CA1332502C

CA1332502C - Well drilling fluid and method

Info

Publication number: CA1332502C
Application number: CA000608166A
Authority: CA
Inventors: James V. Fisk, Jr.
Original assignee: Baroid Technology Inc
Current assignee: Baroid Technology Inc
Priority date: 1988-08-15
Filing date: 1989-08-11
Publication date: 1994-10-18
Anticipated expiration: 2011-10-18
Also published as: DK398889D0; AU3953589A; SG128992G; NO893150D0; IT8967701A0; DE3926970A1; BR8904091A; GB2221940A; GB8917892D0; NO893150L; NL8902056A; AU633262B2; GB2221940B; IT1232916B; DK398889A

Abstract

A drilling fluid comprising an aqueous medium, a water-soluble cationic polymer, a low molecular weight hydroxyethyl cellulose and a generally water-insoluble weighting agent.

Description

-2- 1 332~o2 BackRround Or the Inventlon 1. Fleld of the Inventlon The present ~nventlon relates to drllling rlulds and, more partlcularly, to drllllng rlulds exhlbltlng good rluld 1099 control and stablllzatlon Or shale rormatlons.
2. Descrl~tlon Or the Back~round It 19 known that shale 19 predomlnantly rormed Or clays whlch swell and dlgper9e when contacted wlth a water-based drllllng rluld. Thlg gwelllng and dlsperslon can result ln a phenomena known ag "heavlng" ln which the borehole walls can collapse. To reduce thls tendency Or the clays ln the shale to swell and dlsperse, lt 19 common practlce to add catlonlc salts to render the clays generally hydrophoblc.
However, ln dolng thlg, anlonlc polymerg whlch are commonly used as vlscoslrlers ln drllllng rlulds are also rendered hydrophoblc, thereby loslng thelr ablllty to vlscoslry the drllllng rluld or mud and reduce rluld 1099 rrom the rormatlon .
It 19 known to uge mlxtures Or catlonlc polymers and hlgh molecular welght hydroxyethyl cellulose (HEC) when drllllng shale rormatlons ln order to stablllze the shale by rlocculatlng the clay and lmpart vlscoglrlcatlon. However, prlor art catlonlc drllllng mud gystems contalnlng HEC
surrer rrom the dlsadvantages Or hlgher than deslred rluld 1099 and the lnablllty to errectlvely suspend welghtlng agents, such as barlte, at a vlscoslty whlch permlts pumplng Or the rluld.
It would thererore be deslrable to have a catlonlc polymer-based drllllng rluld whlch would stablllze the shale, exhlblt low rluld 1099, vlscoslry and errectlvely suspend welghtlng agents, such as barlte.

_3_ 1332~02 Summary of the Inventlon It 19 therefore an obJect of the present invention to provide an improved drilling rluid.
Another obJect of the present invention is to provlde a catlonlc polymer-based drllllng rluld exhlbltlng low fluld 1089.
Stlll another obJect of the present lnventlon 19 to provlde catlonlc polymer-baged drllllng flulds which will effectively sugpend weighting agents, exhibit low fluid 1088 and stabillze shale for~atlons.
Yet another obJect of the present invention is to provlde a method of drllllng a borehole using a drllllng fluid containing a cationic polymer and a low molecular weight hydroxyethyl cellulose polymer.
The above and other obJects of the present invention will become apparent from the description given herein and the appended claims.
The drilling fluid of the present invention comprlses an aqueous medlum, a water-goluble catlonic polymer which will stabilize ghale formationg, hydroxyethyl cellulose having a molecular weight of from about 3,000 to about 40,000, and a weighting agent. Preferably, the cationic polymer is selected ~rom the group consisting of (a) branched emulgion polymers of diallyldimethylammonium chloride having a molecular weight of at least 5,000, (b) dialkylaminoalkyl acrylic ester polymers, (c) dialkylaminoalkyl methacrylic ester polymers, (d) dialkylaminoalkyl acryllc acid-acrylamide copolymers, (e) dlalkylamlnoalkyl methacryllc acld-acrylamide copolymers, (f) N-(Dialkylaminoalk~l) acrylamide polymers, (g) N-(Dialkylamlnoalkyl) methacrylamide polymers, (h) poly(Z-vinylimidazioline) ~ (i ) poly(alkyleneamines), ( i ) poly(hydroxalkylene pol~amlnes) and mlxtures thereof.
In cases where the aqueous medium contains a salt Or a multivalent cation, the drllling fluid will also contain a non-water_8wellable cla~ which can be added to the drilling fluid prior to commence ent of drilling or picked up by the drilling fluid, in gitu, during the drilling operation.

