic components, the following elements: a tubular housing 68a fixed to the upper chamber forming wall, designated 70, of the station 52; a first tubular conduit element 72 coupled to the lower end of the conduit 46 by a coupling 74 and extending downwardly therefrom slidably into the housing 6% for rectilinear movement relative thereto; and, a second tubular conduit element 76 received within the housing 680 and around the conduit element 72 for rotational movement relative thereto. The housing 68a has roller guide arms 78 fixed to and extending upwardly therefrom for guiding engagement with the conduit element 72. It is also provided with an involute flushing chamber 80 extending around the element 72 and opening into the element 76. This chamber provides for the supply of flushing fluid to the area between the elements 72 and 76 and is closed at its upper end by an annular seal 82 interposed between the housing 68a and the exterior surface of the element 72. Flushing water is supplied to the chamber 80 by conduit 84 leading to a pump 86 (see FIG. 6) and/or any suitable supply of water. The conduit element 76 is supported in concentric alignment with the element 72 for rotation relative thereto and relative to the housing 68a by annular bearings 88 and 90. A seal 92 is supported by the housing 68a in juxtaposition to the bearing 88 to prevent fluid from escaping past the bearing. The lower end of the conduit element 76 has a thrust collar 94 fixed thereto for rotation therewith. This collar is supported on a thrust surface 96 fixed to member 98a formed to chamber wall 70 from which tubular support 138a depends for the mounting of tension equalizer 106a.
Several matters have been deferred for subsequent treatment mostly relating to the fitting 50, its versatility summarized first to recollect these provisions: to provide fluid communication of an abrading slurry between two rigid tension members (conduit and drill string) compensating for relative stability of their independent supports subject to varying surge effect, compensate for inequalities in transfer rate off reels of the crane and wire system, serve as an expansion joint during changes to the conduit length, provide a fluid seal of two members rotating relative the other, contribute in part to the thrust bearing transmitting drill string weight to the support station and contribute to the construction of the equalizer system as a mounting to the support station.
(In FIG. 10) A pair of magnetic switches 181, 183 mounted to an extension 185 of fitting 50 are spaced so that a vane 189 mounted on conduit 72 becomes engaged with one depending upon position to activate a monitor regulating crane motor speed to correct the end of conduit 72 to neutral position in fitting 50. Any sudden freeing of the bit when retracting the string from the well causing the support station 52 to rise more quickly than the control station 34 is monitored by a magnetic switch 187 which when engaged is done so by the vane 189 at an excessively lowered position. Switch 187 is electrically wired to activate a solenoid opened blow-off valve venting the air chamber of support station 52 to instantly relieve compressive liability to conduit 46 designed only as a tension member. Such relief is also a warning to avoid further supercharging of the buoyant chamber to extract the bit.
DIVERTER ASSEMBLY (In FIG. 21) The diverter assembly 348 is connected between the surface well casing 350 cemented to the floor 152 and the bearing member 174 supported from removable superstructure portion 156 of the drilling station 150. Assembly 348 is separable to permit; removal of the superstructure and drill string for reassemblage as needed, and to divest the well of the string to permit, e.g., lining the bored hole with casing. Thus bottom section 352 remains fixed to the well comprising the diverter portion 347 and a conventional blowout preventer 353 adaptable to seal off the well with the string in place or removed. The top section 354 is remotely securable to the bottom section by jaw assembly 356a locking conically faced flanges 349 as to be disclosed subsequently.
The diverter portion 347 is ported to allow fluid communication to the vessel 20. A valve 351 (preferrably a conventional non-lubriacting plug valve equipped with pneumatic actuated remotely controlled) regulates discharge from the port. A conduit 358 flexibly connected by joints 360, 364 provides limited vertical displacement of the remote conduit 362 extending to the vessel dependent from support 366 representing the support system of Ref. C. A pump 355 and valve 351 are optionally included in the remote conduit assembly.
The top section 354 comprises; a first cylindrical element 368 extending from flange 349to flange 370 with integral cap 372 bearing the annular stuffingbox seal 380 to define the termination of the well annulus, and a second cylindrical element 376 extending from flange 370 to flange 378 connecting top section 354 as an integral assembly with bearing member 174. Element 376 accommodates the initial position of the shuttle mechanism 357 conveying the coupling 148 from the natural water environment in vicinity of the sea floor to a transition chamber 359 separated in the element 368 from a stagnant well fluid chamber 361 by throttle assembly 363.
