NL8601898A - METHOD FOR REVERSIBLE THICKNESS OF A LIQUID - Google Patents

Description

8262

Method for reversibly thickening a liquid.

The present invention relates to a method of providing reversibly thickened liquids for use in a variety of industrial applications.

In many industrial processes it would be useful to have a method of reversibly thickening a liquid. Examples of these methods are slurry pipeline transportation of minerals, removal of the solids produced during well drilling, removal of solids formed in the polishing and grinding of metals, etc. In methods such as this it is advantageously increase the viscosity of the liquid to increase its solids carrying capacity and prevent solids from settling before reaching their desired destination. The most common method of increasing the carrying capacity of a liquid for solids is the addition of a polymer or dispersed solid such as clay which increases the viscosity of the liquid, especially at low shear rates. However, in the above-mentioned methods, it is also necessary to remove the solids from the liquid, either to reuse the liquid or to use the solids. This is often done, for example, by filtering the liquid from the solids, centrifuging the solids from the liquid, or by similar methods. Unfortunately, the additional viscosity that was useful for transporting the solids also makes the desired separation of the solids from the liquid more difficult. Furthermore, if the viscosity is lowered by destruction or removal of the polymer or clay used to increase the viscosity of the liquid, additional polymer or clay is needed to restore the liquid's solids carrying capacity. Also, the liquid or solid may be contaminated and interfere with further use because of the residue 3G resulting from the use of the polymer or clay.

In view of the drawbacks of the prior art, it would be highly desirable if one could provide a method for improving the carrying capacity of a liquid for solids in such a manner that can be easily and quickly reversed for removal. of solids from the liquid when desired and after the solids have been removed to easily and 8601898

St -2- quickly restore the bearing capacity of the liquid for solids.

Accordingly, the present invention is in one aspect a method of reversibly changing the viscosity of a liquid, comprising contacting the liquid with a viscoelastic surfactant to increase the viscosity of the liquid followed by breaking the viscosity of the viscoelastic surfactant-containing liquid in such a way that the liquid need not be subjected to an increase in shear to decrease the viscosity of the liquid and the viscosity of the liquid can then be substantially restored.

It is surprising that when a viscoelastic surfactant is used to impart an increased viscosity to a liquid that the viscosity imparted by the viscoelastic surfactant can be effectively reduced (ie, "broken") and thereafter the viscosity of the liquid can be restored without using additional amounts of the viscoelastic surfactant. In the other case, once the viscosity of a liquid thickened with a soluble high molecular poly-20 is broken, the viscosity of the liquid can substantially not be restored without using further amounts of polymer. Furthermore, the fluids used in the present invention are highly shear resistant and do not experience significant or slight loss of continuous pumping activity while polymer-thickened fluids undergo irreversible mechanical degradation and rapid loss of continuous pumping activity.

Therefore, the method of the present invention is particularly suitable for liquids used in flow systems containing pumps, high speed flows, sudden expansions or contractions, grinding operations, polishing operations and the like.

In many applications, the thickened liquids of the invention are useful in industrial applications where it is desirable to use a liquid with a high solids carrying capacity. In detail, the method of the invention consists of thickening the liquid with a viscoelastic surfactant to yield a liquid with an increased solids carrying capacity compared to an unthickened liquid, suspending 8601898 / * -3- solids in the thickened liquid and subsequent breaking of the viscosity of the liquid such that the solids can be more effectively removed from the fractured liquid than from the thickened liquid.

The method of removing solids is particularly useful in a closed loop continuously circulating method, for example, removing solids from a wellbore drilling liquid. The method provides (1) in a portion of the closed loop a thickened liquid for carrying solids effectively, (2) in another part of the closed loop an effective and effective method of removing solids after breaking the viscosity of the liquid in such a way that increased shear is not required to decrease the viscosity and (3) recover the viscosity and solids carrying capacity of the liquid in yet another part of the loop after removal of the solids. Thus, a continuous and effective process can be performed in which it is not necessary to add significant amounts, if not any, of a viscosity enhancer to the system after repeated fracturing and recovery of the viscosity of the liquid to provide 2w of a liquid with a functionally effective viscosity.

As used herein, the term "liquid" refers to those liquid materials that may be organic or aqueous in nature.

Preferably, the liquid is an aqueous liquid. The term "aqueous liquid" includes liquids containing inorganic electrolytes such as aqueous solutions of inorganic salts, aqueous alkaline or aqueous acidic solutions, depending on the surfactant or electrolyte employed.

Other examples of aqueous liquids include mixtures of water and a water-miscible liquid such as lower alkanols, for example, methanol, ethanol or propanol; glycols and polyglycols and the like, provided that such water-miscible liquids are used in amounts that the thickening effect of the viscoelastic surfactant on the liquid is not significantly or adversely affected. Also included are emulsions var. in non-miscible liquids and aqueous solids suspensions. Generally, however, water and aqueous alkaline, aqueous acidic or aqueous inorganic salt solutions (namely, brine solutions) are most advantageously used as the aqueous liquid used herein. Advantageously, the electrolyte concentration is less than about 75% by weight of the solution.