_4 1~32~02 In the method of the pre~ent inventlon, the drilling fluid de~cribed above 1~ circulated in the borehole during the drilling operation.

_5_ 1332~02 Descrlptlon Or the Preferred Embodlments The aqueous medlum used ln the drilllng fluld composltlong of the present lnventlon can be rresh water, brlnes of monovalent catlons, such as sodlum chlorlde S solutlons, potasslum chlorlde solutlons, brlnes of multlvalent catlons, guch ag calclum chlorlde solutlons, sea water, etc. The nature of the aqueous medlum, as seen hereafter, determlneg the compogltlon Or the drllllng fluld.
The catlonlc polymers whlch are useful ln the composltlons and method Or the pregent lnventlon are those catlonlc polymers whlch wlll gtablllze, l.e. prevent eroslon or dlsperslon, shale contalnlng water-gwellable clays 90 as to -prevent heavlng during the drllllng operatlon, whlch are substantlally water-soluble, or dlgperslble ln the aqueous medlum, and whlch act to effectlvely sugpend weightlng agents, such as barlte. The catlonlc polymers wlll be present ln amountg ranglng from about 0.5 to about 3 pounds per barrel (ppb) of the aqueous medlum. Non-llmltlng examples of sultable catlonlc polymers lnclude (a) branched emulslon polymers of dlallyldlmethylammonlum chloride having a molecular welght of at leagt 5,000, (b) dlalkylamlnoalkyl acryllc ester polymer9, (c) dlalkylamlnoalkyl methacrylic ester polymerg, (d) dialkylaminoalkyl acryllc acld-acrylamlde copolymers, (e) dlalkylamlnoalkyl methacryllc acld-acrylamlde copolymers, (f) N-(Dlalkylaminoalkyl) acrylamlde polymers, (g) N-(Dlalkylamlnoalkyl) methacrylamlde polymer9, (h) poly(2-vlnyllmldazlollne), (1) poly(alkyleneamlnes), (1) poly(hydroxalkylene polyamlnes) and mlxtures thereof.
The dlallyldlmethylammonlum chlorlde polymers useful in the compogitlons and method of the pregent lnventlon can be homopolymerg or copol~merg of other monomers such as acrylamldes. Preferably, the polymers are branched emulslon-type polymer9 whlch can employ branching agents such as triallylmethyla lmonlum chlorlde, tetraallylammonlum chlorlde ag well ag big-dlallylammonlum salts such as tetraallylpeperlzlnlum chlorlde and N,N,N' ,N'-tetraallyl-N,N'-dlmethylhexamethylenedlammonlum chlorlde. The emulsion polymers can be prepared by emulsion or suspension polymerization techniques such as those described in U. S .
Patent No. 3, 968, 037, and may contain from about 95 to about 99 . 99 mole percent diallyldimethylammonium chloride and from about 0 . 01 to about 5 mole percent of one of the aforementioned branching agents. The branched emulsion polymers can have molecular weights ranging from 5, OOo and upward, such branched emulsion polymers wherein the molecular weight is from about 40,000 to about 5,000,000 being preferred. Especially preferred are homopolymers of dimethyldiallylammonium chloride having a molecular weight of from about 1,000,000 to about 5,000,000.
Another cationic polymer especially suitable for use in the compositions and method of the present invention are the N-(Dialkylaminoalkyl) acrylamide polymers, such as, for example, polymers prepared via the Mannich Reaction wherein a polyacryl-amide is reacted with formaldehyde and an amine to produce an aminomethylated polyacrylamide. Especially preferred are such polyacrylamides having molecular weights ranging from about 40,000 to about 4,000,000.
Another preferred type of cationic polymer for use in the compositions and method of the present invention are the dialkylaminoalkyl derivatives of a water-soluble copolymer formed from an ethylenically unsaturated amide monomer and a comonomer selected from the group consisting of acrylic acid, alkyl-substituted acrylic acids and mixtures thereof, such as, for example, the copolymer of acrylamide and methacrylic acid. Such polymers, which can have molecular weights ranging from 40,000 to 4,000,000, can be produced, for example, by the method described in U. S . Patent No. 3, 923, 756 . A particularly preferred class of copolymers are the dialkylaminoalkyl acrylamide-methacrylic acid copolymers wherein the copolymer has a molecular weight ranging from about 40,000 to about 4,000,000. Especially preferred, non-limiting examples of such polymers include the dimethylaminoethyl sulfate and chlorides of copolymers of 13325~2 acrylamide and methacrylic acid.
