CA1232900A - Process for drilling a well - Google Patents
Process for drilling a wellInfo
- Publication number
- CA1232900A CA1232900A CA000471582A CA471582A CA1232900A CA 1232900 A CA1232900 A CA 1232900A CA 000471582 A CA000471582 A CA 000471582A CA 471582 A CA471582 A CA 471582A CA 1232900 A CA1232900 A CA 1232900A
- Authority
- CA
- Canada
- Prior art keywords
- drilling
- drilling fluid
- fluid
- well
- shale
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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
- C09K8/02—Well-drilling compositions
- C09K8/04—Aqueous well-drilling compositions
- C09K8/06—Clay-free compositions
- C09K8/08—Clay-free compositions containing natural organic compounds, e.g. polysaccharides, or derivatives thereof
Abstract
A B S T R A C T
PROCESS FOR DRILLING A WELL
A process for drilling a well in an underground formation in which process a drilling fluid is circulated in said well. The drilling fluid contains a hetero polysaccharide which has been obtained by cultivation of Pseudomonas sp. NCIB 11592. By this process a better efficiency is obtained.
PROCESS FOR DRILLING A WELL
A process for drilling a well in an underground formation in which process a drilling fluid is circulated in said well. The drilling fluid contains a hetero polysaccharide which has been obtained by cultivation of Pseudomonas sp. NCIB 11592. By this process a better efficiency is obtained.
Description
PR~CESS FOR DRILLING A WEIL
The invention relates to a p~ocess for drilling a well in an underground formation i~ which process a drilling fluid is clr-culated in said well, while drilling, characterized in that the drilling fl~id contains a h~teropolysaccharide which has been o~tained b~ cultivation of Pse~domonas s~. NCIB 115920 When drill mg subterranean wells such as, for exa~ple, oil or gas wells, the rotary drilling method is ccmmonly emplcyed. The rotary drillmg method utilizes a bit attached to a drill stem, and a drilling fluid or "mNd" which is circulated through the drill stem to the bottcm of the borehole where it is ejected thrcugh small openings in the drill bit. The fluid is then returned to the surface throu~h the annular space between the drill stem and the borehole wall, or casing if one has been installed. Upon reaching the sur-fa~e, the drilling fluid or "mud" is ordinarily treated to remove cuttings obtained from the borehole, and is then recirculated.
Drilling fluids serve many functions, and should therefore possess a number of desirable physical and rheological proFerties.
Fc,r example, the viscosity of a drilling fluid should be sufficient to permit it to effectivel~ transport bit cuttings from the bottcm of the bcrehole to the surface for removal. A drilling fluid should also prevent excessive amounts of f_uid frQm flowmg from the borehole mto surrounding formation~ by depositing on the walL of the hole a ~hin ~ut substantially impervious filter cake. In ad-dition,~a drilli~g fluid should be able to hold solids in sus-pension, preventing their return to the bottom of the hole when thecirculation is reduced or temporarily interrupted. This property can ; be obtained by utili2ing additives which will impart a gel structure to the drilling fluid to increase viscosities. The gel stN cture, howe~er, i5 preferably such that cuttings can be removed from the ~0 drillL~g fluid by passmg the fluid through filtration equipnent such as a shale shaker and/or sand cyclones prior to recircul~ting ~: :
:
, ~j :'; ' ~ ; ' .
the fluid to the drill bit. A drilling fluid must also exert press-ure on the surrounding formations, thus preventing possible collapse of the borehole or influx of highly pressurized oil or gas in the ~ormQtion. Finally, a drilling fluid should serve as a lubricating and cooling agent for the drill string.
Traditionally, bentoni~e or other clay solids have been utilized to increase the viscosity of the drilling fluid. Today however, 'here is a grcwing belief that bentonite or clay suspensions have serious limltations as a drilling flu1d base. The rheology of bentonite-based fluids is such that the hydraulic horsepcwer delivered to the bit at a given surface pressure is significantly less than with drilling fluids containing certain polymers. The lower viscosity and/or solids content of these polymer muds result in a faster bit penetration rate which in turn decreases the drilling costs. Those working within the industry have att~mpted to s~bsti-tute for the clay solids o~ the older muds by various polymericma~erials including, for example: cellulose compounds such as carboxyethyl cellulose, carboxymethyl cellulose, carboxymethyl hydro~yethyl cellulose, hydroxya1kyl celluloses, aLkylhydroxyaIkyl celluloses, aIkyl celluloses, and aIkylcarboxyalkyl celluloses;
polyacrylamides; Qatural galactcnannans such as guar gum, locust b2an gum, and gums derived frcm endosperm seeds; and various other polysaccharides.