(In FIG. 13) The purpose of the shuttle mechanism 357 is to establish a fluid tight seal between the cap 372 and the drill string 146 and likewise pass the coupling 148 into the assembly. The purpose of the throttle assembly 363 is to mitigate detrimental characteristics of the well fluid to the extent that an environment is established in the transition chamber 359 most conducive for the shuttle to abandon the coupling and also thereafter prolong the effective seal. The environment of the transition chamber359 is sustained by a pnuematic system 365. (In FIG. 22) In the operative position the throttle assembly 363 defines the floor of the transition chamber and provides a lengthened sleeve 367 shrouding that same length of the tubing of the drill string with close annulus clearance 369. Thus the tubing is free to pass through the transition chamber floor with restricted leakage fluid flow into the transition chamber. The close fit of the sleeve to the string rejects entrainment of particles dimensionally in excess of the clearance measurement and the extended length of the sleeve effectively diminishes pressure differential between inlet and exit of the leakage fluid to such an extent that pressure in the transition chamber is markedly less than in the well. For the condition when well pressure is greater than surrounding water pressure then the mitigated conditions within the transition chamber correspondingly diminishes the pressure differential imposed on the shuttle ends. Well fluid confined in the diverter assembly below throttle assembly 363 is virtually stagnant by reason of the restricted leakage; so that solids in suspension settle out providing a classified slurry in chamber 361 seeking entry to the clearance annulus 369. Throttle assembly 363 is a separable means to provide passage through of the coupling 148 with monitoring and control means automatically attending this need so that approximately 98 percent of the drilling time the seal is effectively protected.
(in FIG. 13) Shuttle mechanism within the top section comprises; a tubular cylinder 392 concentrically received within the first and second cylindrical elements 368 and 376 in peripherally sealed engagement with the seal 380 for rectilinear and rotational movement relative thereto; an annular flange 394 fixed to and extending around the upper end of the cylinder 392; an annular disc 396 received around the cylinder 392 beneath the flange 394 and having rods 384 extending therethrough, said disc being slidable around the cylinder to permit the cylinder to rotate thereto; a plurality of compression coil springs 398 each one received around a rod 384 in interposition between the upper surface of the cap 376 and the under surface of the disc 396 to uniformly force the disc, together with the cylinder 392, upwardly; a dashpot type dampener 400 having the piston rod thereof fixedly secured to and extending upwardly from the disc 396 and the cylinder thereof mounted on the bearing member 174; a pair of centrifugal sealing jaws 402 journalled to the cylinder 392 by transverse pivot pins 404 for movement between a position sealingly engaged with the drill string 146 (see the solid line representation in FIG. 13) and a position disengaged from the drilling string (see the phantom line representation in FIG. 13; semicircular gaskets 406a, 406k received within each of the sealing jaws 402 for sealing engagement with the drill string 146 and end of cylinder 392 respectively; a snap ring 408 loosely confined within an annular groove 410 formed in the interior of the cylinder 392 for normal projection partially into the interior of the cylinder; and, a key pin 412 fixed to the cylinder 392 and extending to the interior thereof for slidable engagement with either of two key slots 280 formed in the couplings 148.
The upper end of the cylinder 392 and the lower end of the torque tube are formed with mating 2 jaw coupling surfaces 414 and 416, respectively. When the cylinder 392 is in the upper position, as illustrated by the solid line representation in FIG. 13, these surfaces assume mating engagement and rotational movement of the torque tube 170 is transmitted to the cylinder 392. This movement functions to centrifugally swing the jaws 402 into sealed engagement with the outer periphery of the drill string 146. Torsion springs 418 resiliently urge the jaws 402 to a disengaged position when the cylinder 392 is in at rest nonrotating condition.