It has been found that the molecular weight of the particular cationic polymer has very little efrect on the polymer's abllity to stablllze the ghale or suspend the weightlng agent. Thus, as noted above, cationic polymers of widely varying molecular weights can be employed.
The composltlons Or the present invention also employ hydroxyethyl celluloge a9 a viscosifler and fluld 1089 control addltlve. The HEC, wh~ch wlll generally be present in the compogltlons ln amountg ranglng rrom about 0.5 to about 3 poundg per barrel, preferably 0.5 to 2.5 pounds per barrel, of the aqueous medlum, must have a molecular welght ranglng from about 3,000 to about 40,000 dependlng upon the degree of vlscoslflcatlon deslred. HEC's havlng hlgher molecular welghts cannot be used to form weighted muds as per the compositions of the present invention.
In cases where the drilling fluid of the present invention containg a galt of a multivalent cation, e.g., calcium chloride, sea water or the like, it is necessary, in order to achieve acceptable fluld 1099 control, to include a non-water-swellable clay. Such clayg can be dlspensed with if the aqueous medium is fregh water or contains only the salt of a monovalent cation, such ag godium chloride. The non-water-gwellable cla~ can be added to the drilling fluid at the commencement of the drilling if the formation through which the drilling progre99e9 doe9 not contain a non-water-swellable clay. Alternately, the clay can be picked up, in situ, by the drilling fluid during the actual drilling operation since many rormationg contain such non-water-swellable clayg which rorm part of the drill cuttings. The non-swellable clay will normally be pregent in the drilling rlUid in amount9 rangin~ from about 1 to about 15 pounds per barrel Or the aqueou~ medium. Suitable, non-limiting examples Or guch non-water-gwellable clayg include kaolin, attapulgite, sepiolite, etc.
The compositions or the present invention also include a water-insoluble welghtlng agent such as barlte, although other weighting agent9 guch a9 galena, hematite and other mineral materials may be employed. The weighting agent will generally be present ln the compositions in amounts o~ from about l to about 300 pounds per barrel of the aqueous medium .
The compositons of the present invention may contain other materials or additives, such as additional viscosifiers or fluid 1099 control additives, salts, etc. to tailor the mud to desired needs.
In the method of the present invention, the drilling fluid, if the formation contains a non-water-swellable clay, is circulated ln the well bore, the non-swellable clay belng lncorporated ln sltu lnto the drllllng fluld.
Alternatlvely, the drllllng fluld havlng added non-swellable clay 19 circulated ln the borehole durlng the drllling operation, this being the method utilized when the rormation through which the borehole is being drilled is devoid of non-water-swellable clay.
To more fully illustrate the invention, the following non-limltlng examples are presented.
Example l A serles of drllllng muds were prepared of varylng composltlons and tested. In all cases, unless otherwlse lndlcated in this and all the other examples, the muds were prepared by mixing 20 mlnutes on a Multlmlxer~ followlng by hot rolling for 16 hours at 150F prior to testing. The compositions of the drllllng fluids and test results are shown in Table l below.