In addition to the drilling fluids employed in drilllng sub-terranean wells, it is known thrcughout the industry that other fluids can also be utilized for certain specialized applications.
Fo~ e~ample, fractuL-in~ fluids, spaci~g fluids, plugging fluids, cementing fluids, and ccmp1etian fluids may be utilized in addition bo a drilling fluid to achieve a particular result at one stage or another m ~he drilling operation. It is recognized by those of ordinary skill m the art, however, that ccmpositions exhibiting prcperties desirable for scme specialized application may no~
pexform satisfactorily where employed for another purpose. Unlike fracturing fluids, drilling fluids are recirculated through the well .
many times. Although much of the larger particulate matter, such as bit cut ~lgs, is remaved from the drilling fluid after each cycle through the ~ell, the fine solids content of the fluid kecomes progressively greater with continued circulation. Where the drilling fluid ~cmprises a heteropolysaccharide obtained frcm Pseudomonas sp.
NCIB 11592, it has been found that it tends to encapsulate the drilled solids suspended in the fluid. miS encapsulating charac-teristic prevents disintegration of drilled solids and so im~roves the effectiveness of the drilling fluid, and is considered very desirable.
Notwithstandin~ the advances made in drilling fluid technology in recent years~ there remains a need for a suitable fluid that will significantly improve bit penetration (and hence the drilling rate), will remain shear stable even after being recirculated through the borehole many times, will reduce the pressure losses due to friction in the drill pipe, will p m mote better lifting and therefore less grir~ing of cuttings at the bottom of the borehole, will mamtain borehole cuttings in a suspended state during drilling interruptions, and will encapsulate the drilled solids suspended in the drillirlg fluid.
The drilling fluid used according to the Lnvention has these beneficial properties.
The invention resides in a process for drilling a borehole utiliz mg a rotating drill bit, wherein a drilling fluid is cir-culated past the surface of the drill bit, ccmprising employing as the drilling fluid the aqueous liquid of a heteropolysaccharide obtained from Pseudamona~ sp. N~IB 115g2. The drilling fluid is made by admixing the heteroFolysaccharide with water, circulating the admixture thus formed for a period effective to permit hydration of the p~lymer. ~he hetercpolysaccharlde is disclosed by EuroFean pat~nt application No. 81200479.4 (P~lication No. 0040445). The composition disclosed herein will exhibit extremely desirable physical and rheological prcperties, including improved flow characteristics as well as increased shear stability over a prolonged period of use.
~ ~, ~3~
The drilling fluid of the subject invention is preferably made at the use site by slowly adding a h~teropolysaccharide solution or e~llsion to water circulating through con~lentional blendin~ equip-mnt such as a jet hopper, a~d into the mud pit. The water employed is sui~ably as fresh as is reasonably obtainable, although brines may equally well be employed and may be preferable where shale sloughing or formations with a high clay content are expected to be encountered. m is versatility is another advantage of the drilling fluid of the present invention. When all the polymer has been added, the fluid can be applied withcut extra circulation since hydration of the hetercpolysaccharide was already substantially complete. An effective amount of a suitable buffer may be added if desired to prcm~te hydration, as will be understood by those sXilled in the art.
The unweighted drilling fluid thus formed preferably ccmprises 15 from 0.1 to 10 Xg polymer per m3 of fluid. Most preferably the unweighted drilling fluid ccmprises fro~ 1 to 5 kg polymer per m3.
If desired, the viscosity of the drilling fluid may be increased at a point in time subsequent to the Lmtial preparation of the dril-ling fluid by gradual addition of more polymer and/or crosslinker.
Biopolymers are widely used in drilling, ccmpletion and work~
over fluids. AquRous solutions containing the biopolymers have pronGunced pseudcplastic rheological characteri~tics which give them high carrying capacities at low shearJcirculation rates. Unfortunate-ly, they often cann~t be effectively acid-degraded and are, there-~ore a potential source of formation Lmpairment. It has now been ~und that the hetercpolysaccharide obtained from Pseudo~onas sp.