The term "viscoelastic surfactant" is intended to include compounds that can be broadly classified as surfactants that can impart viscoelasticity to a liquid. The property of viscoelasticity and tests to determine whether a liquid has viscoelastic properties are well known in the art and reference is made to Η. A. Barnes et al., Rheol. Acta, 10 1975 14, pp. 53-60 and S. Gravsholt, Journal of Coll, and Interface

Sci. , 57 (3) pp. 575-6 (1976). See also, N.D. Sylvester et al., Ind. Spooky. Chem, Prod. Res. Dev., 1979, 14, p. 47. Of the test methods specified in these articles, a test has been found to be most useful in determining the viscoelasticity of an aqueous solution in the vortexing of the solution and visually checking whether the bubbles caused by the vortex recoil after the swirling has stopped. Any rebound from the bubbles indicates viscoelasticity.

Surfactants capable of imparting viscoelastic properties to a liquid are well known in the art and are referred to for the purposes of the present invention. As examples of literature references describing viscoelastic surfactants are cited U.S. Pat. Nos. 3,361,213; 3,273,107; 3,406,115; 4,061,580 and 4,534,875. The term "surfactant" is used in its broadest sense and is intended to include any molecule that has a characteristic amphiphatic structure such that it has the property of dissolving colloidal clusters, commonly referred to as micelles.

The viscoelastic surfactants can be either ionic or nonionic. Typically, an ionic viscoelastic surfactant comprises a surfactant having a hydrophobic moiety chemically bonded to an ionic hydrophilic moiety (hereinafter referred to as "surfactant ion") and an amount of a counterion that is a moiety has the ability to combine with the surfactant ion-sufficiently to form a viscoelastic surfactant. A nonionic viscoelastic surfactant comprises a surfactant molecule 8601898% -5- with a hydrophobic moiety chemically bonded to a nonionic hydrophilic moiety.

Examples of ionic surfactants are represented by the formula: „Φ θ Θ §

5 R (Y) X or R (Z) A

φ1 q · * · where R ^ (Y) and R ^ (z) represent surfactant ions with a hydrophobic moiety represented by R and an ionic solubilizing moiety represented by the cationic moiety (Y) or the anionic QQ part (Z} chemically bonded thereto. X and A are the counterions combined with the surfactant ions.

Typically, the hydrophobic portion (namely R 1) of the surfactant ion is hydrocarbyl or inert-substituted hydrocarbyl wherein the term "inert-substituted" refers to hydrocarbyl radicals having one or more substituents, for example halogen groups such as -F , -Cl or -Br or chain links, such as a silicon link (-Si-), which are inert to the aqueous liquid and the components contained therein. Typically, the hydrocarbyl radical is an aralkyl group or a long-chain alkyl or inert-substituted alkyl, which alkyl groups are usually linear and have at least about 12, advantageously at least about 16 carbon atoms. Representative long-chain alkyl and alkenyl groups include dodecyl (lauzyl), tetra-decyl (mvristyl), hexadecyl (cetyl), octadecenyl (oleyl), octadecyl (stearyl) and the derivatives of talc, coconut and soy. Preferred alkyl and alkenyl groups are usually alkyl and alkenyl groups of 14 to 24 carbon atoms with octadecenyl, hexadecyl, erucyl and tetradecyl being most preferred.

0

The cationic, hydrophilic moieties (groups), namely (Y), are usually onium ions in which the term "onium ions" refers to a cationic group that is substantially completely ionized in water over a wide pH range, eg pH value of 2- 12. Representative onium ions include quaternary ammonium groups, namely -N (R) ^, tertiary sulfonium groups, i.e. -S (R), quaternary phosphonium groups, i.e. -P (R) and the like, wherein each R individually is a hydrocarbyl or substituted hydrocarbyl. Furthermore, primary, secondary and tertiary amines, which are -NE ^, -NHR or -N (R) ^, can also be used as the ionic part if the pH of the aqueous liquid used is such that the amine parts in ionic 860 1 898

V

-6- will exist. A pyridinium part can also be used. Preferably, the surfactant ion of the viscoelastic surfactant is prepared from such cationic groups

(B

with quaternary ammonium, which is -N (R) ^; a pyridinium part; an aryl-5 or alkarylpyridinium; or imidazolinium moiety; or tertiary amine, -N (R) 2, groups wherein each R is independently an alkyl group or hydroxyalkyl group having 1-4 carbon atoms, each R preferably being methyl, ethyl or hydroxyethyl.

