AU768819B2 - Method of fracturing a subterranean formation - Google Patents

Description

1 'I

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT Applicant(s): SCHLUMBERGER TECHNOLOGY

CORPORATION

Invention Title: METHOD OF FRACTURING A SUBTERRANEAN

FORMATION

The following statement is a full description of this invention, including the best method of performing it known to me/us: 1A METHOD OF FRACTURING A SUBTERRANEAN FORMATION FIELD OF THE INVENTION 20 This invention relates to a method of fracturing a subterranean formation. This application is a divisional application of Australian Patent Application No. 80662/98.

S *•o H:\Priyanka\Keep\speci\P45169 Div.doc 6/03/02 Idaill/l*ILL 2 SUMMARY OF THE INVENTION i. According to the present invention there is provided a method of treating a subterranean formation comprising the step of pumping a viscoelastic fluid through a wellbore, wherein said viscoelastic fluid comprises: an aqueous medium; a surfactant selected from the group consisting of amphoteric surfactants, zwitterionic surfactants, and mixtures thereof; and a member selected from the group consisting of organic acids, organic acid salts, inorganic salts, and combinations of one or more organic acids or organic acid salts with one or more inorganic salts; wherein said fluid exhibits the property of viscoelasticity.

S 3 H:\Leanne\KeeP\21299-02.doc 10/10/03 3 BRIEF DESCRIPTION OF THE FIGURES Figure 1 shows a viscosity versus shear rate for a viscoelastic surfactant solution prepared by adding percent of disodium tallowiminodipropionate (Mirataine T2C®) and 2.25 percent of phthalic acid to water.

Figure 2 shows the dynamic modulus G' (storage modulus) and G" (loss modulus) at 25 0 C and 50°C of the same solution as Figure 1.

S-Figure 3 shows the viscosity versus shear rate for a "viscoelastic surfactant solution prepared by adding percent of disodium tallowiminodipropionate (Mirataine 15 T2C), 4 percent of NH 4 C1 and 1.75~2.0 percent of phthalic acid to water.

S. Figure 4 shows the viscosity versus shear rate for viscoelastic surfactant solutions prepared by adding 4 or o o H:\Priyanka\Keep\speci\P45169 Di-.doc 6/03/02 WO 98/56497 PCT/US98/12067 percent of disodium oleamidopropyl betaine (Mirataine BET-O), 3 percent of KC1 and 0.5 percent of phthalic acid to water.

Figure 5 shows the dynamic modulus G'(storage modulus) and (loss modulus) at 25 °C and 50 °C of the same solution as Figure 4.

DETAILED DESCRIPTION OF PREFERRED

EMBODIMENTS

The property of viscoelasticity in general is well known and reference is made to S. Gravsholt, Journal of Coll. And Interface Sci., 57(3), 575 (1976); Hoffmann et al., "Influence of Ionic Surfactants on the Viscoelastic Properties of Zwitterionic Surfactant Solutions", Langmuir, 8, 2140-2146 (1992); and Hoffmann et al., The S: 15 Rheological Behaviour of Different Viscoelastic Surfactant Solutions, Tenside Surf. Det., 31, 389-400, 1994. Of the test methods specified by these references to determine whether a liquid possesses viscoelastic properties, one test which has been found to be useful in determining the viscoelasticity of an aqueous solution consists of swirling the solution and visually observing whether the bubbles created by the swirling recoil after the swirling is stopped. Any recoil of the bubbles indicates viscoelasticity. Another useful test is to 25 measure the storage modulus and the loss modulus at a given temperature. If G" at some point or over- some range of points below about 10 rad/see-, typically between about 0.001 to about 10 rad/sec, more typically between about 0.1 and about 10 rad/sec, at a given temperature and if 10-2 Pascals, preferably Pascals, the fluid is typically considered viscoelastic at that temperature. Rheological measurements such as G' and G" are discussed more fully in "Rheological Measurements", Encyclopedia of Chemical Technology, vol.

21, pp. 347-372, (John Wiley Sons, Inc.,

N.Y.,

-4- 1 1-111-11-1111- I jj"- IMIII.-1-1.z WO 98/56497 PCT/US98/12067 1997, 4th To the extent necessary for completion, the above disclosures are expressly incorporated herein by reference.

Viscoelasticity is caused by a different type of micelle formation than the usual spherical micelles formed by most surfactants. Viscoelastic surfactant fluids form worm-like, rod-like or cylindrical micelles in solution. The formation of long, cylindrical micelles creates useful rheological properties. The viscoelastic surfactant solution exhibits shear thinning behavior, and remains stable despite repeated high shear applications.

By comparison, the typical polymeric thickener will irreversibly degrade when subjected to high shear.

In the summary of the invention and this detailed 15 description, each numerical value should be read once as modified by the term "about"(unless already expressly so modified), and then read again as not so modified, unless S: otherwise indicated in context.

The viscoelastic surfactants can be either ionic or nonionic. The present invention comprises an aqueous *viscoelastic surfactant based on amphoteric or zwitterionic surfactants. The amphoteric surfactant is a class of surfactant that has both a positively charged moiety and a negatively charged moiety over a certain pH 25 range typically slightly acidic), only a negatively charged moiety over a certain pH range typically slightly alkaline) and only a positively charged moi-ety at a different pH range typically moderately acidic), while a zwitterionic surfactant has a permanently positively charged moiety in the molecule regardless of pH and a negatively charged moiety at alkaline pH.