NCIB 11592 is very well acid-degradable e.g. it degrades within an hour in the presence of a 10 ~ HCl solution.
Rheological measurements on solutions of the present hetero-polysaccharide show that it is an effective viscoslfier up to 55 C
in fresh water and up to at least 70 C in concentxated brines. me plot of viscosity agaLnst t.emperature is reversible in the sense that identicaL plots are obtained by mcreasing or decreasing .
~ 5 --~?erature. Moreover this heteropolysaccharide is a very pawerful viscosifier and at low shear rate, it has an excellent carrying capQcity.
~ ot-rolling tests are conducted to measure the shear and temperatur~ degrada~ion of the pres2nt heteropolysaccharide. A
~odium chloride brine viscosified by this heteropolysaccharide is hot rolled for 18 hours at 80 C, and its viscosity is measured at 21 C bsfore and after rolling. ~o reduction in viscosity is found.
mis confirms the high shear stability of the present heteropoly-saccharide. A calcium chlorids based drilling fluid containing HEC
IhYdroxYethyl cellulose), the heteropolysaccharide obtained from Pseudcmonas sp. NCIB 11592 and calcium carbonate were formulated and used to drill the production hole of an oil well in the Norwegian Troll field. No mud engineeLing problems occurred and production tests showed the well to be highly unimpaired.
In addition the productivity of the well far exceeded the productivities of the pre~ious ten wells drilled in ~he field using other mud syst~ms.
As mentioned hereinbefore drilling fluids may contain many different substances. The drilling fluid to be used in the process according to the invention preferably contains in addition to the heteropolyaccharide abtained from Pseudomonas sp NC~B 11592, at least one fluld loss additive, at least one thinner, at least one weightlng agent and/or at least one salt.
Especially preferred examples of these materials are bentonite, baryte, one or m~re other polymers, one or more starches, one or more lignosulphonates, gypsum, dolcmite and/or lye. The content of the het~ropolysaccharide obtained frcm Pseudcmanas sp. NCIB 11592 in the drill mg fluid to be used m the present process ~ay vary within wide ranges. Preferably this drilling fluid contains from 0.1 to lO
kg of the hetercpolysaccharide per 1000 kg of fluid.
The invention will ncw be further elucida~ed by mean5 of the follcwing ~xample to which it is ~y no means restric~d.
-~: .
1 :XAME~E
Both cutting encapsul~ting and trlaxlal shale tests were carried ou~ on the relatively water sensitive Pierre shale. In the cutting encapsulation tests, a set amount of Pierre shale cuttings of a specific size distribution (1.7-3.4 mm~ was added to a base mud containing the test polymer. Mud and shale cuttings ~ere hot rolled for either 2 or 16 hc~lrs at 60 C. and the percentage of shale cuttings still hav m g the original size distribution measured. This percentage is termed the "recovery". Composition and properties of the base mud are given in Table 1.
In the standard tri~xial shale test, a 50 mm diameter 25 mm long cylindrical reconstituted shale sample with a 6 mm diameter axial hole through it is put under a confin mg stress and mud is circulated throu~h the hole at a specific rate. When the sample has collapsed due to erosion or the axial hole has closed due to swelling the test is stopped. The time and m~de of failure are recorded and erosion and water content of the samples measured. m e ~d ccmposi-tions, mud properties and test conditions pertaining to these tests are given in Table 2. In essence, the tests ccmpared the performance of a mud cont~inLng hydrolysed polyacrylamide (PA~) and a m~d in which the hydrolysed polyacrylamlde (PAA) was replaced ky the heteropolysaccharlde abtained from Pseudcmonas sp. NCIB 11592.
The res~lts of the cutting encapsulation tests are given in Table 3. They show that the encapsulating properties of the hetero-polysaccharide cbtained from Pseudamonas sp. ~CIB 11592 are excellent. It ls wor~h noti~g that these biopolymers achieved good ~ncapsulating properties without Lncurring excessive plastic ; viscosities.
