CA2181911A1 - Method and apparatus for activation of furnace slag base cement - Google Patents
Method and apparatus for activation of furnace slag base cementInfo
- Publication number
- CA2181911A1 CA2181911A1 CA002181911A CA2181911A CA2181911A1 CA 2181911 A1 CA2181911 A1 CA 2181911A1 CA 002181911 A CA002181911 A CA 002181911A CA 2181911 A CA2181911 A CA 2181911A CA 2181911 A1 CA2181911 A1 CA 2181911A1
- Authority
- CA
- Canada
- Prior art keywords
- mud
- bfs
- activator
- pump
- wellbore
- 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.)
- Abandoned
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
- C09K8/42—Compositions for cementing, e.g. for cementing casings into boreholes; Compositions for plugging, e.g. for killing wells
- C09K8/46—Compositions for cementing, e.g. for cementing casings into boreholes; Compositions for plugging, e.g. for killing wells containing inorganic binders, e.g. Portland cement
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B40/00—Processes, in general, for influencing or modifying the properties of mortars, concrete or artificial stone compositions, e.g. their setting or hardening ability
- C04B40/0028—Aspects relating to the mixing step of the mortar preparation
- C04B40/0032—Controlling the process of mixing, e.g. adding ingredients in a quantity depending on a measured or desired value
Abstract
The invention provides for metering the pumping rate of BFS/mud mixtures pumped to the cementing head on a rig for sealing off the formation from the casing. Since BFS mud mixtures require an activation agent, preferably sodium hydroxide is pumped into the flowline to the cementing head. Feedback from the BFS/mud slurry flowrate is fed to the activator injector pump drive system to regulate ale addition rate of the activating agent in response to varying conditions, such as mud flowrate. The injection rate target can also be adjusted to compensate for any changes in downhole temperature. The risk of fouling surface equipement and the casing internal diameter is minimized because the activation agent is added very close in time to when the BFS/mud mixture enters the cementing head. Even in situations where the anticipated downhole temperature is significantly lower than the surface temperature, a sufficient amount of activating agent is added for the downhole conditions without fear of fouling the casing internal or the surface pumping equipment.
Description
2 1 8 1 ~ l 1 WO 95120095 ~ 01015 METHOD & APPAR~TUS FOR ACTIVA~ON OF
FURNACE St AG BASE CEMENT
5 Field of tne Invention The field of this invention relates to ~ Jal~iul~ and setting of blast-furnace slag mud formulations into a wellbore to cement a casins.
Background of the Invention In the past, casing has been ~,emented downhole using Portland cement-based materials. The Por~and cement is mixed with water or available aqueous solution and drculated to properly l,pot the material for properly sealing off the outside of the casing from the formation. The Portland cementing systems have generally been provided to well operators by oilfield service c~",i,d"ies.
These service ~,u, IlJdl li~55 have brought to the well site, mixing equipment and personnel so that the Portland cen1ent can be Nntinuously mixed with water to obtain the proper ratio of cement to water for proper " "~ on the casing exterior. More recently, an alternative to Portland cement systems has been developed. This system involves the additlon of blast-furnace slag (BFS) to water-based mud for slurry densities in the range of between 10-20 Ibs./gal.,.l~pe"~i"y on the mud weight and the requirements applicable to the specific operation. The thickenins time of BFS/mud mixtures is Nntrolled by activators and retarders. Activators accelerate hydration of BFS and reduce thickening time and improve early cu, I IIJI ~ 1~3 strength development. Some of the more effective activators are alkali materials that increase the mud pH. The additionof BFS and activators to mud has negligible effect on tlle plastic VisNsity, yield point, and ~el strength over and above the properties of the original mud. The ~ol~lyi~al properties can be fur~her adjusted using chemical thinners or 9~ ts, dilution of the mud with water, or a co~ IILil, of both steps.
BFS/mud mixtures can be activated by thermal energy or chemical activation. Chemically, BFS is similar to Portland cement. It is the residue from ore and other additives developed ~n a molterl state, along with iron in a blast wossnooss 218 ~ 9 l 1 F.,II~ 15 0 furnace. BFS is ~ ,lml~d from a biast furnace at a lc""~ re between 2soQ-2900 F and quenched as a moiten siag to produce a glassy, granular material. O~ " , of BFS/mud mixtures puts the solids by volurne content 5 at anywhere in the range between 16-45% and reasonably n~Jlu~ull. - the cu".,~"~r~ ~s of equivaient density Portland cement slurries.
BFS is less reactive than Portland cement. As a consequenr e, BFS/water-based mud mixtures or BFS/water mixtures must be chemically acthated to achieve set in Ohe downhole wellbore environment, and Portiand 1Q cement/water mixtures usuaily must be ch~micaily retarded. Chemical activation is simpler and less expenshe than ~ . Typicaily, sodium hydroxide and sodium carbonate are the most widely used activators for BFS/water-based mud mixtures because Ohey sre commonly available.
Sodium hydroxide has a greater impact on setting time, while sodium carbonate 15 has a greater ~nfluence on the manner of set and the cc""~ e strength.
Above 80 F, sodium carbonate is used in greater ccnc~"o la than sodium hydroxide because there is sufficient thermai energy to reduce setting times, while the higher sodium carbonate cu"ce" ~ aids in the early cu, "~ ":,ive sOrength ~ ".mt:l ll. In temperatures below 80 F, the sodium 20 hydroxide ~o,)~"t,. , can be equal or slightly higher than sodium carbonate cu,,~,~,,t, , because of low thermal energy available to activate the slag hydraO'on. Typically, activator cioncc" dl cdiol~ in the formulations varies between 2-24 Ibs./barrel of slurry for most formulaOons, ck ~,t "~ii"çi on the temperature and the amount of retarding material present. Yet another advantage of using 25 BFS/mud mixtures is uniform cu",~ ssive strençith build-up over Ome in situations where significant ttsll,pt:, Ire ~ , ' exist between top and L"l~lul l ll lultl temperatures.
When using BFS/mud mixtures in the field, Ohe BFS is typically mixed with the mud in Ohe mud pits on the rig. Batch mixing in rig pits or mud premix 'iO tanks or cement mixers is possible. In some instsnres, this has required isolation of mud to be used for batch mixing with the BFS. Testing is ohen separately done on samples of the mixture. Upon c;~lllp~,t;JIl of th~ testing, activators, dia~l ~cu IL~ or oOher additives were added to the isolated fluid. This W0951~0~9~ 21alql I PcTlluS9S~llO~S
was usualiy done pfior to oementing. Use of this proc~3dure involved several O~ Idl consiclt" )~ which could adversely ~ff(3ct the rig equipment and/or the success ot the primary cement job. The possible problems all arise 5 from the potential for prematur~3 set of the slag-mix sluny, if all of the Ccllll~Ju"t"~ are added to the mix mud before the cementing operation is initiated. Generally according to API procedures, BFS is less abrasive than barite and, therefore, undue wear on pumps and othr3r equipment is not a major problem. In the past, ho~ever, corlcerns about eariy set-up of the 1~ BFS/mud mixture in the surfac~ equipment has been an i"~t5di"~t~"l to s~lc~cc* 11 cementing, especially where there are substantial thermal "'' t"~cesbetween ambient It~" ",~ es at the surface, where tl1e activator is added, and bu~lul, ll ,ul~ temperature, where th~3 activator is to perform. Normally, BFS/mud mixtures were designed to have suificient thickening time at the downhole 15 lt".,~.~. re to allow slurry placement. In many situations where the downhole temperature exceeds the surface temperature, the mixture thickening time is longer on the surface. This leavss ample time to flush the lines and other surface equipment of residual fiuid before it sets. However, in de~
:,, " " la, the slurry surface temperature may be hi~her than the bu~ul "l ùlt320 circulating temperature. Thereforr3, slurries designed at the surface for lower bullull!llul~ temperatures will set laster on the surfa~e. In the past, this hasrequired a dedicated line from the mixing tank to the rig pumps to minimize cu, Ital "i, la~iul1 of surface equipment. Additionally, due to flow variability upon pumping of the BFS/cement slurr~l, fine tuning of the amount of activator was 2~ necessary to account for variatiolls in flowrates, as well as any buttull,l,ùle temperature variations. If the batcll was premixed in the mud pits, there would be no opportunity to control the rate of addition of ar,~ivator to the batch blend.