The cylinder 392 is interiorly dimensioned to slidably receive the couplings 148 to permit their rectilinear movement therethrough during drilling. Each coupling is formed with an annular groove 420 which is proportioned and positioned for releasable engagement by the snap ring 408. The manner in which the groove on one of the couplings 148 cooperates with the snap ring 408 during operation is sequentially noticed with an uppermost position of coupling 148 prior to engagement of the groove 420 by the snap ring 408 and with a key pin 412 slidably engaged in one of the keyslots 280 in the coupling. As thus conditioned, the coupling 148 does not impart rectilinear movement to the cylinder 392 and the coupling surfaces on the cylinder and the torque tube 170 remain in engagement to transmit rotation of the tube to the cylinder. The latter condition, in turn, functions to maintain the jaws 402 in sealed engagement with the outer periphery of the drill string 416. When the coupling 148 is descended to a position wherein the snap ring 408 first engages the groove 420, the ring functions to lock the cylinder 392 to the coupling for rectilinear movement therewith in a condition wherein the key pin 412 is retained within the keyslot 280. As thus conditioned,'the cylinder 392 is depressed by the coupling 148 so as to move the coupling surfaces 414 and 416 out of engagement. At the same time, however, rotary movement of the cylinder 392 is continued through interengagement of the key pin 412 and the keyslot 280. As a result, the sealing jaws 402 remain in sealed engagement with the outer periphery of the drill string 146.
When the coupling 148 and cylinder 392 are in the condition which occurs immediately after the cylinder 392 is depressed to a position wherein the disc 396 abuts against the stop post 382, the ring 412 snaps out of the groove 420 and the key pin 412 disengages from the keyslot 280. Thus, the cylinder 392 is released from its rotary connection with both the coupling 148 and the torque tube 170. As a result, the cylinder no longer rotates and the jaws 402 swing to an open nonsealing position (see the phantom line representation at the bottom of FIG. 13). This permits the jaws and cylinder to slide upwardly around the coupling 148 immediately thereabove under the influence of the coil springs 398.
Return of the cylinder 392 to the upper position illustrated in the solid line representation of FIG. 13 once again engages the coupling surfaces 414 and 416 and, as a result, the cylinder 392 is rotatably driven by the torque tube 170. This, in turn, functions to re-engage the jaws 402 with the drill string. As thus conditioned, the shuttle mechanism is once again readied for operation as the drill string passes therethrough during drilling. The pin 412 is mounted within cylinder 392 to be in longitudinal alignment with either jaw of the coupling 414.
It is again emphasized that the primary purpose of the shuttle mechanism is to seal the diverter assembly from the escape of drilling fluid around the drill string 146 while, at the same time, permit the enlarged couplings to pass through the assembly. This sealing function is necessary in order to assure that the discharge of drilling fluid from the annulus will pass into the branch conduit 358, rather than escape into the body of water within which the assembly is positioned.
(In FIG. 21, 22) The actuating mechanism of the throttle assembly 363 is mounted between flanged connection 415 making separable the first cylindrical element 368 into the transition chamber 359 and the stagnant chamber 361.
Details are revealed of means which monitor approach of the coupling 148 to sleeve 367 and the means to accommodate passage of the coupling between chambers. An internal ring flange 417 integral with the upper cylindrical element sealingly reinforces against well pressure the placement of half rings 419 each half integral with split halves of the sleeve 367. Radially extended ribs support the half rings to bear against flange 417 supplanting fluid pressure. Dual power means 421 preferrably pneumatically operated pistons are activated to part the sleeve halves to accommodate passage therethrough of the coupling. With the coupling 148 immediate to the sleeve 367 a cam follower 423 is displaced while in contact with the coupling to tilt a lever 425 bearing a vane 427 to an engaged position with a magnetic switch 429 to electrically activating a solenoid valve 431 to open for charging pressurized air to the power means 421 thus parting the sleeves.
Cam follower 423 remains in displaced position with continued contact over the moving length of coupling and with emergence of the coupling leading face past the sleeve position a second cam follower 433 is displaced to tilt a second lever 435 bearing the second vane 437 to an engaged position with a second magnetic switch 439 connected in parallel with first switch 429, thus the power means is not released until the coupling trailing end is free of the follower 433 and clear of the sleeve. A pair of remotely activated solenoids 441, 443 are linked to levers 425, 435, respectively, to displace cam followers 423, 433 free of interference with retraction of the drill string.