Representative anionic solubilizing moieties (groups) Θ Θ 10 (Z) include sulfate groups, which is -OSCL, ether sulfate groups, ^ 2 sulfonate groups, namely -SO 2, carboxylate groups, phosphate groups, phosphonate groups, and phosphonite groups. Of such anionic groups, the surfactant ion of the viscoelastic surfactants is preferably prepared with a carboxylate or sulfate group. For the purposes of the invention, such anionic solubilizing moieties are less preferred than cationic moieties.

Fluoroaliphatic species suitably used in the practice of the invention include organic compounds represented by 2.0 by the formula: wherein R is a saturated or unsaturated fluoroaliphatic moiety, which t 1 preferably contains an F 2 C moiety and Z is an ionic part or potentially ionic part. The fluoroaliphatic compounds can be perfluoro-carbons. Suitable anionic and cationic parts will be described below. The fluoroaliphatic portion advantageously contains 3-20 carbon atoms, all of which may be completely fluorinated, preferably from 3-10 such carbon atoms. This fluoroaliphatic moiety may be linear, branched or cyclic, is preferably linear and may optionally contain a carbon-bonded hydrogen or halogen other than fluorine, and may contain an oxygen atom or a trivalent nitrogen atom bonded only to carbon atoms in the backbone chain. More preferably, those linear perfluoroaliphatic parts are represented by the formula: cnF2n + i wherein n is in the range of 3-10. Most preferred are those linear perfluoroaliphatic moieties presented in the paragraphs below.

8601898 »» -7-

The fluoroaliphatic species may be a cationic perfluorocarbon and is preferably selected from: CF (CF) SO NH (CH) N®R "X®; R.CH" CHnSCH-CH_N R "_X and ï. 2. λ £ l 3

5 CF (CF) CONH (CH) N R "X

0> 5 ™ IT a S o where X is a counter ion to be described below, R "is lower alkyl of 1-4 carbon atoms, r is 2-15, preferably 2-6 and s is 2-5. Examples of other preferred cationic perfluorocarbons and methods of preparation are those listed in U.S. Patent No. 3,775,126.

The fluoroaliphatic species may be an anionic perfluoro-carbon and is preferably selected from: CF -. (CF.) SO "Ö®A®" 3 2 P 2 Θ ffl CF (CF) SCLNH (CH) S0 "0 A, 3 2 p 2Θ ffl 2 q 2 15 CF (CF) COO A and 3 2? CF (CF) S0 „NH (CH) COO A; 3 2 p 2 2 σ φ where p is 2 - 15, preferably 2 - 6, q is 2 - 4 and A is a counterion to be described below. Examples of other preferred anionic perfluorocarbons as well as methods of preparation are described in U.S. Patent 3,172,910.

0 φ

The counterions (that are X or A) associated with the surfactant midael ions are most suitably ionically charged, organic materials with ionic character opposite to that of the surfactant ion, which combination of counterion and surfactant 25 imparts medium ion viscoelastic properties to an aqueous liquid. The anionic organic material serves as the counterion for a surfactant ion with a cationic hydrophilic moiety, and the cationic organic material serves as the counterion for the surfactant ion with a cationic hydrophilic moiety. anionic, hydrophilic part. Usually, the preferred counterions which exhibit an anionic character contain a carboxylate, sulfonate or phenoxide group, wherein a "phenoxide group" is ArO and Ar represents an aromatic ring or inert substituted aromatic ring. Representative of such anionic counterions which when used with a cationic surfactant ion are able to impart viscoelastic properties to an aqueous liquid include various aromatic carboxylates such as o-hydroxybenzoate; 860189? -. * -8- m- or p-chlorobenzoate, methylene bis-salicylate and 3,4- or 3,5-dichlorobenzoate; aromatic sulfonates such as p-toluene sulfonate and naphthalene sulfonate; phenoxides, especially substituted phenoxides; and the like, where such counterions are soluble; or 4-amino-3,5,6-5 trichloropicolinate. Alternatively, the cationic counterions can contain an onium ion, preferably a quaternary ammonium group. Representative cationic counterions having a quaternary ammonium group include benzyl trimethyl ammonium or alkyl trimethyl ammonium wherein the alkyl group may be octyl, decyl, dodecyl, erucyl and the like; And amines such as cyclohexylamine and hydroxyethylcyclohexylamine. It is highly desirable to avoid stoichiometric amounts of surfactant and counterion when the alkyl group of the counterion is large. The use of a cation as the counterion is usually less preferred than the use of an anion as the counterion. Inorganic counterions, either anionic or cationic, can also be used.

The specific type and amount of surfactant ion and counterion used to prepare a viscoelastic surfactant are interrelated and are chosen such that the combination imparts viscoelastic properties to an aqueous liquid. The combinations of surfactant ions and counterions that will form a viscoelastic surfactant will vary and are readily determined by the test methods described above.