Additlonally, batch mWng presente~ uniformity problems as well as the potential that the batch could solidify if purrlping problems as well as the potential that 3Q the batch could solidify if pumping problems ~l~v4lrlre~l In the pastl radio tracer inje~tion techniques have been used to facilitate foot-by-foot measurements of Portland cement coverage behind a casing. The principle used was injection of a ullifomm tracer material with a short half-life to W0 95/20095 ~ . IOIS
allow measurement of cement placemsnt, mud dialJla~~ , and the mixins that takes place at di~la~.~lllclllL fronts. Tne inj~ction technique for the 'i~ material is illustrated in Figure 1 of IADC/SPE Paper 14778 entitied 5 ~Evaluation of Cementing Practices by Quantitative Radio Tracer Measurements," authored by Kiine, et al., delivered in 1986 at the IADC/SPE
Cu~ l l~ in Dallas, Texas.
The system illustrated in F~gure 1 has many a iVdl Ita9e5 over the prior techniques which have been used to add activator to the BFS/mud slurrv. The 0 apparatus and method illustrated in Figure 1 deal with the possible risks to rig equipment and the success of the primary cement job, for which no answers were available in the l~ ".~ed 1993 arbcie by Cowan, the inver~tor of U.S.
Patent 5,058,679, which is discussed in the detailed i~s,,, i, I below. One of the concerns to the well operator is if attempts are made to continuously mix 5 the activator with the BFS mud/slurry, the operator was required to call out a cementing service company who would bring, at great expense, continuous mixing equipment previously used for Portland cement-based systems to conduct the inline mixing of the BFS with the mud. In order to save rig time and expense, ideas began to develop about using the rig equipment for mixing ~0 the BFS with the mud. The economic incentive was to avoid the cost ~ o. ;,.~Yd with hiring a service company for the mixing operation and to minimize rig time due to delays which could ensue from such an opr~ration with a cementin3 service company. However, as pointed out by Cowan, the risks of batch mixing in the rig pits and adding a precise amount of activator for the~5 expected downhole conditions create certain risks. For example, where the subsurface ~ es were siyl l-r Itly lower than the surface hl "pr~ es, additional activator would have to be added to allow for the lower It" ",u~, Iredownhole. However, this would shorten the set-up time for the BFS/mud slurry and create o~t" Idl problems if the slurry, once activated, was not quickly 30 placed downhole where the expected lower t~ re would be encountered.
Those skilled in the art d~ul~u;":~,d that the pumping of the BFS/mud slurry is not a continuous operation at a smooth flowrate. Upon initial ,ul ~5t~1 " I intothe casing internals, the mud "free falls" until the casing internals are filled ând wossnooss 21 ~ t q 1 1 r~ iD15 the mud starts its progress outside of the casing adjacent bhe formation. At that point, fluid losses could occur due to washouts or hig~1 porous segments, as well as resistance to How can oocl~r, all of which act to put additional resistance 5 on the surface pumping equipment, which in turn indur~es the rig personnel to alter the operabon of the surface pumps to avoid exceeding a ~l~d~,~.lllill~d pressure. This results in a slo~ring down of ths flowrate which in turn can cause problems if a large batch has been mixed in the rig equipment and acUvator already added. Continuous addition of activator on a real-time basis to reflect the actual operating flowrates directly ~"".."~ for flow flllC~tll " la while at the same I:ime ",i"i",i~i"~ the bme between activator inJection and final dia~Jld~;~l "t:"I. In essence, as soon as the activator is added, the mud is pumped through ~he cementing head and toward its hnal d~a~ . If for any reason there is a flow interruption, the surface equipment 15 is essenUally free of activated BFS/mud slurry.
Ar,cordingly, the apparatu~ and method of the present invention have been developed to improve on the systems for acUvator addition to BFS~mud mixtures. The present invention allows for s~nsitivity to changing flowrates andpressure conditions downhole d~lring the placement of the BFS/mud mixture.
2û The method of addition also mi~limizes the risk of lin~ plugging when using surface mud circulating equipment. The activator conc~ dliOI- can be adjusted on a real-Ume basis and precisely added for the expected downhole temperatures to be encountered, while at the same time ",i"i,~ i"g the risk of fouling surface equipment or the inside of the casing.
~5 Summary of the Invention The invention provides for meterin~ the pumping rate of BFS/mud mixtures pumped to the cementielg head on a rig for sea~ing off the formation from the casing. Since BFS/mud mixtures require an activation agent, 3û preferably sodium hydroxide is pl~mped into the flowline to the cementing head.
Feedback from the BFS/mud slul ry flowrate is fed to the activator injector pumpdrive system to regulate the addi~ion rate of the actlvating agent in response to varying conditions, such as mud flowrate. The injection rate tarset can also be 2~1ql 1 WO gS/2009~ 0 adjusted to W~ Jt,l l for any changes in downhole I~ , Ire. The risk of fouling surface equipment and the casing internal diameter is minimked becauss the activaUon agent is added very close in time to when the BFS/mud mixture enters the cementing head. Even in situatlons where the t" Iti~ dttld downhole I~",~ e is siy"~ ~'J lower than the surface Ie,lll~ Ire, a sufficient amount of ar.~tivating agent is added for the downhole conditions without fear of fouling the casing intemal or the surface pumping equipment.
Brief Description of the Drawina Figure 1 is a plan view of a skld-mounted assembly illustratin3 the preferred ~ di~ I of the present invention.
Detailed Description of the Preferred C~ udi~
As previously stated, 1, " 'I~, Portland cement slurried in water has been used as the solidifying agent for sealing off the casing from the formationand to provide r, lelul ,~ li.;dl support for the casing. More recently, to replace the Portland cement-based systems, a technique has been developed to use blast furnace slag as the solidifying agent for water-based mud. This procedure is illustrated in U.S. Patent 5,058,679. Typically, these BFS/mud systems require an activation agent to begin the hardening process. Sodium hydroxide and/or sodium carbonate have proven to be e~fective activating agents for the BFS/mud mixtures. In the preferred ~ i odi~ of the present invention, sodium hydroxide 25-50Yo by weight solution will be used, d~.er,di, Ig on local weather conditions. The apparatus and method of the present invention constitute an i~ u/~ c~I over the prior batch systems used for BFS/mud mixtures. As discussed in a recent article appearing in the October 1993 issue of World Oil, entitled "Solidify Mud to Save Cementing Rme and Reduce Waste," by iCM. Cowan (also the patentee of U.S. Patent 5,058,796), the prior method of adding activators into a batch mix tank, such as the mud tanks, presented numerous problems with plugging of rig equipment or potentially the casing, particularly if the ambient It~"~p~ ~re at the surface where the batch is mixed is substantially higher than the iJUtlUI 1 ~l ,ole I~" ~ re. Rhis type of Q s~noo~ 91 ~ Cl5 It""~ re gradient is encountered in offshore wells in ~ ~, . Iocations.The artic~e concludes that the present technology still makes it di~hcult to i" ,~ " ~ell ,111,~ BFS/mud system using eY~ /el~ the rig equipment, particularly 5 the active circulating system on t~le rig. The apparatus and method of the prr~sent invent~on has very simply answered the inquiry made by Mr. Cowan in the article.
The Apparatus A of the present inventlon is illustrated in Figure 1. In the preferred ~n~L,udi, ~ , a skid 10 is used to facilitate portability of the significant 10 pieces of equipment involved. On l:op of skid 20 is BFS/mud inlet 22. The rigpumps (not shown) are used to su~)ply the BFS/mud mixture which has yet to be activated from the mud pits or ~ther rig equipment to the skid 20. Inlet 22 is cù, " ,e~L~d to meter 5 through line 26 which can be isolated using valves 8.Meter 5 is preferably a magnetic flow meter which is capable of handling 15 slurries. For economy, the meter ~i working pressure may be fairly low in thgorder of about 1000 pounds. However, to avoid over pressure of meter 5, a relief valve 14 can be provided wtlich can be set preferably at or near the working pressure of the meter 5. Da~ "1,~", of relief valve 14 is inline mixer 7. Between inline mixer 7 and relief valve 14 are Cu~llle~:tiù1-5 for activation2û pumps 1. Two pumps are illustra~ed on skid 20 which can be operated in unison or with one operating as a ~ackup unit. In the pr~ferred ~IllL~o~i"~"l, an explosion-proof motor 3 is cu~ .,~d to a variable speed motor reducer which in the preferred ~"ILodi",t:"l can reduce the pump speed with respect to the motor speed by a ratio of dy~lUA;l~ t~ r 6-1. The speed reducer 2 can 25 vary the ratio to alter the operating ~peed of the pump 1 responsive to signals received from control panel 15. A source of activation material, preferably 50%
caustic soda solution, is connected to the inlets as marked on Figure 1. Each of the pumps 1 discharge past a bl~ed valve 11 followed by a block valve 10 and hnally a check valve 12. As indicated in Figure 1, the discharge of pump 30 1 has an outlet to a pressure switch with the switch 13 mounted on a panel.