Brief note is made of several considerations. The power means 421 includes a compression spring 444 to return the sleeve halves to throttling position upon release of pressure in the cylinder by a solenoid valve 445 normally open in a bypass 446 across the piston and with the solenoid 445 electrically wired to respond with solenoid valve 431 normally closed. The levers 425, 435 are counterweighted to seek an inactive position preparatory for interception of a coupling. The configuration of the cam follower surface conforms to the contact profile through the various angular position taken by the lever to accommodate both the rotating and sliding coupling exterior surface. Conventional details are relied on pertaining to the power unit 421 for bearings, seals, etc. The fix of half sleeve to the ring half is merely indicative of the combination with design determining the bore-length ratio of sleeve, sleeve projection into either chamber and butting edges of the sleeves labyrinth in mesh. Likewise the monitoring and control of the split sleeve to be opened may be supplanted by merely nosing the coupling through a flared end of the sleeve relying on the compression spring to return the sleeve to position.
FIG. 15 diagrams a multistage adaption of the throttle assembly to be employed in extreme pressure cases to stepwise reduce the pressure from that in stagnant chamber 361 to that of 359a progressing to a lesser pressure in 359b, etc., to final low pressure in 359n containing seal 402. Transition Chamber Sustained A pneumatic system 365 is dependent upon to include provisions: to minimize pressure differential Environment; Establish and across the shuttle having one end exposed to surrounding seas and the other end within confines of the diverter assembly, to limit rise of liquid level within the diverter assembly, to maximize pressure differential across the throttle. FIG. 21 schematically diagrams the principal elements contained. An air supply is available from the drilling station or the more remote support station. An air supply conduit 371 extends down for fluid communication with the top of an external sump 373 disposed at a level with stagnant chamber 361. A bypass externally circumvents the throttle assembly 363 having conduit 375 with inlet adjacent the floor of the transition chamber 359 and outlet into sump 373 thereby providing fluid transmission of leakage to the sump. A check valve 377 directs flow in a conduit from the sump 373 to communicate with stagnant chamber 361. A valve 379 dominates flow through conduit 375. An electrical supply source indicated by line diagram with power lead 381 directed to electrically activated apparatus and return lead 383 is introduced from an extension attending the drilling station superstructure 156.
A motor 385 drives a compressor 387 receiving air supply by a branch 389 OK supply conduit 371 and discharges pressurized air by a conduit including a check valve 391 for flow into the receiver 393 having conventional appurtenances associated such as pressure limit switches, etc.
A conduit in fluid communication with the top of the transition chamber 359 includes a pressure switch 395 and a check valve 397 directing flow as a branch 399 to supply conduit 71. Pressurized air from receiver 383 is transmitted by a conduit 401 in fluid communication with supply conduit 371 as a branch connection between branch 397 and the sump 373 with flow therefrom dependent upon valve 403. A valve 405 is included in conduit 371 between branch conduit 399 and 401. A liquid level controller 407 of the conventional electrode type is employed in the transition chamber to indicate a low liquid level 409a, and a high level 409b to confine a gas volume 409c in which shuttle 357 abandons the coupling 148. Valve 405 is spring positioned normally open and electrically activate solenoid to close. Valve 403 is spring positioned normally closed and electrically activates a solenoid to open.
Operation of the pneumatic system requires air injection into the diverter assembly by closing switch 41 1 to activate solenoid valves 403 open and 405 closed. Thus air is introduced to sump 373 for discharge via check valve 377 to stagnant chamber 361 to escape through clearance 369 as air volume 4096 occupying transition chamber 359. Thereafter switch 411 is opened to reestablish normal pressure in the sump. With flow of well fluid under pressure to occupy stagnant chamber leakage through clearance 369 will comprise the air with liquid rise to level 409a, whereupon leakage will drain off through checkvalve 379 to the sump 373. With fill of the sump leakage will rise to establish level 409b whereupon switch 407 closes the electric circuit to close valve 405 and open valve 403, thus pressurized air expels fluid from the sump through check valve 377 to the stagnant chamber. In event pressure air volume 407c becomes excessive pressure switch 395 monitors relief valve 413 to bleed otT air to lower pressure system of the drilling station or support station. In
event liquid rises in conduit 371 with possible detrimental efiect to the compressor, the liquid level controller 407 responds as before. Disconnect 407a reestablishes drainage to emptied sump 373.