The results of the triaxial tests are gi~en in Table 4. At first sight, the performance of tne neteropolysaccharide obtained from Pseudc~onas sp WCIB 11592 is far superior to that of the PAA, h~wever, this requlres scme qualification. m e mode of failure is cf. Darley, H.C.H., "A laboratory Investigation of borehole stability". J. Pat. Tech., July 1969, 883-893, TransO AIME, 246.
,, .
~23~
dif~erent for the two polymers. In the case of the PAA mud, no erosion takes place and approximately 5~ water is embibed by the shale resultmg in hole closl~e by swelling. PA~ invades the swollen shale and glues the potentially erodable shale surface particles together and to the shale substrate.
In the case of containLng t~le heteropolysaccharide obtained frcm Pseudomonas sp NCIB 11592, 4% water uptake and 20% erosion akes place prior to failure by collapse.
A possible explanation for the differing performances of the two products lies in their structure. Both are long chain molecules but the heteropolysaccharide abtained frcm Pseud onas sp ~CIB 11592 (which consists of sugar units) is much bulkier due to its branched structure. ~oth m~lecules appear to have the required configuration and charge distribution ~o bind clay platelets but, presumably, the size of the heteropolysaccharide obtained from Pseudcmonas sp NCIB
11592 molecule prevents it invading the shale surface layer.
This uniq~le prcperty opens up new possibilities in the ormu-lation of muds designed to drill swelling shale formations. Tight holes are a ccwmon prablem ~hen drilling with PAA-containin~ mud due to the fact that PAA reduces erosion of swelling shale formations:
PAA is primarily added to the m~d for cutting encapsulation. The possibility now exists of using the heteropolysaccharide obtained fram Pseudcmonas sp NCTR 11592 which will allow controlled erosion of the swellmg shales and prevent shale cutting disintegration.
:
:
:
.
¦Fresh water 8 kg/m3 carboxymethyl plastic viscosity = 15 cP (PV) ~ellulose 10 kg/m3 stabilose LU yield point = 2 Pa (YP) 1 kg/m3 Farafonmaldehyde able 1 - Composition and properties of the base mud used for the cutting encapsulation tests.
7resh water _ _ _ .
30 kg/m3 bentonite Confining pressure : 225 bar
The invention relates to a p~ocess for drilling a well in an underground formation i~ which process a drilling fluid is clr-culated in said well, while drilling, characterized in that the drilling fl~id contains a h~teropolysaccharide which has been o~tained b~ cultivation of Pse~domonas s~. NCIB 115920 When drill mg subterranean wells such as, for exa~ple, oil or gas wells, the rotary drilling method is ccmmonly emplcyed. The rotary drillmg method utilizes a bit attached to a drill stem, and a drilling fluid or "mNd" which is circulated through the drill stem to the bottcm of the borehole where it is ejected thrcugh small openings in the drill bit. The fluid is then returned to the surface throu~h the annular space between the drill stem and the borehole wall, or casing if one has been installed. Upon reaching the sur-fa~e, the drilling fluid or "mud" is ordinarily treated to remove cuttings obtained from the borehole, and is then recirculated.
Drilling fluids serve many functions, and should therefore possess a number of desirable physical and rheological proFerties.
Fc,r example, the viscosity of a drilling fluid should be sufficient to permit it to effectivel~ transport bit cuttings from the bottcm of the bcrehole to the surface for removal. A drilling fluid should also prevent excessive amounts of f_uid frQm flowmg from the borehole mto surrounding formation~ by depositing on the walL of the hole a ~hin ~ut substantially impervious filter cake. In ad-dition,~a drilli~g fluid should be able to hold solids in sus-pension, preventing their return to the bottom of the hole when thecirculation is reduced or temporarily interrupted. This property can ; be obtained by utili2ing additives which will impart a gel structure to the drilling fluid to increase viscosities. The gel stN cture, howe~er, i5 preferably such that cuttings can be removed from the ~0 drillL~g fluid by passmg the fluid through filtration equipnent such as a shale shaker and/or sand cyclones prior to recircul~ting ~: :
:
, ~j :'; ' ~ ; ' .
the fluid to the drill bit. A drilling fluid must also exert press-ure on the surrounding formations, thus preventing possible collapse of the borehole or influx of highly pressurized oil or gas in the ~ormQtion. Finally, a drilling fluid should serve as a lubricating and cooling agent for the drill string.