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r s ~ ~ I I I o I ~o ~ ~ _ -~ . r- U~ N r N 4~ o S S NI I I ~ o NO ~
~ O
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n n R h ~ C
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-- ~ C ~) Z
. ~O>. O R ~ 3 D ~,, m s ~
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--I --I N

As can be seen from the data in Table 1, the drllling fluids of the present invention exhiblt excellent rheologlcal propertles and fluld 1099 control. Wlth reference to Mud No. 4, lt can be seen that when too much HEC having a higher molecular weight, e.g., 40,000, is present, the drilling fluid becomes unacceptably thick.
Indeed, it hag been found that using HEC's having molecular weights of geveral million makeg it virtually impossible to formulate an acceptable drilling fluid contalnlng a water-insoluble weighting agent. Although Mud No. 4a shows acceptable rheological properties, lt has been found that it shows very poor shale stabllity lndicating the necesslty of the presence of the catlonic polymer to achieve shale stability. Note that when the HEC is not present (Mud No.
4b), there is virtually no fluid 1099 control. The data in Table 1 also demonstrates that the weighted muds can contain up to 400 poundg per barrel of the weighting agent and still be an acceptable drilling fluid. However, it is to be noted (See Mud No. 10) that the yield point of such heavily weighted mud i9 higher than would normally be desired.
Exam~le 2 Several drilling fluid formulations were prepared and tested. The compogitiong of the mudg and the test results are shown in Table 2 below.

133250~
1, Table 2 Formulatlon Mud No. 1 Mud No. 2 5Tap water, bbl 0.7 -7 Sea Salt, lb 11 11 LV 214 283 E, lb HEC-10, lb HEC-QP 300, lb 3- 3 10BAROID, lb 3 3 XC Polymer, lb ZEOGEL, lb - 15 BARABRINE DEFOAM, lb .2 .2 Premix (1 bbl Tap Water 15100 lb Kaolin), bbl Plastic Viscosity, cP 60 54 Yield Point, lb/100 sq ft 22 21 10-sec gel, 20lb/100 sq ft 3 4 10-min gel, lb/100 sq ft 4 7 Fluid Temperature, F 74 74 pH7.5 7.4 25API Fluid Loss, ml 50+ 6.0 Mud wt, lb/gal 14.5 14.5 This example shovs that when salts of multivalent cations, such ag are contained in gea salt are present, a non-water-swellable clay must be present in order ror the drilling fluid to exhibit acceptable fluid logs properties.
As can be seen, when no ZEOGEL is present (Mud No. 1), there is virtually no fluid 1088 control. The results in Table 2 are to be contrasted with the results in Table 1 wherein the aqueous medium contain only the salt of a monovalent cation (KCl) and wherein acceptable fluid 1099 control could be achieved even in the ab8ence of any non-water-swellable clay (see Mud No. 9 in Table 1).

1332~02 Exam~e 3 A 3erles of dr~lllng flulds were prepared by mlxing the lngredlents for 20 mlnuteg on a multlmlxer. The drllllng flulds were then hot rolled ror 16 hours at 150F and tested. The composltlong of the mudg and the test results are shown ln Table 3 below.

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E- ~ Z V~ 3 2 ~ e x ~ m ~ ~ ~ ~ ~ ~ ~ ~
u~ o ~ o ~n As can be 3een rrom the data Ln Table 3, drilling fluid~ made in accordance with the present invention have excellent rheological properties and exhibit good rluid loss control. Note that when there i9 no low molecular weight HEC (Mud Nos. 7-10), there is essentially no fluld 1039 control .
Example 4 To demonstrate that the drilling rluids Or the present lnventlon are errectlve ln stablllzlng shale, a serles Or drllling rluldg were prepared and compared with a conventional prior anlonic polymer-based drilllng mud commonly used where ghale gtabilization is important. In testing the ability Or the drilling rluids to stabilize the Ahale, Pierre shale samples weighing 15 grams and having a diameter between 0 . 08 and 0 .19 inche8 were hot rolled at 150F over a gix day period. The shale sample was removed rrom each drilling rluid and re-weighed periodically to determlne the amount Or eroslon that was occurring. The mud compositions and test data are shown in Table 4 below.