The pressure switch is electrically ti~d to motor 3 for shutdown in the event ofsudden loss of pressure during oper~tion which would signal a serious leakage of caustic soda. Due to the safety COnceMs, a rapid shutdown of the caustic WO95/20095 2 1 8 1 9 1 1 .,~, lol~ ~
supply is desirable in the event of a ~iatabllu,ull;-, leak. Both thr~ pumps 1 on the skid 20 are similarly equipped.
D_ Ibl,e,a", of inline mixer 7 which mixes the BFS/mud slurry arriving from inlet 22 with the caustic soda coming from pump 1 is â sample port assembly lg which allows ~u~ltulil,g personnel to obtain a sample of the activated BFS/mud mixture. BlQck valves 8 on line 26 allow isolation of the meter 5, relief valve 14, and inline mixer 7. With valves 8 which are disposed upstream of meter 5 and '~ . . . Ib~l ~al 1 l of sample port assembly 19 both closed and a bypass valve 8 on line 24 open, the entire skid 20 operates as essentiallyas a piece of pipe. During normal operation when caustic soda is added, the valves 8 on line 26 are in the open posiUon while the block valve 8 on Uhe bypass line 24 is closed. The mixture of caust~c soda with the BFS/mud slurry exits from outlet 28 and goes to a cemenUng head (not shown) for pumping 15 down the casing and around the outside of the casing in the normal manner fora cementing operation. The BFS/mud flowrate is indicated on flow indicator controller 4. The flow indicator 4 sends a signal into the electrical control panel 15. Wlthin the panel, in a manner known in the art, the signal from the flow indicator controller 4 is used to generate a signal directed to the variable speed 20 drive 2 to alter the speed of the pump. In the preferred ~" Ibo-3i" ~"l, the pump 1 is of a positive di~ ld~lll~ type where its volume delivery is directional ~u~u~ liu"al to its operating speed.
In operation, the rig pumps (not shown) are oriented for flow communication with inlet 22 with the block valve 8 on the bypass line 24 closed.25 Flow through meter 5 creates a signal on controller 4 which in turn regulatespump 1 at a particular speed through manipulation of variable speed drive 2.
In Uhis manner, a ,c, t,~l~t~l I l lil Idd addition rate, as ~It5lt" " ,i, l~d on r,ontrol panel 15, of caustic soda is attained by regulating the speed of pump 1 to the flowrats meâsured on meter 5. Knowing the properties of the BFS/mud slurry 30 mixture coming into inlet 22, the desired rate of addition of caustic soda can be readily d~t~l " ,i, l~d since the properties of caustic soda are as well also known.
The mixture is thoroughly mixed in inline mixer 7 and then exits the skid 20 through ouUet 28. It then flows to the cemenUng head (not shown) down the ~l~lql 1 ~ WO 95~OOgS 1 ~
casing and around the outside of the casing for ultimat~ cementing between the casing and the formation. It is al , ' that the addition of causbc soda occurs when flow of BFS/mud slurry is initiated. Thr~ addition Nnhnues at a rate pl upcn liùl ,al to the flow. During the initial pumping, the BFS/mud mixture, which has just been activated on skid 20, flows generslly smoothly unbl the BFS/mud mixture reaches the bott~m of bhe casing. Thereafter, fl~ in the flowrate may occur due to rr!sistance to flow c~ffered by bhe formabon around bhe outside of the casing. Variations in flowrate which occur when rig personnel slterbhe speed of the rig pumps to avoid increasing pressure beyond a ~ d value are autul~ acNunted for at the surface by adjustments to the flowrate of caus~ic soda at pump 1 through bhe conhroller 15 acting on a signal received from flowmeter 5. Conveniently, by the time the activated BFS/mud mixture reache!; the bottom of the wellbore to Nme around the casing go up the casing, mo~t, if not all, of th~ caustic soda which is necessary for subsequent hardenillg of the mixture has already been added.
Once that point is reached, the pumps 1 are turned off and blocked in and the skid 20 is operated on bypass line 24 by opening the bypass 8 on line 24 and closing the two inline valves 8 on line 26. At this tims, a pressure buildup is usually tApe~i~"ced at the rig pump as the BFS/mud mixture is forced upwardly outside the casing adjacent the fclrmation. Since the pressure rating of the meter 5 is only 1000 pounds, it can be effectively blocked in casing valves 8 online 26 once the Nndition has ocr urred where no ac~ditional caustic soda is required.
The illustrated system disclc)sed in Figure 1 and described above has several adv~ dlJcr5. First, it is a ct~mpact design which can be used for both onshore and offshore ~ . In locations where space is commonly at a premium, a compact design is ~ften helpful. Apparatus A of the present invention allows the use of rig pumps and equipment to mix the BFS/mud slurry without fear bhat the lines will set up if the pumping procedure is interrupted after a batch activation. Batch activation in mud pits or other equipment can present serious Nncerns of plugging the important rig equipment if pumping problems are enNuntered after ac~ivahon. With apparatus A of the present wo 95/20095 2 1 ~ 1 9 1 1 r~ S
invenUon, there is no activation unUI the slurry is about to enter the cementinghead. If pumping problems develop, the activated inventory in the surface equipment is negligible.
Variations in the pumping rate are measured by the apparatus of the present invention and real time ~u, el.,~, la to the caustic soda addition rate are made in response to such 90W fll ~ s of the BFS/mud slurry. The system can be entirely isolated once a sufficient amount of caustic soda has been added to the charge of BFS/mud slurry which is to be used in the cementing 0 procedure. Typically, the rig location has a mud engineer whose principal lea~JUII ' ' are the physical properties of the mud during the drilling operation. The apparatus of the present invention allows the use of the same mud engineer or even ri3 personnel to monitor of the pé,~u""d"~ of the apparatus A. Accordingly, with the compact dssign o~ the skid 20, the skid can 1 S be made a pel 1 l Idl It71 ~I part of the rig equipment and no i"~;, el 1 ll::l lldl personnel are necessary beyond a mud engineer who would be on location in any event during the drilling operahon for " ,u,, i"g of the mud properties. In short, theapparatus and method of the present invention takes the fear out of batch mixing BFS/mud slurries using existing rig equipment. It also provides a greater degree of control and certainty over the consialel)cy and uniformity of conce"t, dliUI . of activating caustic soda in the mixture. Since the causUc soda is mixed inline with the flowing BFS/mud mixture, a more uniform consia~el-cy can be obtained as opposed to batch mixing in large tanks where the cu, laiaLency of the pe"" ~ , of causUc soda within the BFS/mud mixture is unknown or at best uncertain. By continuously adding the caustic soda, the operator is assured of a more consistent hardening of the BFS/mud mixture throughout the zûne being cemented.
For added safety, a housing 28 shown in dashed lines can be put over meter 5 and relief valve 14, as well as most of the discharge piping from pump 1 so that in the event any lesks develop, personnel on the rig are protected from burns which could occur from skin contact with 50% caustic soda.
It should be noted that other pt~ h~:a of caustic soda can be used without departing from the spirit of the invenUon. Other activators can be used WOgS/20095 2 ~ 8 ~ ;~1 1 r~ C15 at dfflerent cor,~ ~t, ,:, withou~ departin~ from the spirit of the invention.
The ~- u~ul tiu" ~ between the m~asured flowrate and the speed of the pump 1 can be changed to a~ u""" lt dfflerent ~;unc~ , ,s of artivator in the 5 BFS/mud slurry or" , ~ , t~ ccr.,~"l, '~ dfflerent cu"~"t~ ,:, of a~tivator solutions used so that the udimate cu,~ ," , of activator in the finished mixed slurry is in the proper range r~quirement. The BFS
cùl 1~1 f~ ~Lu~) in the mud can also be taken into account when computing the amount of actuator to be added. ~-his is usually r;l~Jt~ . " ,i, Idd before a batch of 1û BFS is mixed with the mud in the rig equipment.
A'though batch mixing facililies use of rig mud equipment, continuous BFS/mud mixing is also within t1e scope of the invention. The desired c~n, ~, Itl , of BFS in the mud is continuously ûbtai~ed and the feed rate of BFS is then measured. The activator is then injected continuously in proportion 15 to the BFS feed rate. In this marmer as soon as the BFS/mud mixture is prepared it is i" ", ,eui. t~ 'y activate~ and sent directly downhole for plc.ce, "~, It prior to any risk of set-up. If pumping problems develop, the surface equipment can easily be cleaned out without risk of plu~ging or set-up.
The advantages of use of th~,3 system as described and shown in Figure 20 1 allow the rig operator to eliminatr~ the use of a rem~anting service company with its necessary equipment for th~ mixing operation. By the use of a simple skid-mounted assemb~y as shown in Figure 1 the cementing procedure using BFS/mud slurries can be carried ol~t using rig personnel who can manually or with the aid of rig equipment batch mix the BFS slurr~ with the mud without the 25 addition of caustic. With the use of the apparatus and method of the present invention, the caustic is only adde~ at the last minute before the BFS/mud slurry goes downhole.
While mWng of two or more fluids inline has been ar. cu" ",l;~. ,ed in the past such as for example in U.S. P.~tents 3 833,718 arld 3 827 495 ever since 30 the ~ " ,uluyy of using BFS/mud ~olut~ons has evolved as described in U.S.
Patent 5,058,679 and the World Oil artic'le by its inYentor Cowan, operators have been struggling with a reliabla method that addresses the risks to rig equipment, particularly i" ~ S where the downhole temperature is W0 9~/20095 2 1 8 1 ~ 1 1 r ~ ~ o Si~JII'~ ,~J below the surface h.l"~l_ IreS when a batch is mixed with an acthlating agent. Temperature gradients of 40-F are possible which rsquire higher actuator co,~ceuh ~.~;Jns which in turn can limit the time before substantlal 5 hardening at surface temperatures to only a few hours. This can be a significant problem for rig u,u~, la if any problems develop during the injection procedure for the BFS/mud slurry after it has been activated. Disposalof the activated slur~y may be a problem especially in an of Ishore ~ " " "~"~.
The apparatus and method of the present invention address and solve this 10 problem.
The foregoing disclosure and d~a~ Jl;ol I of the invention are illustrative and ~ lal y thereof, and various changes in the size, shape and materials, as well as in the details of the illustrated construction, may be made without deparbng from the spirit of the invention.
1~
FURNACE St AG BASE CEMENT
5 Field of tne Invention The field of this invention relates to ~ Jal~iul~ and setting of blast-furnace slag mud formulations into a wellbore to cement a casins.
Background of the Invention In the past, casing has been ~,emented downhole using Portland cement-based materials. The Por~and cement is mixed with water or available aqueous solution and drculated to properly l,pot the material for properly sealing off the outside of the casing from the formation. The Portland cementing systems have generally been provided to well operators by oilfield service c~",i,d"ies.
These service ~,u, IlJdl li~55 have brought to the well site, mixing equipment and personnel so that the Portland cen1ent can be Nntinuously mixed with water to obtain the proper ratio of cement to water for proper " "~ on the casing exterior. More recently, an alternative to Portland cement systems has been developed. This system involves the additlon of blast-furnace slag (BFS) to water-based mud for slurry densities in the range of between 10-20 Ibs./gal.,.l~pe"~i"y on the mud weight and the requirements applicable to the specific operation. The thickenins time of BFS/mud mixtures is Nntrolled by activators and retarders. Activators accelerate hydration of BFS and reduce thickening time and improve early cu, I IIJI ~ 1~3 strength development. Some of the more effective activators are alkali materials that increase the mud pH. The additionof BFS and activators to mud has negligible effect on tlle plastic VisNsity, yield point, and ~el strength over and above the properties of the original mud. The ~ol~lyi~al properties can be fur~her adjusted using chemical thinners or 9~ ts, dilution of the mud with water, or a co~ IILil, of both steps.
BFS/mud mixtures can be activated by thermal energy or chemical activation. Chemically, BFS is similar to Portland cement. It is the residue from ore and other additives developed ~n a molterl state, along with iron in a blast wossnooss 218 ~ 9 l 1 F.,II~ 15 0 furnace. BFS is ~ ,lml~d from a biast furnace at a lc""~ re between 2soQ-2900 F and quenched as a moiten siag to produce a glassy, granular material. O~ " , of BFS/mud mixtures puts the solids by volurne content 5 at anywhere in the range between 16-45% and reasonably n~Jlu~ull. - the cu".,~"~r~ ~s of equivaient density Portland cement slurries.
BFS is less reactive than Portland cement. As a consequenr e, BFS/water-based mud mixtures or BFS/water mixtures must be chemically acthated to achieve set in Ohe downhole wellbore environment, and Portiand 1Q cement/water mixtures usuaily must be ch~micaily retarded. Chemical activation is simpler and less expenshe than ~ . Typicaily, sodium hydroxide and sodium carbonate are the most widely used activators for BFS/water-based mud mixtures because Ohey sre commonly available.
Sodium hydroxide has a greater impact on setting time, while sodium carbonate 15 has a greater ~nfluence on the manner of set and the cc""~ e strength.
Above 80 F, sodium carbonate is used in greater ccnc~"o la than sodium hydroxide because there is sufficient thermai energy to reduce setting times, while the higher sodium carbonate cu"ce" ~ aids in the early cu, "~ ":,ive sOrength ~ ".mt:l ll. In temperatures below 80 F, the sodium 20 hydroxide ~o,)~"t,. , can be equal or slightly higher than sodium carbonate cu,,~,~,,t, , because of low thermal energy available to activate the slag hydraO'on. Typically, activator cioncc" dl cdiol~ in the formulations varies between 2-24 Ibs./barrel of slurry for most formulaOons, ck ~,t "~ii"çi on the temperature and the amount of retarding material present. Yet another advantage of using 25 BFS/mud mixtures is uniform cu",~ ssive strençith build-up over Ome in situations where significant ttsll,pt:, Ire ~ , ' exist between top and L"l~lul l ll lultl temperatures.
When using BFS/mud mixtures in the field, Ohe BFS is typically mixed with the mud in Ohe mud pits on the rig. Batch mixing in rig pits or mud premix 'iO tanks or cement mixers is possible. In some instsnres, this has required isolation of mud to be used for batch mixing with the BFS. Testing is ohen separately done on samples of the mixture. Upon c;~lllp~,t;JIl of th~ testing, activators, dia~l ~cu IL~ or oOher additives were added to the isolated fluid. This W0951~0~9~ 21alql I PcTlluS9S~llO~S
was usualiy done pfior to oementing. Use of this proc~3dure involved several O~ Idl consiclt" )~ which could adversely ~ff(3ct the rig equipment and/or the success ot the primary cement job. The possible problems all arise 5 from the potential for prematur~3 set of the slag-mix sluny, if all of the Ccllll~Ju"t"~ are added to the mix mud before the cementing operation is initiated. Generally according to API procedures, BFS is less abrasive than barite and, therefore, undue wear on pumps and othr3r equipment is not a major problem. In the past, ho~ever, corlcerns about eariy set-up of the 1~ BFS/mud mixture in the surfac~ equipment has been an i"~t5di"~t~"l to s~lc~cc* 11 cementing, especially where there are substantial thermal "'' t"~cesbetween ambient It~" ",~ es at the surface, where tl1e activator is added, and bu~lul, ll ,ul~ temperature, where th~3 activator is to perform. Normally, BFS/mud mixtures were designed to have suificient thickening time at the downhole 15 lt".,~.~. re to allow slurry placement. In many situations where the downhole temperature exceeds the surface temperature, the mixture thickening time is longer on the surface. This leavss ample time to flush the lines and other surface equipment of residual fiuid before it sets. However, in de~
:,, " " la, the slurry surface temperature may be hi~her than the bu~ul "l ùlt320 circulating temperature. Thereforr3, slurries designed at the surface for lower bullull!llul~ temperatures will set laster on the surfa~e. In the past, this hasrequired a dedicated line from the mixing tank to the rig pumps to minimize cu, Ital "i, la~iul1 of surface equipment. Additionally, due to flow variability upon pumping of the BFS/cement slurr~l, fine tuning of the amount of activator was 2~ necessary to account for variatiolls in flowrates, as well as any buttull,l,ùle temperature variations. If the batcll was premixed in the mud pits, there would be no opportunity to control the rate of addition of ar,~ivator to the batch blend.