The viscoelastic fluid comprises water, surfactant, and a water-soluble compound selected from the group consisting of organic acids, organic acid salts, inorganic salts, and mixtures thereof. Alternatively, i.'1 T 4 WO 98/56497 PCT/US98/12067 the viscoelastic fluid can comprise water, an amine oxide surfactant and an anionic surfactant containing a hydrophobe having at least about 14 carbon atoms. The viscoelastic surfactant solution is useful as a fracturing fluid or water-based hydraulic fluid. The viscoelastic fluid used as a fracturing fluid may optionally contain a gas such as air, nitrogen or carbon dioxide to provide an energized fluid or a foam.

The component of the fluid which will be present in the greatest concentration is water, i.e. typically water will be a major amount by weight of the viscoelastic fluid. Water is typically present in an amount by weight greater than or equal to about 50% by weight of the fluid. The water can be from any source so long as the 15 source contains no contaminants which are incompatible with the other components of the viscoelastic fluid by causing undesirable precipitation). Thus, the water need not be potable and may be brackish or contain other materials typical of sources of water found in or near oil fields.

Examples of zwitterionic surfactants useful in the present invention are represented by the formula: .R2 Ri R 4

COO'

R3 wherein RI represents a hydrophobic moiety of alk'yl, alkylarylalkyl, alkoxyalkyl, alkylaminoalkyl and alkylamidoalkyl, wherein alkyl represents a group that contains from about 12 to about 24 carbon atoms which may be branched or straight chained and which may be saturated or unsaturated. Representative long chain alkyl groups include tetradecyl (myristyl), hexadecyl (cetyl), octadecentyl (oleyl), octadecyl (stearyl), docosenoic (erucyl) and the derivatives of tallow, coco, II 1.11~1~1-1.1 .1 IYYI. ltl IIIIYI- YII. 111 I~ 1.^1 Itl*ll. l-"ilji:llliill"FUir~lilllli.i~(lr~li -Ili_~~*ljjililW~..~j~yil~i*~l*(UilllY~* yVIIIYII ~III~I.-II.~YI)IW*IIIIYIMl~i~h~ O/~~l~!llilYi611 i: ii;i~Z~n~ WO 98/56497 PCT/US98/12067 soya and rapeseed oils. The preferred alkyl and alkenyl groups are alkyl and alkenyl groups having from about 16 to about 22 carbon atoms. Representative of alkylamidoalkyl is alkylamidopropyl with alkyl being as described above.

R

2 and R 3 are independently an aliphatic chain (i.e.

as opposed to aromatic at the atom bonded to the quaternary nitrogen, alkyl, alkenyl, arylalkyl, hydroxyalkyl, carboxyalkyl, and hydroxyalkylpolyoxyalkylene, e.g. hydroxyethyl-polyoxyethylene or hydroxypropyl-polyoxypropylene) having from 1 to about atoms, preferably from about 1 to about 20 atoms, more preferably from about 1 to about 10 atoms and most preferably from about 1 to about 6 atoms in which the 15 aliphatic group can be branched or straight chained, saturated or unsaturated. Preferred alkyl chains are methyl, ethyl, preferred arylalkyl is benzyl, and preferred hydroxyalkyls are hydroxyethyl or hydroxypropyl, while preferred carboxyalkyls are acetate and propionate.

R

4 is a hydrocarbyl radical alkylene) with chain length 1 to 4. Preferred are methylene or ethylene S° e groups..

SSpecific examples of zwitterionic surfactants 25 include the following structures:

CH

2

CH

2

OH

II. RI CH 2

COO-

2CH2

CH

2

CH

2

OH

i I. i-il:rlni l-jn .~r.VLI1. il~ll: i iiilli.ryi i l ililYI.I*lil rWIL~IL 4ill*il Ij IIIIIVLZI~YIUI C" yrurr"I~*nii?*l.~.l.-i*"l Ir~inui'~LubllujiliViill:ILiyy~ li~j.b! WO 98/56497 PCT/US98/12067

CH

3 III. Ri CH2COO-

CH

3

RICONHCH

2

CH

2

CH

2

_CH

2 COO0

CH

2

CH

2 0H

RICONHCH

2

CHCH

2

CH

2

COOH

CH

2

CH

2

COO"

wherein RI has been previously defined herein.

Examples of amphoteric surfactants include those represented by formula VI: r VI. Ri J H+ R4COowherein RI, R 2 and R 4 are the same as defined above.

-Other specific examples of amphoteric surfactants include the following structures:

CH

2

CH

2

COO-

VII.Ri_ N H"

CH

2

CH

2 COO X4 1 11 11- I*~I illxn. *i xy~~i tVVllirrrijr*i liri u~lli(u ,lirr lil Y'ir* uii(n*i~i~i'l rylu*jlrrn~,ui,*irl;irl;l Ir~il.ai rlill "f)s*i~n ll)i *~-/*i~"~Vlmll*jilllI~ii~LKT lii lil*i4~ Ililiiil\l~i~lY~*~~l*WL1I1~Xj~n~*llii~y/ Li i:~ WO 98/56497 PCT/US98/12067

CH

2 VIII. RICONHCH 2

CH

2 CH

SH

2

CH

2

COO-

wherein RI has been previously defined herein, and X' is an inorganic cation such as Na', NH 4 associated with a carboxylate group or hydrogen atom in an acidic medium.