Traditionally, bentoni~e or other clay solids have been utilized to increase the viscosity of the drilling fluid. Today however, 'here is a grcwing belief that bentonite or clay suspensions have serious limltations as a drilling flu1d base. The rheology of bentonite-based fluids is such that the hydraulic horsepcwer delivered to the bit at a given surface pressure is significantly less than with drilling fluids containing certain polymers. The lower viscosity and/or solids content of these polymer muds result in a faster bit penetration rate which in turn decreases the drilling costs. Those working within the industry have att~mpted to s~bsti-tute for the clay solids o~ the older muds by various polymericma~erials including, for example: cellulose compounds such as carboxyethyl cellulose, carboxymethyl cellulose, carboxymethyl hydro~yethyl cellulose, hydroxya1kyl celluloses, aLkylhydroxyaIkyl celluloses, aIkyl celluloses, and aIkylcarboxyalkyl celluloses;
polyacrylamides; Qatural galactcnannans such as guar gum, locust b2an gum, and gums derived frcm endosperm seeds; and various other polysaccharides.
In addition to the drilling fluids employed in drilllng sub-terranean wells, it is known thrcughout the industry that other fluids can also be utilized for certain specialized applications.
Fo~ e~ample, fractuL-in~ fluids, spaci~g fluids, plugging fluids, cementing fluids, and ccmp1etian fluids may be utilized in addition bo a drilling fluid to achieve a particular result at one stage or another m ~he drilling operation. It is recognized by those of ordinary skill m the art, however, that ccmpositions exhibiting prcperties desirable for scme specialized application may no~
pexform satisfactorily where employed for another purpose. Unlike fracturing fluids, drilling fluids are recirculated through the well .
many times. Although much of the larger particulate matter, such as bit cut ~lgs, is remaved from the drilling fluid after each cycle through the ~ell, the fine solids content of the fluid kecomes progressively greater with continued circulation. Where the drilling fluid ~cmprises a heteropolysaccharide obtained frcm Pseudomonas sp.
NCIB 11592, it has been found that it tends to encapsulate the drilled solids suspended in the fluid. miS encapsulating charac-teristic prevents disintegration of drilled solids and so im~roves the effectiveness of the drilling fluid, and is considered very desirable.
Notwithstandin~ the advances made in drilling fluid technology in recent years~ there remains a need for a suitable fluid that will significantly improve bit penetration (and hence the drilling rate), will remain shear stable even after being recirculated through the borehole many times, will reduce the pressure losses due to friction in the drill pipe, will p m mote better lifting and therefore less grir~ing of cuttings at the bottom of the borehole, will mamtain borehole cuttings in a suspended state during drilling interruptions, and will encapsulate the drilled solids suspended in the drillirlg fluid.
The drilling fluid used according to the Lnvention has these beneficial properties.
The invention resides in a process for drilling a borehole utiliz mg a rotating drill bit, wherein a drilling fluid is cir-culated past the surface of the drill bit, ccmprising employing as the drilling fluid the aqueous liquid of a heteropolysaccharide obtained from Pseudamona~ sp. N~IB 115g2. The drilling fluid is made by admixing the heteroFolysaccharide with water, circulating the admixture thus formed for a period effective to permit hydration of the p~lymer. ~he hetercpolysaccharlde is disclosed by EuroFean pat~nt application No. 81200479.4 (P~lication No. 0040445). The composition disclosed herein will exhibit extremely desirable physical and rheological prcperties, including improved flow characteristics as well as increased shear stability over a prolonged period of use.
~ ~, ~3~
The drilling fluid of the subject invention is preferably made at the use site by slowly adding a h~teropolysaccharide solution or e~llsion to water circulating through con~lentional blendin~ equip-mnt such as a jet hopper, a~d into the mud pit. The water employed is sui~ably as fresh as is reasonably obtainable, although brines may equally well be employed and may be preferable where shale sloughing or formations with a high clay content are expected to be encountered. m is versatility is another advantage of the drilling fluid of the present invention. When all the polymer has been added, the fluid can be applied withcut extra circulation since hydration of the hetercpolysaccharide was already substantially complete. An effective amount of a suitable buffer may be added if desired to prcm~te hydration, as will be understood by those sXilled in the art.