Remountable Flange Mechanism (In FIG. 23) The mating faces of flange 349 are conical tapering down to the well to obviate accummulation of debris between those faces that would interfere with the effectiveness of the 0 ring gasket seal 447 provided in a groove formed in the upper face. The jaw mechanism 356a is mounted to the body of the preventer 353. Jaws 448 formed to engage with the back of the upper flange are pivotally mounted by journals 449 extending beyond a pair of lugs 450 formed to the preventer and space to accommodate the jaw between. Each lug 450 is bored to receive an eccentric 451 having an ofiset hole accommodating bearing of the journal 449. A lever integral with the eccentric has a lower pivotal position to establish a minimum measurement of the center of the offset hole below the back of the upper flange and has an upper position that establishes a maximum said measurement. Each jaw 448 has a lower projecting arm 453 adapted to embrace a compression spring 454 to the body of the preventer 353 by a sustaining reaction of the jaw 448 bearing to the circumference of the flange 349. A power means 455, preferrably a pneumatic jack, is pivotally connected to the arm 453 and a cylindrical housing 456 surrounding and fixed to the preventer 353.
Jaws 448 have beveled projections to provide a reach for a slightly misaligned assembly 348 to serve as a centering guide when flange 348 is to be made up. The jaws 448 are pivotally displaced with lowering of the upper flange against increased spring compression with lever 452 in lower position; so that with abutment of the flanges the jaws freely return to position with clearance 457 above the flange. The power means 455 is remotely activated to force the arm 453 to compress spring 454 thus disengaging the jaws 448 to free flanges for removal of assembly 348.
A multiplicity of jaws 448 are equally spaced around the circumference of the flange 349 and are readily engageable because of the clearance provision 457. The jaws are cinched down by the levers 452 all simultaneously by a remotely controlled follower ring 458 guided for concentric travel by bearing 459 sliding on the housing 456. A number of power means 460, preferrably pneumatic jacks, are mounted to housing 456 with pivotal connection to follower 458 in staggered relation to the levers 452. In sweep of the levers 452 upward by the powered follower 458 from the lower position schematically illustrated through an arc a-b designating travel of the lever end, a wedge 461 held in a lower position by compression spring 462 was intercepted by the lever end and temporarily displaced permitting the lever to reach its upper position. Whereupen the wedge still being forced down bears with the lever end at an angle intercepting the arc, thus prevents the lever from seeking a lower position upon retraction of the follower ring. Each wedge is provided with grooves 463 accommodating fixed guide rails 464 to establish vertical travel of the wedges and provide backing up of the locking feature of the wedge. To
release the levers from their cinching position the wedges are simultaneously withdrawn by raising them with solenoids 465 remotely activated or by other suitable means. A canopy 466 shrouds the mechanism 356 as an added protective means with housing 456. It is considered obvious to so engage levers 452 to follower 458 that power could be employed to return levers 452 for release of the cinch effect by the eccentrics.
An alternate arrangement of the upper wire portion 99 inverting the method shown in FIGS. 1 and 7 as submitted in Ref. A, is depicted in FIGS. 1 and 6 with emphasis here on the fastening of the equalizer device 106b to housing 68a of fitting 50. The two beams 108b and llb are pivotally mounted to housing 48a by axis 191a and 193a, respectively, extending substantially normal to and at the longitudinal centerline of housing 68a and oriented to provide the extension of the wires 100, 102 and 104 upward past and clear of conduit 84 and pump 86. Ref. A is cited for a disclosure of the interrelationship of beams to equalize wire stresses. The details of reels 1l8b preferrably like that disclosed in Ref. B complete the inverted arrangement by being mounted to frame 41 likewise used to provide the support of joint 38.
As viewed in FIG. 6 the tension equalizers 106a and b are fitted with leveling devices 301 to monitor reels 118a and b for length adjustment of wires 100a, 102a and 100, 102 to retain beams 108a, 110a and 108b, ll0b in level position. One such beam ll0b in FIG. 9 is shown to have a mercoid type switch 303 that completes a circuit through bodily displacement of a liquid mercury 305 to immerse one of two electrodes 307, 309 depending upon directional tilt of the beam with a common electrode 311 permanently immersed. Flexible tubing 313 encasing electric leads to chamber 315 also transmits gaseous pressure to switch 303 equalizing internal pressure in the switch with that of the environment to which it is subjected.