Of the various surfactant ions and counterions that can be used to prepare a viscoelastic surfactant, the preferred viscoelastic surfactants represented by the formula include:

R

'Φ Θ CH -R'-N -R X 3 n,

30 R

wherein R 'is saturated or unsaturated alkyl, n is an integer from 13 to 23, preferably from 15 to 21, representing the number of carbon atoms in R'; each R is independently hydrogen or an alkyl group, or alkylaryl, or a hydroxyalkyl group having 1 to 4 carbon atoms, preferably each R independently, depending on methyl, hydroxyethyl, ethyl or benzyl, and X is o-hydroxy benzoate, m- or p-halobenzoate or an alkylphenate in which the alkyl group advantageously contains 1-4 carbon atoms. Furthermore, the groups R can form an 8601890-9 pyridinium part. Particularly preferred surfactant ions include cetyl trimethyl ammonium, oleyl trimethyl ammonium, erucyl trimethyl ammonium and cetyl pyridinium.

Other preferred surfactants include those represented by the formula: Θ

CF - (CF +) -SO.NH— (CH) -N -R X

3 2 n 2 2 m f

R

wherein n is an integer from 3-15, preferably from 3-8; m is an integer from 2 to 10, preferably from 2 to 5; R is as previously described Θ 10, preferably methyl; and x is as previously described.

The viscoelastic surfactants are readily prepared by mixing the basic form of the desired cationic surfactant ion (or acidic form of the desired anionic surfactant ion) with the desired amount 15 of the acidic form of the desired cationic counterion (or the basic form of the desired anionic counterion). Alternatively, the desired amounts of the salts of the cationic surfactant ion and the anionic counterion (or equimolar amounts of the anionic surfactant ion and cationic counterion) can be mixed to form the desired viscoelastic surfactant. See, for example, the method described in U.S. Patent No. 2,541,816.

Depending on the specific surfactant ion and associated counterion, less than a stoichiometric amount of the counterion can be applied to impart viscoelastic properties to a liquid. For example, when the surfactant ion is a long-chain alkyl bonded to a quaternary ammonium and the counterion is salicylate, although greater than stoichiometric amounts of an electrolyte which generates a salicylate anion upon dissociation may be used, water and other aqueous liquids can be effectively thickened by using stoichiometric or even smaller amounts of the electrolyte. However, in many cases, especially when the counterion is an inorganic ion such as chloride ion, viscoelastic properties to an aqueous liquid are imparted only when an electrolyte is used in stoichiometric excess. For example, in such cases the surfactant may impart undesirable viscoelastic properties to water, but will give desirable viscoelastic properties to a salt solution such as brine. When used, "viscoelastic surfactant" refers only to the surfactant ion and that amount of counterion actually used when the counterion is used in stoichiometric or smaller amounts. the surfactant ion used, the term "viscoelastic surfactant" refers to the surfactant ion and stoichiometric amount of counterion (ie, it is the excess amount of electrolyte if any present, excludes).

Typically, surfactants having a hydrophobic moiety are chemically bonded to a nonionic hydrophilic moiety which are nonionic surfactants that exhibit a viscoelastic character and are typically described in U.S. Patent 3,373,107; and those alkylphenoxyethoxylates as described by Shinoda in Solvent Properties of Surfactant Solutions, Marcel Dekker,

Ine. (1967) and Zakin, J.L. and Liu, H.L. in "Variables Affecting Drag Reduction by Nonionic Surfactant Additives", Chem. Eng Commun., Vol. 23, 20 pp 77-88 (1983). Preferred nonionic surfactants are those tertiary amine oxide surfactants that exhibit viscoelastic character. Usually, the hydrophobic portion can be represented as the previously described R. It is also desirable to use an additive such as an alkanol in the aqueous liquid to which the nonionic surfactant is added to make the surfactant viscoelastic.

Other viscoelastic surfactants that can be used in the method of the invention are described by D. Saul et al., J. Chem. Soc, Faraday Trans., 1 (1974) 70 (1), pp 30 163-170; or C.A. Barker et al., Ibid., Pp. 165-162.

The viscoelastic surfactant (either ionic or non-ionic in character) is used in an amount sufficient to measurably increase the viscosity of the liquid in which it is used. The amount of the most advantageous viscoelastic surfactant used will vary depending on a variety of factors including the desired viscosity of the liquid, the composition of the solvent, 8 6 0 t 8 9 8 * * -11- sina and the final application of the liquid, including the temperatures and shear strengths to which the flowing liquid will be exposed. In aqueous liquids, the viscoelastic surfactant is usually used in a sufficient amount such that the viscosity of the liquid is at least about 100, and preferably at least about 250, and more preferably at least about 500 centipoise at 25 ° C when determined using a Brookfield viscometer, type LVT, spindle No. 1 at 6 revolutions per minute. Usually, the concentration of each specific viscoelastic surfactant used to impart the desired viscosity to the liquid is easily determined by the experiment. Usually, the viscoelastic surfactants are preferably used in amounts ranging from 0.01-10% by weight based on the weight of the viscoelastic surfactant and the liquid. The viscoelastic surfactant is more preferably used in amounts of 0.05-3% based on the weight of the liquid and the viscoelastic surfactant.

As mentioned, the viscoelastic surfactant 20 can be prepared using greater than stoichiometric amounts of an electrolyte with an ionic character opposite to that of the surfactant ion and capable of being combined as a counterion (e.g., an organic counterion) with the surfactant ion. The use of additional electrolyte soluble in the liquid containing the viscoelastic surfactant will also allow the liquid to retain its higher temperature viscosity and / or the thickened liquid's resistance to the presence of oils. or other water-insoluble materials such as hydrocarbons which may come into contact with the liquid as well as various water-soluble materials such as the lower alcohols and the like are increased. For example, it is possible that the thickened liquid contains oil or other organic material in a concentration of 0.05 - 80% by weight, based on the total weight of the thickened liquid and oil or other organ. nical material. Usually, the viscoelastic properties and therefore the viscosity of the liquid tend to be lost or significantly reduced in the presence of similar materials. Liquids containing the viscoelastic surfactant and excess amounts of electrolyte are able to retain their viscoelastic properties for longer periods of time than a similar liquid that does not contain the excess amounts of electrolyte. Fluorinated viscoelastic surfactants are more resistant to the presence of organic materials and are capable of adding many organic materials in amounts up to 80% by weight, most preferably up to 20% by weight, based on the weight of the thickened liquid (ie the liquid and the fluorinated surfactant).

Usually, electrolytes (including salts, acids, and bases) that form organic ions upon dissociation with the surfactant ion to form a viscoelastic surfactant are preferred. For example, the oil resistance and / or the temperature resistance of a liquid containing a viscoelastic surfactant containing a cationic surfactant ion can often be increased by using an organic electrolyte which dissociates a anion. Examples of such anionic organic electrolytes include the alkali metal salts of various aromatic carboxylates, for example, sodium sageylate and potassium salicylate and disodium methylene bis (salicylate); alkali metal ar-halobenzoates, for example sodium p-chlorobenzoate, potassium m-chlorobenzoate, sodium 2,4-dichlorobenzoate and potassium 3,5-dichlorobenzoate; aromatic sulfonic acids such as p-toluenesulfonic acid and its alkali metal salts; naphthalene sulfonic acid; substituted phenols and alkali metal salts thereof, for example ar, ar-dichlorophenols, 2,4,5-trichlorophenol, t-butylphenol, t-butylhydroxyphenol, ethylphenol, and the like.

On the other hand, the oil and / or temperature resistance of a liquid containing a viscoelastic surfactant with an anionic surfactant ion can often be increased by using a cationic organic electrolyte that forms a cation upon dissociation. Although cationic organic electrolytes are less preferred than the above-mentioned anionic organic electrolytes, examples of suitable cationic electrolytes include the quaternary ammonium salts such as alkyl trimethyl ammonium halides and alkyl triethyl ammonium halides in which the alkyl group can contain 4-22 carbon atoms 8601898 rff-% -13. and the halide is advantageously chloride; aryl and aralkyl trimethyl ammonium halides such as phenyl trimethyl and benzyl trimethyl ammonium chloride; alkyl trimethylphosphonium halides and the like.

Preferably, the electrolyte is the same or generates the same ion associated with the surfactant ion of the viscoelastic surfactant present in the aqueous liquid, for example, alkali metal salicylate is advantageously used as the attached electrolyte when the viscoelastic surfactant originally has a salicylate counterion. The most preferred organic electrolytes are the alkali metal salts of an aromatic carboxylate, for example sodium salicylate. However, it will also be clear that the electrolyte of the counter ion used may differ.

The concentration of the electrolyte required in the liquid to raise the temperature to which the liquid will retain its viscoelastic properties and therefore its viscosity is dependent on a variety of factors including the specially used liquid, viscoelastic surface active agent and electrolyte (e.g. organic electrolyte) and the desired viscosity obtained. Usually, the concentration of the electrolyte will advantageously range from 0.1 to 20, preferably from 0.5 to 5 moles, per mole of the viscoelastic surfactant.

The liquids useful in the invention which exhibit the desired reversible viscosity properties are prepared by mixing the desired amounts of viscoelastic surfactant and using the added electrolyte to form a liquid solution. Alternatively, the nonionic surfactant is contacted with the liquid to form an aqueous liquid solution. The solutions obtained are stable 50 and can be stored for long periods of time. The liquids may also contain additives so that the liquid can be used for many industrial purposes, such as drilling fluids, finishing fluids, processing fluids and fracturing fluids, cutting fluids, pipeline use, slurry transport, district heating applications and the like.

The term "breaking" as used herein refers to a measurable decrease in the viscosity of the fluid, which visco-elastic 8601898

w V

-14- contains surfactant mixture. The viscosity of liquids thickened with viscoelastic surfactants can be broken by multifarious agents. For example, aqueous liquids thickened with hydrocarbyl or inert-substituted hydrocarbyl viscoelastic elastic surfactants can be broken by the addition of effective amounts of a miscible or immiscible hydrocarbon or substituted hydrocarbon such as methanol, ethanol, isopropanol (i.e. lower alcohols) acetone, methyl ethyl ketone, trichlorethylene, toluene, xylenes, mineral oils, glycols, glycol ethers and the like. Aqueous liquids containing the fluoroaliphatic species as viscoelastic surfactants can be effectively broken using lower alcohols (i.e., alcohols having 1-3 carbon atoms) such as isopropanol.

The amount of hydrocarbon or substituted hydrocarbon that must be added to break the viscosity of the thickened liquid depends on the specially used viscoelastic surfactant and its concentration as well as the special hydrocarbon or substituted hydrocarbon used. For example, such a small amount as 0.1 wt%, based on the weight of the thickened liquid, toluene can often be added to the liquid to break its viscosity while more than 75 wt% ethylene glycol may need to be added to break the same thickened liquid. In most cases, the hydrocarbon or substituted hydrocarbon will advantageously be selected to break viscosity when added in an amount of 0.1 - 50, preferably 0.2 - 20, more preferably 0.2 - 20 10 wt% based on the weight of the liquid.

Other methods of breaking the viscoelastic surfactant mixtures involve changing the pH of the liquid, heating or cooling the system above or below the temperature at which the liquid loses its viscoelasticity, changing the composition of the viscoelastic surfactants. Although the application of shearing forces greater than what the surfactant micelles are resistant to can also be used to break the viscoelastic properties imparted to the liquid by the surfactant, the use of excessively large shearing forces not a practical means of lowering the viscosity of the liquid 8601898 *? - * -15-. It is noted that more than one means of crushing the viscoelastic surfactant mixtures can be used simultaneously. Preferably, the viscosity of the liquid is broken by contacting the thickened liquid with an effective amount of hydrocarbon or substituted hydrocarbon. For those compositions containing viscoelastic surfactant blends and intended for use over a wide temperature range, temperature change is not the best means of breaking the viscoelastic surfactant.

Recovery of the viscosity of the industrial liquid can be accomplished by using a variety of techniques. The term "viscosity recovery" is understood to mean that the viscosity of the liquid that has been broken can be increased without the addition of additional viscoelastic surfactant to the liquid being required. Thus, the term "reversible fracture" as used with respect to the fluids of the invention refers to the repeated fracturing and substantial restoration of the viscosity of the original fluid. Examples of techniques suitable for reversing the crushing process or restoring the viscosity of the liquid include removal of the aforementioned hydrocarbon using techniques such as applying a vacuum and / or heating the liquid. That is, the hydrocarbon can be removed from the liquid by subjecting the liquid to conditions such that the hydrocarbon evaporates. For that reason it is; very desirable to use a hydrocarbon for fracturing which has a fairly high vapor pressure under the conditions of removal. Hydrocarbons can also be removed by absorbing the hydrocarbon using a suitable absorbent material (ie, a material that removes the hydrocarbon but not significant amounts of the viscoelastic surfactant mixture). For example, the hydrocarbon can be removed using polymer grains, columns containing such grains, carbon, colloidal silica, etc. Other methods of recovering the viscosity of the broken liquid include adjusting the pH, heating or adjusting. cooling the system to the point where the viscoelasticity is restored.

.601898

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-16-

In one aspect of the present invention, a fluid containing a viscoelastic surfactant can be used to remove suspended particulate matter during drilling operations, such as oil well drilling, without significant loss of time or loss of fluid. In particular, the thickened liquid can be used to transport the solids and the viscosity of the liquid can be broken afterwards, allowing easy removal of the solids from the liquid by conventional techniques such as filtration. The viscosity of the broken liquid can then be restored and the liquid reused.

According to a very highly preferred embodiment of this aspect of the invention, oil well drilling fluids such as those containing large amounts of brine can be recycled in an efficient and effective manner. For example, oil well drilling fluids are thickened using the viscoelastic surfactants of the invention and used to bring debris to the surface, broken, subjected to a solid removal treatment using conventional agents such as vibratory screens, hydrocyclones or centrifuges, subject to viscosity recovery and recycled for further use.

The examples below are illustrative of the invention and should not be construed as any limitation on its scope. All percentages and parts are by weight unless stated otherwise.

Example I.

A thickened brine preparation is prepared by contacting 350 ml of a 13-pound per gallon (1557 kg / m3) calcium chloride / calcium bromide brine with 3 g of a viscoelastic surfactant mixture containing 1.5 g talc trimethyl ammonium chloride in a 1.5 g isopropanol and water mixture. To the composition is added 5 g of a solid clay / quartz dust, which is to simulate drill cuttings and sold commercially as Rev Dust Aldoor Millwhite Corporation, Houston, Texas. This sample is referred to as sample No. 1.

In the same manner, but for comparison, a thickened brine preparation containing clay / quartz and 1 g of a hydroxyethyl cellulose polymer and not a viscoelastic surfactant mixture is prepared. This sample is referred to as sample No. C-1.

8601890 mt -17-

The ability of the liquid containing the viscoelastic surfactant to be broken, treated and recovered is illustrated using the following method:

Step A.: The viscosities of samples No 1 and C-1 without solids are measured using a Fann 35 viscometer at about 24 ° C. The viscosities are measured at different shear rates ranging from 3 to 600 revolutions per minute, (rpm)

Step B.: The viscosities of the samples No. 1 and C-1 with no solids present are measured as in step A.

10 Step C .: Each of the samples No. 1 and C-1 is filtered by placing 200 ml of liquid in a cell, applying 100 psi (689 kPa) of pressure with nitrogen gas and determining the amount of liquid passing through Whatman 50 filter paper per unit time.

Step D .: 45 drops of trichlorethylene 15 are added to each of the samples, thereby breaking the viscoelastic surfactant. The viscosity of the samples is measured as described above, but at about 29 ° C.

Step E .: Each of the samples is filtered as described in Step C.

Step F .: The liquid used for crushing is removed from the samples processed in Step E. By vacuum distillation of each sample at 25 ° C using a laboratory flask, receiver and dry ice cold trap connected to a vacuum pump and further in vacuo distilling each sample at 65 ° C for five minutes. The viscosities of each sample are determined as described above at 27.5 ° C and 27 ° C, respectively.

The results are shown in Table A.

8601898 -18-

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CD f "Ο CO CO Ο Ο CO ι — ι CM ^ ΙΛ ο <υ μ ft <# ie> c in ui cN ^ mr ^ cMO 5 ω <ϋ 0 μ> * Η Ρη.

ω ιΰ Ό ο μ ---> μ R ^ ë οοοοοοη οοοοοηη $ "ιβ ο οοοο οοοο λ> e - vDcncMr-i ώ η Ν η u ο ο μ> ω

μ. G

CD ο * <υ

C Ζ fH R

° ι Η ° s υ «8601898 * s> -19-

The numbers in Table A indicate that a thickened sample is difficult to filter (i.e., Step C). However, the viscosity of the thickened sample can be broken (namely, step D), the sample can be easily filtered (i.e., step E), and the viscosity text can be substantially restored (step F).

Example II.

0.22 - 0.34 g of a 50% active anionic surfactant (dodecyldiphenyloxydedisulfonate) in water are added to 100 g of a 0.01 N aqueous cetyltrimethylammonium chloride solution, which exhibits a viscosity comparable to water. , making the solution highly viscous. However, when 0.59 g of the 50% active anionic surfactant is added to the solution, the viscosity of the solution becomes similar to that of water and the system becomes opaque (i.e., substantially equal amounts of anionic and cationic surfactant are present). Addition of 0.85-0.92 g of anionic surfactant gives a viscous solution.

The example illustrates that a large excess of a surfactant does not impart viscosity to the liquid. Thus, a means for breaking a thickened liquid is provided.

The example also illustrates that an equivalent amount of anionic and cationic surfactant provides a means of breaking the liquid if it is desired to remove the surfactant.

Example III. /

A liquid used in a thickened state at a high temperature can be reversibly broken by subjecting the liquid to a lower temperature. A drilling fluid is simulated by charging 1.5 l of cetylmethyl-bis-hydroxyethyl ammonium chloride at 14.2 pounds per gallon (1701 kg, m3) of CaBr0 aqueous

Ate liquid. The viscosity of the liquid at 85 ° C as measured using the Haake Rotovisco Model RV-3 rotary viscometer with an "NV cup and bob" measuring system at 170 sec 1 is 169 cp while at 25 ° C the viscosity is 62 cp .

8601898 V V- -20-

Example IV.

A thickened aqueous liquid is prepared by dissolving soy bis (2-hydroxyethyl) amine in water such that a 1% active surfactant concentration is obtained. The pH of the liquid is changed using hydrochloric acid. Maximum thickening is observed in the pH range of 4.8 - 5.7. At higher and lower pH ranges, the liquid shows a low viscosity. The viscosity of the system can be restored and broken by adding sodium hydroxide alternately with hydrochloric acid.

10 Example V,

A thickened aqueous liquid is prepared and has 99.5% water, 0.23% cetyl trimethyl ammonium salicylate and 0.23% sodium salicylate. The liquid is clear and has viscoelastic properties. Toluene is added portionwise to that liquid. After an amount of toluene is added so that the concentration is about 0.1%, the liquid becomes opaque and the viscoelastic properties are lost.

About 20 g of the broken liquid thus treated are passed through a column using about 10 psi (68.9 kPa) of pressure. The column is a copper tube of 1.3 mm O with a length of 70 cm and is filled with about 50 g of an even mixture of 80% 20 - 40 mesh silica sand and 20% styrene / divinyl benzene copolymer suspension grains with a particle size in the range of 200 ym. Liquid passing through the column is thicker than the broken liquid, but cloudy. The liquid is passed through the column a second time using 60 psi (413 kPa) pressure. The liquid passing through the column is clear and has viscoelastic properties.

8601898

Claims (19)

1. A method of reversibly changing the viscosity of a liquid, comprising contacting the liquid with a viscoelastic surfactant to increase the viscosity of the liquid and changing the viscosity of the liquid, which containing the viscoelastic surfactant, it breaks in such a way that the liquid need not be subjected to an increase in shearing forces to decrease the viscosity of the liquid, after which the viscosity of the liquid can be substantially restored. A method according to claim 1, characterized in that the viscoelastic surfactant is an ionic viscoelastic surfactant comprising a surfactant ion that has a hydrophobic moiety chemically bonded to an ionic hydrophilic moiety and an amount of a counter ion which has a moiety which is able to associate with the surfactant ion sufficiently to form a viscoelastic surfactant. A method according to claim 2, characterized in that the viscoelastic surfactant is represented by the formula: JG R (z ") A + wherein R is a hydrophobic part, Z is an anionic solubilizing part chemically bonded to and A is a counterion united with Z. A method according to claim 2, characterized in that the viscoelastic surfactant is represented by the formula: R1 (Y +) X ~ in which is a hydrophobic moiety, Y + is a cationic solubilizing moiety chemically bonded to and X is a Y + joined counterion. Method according to claim 2, characterized in that the viscoelastic compound is a fluoroaliphatic species. A method according to claim 2, characterized in that the liquid contains a stoichiometric excess of an electrolyte which is required to act as a counterion based on the amount of surfactant ion. 8601898 V- -22- A method according to claims 1-6, characterized in that the liquid is an aqueous liquid and the surfactant mixture is used in an amount such that the aqueous liquid is 0.01-10% by weight of the viscoelastic surface active agent, based on the weight of viscoelastic surfactant and aqueous liquid. 8. A method according to claims 1-7, characterized in that the viscosity of said liquid is broken by contacting said liquid with an effective amount of a miscible or immiscible hydrocarbon or substituted hydrocarbon. 9. A method according to claim 8, characterized in that the viscosity of said liquid is substantially restored by subjecting the liquid to conditions such that said hydrocarbon or substituted hydrocarbon evaporates or is absorbed using a suitable absorbent material. Process according to claim 9, characterized in that said hydrocarbon or substituted hydrocarbon is an alcohol of 1 to 3 carbon atoms. 11. Method according to claims 1 - 7, characterized in that after the viscosity of said liquid has been substantially restored, a further amount of surfactant mixture is added 12. A method according to claim 1, characterized in that the viscoelastic surfactant is a non-ionic viscoelastic surfactant comprising a surfactant molecule 25 having a hydrophobic moiety chemically bonded to a non-ionic hydrophilic part. 13. A method of using a thickened liquid for carrying solids, characterized in that the liquid is thickened with an amount of a viscoelastic surfactant 30, whereby the liquid has an increased carrying capacity for solids of a non-thickened liquid, suspends solids in the thickened liquid, then breaks the viscosity of the liquid without requiring increased shearing forces so that the solids can be more effectively removed from the liquid than from the thickened liquid. Method according to claim 13, characterized in that the viscosity is broken in such a way that the viscosity of the liquid 8601898 -23- can be substantially restored without an additional amount of viscoelastic surfactant being required to the liquid. to be added. A method according to claim 13, characterized in that the liquid 5 is an aqueous liquid and the viscoelastic surfactant is represented by the formulas: Rj (Z ~) A + or R1 (Y +) X ”wherein R ^ is a hydrophobic part; Z is an anionic solubilizing moiety chemically bonded to; A + is a Z-associated counterion; Y + is a cationic solubilizing moiety chemically bonded to and X is a Y-associated counterion. A method according to claim 13, 14 or 15, characterized in that the liquid is an aqueous liquid and the viscoelastic surfactant is a fluoroaliphatic species. A method according to claims 13-16, characterized in that the liquid contains an amount of electrolyte that is greater than the stoichiometric amount of electrolyte required based on the amount of surfactant ion. 18. A method according to claim 17, characterized in that said viscoelastic surfactant is used in an amount such that the aqueous liquid contains 0.01-10% by weight of the viscoelastic surfactant, based on the weight of the viscoelastic surfactant and the aqueous liquid. A method according to claim 13, characterized in that the viscosity of said liquid is broken by contacting said liquid with. an effective amount of a miscible or immiscible hydrocarbon or substituted hydrocarbon. 2G. Method according to claim 19r, characterized in that the viscosity of said liquid is substantially restored by subjecting the liquid to conditions such that said hydrocarbon or substituted hydrocarbon evaporates or is absorbed by using a suitable absorbent material. 8601898