The unweighted drilling fluid thus formed preferably ccmprises 15 from 0.1 to 10 Xg polymer per m3 of fluid. Most preferably the unweighted drilling fluid ccmprises fro~ 1 to 5 kg polymer per m3.
If desired, the viscosity of the drilling fluid may be increased at a point in time subsequent to the Lmtial preparation of the dril-ling fluid by gradual addition of more polymer and/or crosslinker.
Biopolymers are widely used in drilling, ccmpletion and work~
over fluids. AquRous solutions containing the biopolymers have pronGunced pseudcplastic rheological characteri~tics which give them high carrying capacities at low shearJcirculation rates. Unfortunate-ly, they often cann~t be effectively acid-degraded and are, there-~ore a potential source of formation Lmpairment. It has now been ~und that the hetercpolysaccharide obtained from Pseudo~onas sp.
NCIB 11592 is very well acid-degradable e.g. it degrades within an hour in the presence of a 10 ~ HCl solution.
Rheological measurements on solutions of the present hetero-polysaccharide show that it is an effective viscoslfier up to 55 C
in fresh water and up to at least 70 C in concentxated brines. me plot of viscosity agaLnst t.emperature is reversible in the sense that identicaL plots are obtained by mcreasing or decreasing .
~ 5 --~?erature. Moreover this heteropolysaccharide is a very pawerful viscosifier and at low shear rate, it has an excellent carrying capQcity.
~ ot-rolling tests are conducted to measure the shear and temperatur~ degrada~ion of the pres2nt heteropolysaccharide. A
~odium chloride brine viscosified by this heteropolysaccharide is hot rolled for 18 hours at 80 C, and its viscosity is measured at 21 C bsfore and after rolling. ~o reduction in viscosity is found.
mis confirms the high shear stability of the present heteropoly-saccharide. A calcium chlorids based drilling fluid containing HEC
IhYdroxYethyl cellulose), the heteropolysaccharide obtained from Pseudcmonas sp. NCIB 11592 and calcium carbonate were formulated and used to drill the production hole of an oil well in the Norwegian Troll field. No mud engineeLing problems occurred and production tests showed the well to be highly unimpaired.
In addition the productivity of the well far exceeded the productivities of the pre~ious ten wells drilled in ~he field using other mud syst~ms.
As mentioned hereinbefore drilling fluids may contain many different substances. The drilling fluid to be used in the process according to the invention preferably contains in addition to the heteropolyaccharide abtained from Pseudomonas sp NC~B 11592, at least one fluld loss additive, at least one thinner, at least one weightlng agent and/or at least one salt.
Especially preferred examples of these materials are bentonite, baryte, one or m~re other polymers, one or more starches, one or more lignosulphonates, gypsum, dolcmite and/or lye. The content of the het~ropolysaccharide obtained frcm Pseudcmanas sp. NCIB 11592 in the drill mg fluid to be used m the present process ~ay vary within wide ranges. Preferably this drilling fluid contains from 0.1 to lO
kg of the hetercpolysaccharide per 1000 kg of fluid.
The invention will ncw be further elucida~ed by mean5 of the follcwing ~xample to which it is ~y no means restric~d.
-~: .
1 :XAME~E
Both cutting encapsul~ting and trlaxlal shale tests were carried ou~ on the relatively water sensitive Pierre shale. In the cutting encapsulation tests, a set amount of Pierre shale cuttings of a specific size distribution (1.7-3.4 mm~ was added to a base mud containing the test polymer. Mud and shale cuttings ~ere hot rolled for either 2 or 16 hc~lrs at 60 C. and the percentage of shale cuttings still hav m g the original size distribution measured. This percentage is termed the "recovery". Composition and properties of the base mud are given in Table 1.
In the standard tri~xial shale test, a 50 mm diameter 25 mm long cylindrical reconstituted shale sample with a 6 mm diameter axial hole through it is put under a confin mg stress and mud is circulated throu~h the hole at a specific rate. When the sample has collapsed due to erosion or the axial hole has closed due to swelling the test is stopped. The time and m~de of failure are recorded and erosion and water content of the samples measured. m e ~d ccmposi-tions, mud properties and test conditions pertaining to these tests are given in Table 2. In essence, the tests ccmpared the performance of a mud cont~inLng hydrolysed polyacrylamide (PA~) and a m~d in which the hydrolysed polyacrylamlde (PAA) was replaced ky the heteropolysaccharlde abtained from Pseudcmonas sp. NCIB 11592.