Table 4 Formulation No. 1 No. 2 No. 3 No. 4 No. 5 5Tap water, bbl KCl, lb 25 25 25 25 25 KOH, lb 0.5 0.5 0-5 0-5 0-5 HEC-QP 300, lb 3.0 - - - 3.0 E-905, lb 1 - - - -10Drlspac1, lb - _ 1.5 PAC-L2, lb - - 1.0 1.5 EZ-MUD3, lb THERM-CHEK4, lb - 3 Kaolln, lb 10 10 5 10 10 erosion values at various times 6 hr 0 0 0 1 0 2024 hr 9 0 9.2 15.5 28.5 15.2 48 hr 27.4 29.2 53.5 53.6 38.9 72 hr 47.o 47.8 73.5 70.1 55.2 144 hr 77- 4 - 89 . 3 88 . 6 78 . 5 25lTrade mark of carboxymethyl cellulose marketed by NL
Baroid, Inc.
2Trademark of a low molecular weight carboxymethyl cellulose marketed by NL Barold, Inc.
3Trade mark of a partially hydrolyzed polyacrylamide (anionic polymer) marketed by NL Baroid, Inc.
4Trademark of a suli`onated acrylamide copolymer marketed aA
a fluid 109s additive by NL Baroid, Inc.
Mud No. 2 is a commonly u3ed prior art anionic polymer-based drilling fluid u3ed in drilling shale formations.
While as can be seen, Mud No. 2 shows acceptable shale stabilization, it cannot be ei`fectively weighted with weighting agents such as barlte or other generally non-~,~

1332~02 water-soluble weightlng agents. On the other hand, Mud No.
1 made ln accordance wlth the present inventlon is equally as effectlve at shale stabillzatlon and as shown ln prevlous data can be easlly welghted wlth barlte. As can also be seen, drllllng flulds whlch contaln nelther the catlonlc polymer nor HEC are not erfectlve at gtablllzlng the shale (see Mud No. 3 and Mud No. 4). It can also be seen (Mud No.
5) that unless both the catlonlc polymer and the low molecular welght HEC are present, the drllllng rlulds are not as efrectlve ln stablllzlng the shale, even ln the presence Or an anlonlc polymer commonly used for shale stablllzatlon.
It can thus be seen that the drllllng flulds of the present lnventlon are effectlve at ghale stablllzatlon, exhlblt low rluld 1089 and can be easlly welghted wlth commonly used, generally water-lnsoluble welghtlng agents such as barlte.
The foregolng disclosure and descrlptlon o~ the lnventlon 19 lllustratlve and explanatory thereof, and varlous changeg ln the method gtepg may be made wlthln the scope o~ the appended clalmg wlthout departing f`rom the spirit of the inventlon.

Claims

1. A drilling fluid comprising an aqueous medium, from about 0.5 to about 3 pounds per barrel of said aqueous medium of a water-soluble cationic polymer, from about 0.5 to about 3 pounds per barrel of said aqueous medium of hydroxyethyl cellulose having a molecular weight of from about 3,000 to about 40,000, and from about 1 to about 300 pounds per barrel of said aqueous medium of a generally water-insoluble weighting agent.

2. The drilling fluid of Claim 1 wherein said cationic polymer is selected from the group consisting of (a) branched emulsion polymers of diallyldimethylammonium chloride having a molecular weight of at least 5,000, (b) dialkylaminoalkyl acrylic ester polymers, (c) dialkylaminoalkyl methacrylic ester polymers, (d) dialkylaminoalkyl acrylic acid-acrylamide copolymers, (e) dialkylaminoalkyl methacrylic acid-acrylamide copolymers, (f) N-(Dialkylaminoalkyl) acrylamide polymers, (g) N-(Dialkylaminoalkyl) methacrylamide polymers, (h) poly(2-vinylimidazioline), (i) poly(alkyleneamines), (i) poly(hydroxalkylene polyamines) and mixtures thereof.

3. The drilling fluid of Claim 2 wherein said branched emulsion polymer has a molecular weight of from about 40,000 to about 5,000,000.

4. The drilling fluid of Claim 3 wherein a member selected from the group consisting of triallylmethylammonium chloride, tetraallylammonium chloride, tetraallylpiperazinium chloride and N,N,N',N',-tetraallyl-N,N'-dimethylhexamethylenediammonium chloride is utilized as a branching agent in forming said branched emulsion polymers, said branched polymers containing from about 95 to about 99.99 mole percent diallylmethylammonium chloride and from about 0.01 to about 5 mole percent of said branching agent.

5. The drilling fluid of Claim 1 wherein said water-soluble cationic copolymer comprises a dimethylaminoalkyl acrylamide-methacrylic acid copolymer.

6. The drilling fluid of Claim 5 wherein the molecular weight of said dimethylaminoalkyl acrylamide-methacrylic acid copolymer is from about 40,000 to about 4,000,000.

7. The drilling fluid of Claim 1 wherein said weighting agent comprises barite.

8. The drilling fluid of Claim 1 wherein said aqueous medium contains a salt of a monovalent cation.

9. The drilling fluid of Claim 1 wherein said aqueous medium contains a salt of a multivalent cation and said drilling fluid contains a non-water-swellable clay.

10. A method of drilling an earth borehole comprising circulating in said borehole during the drilling operation a drilling fluid comprising an aqueous medium, from about 0.5 to about 3 pounds per barrel of said aqueous medium of a water-soluble cationic polymer, from about 0.5 to about 3 pounds per barrel of said aqueous medium of hydroxyethyl cellulose having a molecular weight of from about 3,000 to about 40,000, from about 1 to about 300 pounds per barrel of said aqueous medium of a generally water-insoluble weighting agent and from about 1 to about 15 pounds per barrel of said aqueous medium of a non-water-swellable clay.

11. The method of Claim 10 wherein said cationic polymer is selected from the group consisting of (a) branched emulsion polymers of diallyldimethylammonium chloride having a molecular weight of at least 5,000, (b) dialkylaminoalkyl acrylic ester polymers, (c) dialkylaminoalkyl methacrylic ester polymers, (d) dialkylaminoalkyl acrylic acid-acrylamide copolymers, (e) dialkylaminoalkyl methacrylic acid-acrylamide copolymers, (f) N-(Dialkylaminoalkyl) acrylamide polymers, (g) N-(Dialkylaminoalkyl) methacrylamide polymers, (h) poly(2-vinylimidazioline), (i) poly(alkyleneamines), (j) poly(hydroxalkylene polyamines) and mixtures thereof.

12. The method of Claim 11 wherein said branched emulsion polymer has a molecular weight of from about 40,000 to about 5,000,000.

13. The method of Claim 12 wherein a member selected from the group consisting of triallylmethylammonium chloride, tetraallylammonium chloride, tetraallylpiperazinium chloride and N,N,N',N',-tetraallyl-N,N'-dimethylhexamethylenedimonium chloride is utilized as a branching agent in forming said branched emulsion polymers, said branched polymers containing from about 95 to about 99.99 mole percent diallylmethylammonium chloride and from about 0.01 to about 5 mole percent of said branching agent.

14. The method of Claim 13 wherein said water-soluble cationic polymer comprises dimethylaminoalkyl acrylamide-methacrylic acid copolymer.

15. The method of Claim 14 wherein the molecular weight of said dimethylaminoalkyl acrylamide-methacrylic acid copolymer is from about 40,000 to about 4,000,000.

16. The method of Claim 10 wherein said weighting agent comprises barite.

17. The method of Claim 10 wherein said aqueous medium contains a salt of a monovalent cation.