A typical chemical process to synthesize dihydroxy ethoxylate glycinate starting from ethoxylated alkylamine is as follows: (CH2CH 2 0)xH (CH2CH 2 0)xH I CICH 2 COONa I

R

1 -N RI-N-CH 2 COONa (CH2CH 2 0)yH (CH2CH 2 0)yH x y 2-10 20 The final products may also include some unreacted starting dihydroxy ethyl alkyl amine, and small amounts of sodium glycolate, diglycolate and sodium chloride as by products. A similar process can be used to prepare propoxylated analogues.

25 A typical chemical process to synthesize alkyliminiodipropionate from alkyl amine is as follows: S- WO 98/56497 WO 9856497PCT/US98/12067 CH2CH2COOMe RiNH2 2 CH 2 CHCOOMe o, R, -N CH2CH2COOMe jH2OINaOH CH2CH2COONa RI -N CHr2C-H2COONa The final products will also include a small amount of methanol, unreacted acrylic acid, alkylamine and some oligomeric acrylate or acid as by products.

A typical chemical process to synthesize alkylamidopropyl betaine from alkyl amine is as follows: CH2 -OOCRi CH OOCRI +HNCH 2

CH

2

GH

2

N(CH

3 )2 RI CONHCH2CH 2

CH

2 N(CH3) 2

CH

2 -OOCRi ::.*CICH2COONa

CH

3 1+- R C-NHCH2CH 2 CH!- N- CH2COO CH3 The final products will also include a small amount of sodium glycolate, diglycolate, sodium chloride and glycerine as by products.

In still another embodiment of the invention, the zwitterionic surfactant selected is an amine oxide. This material has the following structure: WO 98/56497 PCT/US98/12067

R

2 R, -N R3 where RI, R 2 and R 3 are as defined above.

The surfactants are used in an amount which in combination with the other ingredients is sufficient to form a viscoelastic fluid, which amount will typically be a minor amount by weight of the fluid less than about 50% by weight). The concentration of surfactant can range from about 0.5% to about 10% percent by weight of ee 15 the fluid, more typically from about 0.5% to about 8%, and even more typically from about 0.5% to about 6%.

I Optimum concentrations for any particular set of *5 parameters can be determined experimentally.

The. fluid also comprises one or more members from 20 the group of organic acids, organic acid salts, and inorganic salts. Mixtures of the above members are specifically contemplated as falling within the scope of the invention. This member will typically be present in only a minor amount less than about 20% by weight of the fluid).

The organic acid is typically a sulfonic acid or a carboxylic acid and the anionic counter-ion of the organic acid salts are typically sulfonates or carboxylates. Representative of such organic molecules include various aromatic sulfonates and carboxylates such as p-toluene sulfonate, naphthalene sulfonate, chlorobenzoic acid, salicylic acid, phthalic acid and the like, where such counter-ions are water-soluble. Most preferred are salicylate, phthalate, p-toluene sulfonate, hydroxynaphthalene carboxylates, e.g. naphthoic acid, 6-hydroxy-l-naphthoic acid, 7-hydroxy-lnaphthoic acid, l-hydroxy-2-naphthoic acid, preferably 3-hydroxy-2-naphthoic acid, 5-hydroxy-2-naphthoic acid, 1'1' Lc- 11 i~ l l WO 98/56497 PCT/US98/12067 7-hydroxy-2-naphthoic acid, and 1,3-dihydroxy-2-naphthoic acid and 3,4-dichlorobenzoate. The organic acid or salt thereof typically aids the development of increased viscosity which is characteristic of preferred fluids.

Without wishing to be bound by any theory unless expressly noted otherwise in context, it is thought that association of the organic acid or salt thereof with the micelle decreases the aggregation curvature of the micelle and thus promotes the formation of a worm-like or rod-like micelle. The organic acid or salt thereof will typically be present in the viscoelastic fluid at a weight concentration of from about 0.1% to about more typically from about 0.1% to about and even more typically from about 0.1% to about 6%.

15 The inorganic salts that are particularly suitable for use in the viscoelastic fluid include water-soluble potassium, sodium, and ammonium salts, such as potassium chloride and ammonium chloride. Additionally, calcium chloride, calcium bromide and zinc halide salts may also 20 be used. The inorganic salts may aid in the development of increased viscosity which is characteristic of preferred fluids. Further, the inorganic salt may assist in maintaining the stability of a geologic formation to which the fluid is exposed. Formation stability and in 25 particular clay stability (by inhibiting hydration of the clay) is -achieved at a concentration level of a few percent by weight and as such the density of fluid is not significantly altered by the presence of the inorganic salt unless fluid density becomes an important consideration, at which point, heavier inorganic salts may be used. The inorganic salt will typically be present in the viscoelastic fluid at a weight concentration of from about 0.1% to about 30%, more typically from about 0.1% to about 10%, and even more typically from about 0.1% to about Organic salts, e.g. trimethylammonium hydrochloride and tetramethylammonium chloride, may also -12- -1 I "L I wl' "I'I4I'-II- 11 WO 98/56497 PCT/US98/12067 be useful in addition to, or as a replacement for, the inorganic salts.

As an alternative to the organic salts and inorganic salts, or as a partial substitute therefor, one can use a medium to long chain alcohol (preferably an alkanol), preferably having five to ten carbon atoms, or an alcohol ethoxylate (preferably an alkanol ethoxylate) preferably of a 12 to 16 carbon alcohol and having 1 to 6, preferably 1-4, oxyethylene units.

In the embodiment where the surfactant selected is an amine oxide, it is preferably used in combination with an anionic surfactant containing a hydrophobe having at least about 14 carbon atoms. Examples of suitable anionic surfactants include alkyl sulfates or sulfonates I. 15 having alkali metal counter, ions or alkyl carboxylates, wherein alkyl represents a group that contains from about 14 to about 24 carbon atoms which may be branched or straight chained and which may be saturated or unsaturated, and more preferably contains between about 20 16 and about 22 carbon atoms.

For this embodiment (amine oxide/anionic surfactant) the weight ratio of the amine oxide to anionic surfactant is from about 100:1 to about 50:50.

In addition to the water-soluble salts and 25 thickening agents described hereinbefore, the viscoelasti'c fluid used as a hydraulic fracturing fluid may contain other conventional constituents which perform specific desired functions, corrosion inhibitors, fluid-loss additives and the like. A proppant can be suspended in the fracturing fluid. The pH of the fluid will typically range from strongly acidic less than a pH of about 3) to slightly alkaline from a pH just greater than 7.0 to about 8.5, more typically to about 8.0) or moderately alkaline a pH of about to about Strongly alkaline pHs above a pH of about 10) should be avoided.

11., 1 1111 1 Ill WO 98/56497 PCT/US98/12067 It is also conceivable to combine the above amphoteric/zwitterionic surfactants with conventional anionic, nonionic and cationic surfactants to get the desired viscoelastic fluid for a skilled worker. In typical embodiments, the amphoteric/zwitterionic surfactant is typically present in a major amount by weight of all surfactants, and more typically is essentially the only surfactant present. Typically, the viscoelastic fluid will be essentially free of anionic surfactants, e.g. it will contain less than about more typically less than about even more typically less than 0.1% by weight of anionic surfactants.

To prepare the aqueous fluids, the surfactant is :added to an aqueous 15 solution in which has been dissolved a water-soluble o. inorganic salt, e.g. potassium chloride or ammonium chloride and/or at least one organic acid or watersoluble organic acid salt to provide selective control of the loss: of particle suspension properties. In the 20 embodiment wherein the fluid is a mixture of water, and amine oxide surfactant and an anionic surfactant, a simple mixture of the three components is utilized.

Standard mixing procedures known in the art can be employed since heating of the solution and special 25 agitation conditions are normally not necessary. Of course, if Ised under conditions of extreme cold such .as found in Alaska, normal heating procedures should'-:be employed. It has been found in some instances preferable to dissolve the thickener into a lower molecular weight alcohol prior to mixing it with the aqueous solution. The lower molecular weight alcohol, for instance isopropanol, functions as an aid to solubilize the thickener. Other similar agents may also be employed. Further, a defoaming agent such as a polyglycol may be employed to prevent undesirable foaming during the preparation of the viscoelastic fluid if a foam is not desirable under the -14- I- I 11 1. .1 w- 1, I .1 11. 1 i I w- 1, ip -1 I I i 1 w w F 1 .4 1 .1 1, I 114, L l 111 T I .1C WO 98/56497 PCT/US98/12067 conditions of the treatment. If a foam or gas-energized fluid is desired, any gas such as air, nitrogen, carbon dioxide and the.like may be added.

The fluid is particularly useful in the handling of particles generated during the excavation of a geologic formation, e.g. digging, drilling, blasting, dredging, tunneling, and the like, for example in the course of constructing roads, bridges, buildings, mines, tunnels and the like. The particles are mixed with the viscoelastic fluid by means which are effective to disperse the particles in the fluid. The particles generally have a particle size ranging from a fine powder to coarse gravel, e.g. dust, sand, and gravel. Particle size affects the suspendability of excavation processing wastes. For example, small particles suspend better than large particles, and very fine particles suspend so well that the mixture may become too thick to transport by pump or similar means.

The distribution of excavation processing waste sizes is 20 also important, as waste which contains particles which span a wide range of sizes is more easily suspended than o waste wherein the particles are of about the same size.

Therefore, it may be preferred to screen the waste particles prior to applying the present method to scalp off the particles that are too large to suspend to obtain a better particle size distribution.

The viscoelastic fluids can be utilized to carry earth or materials excavated during boring, excavating and trenching operations in the deep foundation construction industry, the subterranean construction industry and in tunneling, in well drilling and in other applications of earth support fluids. The ability of the excavation tools or systems to hold and remove increased loading of earth is improved by the suspending properties and lubricating properties of the surfactant viscoelastic fluids.

I'll.. m'j- I I- 111- ll- l~cu,- i WO 98/56497 PCT/US98/12067 In one preferred embodiment, the surfactant can be combined with some fluid-loss control additives known in the industry like water-soluble or water-dispersible polymers (guar and guar derivatives, xanthan, polyacrylamide, starch and starch derivatives, cellulosic derivatives, polyacrylates, polyDADMAC [poly(diallyl dimethyl ammonium chloride] and combinations thereof), clay (Bentonite and attapulgite) in order to give fluid-loss control properties to the excavating fluid and contribute to the stabilization of the wall of the excavation.

More comprehensive information can be found in The University of Houston, Department of Chemical Engineering, Publication No UHCE 93-1 entitled, Effect of 15 Mineral and Polymer slurries on Perimeter Load Transfer in Drilled shafts, published in January 1993, and PCT WO 96/23849, the disclosures of which are incorporated by reference.

The above method for suspending solids has many 20 applications, particularly in mining and the handling of mine tailings. The disclosure of U.S. Patent No.

5,439,317 (Bishop et al.) is incorporated by reference in this regard. One application is to transport and place mineral processing waste in underground caverns or below grade cavities. Another application is for backfilling of open pits or quarries without the use of costly and labor intensive equipment for deployment. Additionally, the method can be used to place clay or other liners in holding or storage ponds that are used to hold liquids and to prevent the entry of these liquids into the ground water regime and/or to place liners in landfills for a similar purpose. Another application of the method, is for the extinguishing and/or containment of coal mine fires by deploying quantities of solids below ground to seal the fire from sources of oxygen. Still another -16ll liill V~il lll~. il~ ii* lI.- ii:t il~ lllii li iiii-ij ii.; i~ir h ~i C lL'i.rW i IX~~II!/ ClUl ~il 11I~~ WO 98/56497 WO 9856497PCT/US98/12067 application of the method is to place solids in previously mined cavities to prevent surface subsidence.

Thcn h-c~rPulic fracturing method uses otherwise conventional techniques. The disclosure of U.S. Patent No. 5,551,516 (Norman et al.) is incorporated by reference in this regard. Oil-field applications of various materials are described in "Oilfield Applications", Encyclopedia of Polymer Science and Engineering, vol. 10, pp. 328-366 (John Wiley Sons, Inc., New York, New York, 1987) and references cited therein, the disclosures of which are incorporated herein 406VOby reference thereto.

00 soHydraulic fracturing is a term that has been applied 0 0: to a variety of methods used to stimulate the production 15 of fluids such as oil,. natural gas etc., from .00.0 Ssubterranean formations.. In hydraulic fracturing, a fracturing fluid is injected through a wellbore and against the face of the formation at a pressure and flow :90 rate at least sufficient to overcome the overburden O&S. 20 pressure and to initiate and/or extend a fracture(s) into the formation. The fracturing fluid usually carries a 0proppant s uch as 20-40 mesh sand, bauxite, glass beads, *se0 etc., suspended in the fracturing fluid and transported into a fracture. The proppant then keeps the formation 00.25 from closing back down upon itself when the pressure is released. The proppant filled fractures provide permeable channels through which the formation fluids can flo%4 to the wellbore and thereafter be withdrawn. Viscoelastic fluids have also been extensively used in gravel pack treatment.

In addition to the applications discussed above, the viscoelastic fluids may also be used as -an industrial drift control agent, or as a rheology modifier for personal care formulations cleansers, conditioners, etc.) and household cleansers detergent formulations) A detergent formulation of the WO 98/56497 PCT/US98/12067 viscoelastic fluids of this invention will further comprise a detersive surfactant. Examples of detersive surfactants and other conventional ingredients of detergent and/or personal care formulations are disclosed in U.S. Serial No. 08/726,437, filed October 4, 1996, the disclosure of which is incorporated herein by reference.

Typically, the detersive surfactant will be anionic or nonionic. Preferred water-soluble anionic organic surfactants herein include linear alkyl benzene sulfonates containing from about 10 to about 18 carbon atoms in the alkyl group; branched alkyl benzene sulfonates containing from about 10 to about 18 carbon atoms in the alkyl group; the tallow range alkyl S.sulfates; the coconut range alkyl glyceryl sulfonates; 15 alkyl ether (ethoxylated) sulfates wherein the alkyl moiety contains from about 12 to 18 carbon atoms and wherein the average degree of ethoxylation varies between 1 and 12, especially 3 to 9; the sulfated condensation products of tallow alcohol with from about 3 to 12, especially 6 to 9, moles of ethylene oxide; and olefin sulfonates containing from about 14 to 16 carbon atoms.

Specific preferred anionics for use herein include: the linear Cio-C 14 alkyl benzene sulfonates (LAS); the branched C 10

-C

14 alkyl benzene sulfonates (ABS); the tallow 25 alkyl sulfates, the coconut alkyl glyceryl ether sulfonates; the sulfated condensation products of mixed Clo-Cis tallow alcohols with from about 1 to about 14 moles of ethylene oxide; and the mixtures of higher fatty acids containing from 10 to 18 carbon atoms.

Particularly preferred nonionic surfactants for use in liquid, powder, and gel applications include the condensation product of C-c alcohol with 3 moles of ethylene oxide; the condensation product of tallow alcohol with 9 moles of ethylene oxide; the condensation product of coconut alcohol with 5 moles of ethylene oxide; the condensation product of coconut alcohol with 6 -18- I I k' 1.1 1, I, 1 1 I WO 98/56497 WO 9856497PCT/US98/I 2067 moles of ethylene oxide; the condensation product of C1 2 alcohol with 5 moles of ethylene oxide; the condensation product Of C 1 2 -1 3 alcohol with 6.5 moles of ethylene oxide, and the same condensation product -which is stripped so as to remove substantially all lower ethoxylate and nonethoxylated fractions; the condensation product Of C1 2 13 alcohol with 2.3 moles of ethylene oxide, and the same condensation product which is stripped so as to remove substantially all lower ethoxylated and non-ethoxylated fractions; the condensation product Of C 12 1 3 alcohol with 9 moles of ethylene oxide; the condensation product of

*C

14 1 5 alcohol with 2.25 moles of ethylene oxide; the condensation product Of C 14 1 5 alcohol with 4 moles of ethylene oxide; the condensation product Of C 14 15 alcohol with 7 moles of ethylene .oxide; and the condensation product of C 14 15 alcohol. with 9 moles of ethylene oxide.

Particular detersive applications for which the :viscoelastic fluid will be useful include as a thickener for acidic bathroom cleaners, such as those disclosed in U.S. Patent No. 5,639,722 (Kong et al.) and shower gels such as those disclosed in U.S. Patent No. 5,607,678 (Moore et the disclosures of which are incorporated by reference. The viscoelastic fluids will also be **useful in the manufacture of building products based on plaster, plaster/lime, lime/cement or cement such as those disclosed in U.S. Patent No. 5,470,383 (Schermann et al.) and foam fluids such as those disclosed in U.S.

Patent No. 5,258,137 (Bonekamp et the disclosures of which are incorporated by reference. In particular, the fluid will be useful for improving the water retention of cement slurries and grouts allowing better pumpability and workability with minimal free water. The fluids will also be useful as thickeners for acidic (e.g.

a pH of less than about 5) aqueous slurries of mineral carbonates or oxides, e.g. iron oxide, cerium oxide, silica suspensions, titanium oxide, calcium carbonate, WO 98/56497 PCT/US98/12067 and zirconium oxide. In this regard, the disclosure of U.S. Patent No. 4,741,781 (De Witte) is incorporated by reference.

The viscoelastic fluid will also be useful in formulations for the agricultural delivery of solid fertilizers and pesticides such as micronutrients, biologicals, insecticides, herbicides, fungicides, and plant growth regulators. Such formulations are typically aqueous suspensions or solutions comprised of a major amount of water and an agriculturally effective amount of an agriculturally useful chemical. The viscoelastic fluid is typically combined with the other ingredients of the formulation in an amount that effectively reduces the number of droplets S 15 below about 150 microns, i.e. the droplets most responsible for drift problems.

The following examples are presented to illustrate the preparation and properties of aqueous viscoelastic surfactant based hydraulic fluids -All percentagesconcentrations, ratios, parts, etc. are by weight unless otherwise noted or apparent from the context of their use.

25

EXAMPLES

EXAMPLE 1 Viscoelastic surfactant solutions are prepared by adding 5 percent of ammonium chloride and 3 to 5 percent of dihydroxyethyl tallow glycinate (Mirataine TM®) to water. The systems were stirred until all of the surfactant dissolved. All of the samples were observed to be viscoelastic by the bubble recoil test. Rheology of WO 98/56497 PCT/US98/12067 c solution was measured by Rheometric ARES at 25 OC. The results are given below in Table 1.

Table 1 Shear rate Viscosity (cps) in 5% NH 4 Cl (sec 3% 4% Surfactant 5% Surfactant Surfactant 1692.4 2619.8 3774.7 18 967.7 1490.6 2144 32 555.5 851.6 1214.3 56 319.2 483.2 688.1 100 184.6 278 393.6 178 107.5 159.3 225.4 EXAMPLE 2 In a manner similar to Example 1, 0.3 percent of phthalic acid and 2 to 4 percent of dihydroxyethyl tallow glycinate (Mirataine TM®) were put into solution. All of the samples were observed to be viscoelastic by the bubble recoil test. Rheological measurements were performed in the manner described in Example 1 at 25 OC.

The results are shown below in Table 2: Table 2 Shear rate Viscosity (cps) in 0.3% phthalic acid (sec 2% Surfactant 3% Surfactant 4% Surfactant 791.5 1474.6 1968.7 18 455.3 840.9 1101.5 32 262.4 490 564.5 56 152 279.2 361.7 100 88 160.9 356.6 178 53 91.6 342.3 EXAMPLE 3 The rheological measurements were also performed at higher temperatures by FANN Rheometer. The results for 4 percent dihydroxyethyl tallow glycinate (Mirataine TM®) and 0.3 percent of phthalic acid solution are shown below in Table 3: WO 98/56497 PCT/US98/12067 Table 3 Temperature (oF) Viscosity at 100 rpm (cps) 82 170 129 51 189 239 22 288 EXAMPLE 4 The viscoelastic surfactant solutions are prepared by adding 5 percent of disodium tallowiminodipropionate (Mirataine T2C and 2.25 percent of phthalic acid to water. The systems were stirred and warmed up to 50 °C until all of the phthalic acid dissolved. All of the 10 samples were observed to be viscoelastic by the bubble recoil test. Rheology was measured for viscosity and dynamic modulus G'(storage modulus) and (loss modulus) by a Rheometric SR-200 at 25 OC and 50 OC. The results are shown in Figures 1 and 2.

EXAMPLE In a manner similar to Example 4, 5 percent of disodium tallowiminodipropionate (Mirataine T2C®), 4 percent of NH 4 Cl and 1.75~2.0 percent of phthalic acid in 20 water were mixed together. All of the samples were observed to be viscoelastic by the bubble recoil test.

Rheological measurements were performed in the manner described in Example 4 at 25 oC. The results are shown in Figure 3.

EXAMPLE 6 The viscoelastic surfactant solutions are prepared by addition of 4~5% percent of oleamidopropyl betaine (Mirataine BET-O®), 3% KCI and 0.5% phthalic acid to water. The system was stirred until all phthalic acid ,111'11 -1 -11 F. iil, -,111 11 I*,"illi l, li I ;li 1 WO 98/56497 PCT/US98/12067

I

o dissolved. Rheology was measured for steady viscosity and dynamic modulus by Rheometric ARES at 25 OC. The results are shown in Figures 4 and EXAMPLE 7 A viscoelastic surfactant solution is prepared by mixing together in 95.65 parts of water 4 parts of euricic amido propylene dimethyl amine oxide and 0.35 parts of sodium 10 oleyl sulfate. The pH 'is adjusted to 8 by the addition of NaOH. Its temperature stability is determined by measuring its viscosity in cps (at shear rate of 100 sec 1 The results are shown in Table 4.

EXAMPLE 8 A viscoelastic surfactant solution is prepared by mixing together in 95.50 parts of water 4.0 parts of euricic amido propylene dimethyl amine oxide and 0.50 parts of sodium oleyl sulfate. Its temperature stability is determined by measuring its viscosity in cps(at shear rate of 100 sec The results are shown in Table 4.

Table 4 Temperature (OF) Viscosity Viscosity Example 8 Example 7 100 282 247 120 302 293 140 308 305 160 168 237 180 162 166 200 230 231 220 119 193 240 50 63 250 36 36 260 30 27 270 16 WO 98/56497 PCT/US98/12067 EXAMPLE 9 A viscoelastic surfactant solution is prepared by mixing together in 96.1 parts of water 3.0 parts of euricic amidopropyl amine oxide and 0.9 parts of sodium behenyl sulfate. The pH is adjusted to 9 by the addition of NaOH. Its temperature stability is determined by measuring its viscosity in cps (at shear rate of 100 The results are shown in Table EXAMPLE A viscoelastic surfactant solution is prepared by mixing together in 94.8 parts of water 4.0 parts of euricic amidopropyl amine oxide and 1.2 parts of sodium behenyl sulfate. The pH is adjusted to 9 by the addition of NaOH. Its temperature stability is determined by measuring its viscosity in cps (at shear rate of 100 sec The results are shown in Table r r r r o Table Temperature Viscosity Viscosity Example 9 Example 100 175 234 120 168 226 140 169 297 160 256 518 180 309 454 200 276 173 220 140 214 240 154 284 260 94 351 270 52 215 280 31 290 25 300 17 4 25 For the purposes of this specification it will be clearly understood that the word "comprising" means "including but not limited to", and that the word "comprises" has a corresponding meaning.

It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art, in Australia or in any other country.

H:\Priyanka\Keep\speci\P45169 Div.doc 6/03/02

Claims (20)

1. 2. A method of treating a subterranean formation comprising the step of pumping a viscoelastic fluid through a wellbore, wherein said viscoelastic fluid comprises: an aqueous medium; a surfactant selected from the group consisting of amphoteric surfactants, zwitterionic surfactants, and mixtures thereof; and a member selected from the group consisting of organic acids, organic acid salts, inorganic salts, and combinations of one or more organic acids or organic acid salts with one or more inorganic salts; wherein said fluid exhibits the property of viscoelasticity. 2. The method of Claim 1 wherein said method of treating is a method of fracturing wherein said step of pumping is conducted at a pressure sufficient to fracture said formation. 25 2 S3. The method of Claim 2 wherein said viscoelastic fluid further comprises a mineral acid at a concentration sufficient to reduce the pH of said viscoelastic fluid to about 3 or less.
2. 4. The method as claimed in any one of the preceding claims wherein the amount of said surfactant is from about to about 6% by weight of said fluid. H\Leanne\Keep\21299-02.doc 10/10/03 I~ 27 The method as claimed in any one of the preceding claims wherein said surfactant is a zwitterionic surfactant comprising a quaternary ammonium hydrophilic moiety covalently bonded with an alkyl or a hydroxyalkyl group.
3. 6. The method as claimed in any one of the preceding claims wherein said surfactant comprises a carboxylate hydrophilic moiety.
4. 7. The method as claimed in any one of the preceding claims wherein said member comprises an aromatic moiety selected from the group consisting of sulfonic moieties, sulfonate moieties, carboxylic moieties, and carboxylate moieties.
5. 8. The method as claimed in Claim 7 wherein said aromatic moiety is selected from the group consisting of salicylate ions and phthalate ions, hydroxynaphthalene carboxylate ions, and mixtures thereof.
6. 9. The method as claimed in any one of the preceding claims wherein said viscoelastic fluid further comprises a particulate proppant suspended therein.
7. 10. The method as claimed in any one of the preceding claims wherein said viscoelastic fluid further comprises an additive selected from the group consisting of corrosion inhibitors and fluid-loss additives and mixtures thereof. S S
8. 11. The method as claimed in any one of the preceding claims wherein said member is present in an amount of from about 0.1% to about 30% by weight, preferably in an amount 35 of from about 0.1% to about 8% by weight. H:\Leanne\Keep\21299-02.doc 10/10/03 28
9. 12. The method as claimed in any one of the preceding claims wherein said surfactant is represented by the formula R2 Ri-- N R 4 COO R 3 or the formula (II): R2 RI- N--R 4 COO- H wherein RI represents alkyl, alkenyl, alkylarylalkylene, alkenylarylalkylene, alkylaminoalkylene, alkenylaminoalkylene, alkylamidoalkylene, or alkenylamidoalkylene, wherein each of said alkyl groups contains from about 14 to about 24 carbon atoms and may be branched or straight chained and saturated or unsaturated, S" 25 and wherein said alkylene groups have from about 1 to about 6 carbon atoms; R 2 and R 3 are independently aliphatic chains having from about 1 to about 30 carbon atoms, and R 4 is a hydrocarbyl radical with a chain length of about 1 to about 4. O 13. The method of Claim 12 wherein RI is selected from the group consisting of tetradecyl, hexadecyl, and octadecyl.
10. 14. The method of Claim 12 wherein Ri is an alkyl group derived from tallow, coco, soya bean, or rapeseed oil. H:\Leanne\Keep\21299-02.doc 10/10/03 h--r ri -r ll I IIIII Y~ .i 29 The method of Claim 12 wherein R 2 and R 3 are independently alkyl, alkenyl, arylalkyl, hydroxyalkyl, carboxyalkyl, or hydroxyalkyl-polyoxyalkylene, each having from about 1 to about 10 carbon atoms and preferably are methyl, ethyl, benzyl, hydroxyethyl, hydroxypropyl, carboxymethyl, or carboxyethyl.
11. 16. The method of Claim 12 wherein Ri is RCONHCH 2 CH 2 CH 2 wherein R is alkyl group containing from about 14 to about 24 carbon atoms which may be branched or straight chained and which may be saturated or unsaturated and R 2 and R 3 are each beta-hydroxyethyl.
12. 17. The method of Claim 16 wherein R 2 is beta-carboxyethyl and R 4 is ethylene.
13. 18. The method of any one of Claims 1 through 11 wherein said surfactant is selected from the group consisting of dihydroxyethyl glycinates, alkenylamidoalkyl betaines, and amphoteric imidazoline-derived dipropionates, most preferably form the group consisting of dihydroxyethyl •tallow glycinate, disodium tallowiminodipropionate and So oleamidopropyl betaine.
14. 19. The method of Claim 18 wherein said surfactant is an alkenylamidoalkyl betaine. The method of Claim 18 or 19, wherein the fluid comprises from about 0.5% to about 6% of the surfactant and from about 0.1% to about 6% of a combination of a member selected from the group consisting of p-toluene sulfonate, naphthalene sulfonate, chlorobenzoic acid, salicylic acid and phthalic acid, with a member comprising 35 one or more water-soluble ammonium salts. ooe•. H:\Leanne\Keep\21299-02.doc 10/10/03 30
15. 21. The method of any one of claims 1 through 11 wherein said surfactant is an amine oxide surfactant and said member is an anionic surfactant containing a hydrophobe having at least 14 carbon atoms.
16. 22. The method according to Claim 21 wherein said amine oxide surfactant is of R 2 N--O R 3 formula wherein Ri represents alkyl, alkenyl, alkylarylalkylene, alkenylarylalkylene, alkylaminoalkylene, alkenylaminoalkylene, alkylamidoalkylene, or alkenylamidoalkylene, wherein each of said alkyl groups contains from about 14 to about 24 carbon atoms and may be branched or straight chained and saturated or unsaturated, and wherein said alkylene groups have from about 1 to S° about 6 carbon atoms; and R 2 and R 3 are independently aliphatic chains having from about 1 to about 30 carbon S•atoms.
17. 23. The method according to Claim 21 wherein said anionic surfactant is an alkyl sulfate or sulfonate having alkali metal counterions or an alkyl carboxylate, wherein alkyl represents a group that contains from about 14 to about 24 30 carbon atoms, preferably from 16 to about 22 carbon atoms, which may be branched or straight chained and which may be saturated or unsaturated.
18. 24. The method according to Claim 21 wherein the weight 35 ratio of amine oxide surfactant to anionic surfactant ranges from about 100:1 to about 50:50. H:\Leanne\Keep\21299-02.doc 10/10/03 31 The method according to Claim 21 wherein said fracturing step takes place at temperatures greater than about 100 0 F.
19. 26. The method according to any one of the preceding claims wherein said viscoelastic fluid is foamed or energized by the addition of air, nitrogen or carbon dioxide.
20. 27. The method of any one of the preceding claims and substantially as herein described with reference to the accompanying drawings. Dated this 10th day of October 2003 SCHLUMBERGER TECHNOLOGY CORPORATION By their Patent Attorneys GRIFFITH HACK Fellows Institute of Patent and Trade Mark Attorneys of Australia H:\Leanne\Keep\21299-02.doc 10/10/03