The res~lts of the cutting encapsulation tests are given in Table 3. They show that the encapsulating properties of the hetero-polysaccharide cbtained from Pseudamonas sp. ~CIB 11592 are excellent. It ls wor~h noti~g that these biopolymers achieved good ~ncapsulating properties without Lncurring excessive plastic ; viscosities.
The results of the triaxial tests are gi~en in Table 4. At first sight, the performance of tne neteropolysaccharide obtained from Pseudc~onas sp WCIB 11592 is far superior to that of the PAA, h~wever, this requlres scme qualification. m e mode of failure is cf. Darley, H.C.H., "A laboratory Investigation of borehole stability". J. Pat. Tech., July 1969, 883-893, TransO AIME, 246.
,, .
~23~
dif~erent for the two polymers. In the case of the PAA mud, no erosion takes place and approximately 5~ water is embibed by the shale resultmg in hole closl~e by swelling. PA~ invades the swollen shale and glues the potentially erodable shale surface particles together and to the shale substrate.
In the case of containLng t~le heteropolysaccharide obtained frcm Pseudomonas sp NCIB 11592, 4% water uptake and 20% erosion akes place prior to failure by collapse.
A possible explanation for the differing performances of the two products lies in their structure. Both are long chain molecules but the heteropolysaccharide abtained frcm Pseud onas sp ~CIB 11592 (which consists of sugar units) is much bulkier due to its branched structure. ~oth m~lecules appear to have the required configuration and charge distribution ~o bind clay platelets but, presumably, the size of the heteropolysaccharide obtained from Pseudcmonas sp NCIB
11592 molecule prevents it invading the shale surface layer.
This uniq~le prcperty opens up new possibilities in the ormu-lation of muds designed to drill swelling shale formations. Tight holes are a ccwmon prablem ~hen drilling with PAA-containin~ mud due to the fact that PAA reduces erosion of swelling shale formations:
PAA is primarily added to the m~d for cutting encapsulation. The possibility now exists of using the heteropolysaccharide obtained fram Pseudcmonas sp NCTR 11592 which will allow controlled erosion of the swellmg shales and prevent shale cutting disintegration.
:
:
:
.
¦Fresh water 8 kg/m3 carboxymethyl plastic viscosity = 15 cP (PV) ~ellulose 10 kg/m3 stabilose LU yield point = 2 Pa (YP) 1 kg/m3 Farafonmaldehyde able 1 - Composition and properties of the base mud used for the cutting encapsulation tests.
7resh water _ _ _ .
30 kg/m3 bentonite Confining pressure : 225 bar
2.15 kg/m3 polymer pump speed : 6 l/mun ~e~fective concentration) _ 100 kg/m3 XCl plastic viscosity - 10 cP
yieLd F int = 2 5 Pa able 2 - ~ud ccmposition and properties and ~est conditions in the triaxial shale test.
polymer is either hydnolysed polyacrylamide (PAA) or the heteropolysaccharide obtaln~d from Pseudomonas sp NCIB 11592.
**
Plastic viscosity is defined o~ page 735 of the book "Drilling and drilling fluids" by G.V. Chilingarian and P. Varabutr (El~evier Scientific Publishing Co. 1981).
Yield point is def;ned on page 740 of the above bcok.
.
-` ;
- - - ~ -~ ~ ~ ~ o ~-9 ~ ~.
*~;~v ~
~P ~ o U~OC~
~ ~ ~ ~ d~
~ ~ co ~ u~ a) a~
_ ~ U~ Lnll .
~ ~i ~
~ - ~o ~
~ ~, ~ ,~ ~ ~ o 8 ~ rQ ~ ~ : ;~ ~) ~ ~
8 ~ ~ i~ _ m ~ ,, .
yieLd F int = 2 5 Pa able 2 - ~ud ccmposition and properties and ~est conditions in the triaxial shale test.
polymer is either hydnolysed polyacrylamide (PAA) or the heteropolysaccharide obtaln~d from Pseudomonas sp NCIB 11592.
**
Plastic viscosity is defined o~ page 735 of the book "Drilling and drilling fluids" by G.V. Chilingarian and P. Varabutr (El~evier Scientific Publishing Co. 1981).