Additlonally, batch mWng presente~ uniformity problems as well as the potential that the batch could solidify if purrlping problems as well as the potential that 3Q the batch could solidify if pumping problems ~l~v4lrlre~l In the pastl radio tracer inje~tion techniques have been used to facilitate foot-by-foot measurements of Portland cement coverage behind a casing. The principle used was injection of a ullifomm tracer material with a short half-life to W0 95/20095 ~ . IOIS
allow measurement of cement placemsnt, mud dialJla~~ , and the mixins that takes place at di~la~.~lllclllL fronts. Tne inj~ction technique for the 'i~ material is illustrated in Figure 1 of IADC/SPE Paper 14778 entitied 5 ~Evaluation of Cementing Practices by Quantitative Radio Tracer Measurements," authored by Kiine, et al., delivered in 1986 at the IADC/SPE
Cu~ l l~ in Dallas, Texas.
The system illustrated in F~gure 1 has many a iVdl Ita9e5 over the prior techniques which have been used to add activator to the BFS/mud slurrv. The 0 apparatus and method illustrated in Figure 1 deal with the possible risks to rig equipment and the success of the primary cement job, for which no answers were available in the l~ ".~ed 1993 arbcie by Cowan, the inver~tor of U.S.
Patent 5,058,679, which is discussed in the detailed i~s,,, i, I below. One of the concerns to the well operator is if attempts are made to continuously mix 5 the activator with the BFS mud/slurry, the operator was required to call out a cementing service company who would bring, at great expense, continuous mixing equipment previously used for Portland cement-based systems to conduct the inline mixing of the BFS with the mud. In order to save rig time and expense, ideas began to develop about using the rig equipment for mixing ~0 the BFS with the mud. The economic incentive was to avoid the cost ~ o. ;,.~Yd with hiring a service company for the mixing operation and to minimize rig time due to delays which could ensue from such an opr~ration with a cementin3 service company. However, as pointed out by Cowan, the risks of batch mixing in the rig pits and adding a precise amount of activator for the~5 expected downhole conditions create certain risks. For example, where the subsurface ~ es were siyl l-r Itly lower than the surface hl "pr~ es, additional activator would have to be added to allow for the lower It" ",u~, Iredownhole. However, this would shorten the set-up time for the BFS/mud slurry and create o~t" Idl problems if the slurry, once activated, was not quickly 30 placed downhole where the expected lower t~ re would be encountered.
Those skilled in the art d~ul~u;":~,d that the pumping of the BFS/mud slurry is not a continuous operation at a smooth flowrate. Upon initial ,ul ~5t~1 " I intothe casing internals, the mud "free falls" until the casing internals are filled ând wossnooss 21 ~ t q 1 1 r~ iD15 the mud starts its progress outside of the casing adjacent bhe formation. At that point, fluid losses could occur due to washouts or hig~1 porous segments, as well as resistance to How can oocl~r, all of which act to put additional resistance 5 on the surface pumping equipment, which in turn indur~es the rig personnel to alter the operabon of the surface pumps to avoid exceeding a ~l~d~,~.lllill~d pressure. This results in a slo~ring down of ths flowrate which in turn can cause problems if a large batch has been mixed in the rig equipment and acUvator already added. Continuous addition of activator on a real-time basis to reflect the actual operating flowrates directly ~"".."~ for flow flllC~tll " la while at the same I:ime ",i"i",i~i"~ the bme between activator inJection and final dia~Jld~;~l "t:"I. In essence, as soon as the activator is added, the mud is pumped through ~he cementing head and toward its hnal d~a~ . If for any reason there is a flow interruption, the surface equipment 15 is essenUally free of activated BFS/mud slurry.
Ar,cordingly, the apparatu~ and method of the present invention have been developed to improve on the systems for acUvator addition to BFS~mud mixtures. The present invention allows for s~nsitivity to changing flowrates andpressure conditions downhole d~lring the placement of the BFS/mud mixture.
2û The method of addition also mi~limizes the risk of lin~ plugging when using surface mud circulating equipment. The activator conc~ dliOI- can be adjusted on a real-Ume basis and precisely added for the expected downhole temperatures to be encountered, while at the same time ",i"i,~ i"g the risk of fouling surface equipment or the inside of the casing.
~5 Summary of the Invention The invention provides for meterin~ the pumping rate of BFS/mud mixtures pumped to the cementielg head on a rig for sea~ing off the formation from the casing. Since BFS/mud mixtures require an activation agent, 3û preferably sodium hydroxide is pl~mped into the flowline to the cementing head.
Feedback from the BFS/mud slul ry flowrate is fed to the activator injector pumpdrive system to regulate the addi~ion rate of the actlvating agent in response to varying conditions, such as mud flowrate. The injection rate tarset can also be 2~1ql 1 WO gS/2009~ 0 adjusted to W~ Jt,l l for any changes in downhole I~ , Ire. The risk of fouling surface equipment and the casing internal diameter is minimked becauss the activaUon agent is added very close in time to when the BFS/mud mixture enters the cementing head. Even in situatlons where the t" Iti~ dttld downhole I~",~ e is siy"~ ~'J lower than the surface Ie,lll~ Ire, a sufficient amount of ar.~tivating agent is added for the downhole conditions without fear of fouling the casing intemal or the surface pumping equipment.
Brief Description of the Drawina Figure 1 is a plan view of a skld-mounted assembly illustratin3 the preferred ~ di~ I of the present invention.
Detailed Description of the Preferred C~ udi~
As previously stated, 1, " 'I~, Portland cement slurried in water has been used as the solidifying agent for sealing off the casing from the formationand to provide r, lelul ,~ li.;dl support for the casing. More recently, to replace the Portland cement-based systems, a technique has been developed to use blast furnace slag as the solidifying agent for water-based mud. This procedure is illustrated in U.S. Patent 5,058,679. Typically, these BFS/mud systems require an activation agent to begin the hardening process. Sodium hydroxide and/or sodium carbonate have proven to be e~fective activating agents for the BFS/mud mixtures. In the preferred ~ i odi~ of the present invention, sodium hydroxide 25-50Yo by weight solution will be used, d~.er,di, Ig on local weather conditions. The apparatus and method of the present invention constitute an i~ u/~ c~I over the prior batch systems used for BFS/mud mixtures. As discussed in a recent article appearing in the October 1993 issue of World Oil, entitled "Solidify Mud to Save Cementing Rme and Reduce Waste," by iCM. Cowan (also the patentee of U.S. Patent 5,058,796), the prior method of adding activators into a batch mix tank, such as the mud tanks, presented numerous problems with plugging of rig equipment or potentially the casing, particularly if the ambient It~"~p~ ~re at the surface where the batch is mixed is substantially higher than the iJUtlUI 1 ~l ,ole I~" ~ re. Rhis type of Q s~noo~ 91 ~ Cl5 It""~ re gradient is encountered in offshore wells in ~ ~, . Iocations.The artic~e concludes that the present technology still makes it di~hcult to i" ,~ " ~ell ,111,~ BFS/mud system using eY~ /el~ the rig equipment, particularly 5 the active circulating system on t~le rig. The apparatus and method of the prr~sent invent~on has very simply answered the inquiry made by Mr. Cowan in the article.
The Apparatus A of the present inventlon is illustrated in Figure 1. In the preferred ~n~L,udi, ~ , a skid 10 is used to facilitate portability of the significant 10 pieces of equipment involved. On l:op of skid 20 is BFS/mud inlet 22. The rigpumps (not shown) are used to su~)ply the BFS/mud mixture which has yet to be activated from the mud pits or ~ther rig equipment to the skid 20. Inlet 22 is cù, " ,e~L~d to meter 5 through line 26 which can be isolated using valves 8.Meter 5 is preferably a magnetic flow meter which is capable of handling 15 slurries. For economy, the meter ~i working pressure may be fairly low in thgorder of about 1000 pounds. However, to avoid over pressure of meter 5, a relief valve 14 can be provided wtlich can be set preferably at or near the working pressure of the meter 5. Da~ "1,~", of relief valve 14 is inline mixer 7. Between inline mixer 7 and relief valve 14 are Cu~llle~:tiù1-5 for activation2û pumps 1. Two pumps are illustra~ed on skid 20 which can be operated in unison or with one operating as a ~ackup unit. In the pr~ferred ~IllL~o~i"~"l, an explosion-proof motor 3 is cu~ .,~d to a variable speed motor reducer which in the preferred ~"ILodi",t:"l can reduce the pump speed with respect to the motor speed by a ratio of dy~lUA;l~ t~ r 6-1. The speed reducer 2 can 25 vary the ratio to alter the operating ~peed of the pump 1 responsive to signals received from control panel 15. A source of activation material, preferably 50%
caustic soda solution, is connected to the inlets as marked on Figure 1. Each of the pumps 1 discharge past a bl~ed valve 11 followed by a block valve 10 and hnally a check valve 12. As indicated in Figure 1, the discharge of pump 30 1 has an outlet to a pressure switch with the switch 13 mounted on a panel.
The pressure switch is electrically ti~d to motor 3 for shutdown in the event ofsudden loss of pressure during oper~tion which would signal a serious leakage of caustic soda. Due to the safety COnceMs, a rapid shutdown of the caustic WO95/20095 2 1 8 1 9 1 1 .,~, lol~ ~
supply is desirable in the event of a ~iatabllu,ull;-, leak. Both thr~ pumps 1 on the skid 20 are similarly equipped.
D_ Ibl,e,a", of inline mixer 7 which mixes the BFS/mud slurry arriving from inlet 22 with the caustic soda coming from pump 1 is â sample port assembly lg which allows ~u~ltulil,g personnel to obtain a sample of the activated BFS/mud mixture. BlQck valves 8 on line 26 allow isolation of the meter 5, relief valve 14, and inline mixer 7. With valves 8 which are disposed upstream of meter 5 and '~ . . . Ib~l ~al 1 l of sample port assembly 19 both closed and a bypass valve 8 on line 24 open, the entire skid 20 operates as essentiallyas a piece of pipe. During normal operation when caustic soda is added, the valves 8 on line 26 are in the open posiUon while the block valve 8 on Uhe bypass line 24 is closed. The mixture of caust~c soda with the BFS/mud slurry exits from outlet 28 and goes to a cemenUng head (not shown) for pumping 15 down the casing and around the outside of the casing in the normal manner fora cementing operation. The BFS/mud flowrate is indicated on flow indicator controller 4. The flow indicator 4 sends a signal into the electrical control panel 15. Wlthin the panel, in a manner known in the art, the signal from the flow indicator controller 4 is used to generate a signal directed to the variable speed 20 drive 2 to alter the speed of the pump. In the preferred ~" Ibo-3i" ~"l, the pump 1 is of a positive di~ ld~lll~ type where its volume delivery is directional ~u~u~ liu"al to its operating speed.
In operation, the rig pumps (not shown) are oriented for flow communication with inlet 22 with the block valve 8 on the bypass line 24 closed.25 Flow through meter 5 creates a signal on controller 4 which in turn regulatespump 1 at a particular speed through manipulation of variable speed drive 2.
In Uhis manner, a ,c, t,~l~t~l I l lil Idd addition rate, as ~It5lt" " ,i, l~d on r,ontrol panel 15, of caustic soda is attained by regulating the speed of pump 1 to the flowrats meâsured on meter 5. Knowing the properties of the BFS/mud slurry 30 mixture coming into inlet 22, the desired rate of addition of caustic soda can be readily d~t~l " ,i, l~d since the properties of caustic soda are as well also known.
The mixture is thoroughly mixed in inline mixer 7 and then exits the skid 20 through ouUet 28. It then flows to the cemenUng head (not shown) down the ~l~lql 1 ~ WO 95~OOgS 1 ~
casing and around the outside of the casing for ultimat~ cementing between the casing and the formation. It is al , ' that the addition of causbc soda occurs when flow of BFS/mud slurry is initiated. Thr~ addition Nnhnues at a rate pl upcn liùl ,al to the flow. During the initial pumping, the BFS/mud mixture, which has just been activated on skid 20, flows generslly smoothly unbl the BFS/mud mixture reaches the bott~m of bhe casing. Thereafter, fl~ in the flowrate may occur due to rr!sistance to flow c~ffered by bhe formabon around bhe outside of the casing. Variations in flowrate which occur when rig personnel slterbhe speed of the rig pumps to avoid increasing pressure beyond a ~ d value are autul~ acNunted for at the surface by adjustments to the flowrate of caus~ic soda at pump 1 through bhe conhroller 15 acting on a signal received from flowmeter 5. Conveniently, by the time the activated BFS/mud mixture reache!; the bottom of the wellbore to Nme around the casing go up the casing, mo~t, if not all, of th~ caustic soda which is necessary for subsequent hardenillg of the mixture has already been added.
Once that point is reached, the pumps 1 are turned off and blocked in and the skid 20 is operated on bypass line 24 by opening the bypass 8 on line 24 and closing the two inline valves 8 on line 26. At this tims, a pressure buildup is usually tApe~i~"ced at the rig pump as the BFS/mud mixture is forced upwardly outside the casing adjacent the fclrmation. Since the pressure rating of the meter 5 is only 1000 pounds, it can be effectively blocked in casing valves 8 online 26 once the Nndition has ocr urred where no ac~ditional caustic soda is required.
The illustrated system disclc)sed in Figure 1 and described above has several adv~ dlJcr5. First, it is a ct~mpact design which can be used for both onshore and offshore ~ . In locations where space is commonly at a premium, a compact design is ~ften helpful. Apparatus A of the present invention allows the use of rig pumps and equipment to mix the BFS/mud slurry without fear bhat the lines will set up if the pumping procedure is interrupted after a batch activation. Batch activation in mud pits or other equipment can present serious Nncerns of plugging the important rig equipment if pumping problems are enNuntered after ac~ivahon. With apparatus A of the present wo 95/20095 2 1 ~ 1 9 1 1 r~ S
invenUon, there is no activation unUI the slurry is about to enter the cementinghead. If pumping problems develop, the activated inventory in the surface equipment is negligible.
Variations in the pumping rate are measured by the apparatus of the present invention and real time ~u, el.,~, la to the caustic soda addition rate are made in response to such 90W fll ~ s of the BFS/mud slurry. The system can be entirely isolated once a sufficient amount of caustic soda has been added to the charge of BFS/mud slurry which is to be used in the cementing 0 procedure. Typically, the rig location has a mud engineer whose principal lea~JUII ' ' are the physical properties of the mud during the drilling operation. The apparatus of the present invention allows the use of the same mud engineer or even ri3 personnel to monitor of the pé,~u""d"~ of the apparatus A. Accordingly, with the compact dssign o~ the skid 20, the skid can 1 S be made a pel 1 l Idl It71 ~I part of the rig equipment and no i"~;, el 1 ll::l lldl personnel are necessary beyond a mud engineer who would be on location in any event during the drilling operahon for " ,u,, i"g of the mud properties. In short, theapparatus and method of the present invention takes the fear out of batch mixing BFS/mud slurries using existing rig equipment. It also provides a greater degree of control and certainty over the consialel)cy and uniformity of conce"t, dliUI . of activating caustic soda in the mixture. Since the causUc soda is mixed inline with the flowing BFS/mud mixture, a more uniform consia~el-cy can be obtained as opposed to batch mixing in large tanks where the cu, laiaLency of the pe"" ~ , of causUc soda within the BFS/mud mixture is unknown or at best uncertain. By continuously adding the caustic soda, the operator is assured of a more consistent hardening of the BFS/mud mixture throughout the zûne being cemented.
For added safety, a housing 28 shown in dashed lines can be put over meter 5 and relief valve 14, as well as most of the discharge piping from pump 1 so that in the event any lesks develop, personnel on the rig are protected from burns which could occur from skin contact with 50% caustic soda.
It should be noted that other pt~ h~:a of caustic soda can be used without departing from the spirit of the invenUon. Other activators can be used WOgS/20095 2 ~ 8 ~ ;~1 1 r~ C15 at dfflerent cor,~ ~t, ,:, withou~ departin~ from the spirit of the invention.
The ~- u~ul tiu" ~ between the m~asured flowrate and the speed of the pump 1 can be changed to a~ u""" lt dfflerent ~;unc~ , ,s of artivator in the 5 BFS/mud slurry or" , ~ , t~ ccr.,~"l, '~ dfflerent cu"~"t~ ,:, of a~tivator solutions used so that the udimate cu,~ ," , of activator in the finished mixed slurry is in the proper range r~quirement. The BFS
cùl 1~1 f~ ~Lu~) in the mud can also be taken into account when computing the amount of actuator to be added. ~-his is usually r;l~Jt~ . " ,i, Idd before a batch of 1û BFS is mixed with the mud in the rig equipment.
A'though batch mixing facililies use of rig mud equipment, continuous BFS/mud mixing is also within t1e scope of the invention. The desired c~n, ~, Itl , of BFS in the mud is continuously ûbtai~ed and the feed rate of BFS is then measured. The activator is then injected continuously in proportion 15 to the BFS feed rate. In this marmer as soon as the BFS/mud mixture is prepared it is i" ", ,eui. t~ 'y activate~ and sent directly downhole for plc.ce, "~, It prior to any risk of set-up. If pumping problems develop, the surface equipment can easily be cleaned out without risk of plu~ging or set-up.
The advantages of use of th~,3 system as described and shown in Figure 20 1 allow the rig operator to eliminatr~ the use of a rem~anting service company with its necessary equipment for th~ mixing operation. By the use of a simple skid-mounted assemb~y as shown in Figure 1 the cementing procedure using BFS/mud slurries can be carried ol~t using rig personnel who can manually or with the aid of rig equipment batch mix the BFS slurr~ with the mud without the 25 addition of caustic. With the use of the apparatus and method of the present invention, the caustic is only adde~ at the last minute before the BFS/mud slurry goes downhole.
While mWng of two or more fluids inline has been ar. cu" ",l;~. ,ed in the past such as for example in U.S. P.~tents 3 833,718 arld 3 827 495 ever since 30 the ~ " ,uluyy of using BFS/mud ~olut~ons has evolved as described in U.S.
Patent 5,058,679 and the World Oil artic'le by its inYentor Cowan, operators have been struggling with a reliabla method that addresses the risks to rig equipment, particularly i" ~ S where the downhole temperature is W0 9~/20095 2 1 8 1 ~ 1 1 r ~ ~ o Si~JII'~ ,~J below the surface h.l"~l_ IreS when a batch is mixed with an acthlating agent. Temperature gradients of 40-F are possible which rsquire higher actuator co,~ceuh ~.~;Jns which in turn can limit the time before substantlal 5 hardening at surface temperatures to only a few hours. This can be a significant problem for rig u,u~, la if any problems develop during the injection procedure for the BFS/mud slurry after it has been activated. Disposalof the activated slur~y may be a problem especially in an of Ishore ~ " " "~"~.
The apparatus and method of the present invention address and solve this 10 problem.
The foregoing disclosure and d~a~ Jl;ol I of the invention are illustrative and ~ lal y thereof, and various changes in the size, shape and materials, as well as in the details of the illustrated construction, may be made without deparbng from the spirit of the invention.
1~
Claims (17)
1. A method of preparation of formulations for cementing a wellbore, comprising:
mixing drilling mud with blast furnace slag (BFS) in rig equipment normally used for mud circulation during drilling;
pumping the mixture of mud and BFS into the wellbore; and injecting activator inline into the BFS/mud mixture before it enters the wellbore.
mixing drilling mud with blast furnace slag (BFS) in rig equipment normally used for mud circulation during drilling;
pumping the mixture of mud and BFS into the wellbore; and injecting activator inline into the BFS/mud mixture before it enters the wellbore.
2. The method of claim 1, further comprising the steps of:
measuring the BFS/mud flowrate;
creating a signal based on said measuring; and controlling the flow of injected activator based on said measuring.
measuring the BFS/mud flowrate;
creating a signal based on said measuring; and controlling the flow of injected activator based on said measuring.
3. The method of claim 2, wherein said injecting step further comprises.
pumping the activator into the BFS/mud mixture adjacent an inline mixer.
pumping the activator into the BFS/mud mixture adjacent an inline mixer.
4. The method of claim 2, further comprising the steps of:
using a controller to convert the measured signal relating to BFS/mud flowrate into an output signal; and using said output signal to regulate delivery of said activator.
using a controller to convert the measured signal relating to BFS/mud flowrate into an output signal; and using said output signal to regulate delivery of said activator.
5. The method of claim 4, further comprising the step of:
using a positive displacement pump to deliver the activator.
using a positive displacement pump to deliver the activator.
6. The method of claim 5, further comprising the steps of:
providing a variable speed drive on said positive displacement pump; and using said output signal from said controller to regulate said variable speed drive.
providing a variable speed drive on said positive displacement pump; and using said output signal from said controller to regulate said variable speed drive.
7. The method of claim 6, further comprising the step of:
setting said controller to regulate delivery of activator material, in solution, in proportion to the rate of BFS flowing with the mud
setting said controller to regulate delivery of activator material, in solution, in proportion to the rate of BFS flowing with the mud
8. The method of claim 3, further comprising:
skid mounting said activator pump, said variable speed drive, said mixer, said controller, and interconnecting signal lines for compactness when used on a drilling rig.
skid mounting said activator pump, said variable speed drive, said mixer, said controller, and interconnecting signal lines for compactness when used on a drilling rig.
9. The method of claim 8, further comprising the step of:
providing a bypass on said skid to allow BFS/mud slurry to pass through said skid while isolating activator from the BFS/mud flow line.
providing a bypass on said skid to allow BFS/mud slurry to pass through said skid while isolating activator from the BFS/mud flow line.
10. The method of claim 9, further comprising the step of:
using a liquid activator.
using a liquid activator.
11. A method of cementing a wellbore, comprising:
mixing blast furnace slag with drilling mud at the surface;
pumping as yet unactivated BFS/mud mixture toward the wellbore; and injecting an activator inline into the flowing BFS/mud mixture shortly before it enters the wellbore.
mixing blast furnace slag with drilling mud at the surface;
pumping as yet unactivated BFS/mud mixture toward the wellbore; and injecting an activator inline into the flowing BFS/mud mixture shortly before it enters the wellbore.
12. The method of claim 11, further comprising the steps of:
measuring the BFS/mud flowrate;
regulating the activator feed rate; and obtaining a targeted activator concentration.
measuring the BFS/mud flowrate;
regulating the activator feed rate; and obtaining a targeted activator concentration.
13. The method of claim 12, further comprising the steps of:
using a positive displacement pump to feed the activator;
supplying a variable speed drive to drive said pump;
adjusting the pump drive rate with said variable speed drive in response to a signal resulting from measurement of said BFS/mud flowrate.
using a positive displacement pump to feed the activator;
supplying a variable speed drive to drive said pump;
adjusting the pump drive rate with said variable speed drive in response to a signal resulting from measurement of said BFS/mud flowrate.
14. A method of cementing 8 wellbore, comprising the steps of:
continuously mixing BFS into drilling mud to a predetermined value;
continuously adding inline an activator to a predetermined proportion of BFS in the mud.
continuously mixing BFS into drilling mud to a predetermined value;
continuously adding inline an activator to a predetermined proportion of BFS in the mud.
15. The method of claim 14 further comprising the steps of:
using a pump to add activator into a BFS/mud flowline;
regulating pump output in relation to measured BFS addition rate in the mud.
using a pump to add activator into a BFS/mud flowline;
regulating pump output in relation to measured BFS addition rate in the mud.
16. The method of claim 15, further comprising:
using an inline mixer to mix the activator with the BFS/mud mixture.
using an inline mixer to mix the activator with the BFS/mud mixture.
17. The method of claim 15 further comprising:
using a variable speed drive on said pump;
adjusting pump output responsive to BFS addition rate in flowing BFS/mud mixture by varying pump speed with said variable speed drive.
using a variable speed drive on said pump;
adjusting pump output responsive to BFS addition rate in flowing BFS/mud mixture by varying pump speed with said variable speed drive.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US08/186,438 US5437329A (en) | 1994-01-25 | 1994-01-25 | Method and apparatus for activation of furnace slag base cement |
| US08/186,438 | 1994-01-25 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2181911A1 true CA2181911A1 (en) | 1995-07-27 |
Family
ID=22684963
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002181911A Abandoned CA2181911A1 (en) | 1994-01-25 | 1995-01-25 | Method and apparatus for activation of furnace slag base cement |
Country Status (6)
| Country | Link |
|---|---|
| US (1) | US5437329A (en) |
| AU (1) | AU1834295A (en) |
| CA (1) | CA2181911A1 (en) |
| GB (1) | GB2301384B (en) |
| NO (1) | NO963087L (en) |
| WO (1) | WO1995020095A1 (en) |
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| US5978379A (en) | 1997-01-23 | 1999-11-02 | Gadzoox Networks, Inc. | Fiber channel learning bridge, learning half bridge, and protocol |
| US7430171B2 (en) | 1998-11-19 | 2008-09-30 | Broadcom Corporation | Fibre channel arbitrated loop bufferless switch circuitry to increase bandwidth without significant increase in cost |
| US7239636B2 (en) | 2001-07-23 | 2007-07-03 | Broadcom Corporation | Multiple virtual channels for use in network devices |
| US7295555B2 (en) | 2002-03-08 | 2007-11-13 | Broadcom Corporation | System and method for identifying upper layer protocol message boundaries |
| US7411959B2 (en) | 2002-08-30 | 2008-08-12 | Broadcom Corporation | System and method for handling out-of-order frames |
| US7934021B2 (en) | 2002-08-29 | 2011-04-26 | Broadcom Corporation | System and method for network interfacing |
| US7346701B2 (en) | 2002-08-30 | 2008-03-18 | Broadcom Corporation | System and method for TCP offload |
| US8180928B2 (en) | 2002-08-30 | 2012-05-15 | Broadcom Corporation | Method and system for supporting read operations with CRC for iSCSI and iSCSI chimney |
| US7313623B2 (en) | 2002-08-30 | 2007-12-25 | Broadcom Corporation | System and method for TCP/IP offload independent of bandwidth delay product |
| US8083849B2 (en) * | 2007-04-02 | 2011-12-27 | Halliburton Energy Services, Inc. | Activating compositions in subterranean zones |
| US9879519B2 (en) | 2007-04-02 | 2018-01-30 | Halliburton Energy Services, Inc. | Methods and apparatus for evaluating downhole conditions through fluid sensing |
| US8316936B2 (en) * | 2007-04-02 | 2012-11-27 | Halliburton Energy Services Inc. | Use of micro-electro-mechanical systems (MEMS) in well treatments |
| US8162050B2 (en) * | 2007-04-02 | 2012-04-24 | Halliburton Energy Services Inc. | Use of micro-electro-mechanical systems (MEMS) in well treatments |
| US8162055B2 (en) * | 2007-04-02 | 2012-04-24 | Halliburton Energy Services Inc. | Methods of activating compositions in subterranean zones |
| US8291975B2 (en) * | 2007-04-02 | 2012-10-23 | Halliburton Energy Services Inc. | Use of micro-electro-mechanical systems (MEMS) in well treatments |
| US8297353B2 (en) * | 2007-04-02 | 2012-10-30 | Halliburton Energy Services, Inc. | Use of micro-electro-mechanical systems (MEMS) in well treatments |
| US9822631B2 (en) | 2007-04-02 | 2017-11-21 | Halliburton Energy Services, Inc. | Monitoring downhole parameters using MEMS |
| US20110187556A1 (en) * | 2007-04-02 | 2011-08-04 | Halliburton Energy Services, Inc. | Use of Micro-Electro-Mechanical Systems (MEMS) in Well Treatments |
| US8297352B2 (en) * | 2007-04-02 | 2012-10-30 | Halliburton Energy Services, Inc. | Use of micro-electro-mechanical systems (MEMS) in well treatments |
| US8302686B2 (en) * | 2007-04-02 | 2012-11-06 | Halliburton Energy Services Inc. | Use of micro-electro-mechanical systems (MEMS) in well treatments |
| US9200500B2 (en) | 2007-04-02 | 2015-12-01 | Halliburton Energy Services, Inc. | Use of sensors coated with elastomer for subterranean operations |
| US9494032B2 (en) | 2007-04-02 | 2016-11-15 | Halliburton Energy Services, Inc. | Methods and apparatus for evaluating downhole conditions with RFID MEMS sensors |
| US9732584B2 (en) * | 2007-04-02 | 2017-08-15 | Halliburton Energy Services, Inc. | Use of micro-electro-mechanical systems (MEMS) in well treatments |
| US9194207B2 (en) | 2007-04-02 | 2015-11-24 | Halliburton Energy Services, Inc. | Surface wellbore operating equipment utilizing MEMS sensors |
| US10358914B2 (en) | 2007-04-02 | 2019-07-23 | Halliburton Energy Services, Inc. | Methods and systems for detecting RFID tags in a borehole environment |
| US8342242B2 (en) * | 2007-04-02 | 2013-01-01 | Halliburton Energy Services, Inc. | Use of micro-electro-mechanical systems MEMS in well treatments |
| US8047282B2 (en) * | 2009-08-25 | 2011-11-01 | Halliburton Energy Services Inc. | Methods of sonically activating cement compositions |
| CN102827593B (en) * | 2012-09-14 | 2015-10-21 | 中国石油大学(华东) | A kind of deepwater well cementing mortar architecture activated based on slag |
| CN104457858B (en) * | 2013-09-13 | 2019-04-16 | 袁璞 | A kind of adaptive speed limit filtering and the real-time observer of catalyst flow |
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| US3603399A (en) * | 1969-11-10 | 1971-09-07 | Chevron Res | Formation permeability maintenance with hydroxy-aluminum solutions |
| US3833718A (en) * | 1971-04-02 | 1974-09-03 | Chevron Res | Method of mixing an aqueous aluminum salt solution and an alkaline base solution in a jet mixer to form a hydroxy-aluminum solution |
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| FR2302789A1 (en) * | 1975-03-06 | 1976-10-01 | Campenon Bernard Sa | Additive injector for concrete pump - has liquid accelerator mixed with compressed air and fed through sloping channels around jet |
| US4158510A (en) * | 1978-03-24 | 1979-06-19 | Halliburton Company | Cementing skid with recirculating mixer |
| US4470727A (en) * | 1982-04-15 | 1984-09-11 | The Dow Chemical Company | Apparatus and process for foamed cementing |
| US4867256A (en) * | 1987-06-05 | 1989-09-19 | Snead Eddie L | Injection of polymer chemicals into drilling mud |
| US4883125A (en) * | 1987-12-11 | 1989-11-28 | Atlantic Richfield Company | Cementing oil and gas wells using converted drilling fluid |
| GB2227263A (en) * | 1988-10-03 | 1990-07-25 | Fosroc International Ltd | Placement of grout in a void |
| US4953618A (en) * | 1989-01-12 | 1990-09-04 | Haliburton Company | Injection manifold and method |
| NO167649C (en) * | 1989-04-10 | 1993-07-06 | Norske Stats Oljeselskap | PROCEDURE FOR THE ADDITION OF SILICIDE OXIDE IN A HYDRAULIC CEMENT SUSPENSION |
| US5058678A (en) * | 1990-09-28 | 1991-10-22 | Halliburton Company | Method for preventing the formation of sludge in crude oil |
| US5213446A (en) * | 1991-01-31 | 1993-05-25 | Union Oil Company Of California | Drilling mud disposal technique |
| US5314022A (en) * | 1992-10-22 | 1994-05-24 | Shell Oil Company | Dilution of drilling fluid in forming cement slurries |
| US5327968A (en) * | 1992-12-30 | 1994-07-12 | Halliburton Company | Utilizing drilling fluid in well cementing operations |
-
1994
- 1994-01-25 US US08/186,438 patent/US5437329A/en not_active Expired - Fee Related
-
1995
- 1995-01-25 CA CA002181911A patent/CA2181911A1/en not_active Abandoned
- 1995-01-25 GB GB9615667A patent/GB2301384B/en not_active Expired - Fee Related
- 1995-01-25 AU AU18342/95A patent/AU1834295A/en not_active Abandoned
- 1995-01-25 WO PCT/US1995/001015 patent/WO1995020095A1/en active Application Filing
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1996
- 1996-07-24 NO NO963087A patent/NO963087L/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| GB9615667D0 (en) | 1996-09-04 |
| US5437329A (en) | 1995-08-01 |
| NO963087L (en) | 1996-09-20 |
| GB2301384B (en) | 1997-10-08 |
| WO1995020095A1 (en) | 1995-07-27 |
| NO963087D0 (en) | 1996-07-24 |
| AU1834295A (en) | 1995-08-08 |
| GB2301384A (en) | 1996-12-04 |
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| Date | Code | Title | Description |
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| FZDE | Discontinued |