An alternate arrangement to alignment mechanism 296 presented in Ref. A per FIG. 11 is herein depicted in FIGS. 7a and 8 and differs in the amplification to the monitoring means of mechanism 296a of the movement of the stations 34 and 52 from a vertical. Three rods 298a fixed to and depending downwardly from support station 52 in oriented alignment with wires 100a, 102a, 104a terminates with an axis 317 serving as the fulcrum of a lever 319 pivoted about axis 317. A ring 310a supported by wires 100a, 102a, 104a at a level with the extension of the lever short arm 321 is connected to arm 321 by radially extended links 323. The lever long arm 325 terminates with a vane 304a that has an erect posture 327 and a displaced position 329 there to activate a magnetic switch 316a fixed to support station 52. Thus the displacement of support station 52 occurring with slant wires 100a, 102a, 104a displaces the lever 319 with corresponding end movement proportional to the lever arm ratio so that the monitoring means is more responsive to movement of the array. Aside from the observation that lever 319 is counterweighted to be self balancing, the mechanism 296a functions as disclosed in Ref. A and it is understood similar treatment for vessel applies.
(In FIG. 6) Support station 52 is dependent upon ad justable buoyant gas chamber 315 formed by elliptical upper wall 70 reinforced by membrane 475 having ports 476 through which water is exchanged with the seas to establish a liquid level 477. The chamber is penetrated by a cylindrical member 138a to provide central passage through of drill string 146 and the volume of the chamber is monitored by structure 500 including a motor 498 remotely controlled to adjust the buoyant capacity with a corresponding residual unsupported load representing the force applied by the bit 284 on the hole bottom. Upon initial immersion of the pontoon to establish a gas volume 315 a supply of neutral liquid compound is pumped into the chamber to float on the trapped water as a barrier 478 for corrosion prevention of appurtenance mounted therein.
Pontoons 40 control station 34 similarly have elliptical upper walls, membrane with ports for the free exchange of water with the sea as monitored by structure 500 with the motors responding to regulator 51 and leveler 47. A protective barrier separates the water from the gas chamber accommodating mounting of appurtenances best maintained above liquid levels.
Pontoons 71 are similarly treated to sectionally support the conduit 46 and upper wire portion 99b, however, it is contemplated for normal conditions to construct them as solid spheres of light material developed in the market for pressure conditions when cased with aluminum armour. (In FIG. 4) The base portion 154 of drilling station is treated similar to the support station having an elliptical shell 158 membrane 479 with ports 480 to establish a liquid level 179. The significance of well and alley 177 has been previously covered. The liquid level is monitored and regulated by structure 500 responsive to leveler 248 as will be covered subsequently.
Upon initial immersion of the pontoon to establish a gas volume 481 a supply of neutral liquid compound is pumped into the chamber to float on the trapped water as a barrier 482 for corrosion prevention of appurtenances mounted therein.
A rotary type limit switch 208 mounted on jack shaft 238 establishes maximum turns of the shaft commensurate with full extension of telescopic leg 182 requiring reversal of motor 200 to retract the leg for disposition of the drilling station to a more accommodating floor contour. The leveler 248 also serves as a constant sentinel to the erect posture of the drilling station to reestablish firm footing if effected so as not to bend the drill string. (In FIG. 11) Leveling device 47 comprises:
A closed toroidal reservoir 250a tiltably supported to the superstructure 36 by pivoted mount 331; a volume of oil 252a sustaining a toroidal float 254a bearing switch contacts 256a, 258a free from electric terminals when in a level situation. A subsequent discussion relates the level device 47 with the pneumatic controls as per FIG. 24. (In FIG. 12) Regulator 51 comprises:
A shaft 333, 2 journals 335 in support of shaft 333, a tank 337 mounted by brackets 339 to a rod 341 adapted to vertical adjustment to vary the elevated position of regulator 51. Standing vent pipe 343 part of tank 337 supports magnetic switches 468, 469 that are activated by vane 470 mounted on shaft 333 responsive to movement of a float 471 slidably mounted on shaft 333 between stops 472. An adjustable port 473 selectively determines the rate of flow of liquid to and from the chamber provided by tank 337. Vent pipe 343 terminates well above water surface 28 so that the tank in-