Yield point is def;ned on page 740 of the above bcok.
.
-` ;
- - - ~ -~ ~ ~ ~ o ~-9 ~ ~.
*~;~v ~
~P ~ o U~OC~
~ ~ ~ ~ d~
~ ~ co ~ u~ a) a~
_ ~ U~ Lnll .
~ ~i ~
~ - ~o ~
~ ~, ~ ,~ ~ ~ o 8 ~ rQ ~ ~ : ;~ ~) ~ ~
8 ~ ~ i~ _ m ~ ,, .
Claims (4)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for drilling a well in an underground forma-tion in which process a drilling fluid is circulated in said well, while drilling, characterized in that the drilling fluid contains a hetero polysaccharide which has been obtained by cultivation of Pseudomonas sp. NCIB 11592.
2. A process as claimed in claim 1, characterized in that the drilling fluid contains 0.1 to 10 kg heteropolysaccharide per 1000 kg of fluid.
3. A process as claimed in claim 1, characterized in that the drilling fluid contains in addition to the heteropolysaccha-ride, at least one fluid loss additive, at least one thinner, at least one clay, at least one weighting agent, and/or at least one salt.
4. A process as claimed in claim 3, characterized in that the drilling fluid contains bentonite, baryte, one or more polymers, one or more starches, one or more lignosulphonates, gypsum, dolomite and/or lye.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08400640A GB2152552B (en) | 1984-01-11 | 1984-01-11 | Process for drilling a well |
| GB8400640 | 1984-01-11 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1232900A true CA1232900A (en) | 1988-02-16 |
Family
ID=10554811
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000471582A Expired CA1232900A (en) | 1984-01-11 | 1985-01-07 | Process for drilling a well |
Country Status (8)
| Country | Link |
|---|---|
| AU (1) | AU3764685A (en) |
| CA (1) | CA1232900A (en) |
| DE (1) | DE3500525A1 (en) |
| GB (1) | GB2152552B (en) |
| IT (1) | IT1182341B (en) |
| NL (1) | NL8403833A (en) |
| NO (1) | NO850093L (en) |
| OA (1) | OA07931A (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4743383A (en) * | 1986-11-24 | 1988-05-10 | Phillips Petroleum Company | Drilling fluid additives for use in hard brine environments |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3988246A (en) * | 1974-05-24 | 1976-10-26 | Chemical Additives Company | Clay-free thixotropic wellbore fluid |
| GB1591313A (en) * | 1976-08-09 | 1981-06-17 | Brinadd Co | Wellbore fluids and dry mix additive packages for use in such fluids |
| GB1546560A (en) * | 1978-02-10 | 1979-05-23 | Texaco Development Corp | Viscous aqueus polysaccaride solutions and oil recovery process |
| CA1173771A (en) * | 1980-05-21 | 1984-09-04 | Roger E. Cripps | Fluid displacement with heteropolysaccharide solutions, and the microbial production of heteropolysaccharides |
-
1984
- 1984-01-11 GB GB08400640A patent/GB2152552B/en not_active Expired
- 1984-12-18 NL NL8403833A patent/NL8403833A/en not_active Application Discontinuation
-
1985
- 1985-01-07 CA CA000471582A patent/CA1232900A/en not_active Expired
- 1985-01-08 IT IT67012/85A patent/IT1182341B/en active
- 1985-01-09 DE DE19853500525 patent/DE3500525A1/en not_active Withdrawn
- 1985-01-09 NO NO850093A patent/NO850093L/en unknown
- 1985-01-11 OA OA58504A patent/OA07931A/en unknown
- 1985-01-14 AU AU37646/85A patent/AU3764685A/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| NO850093L (en) | 1985-07-12 |
| GB2152552A (en) | 1985-08-07 |
| IT1182341B (en) | 1987-10-05 |
| IT8567012A0 (en) | 1985-01-08 |
| NL8403833A (en) | 1985-08-01 |
| IT8567012A1 (en) | 1986-07-08 |
| GB2152552B (en) | 1987-08-05 |
| OA07931A (en) | 1987-01-31 |
| DE3500525A1 (en) | 1985-08-14 |
| GB8400640D0 (en) | 1984-02-15 |
| AU3764685A (en) | 1985-09-12 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |