MXPA06008015A - Additive for viscoelastic fluid - Google Patents

Abstract

Composition and method for shortening the shear recovery time of cationic, zwitterionic, and amphoteric viscoelastic surfactant fluid systems by adding an effective amount of a co-gelling agent selected from triblock oligomeric compounds having hydrophilic (for example polyether) and hydrophobic (for example alkyl) portions. The co-gelling agent also increases fluid viscosity and very low co-gelling agent concentration is needed. Preferred surfactants are betaines and quaternary amines. The fluids are useful in oilfield treatments, for example fracturing and gravel packing.

Description

ADDITIVE FOR VISCOELASTIC FLUID BACKGROUND OF THE INVENTION The invention relates to co-gelling agents for fluid systems of viscoelastic surfactant. More particularly, this relates to the selection and optimization of gelling co-agents for fluid systems that are to be used across wide ranges of salinity and temperature. More particularly, it relates to co-gelling agents to shorten the shear recovery times and increase the viscosity of the ATVs for use in oilfield treatment fluids. Certain surfactants, when in aqueous solution, form viscoelastic fluids. Such surfactants are referred to as "viscoelastic surfactants" or "ATV". Other components, such as additional ATVs, regulators, acids, solvents and salts, are optional or necessary and, among other functions, can increase the stability (especially thermal stability) or increase the viscosity of the systems by modifying and / or stabilizing the micelles; All of these components as a whole are referred to as a viscoelastic surfactant fluid system. Not being limited by theory, but many systems of viscoelastic surfactant form long cholines as canes or in the form of worms in aqueous solution. The entanglement of these micelle structures gives viscosity and elasticity to the fluid. For a fluid to have a good viscosity and elasticity under certain given conditions, appropriate micelles must be formed and proper entanglement is needed. This requires that the structure of the surfactant satisfy certain geometrical requirements and requires that the micelles have sufficient length or interconnection to form the appropriate entanglements. It is known that many chemical additives improve the rheological behavior (higher viscosity and / or greater stability and / or higher tolerance to brine and / or lower sensitivity to shear and / or faster restoration if the micelles are fragmented, for example by shear strength) . Said materials are generally referred to as co-surfactants, co-gelling agents, rheology modifiers or agents that improve rheology, etc. and typically are alcohols, organic acids such as carboxylic acids and sulfonic acids, sulfonates and others. In the present, the term co-gelling agents will be used. Such materials often have different effects, depending on their exact composition and concentration, relative to the exact composition of surfactant (eg, hydrocarbon chain lengths of groups in the surfactant and co-surfactant) and their concentration. For example, such materials can be beneficial in certain concentrations and harmful (less viscosity, reduced stability, greater sensitivity to shear stress, longer recovery times) in others. In particular, there is a need for chemical additives that are effective to increase the viscosity of the ATV systems at a given temperature and / or to increase the temperature at which said ATV systems maintain the viscosities that make the fluids useful. Also, many ATV fluid systems show extensive viscosity recovery times after experiencing a large prolonged shear stress. A slow recovery after shear stress negatively impacts the drag reduction as well as the ability to transport the holding agent, which consequently leads to high undesirable treatment pressures as well as leakage risks close to the wellbore. In order to overcome the detrimental disadvantages of slow shear recovery, sometimes higher concentrations of ATV can be used. There is a need for additives that expand the conditions under which ATV systems can be used as well as reduce the amount of surfactant needed, which in turn reduces the cost and improves cleaning in many uses, such as, but not limited to, uses in treatment fluids for oil fields, especially stimulation fluids, especially hydraulic fracture fluids. Although it is known that additives can shorten ATV recovery times after shear stress "and increase their viscosities (see, e.g., U.S. Patent Applications Nos. 10 / 994,664 and 11 / 012,446, both of which were assigned to the same assignee hereof and are incorporated herein by reference in their entirety), there is still a need for agents that improve rheology that are simple and economical.

COMPENDIUM OF THE INVENTION A configuration is an aqueous treatment composition for a petroleum reservoir containing a viscoelastic surfactant and a co-gelling agent. The gelation co-agent has a structure selected from ABC and BAD, in which A and B are linked by an ether bond or an ester bond, B and C are linked by an ether bond or an ester bond, A and D are linked by an ether bond or an ester bond, the two bonds in the co-gelling agent may be the same or different, A and C are hydrophobic and may be the same or different and may contain amine groups , amide and ester, and B and D are hydrophilic and can be the same or different. A and C are linear or branched alkyl, saturated or unsaturated and may contain one or more aromatic rings; A and C are the same or different, and B and D are ionic or non-ionic, and may be the same or different. Examples of the gelling co-agent composition include H (CH2) x (OCH2CH2) and O (CH2) ZH, H (CH2) XC0 (OCH2CH2) y0C0 (CH2) ZH, HO (CH2CH20) x < C0 (CH2) CO (0CH2CH2) z.OH, HO (CH2CH20) x. (CH3) and. (OCH2CH2) ZOH in which "y" is from about 10 to about 50, preferably from about 24 to about 36; "and" 'is from about 4 to about 50, preferably from about 6 to about 24; "x" and "z" are from about 6 to about 22, preferably from about 8 to about 16, wx '"and wz'" are from about 1 to about 50, preferably from about 3 to about 40. The values of "x" and "z", as well as "x" 'and "z"', can be the same. The concentration of the co-gelling agent is from about 0.005 to about 3, preferably from about 0.01 to about 0.5%, most preferably from about 0.01 to about 0.1%. The composition may contain a polynaphthalene sulfonate. In a further configuration, the viscoelastic surfactant may have the formula: RCONH- (CH2) a (CH2CH20) m (CH2) b -N + (CH3) 2- (CH2) a- (CH2CH20) m- (CH2) b ' COO 'wherein R is an alkyl group containing from about 17 to about 23 carbon atoms which may be straight or branched chain and which may be saturated or unsaturated, "a", "b", "a"' and ,? b '"are each from 0 to 10 and" m "and" m "are each from 0 to 13," a "and" b "are each 1 or 2 if" m "is not 0, and , (a + b) is from 2 to 10 if m is 0; "a" 'and "b"' are each 1 or 2 when ?? m '"is not 0, y, (a' + b ') is from 1 to 5 if m 'is 0; (m + m ') is from 0 to 14; and CH2CH20 can also be OCH2CH2. As an example, the zwitterionic surfactant has the structure of betaine: wherein R is a hydrocarbyl group which may be straight or branched chain, aromatic, aliphatic or olefinic and has from about 14 to about 26 carbon atoms and may contain an amine; "n" is from about 2 to about 4; and "p" is from 1 to about 5, as well as mixtures of these compounds. Examples of the structure of betaine is oleylamidopropyl betaine and erucylamidopropyl betaine. The fluid may also contain a co-surfactant. An example of an aqueous field oil treatment composition is one in which the viscoelastic surfactant contains erucyl amidopropyl betaine and the gelation coagent contains H (CH2) xCO (OCH2CH2) and OCO (CH2) ZH in which "x" and "z" are 12, e, "and" is 32. Even in a further configuration, the viscoelastic surfactant contains a cationic surfactant, for example a surfactant or mixture of surfactants having the structure: RXN + (R2) ( R3) (R4) X "wherein Rx has from about 14 to about 26 carbon atoms and can be straight or branched chain, aromatic, saturated or unsaturated, and can comprise a carbonyl, an amide, a retroamide, an imine , a urea, or an amine; R2, R3 and R are each independently hydrogen or an Ci aliphatic group up to about C6 which may be the same or different, straight or branched chain, saturated or unsaturated and one or more of one thereof may be substituted with a group that makes the group R2, R3 and R4 more hydrophilic; the groups R2, R3 and R4 can be incorporated into a 5- or 6-membered heterocyclic ring structure including the nitrogen atom; the groups R2, R3 and R may be the same different; the groups Ra, R2, R3 and / or R4 may contain one or more units of ethylene oxide and / or propylene oxide; and X "is an anion, as well as mixtures of these compounds.

As a further example, Rx comprises from about 18 to 22 carbon atoms and may comprise a carbonyl, an amide or an amine; R2, R3 and R4 comprise from about 1 to about 3 carbon atoms, and X "is a halide, inclusive as an additional example Rx comprises from about 18 to 22 carbon atoms and may comprise a carbonyl, an amide or an amine; and R2, R3 and R4 are the same and others and comprise from 1 to about 3 carbon atoms In another configuration, the cationic surfactant may also contain an amine, for example, having the structure: R? N (R2 (R3) wherein, Ri, R2 and R3 are as defined above, the amine may be present at a concentration between about 0.01 and about 1 percent In another configuration, the viscoelastic surfactant contains an amine Even in another configuration, the aqueous oilfield treatment composition may optionally contain an acid selected from hydrochloric acid, hydrofluoric acid, formic acid , acetic acid, lactic acid, glycolic acid, sulphamic acid, malic acid, citric acid, tartaric acid, maleic acid, methylsulfamic acid, chloroacetic acid, as well as mixtures of these acids. A further configuration is a concentrate for addition to an aqueous fluid in order to form a viscoelastic fluid, the concentrate contains an agent that reduces freezing point, less than about 60% water, a co-gelling agent as describes lines above, and a viscoelastic surfactant.

A further configuration is a method for shortening the recovery time to the shear stress of a viscoelastic surfactant that is based on a fluid that involves a) supplying a fluid containing a viscoelastic surfactant and b) mixing a gelling co-agent with the fluid in the fluid. a sufficient concentration to shorten the recovery time to the shear stress of the fluid. The gelation co-agent has a structure selected from ABC and BAD, in which A and B are linked by an ether bond or an ester bond, B and C are linked by an ether bond or an ester bond, A and D are linked by an ether bond or an ester bond, the two bonds in the co-gelling agent may be the same or different, A and C are hydrophobic and may be the same or different and may contain amine groups , amide and ester, and B and D are hydrophilic and can be the same or different. Even yet another configuration is a method for the treatment of an oilfield which involves a) providing a fluid containing a viscoelastic surfactant and a co-gelling agent having a structure selected from ABC and BAD, in which A and B are linked by an ether bond or an ester bond, B and C are linked by an ether bond or an ester bond, A and D are linked by an ether bond or an ester bond, the two bonds in the co-gelling agent can be the same or different, A and C are hydrophobic and can be the same or different and can contain amine, amide and ester groups, and B and D are hydrophilic and can be the same or different, and b) Inject the fluid into a well.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows the viscosity of the ATV fluid systems, with and without the co-gelling agents of the invention, as a function of temperature.

DETAILED DESCRIPTION OF THE INVENTION When viscosity is given to fluids by the addition of viscoelastic surfactant systems, it is considered that the increase in viscosity is due to the formation of micelles, for example micelles in the form of worms, with a matting that It gives structure to the fluid which leads to viscosity. In addition to the viscosity itself, an important aspect of the properties of a fluid is the degree and rate of recovery of the viscosity or restoration when the fluid is subjected to high shear stress and then the shear stress is reduced. For ATV fluids, the shear stress can fragment the structure of the micelle, after which the structure is reformed. The control of the degree and rate of reassembly of the structure of the micelle (restoration) is necessary to maximize the performance of the surfactant system for different applications. For example, in hydraulic fracturing it is critical that the fluid recover its viscosity as quickly as possible after leaving the region of shear stress in the tubular elements and enter the environment of low shear stress in the hydraulic fracture. On the other hand, it is beneficial in the continuous pipe cleanings to impart a slight delay in the recovery of the total viscosity in order to "squirt" the solids from the bottom of the well bore in a more efficient manner towards the ring. Once in the ring, the recovered viscosity ensures that the solids are transported effectively to the surface. This viscosity and rate of restoration to shear stress are both important rheological properties of the fluid. Although viscoelastic surfactant fluid systems have been shown to have excellent viscoelastic properties for hydraulic fracture applications, the shear recovery time, not the viscosity of the fluid, often dictates the minimum concentration of surfactant that is required. For example, a fluid made with a certain concentration of surfactant may show adequate viscosity for the fracture at a given temperature, but the minimum usable concentration may be higher due to the slow shear recovery at the lower concentration. It is considered that an acceptable shear recovery time is around 15 seconds. A time of more than 15 seconds will negatively impact the reduction of drag and transport of the support agent. The shortening of the viscosity recovery time makes possible the use of ATV fluid systems and / or concentrations that would otherwise not be suitable in many applications. In addition, when an agent that modifies the rheology also increases the viscosity of the fluid, then less surfactant is needed to provide a given viscosity. Examples of agents that improve rheology are given in the U.S. Patent Application Inscription No. 10 / 994,664. It has been found that certain simple chemical additives, when included in certain viscoelastic surfactant fluids systems (such as the cationic, amphoteric and zwitterionic viscoelastic surfactant fluid systems, especially the viscoelastic zwitterionic betaine surfactant fluid systems ), at the appropriate concentrations in relation to the active ingredients of the surfactant, a) significantly shorten the recovery times to the shear stress of the systems, b) increase the viscosities of the ATV systems at a given temperature, and, c) increase the temperatures at which said ATV systems maintain viscosities that make the fluids useful for many purposes, such as, but not limited to, uses in oilfield treatment fluids, especially stimulation fluids, very especially as hydraulic fracture fluids. In many cases, shear recovery is almost instantaneous. These materials are referred to herein as "co-gelling agents". The co-gel agents expand the conditions under which ATV systems can be used, and reduce the amount of surfactant needed, which in turn reduces cost and improves cleanliness. In general, the formulas of the categories representative of the chemistries that serve as co-gelling agents are oligomers of three blocks whose structure can be written as ABC or BAD, wherein A and C are hydrophobic and may be the same or different and may contain amine, amide and ester groups, and may be an alkyl group (saturated or unsaturated, linear or branched, or containing one or more aromatic rings) , and B and D are hydrophilic and can be the same or different, and can be ionic, for example, they can be polyacrylate, or non-ionic, being better for the betaine systems to be non-ionic, and a polyether being preferred. Four examples are shown below: H (CH2) x (OCH2CH2) and O (CH2) zH 1 H (CH2) XC0 (OCH2CH2) y0C0 (CH2) ZH2 HO (CH2CH20) X-C0 (CH2) rCO (OCH2CH2) Z.0H 3 HO (CH2CH20) x. (CH2) and <; (OCH2CH2) z > OH 4 In these formulas, "and" is from about 10 to about 50, preferably from about 24 to about 36; "y '" is from about 4 to about 50, preferably from about 6 to about 24; "x" and "z" are from about 6 to about 22, preferably from about 8 to about 16, "x" and "z" 'are from about 1 to about 50, preferably from about 3 to about 40. ABA systems are preferred in which "x" is equal to "z" and "x" 'is equal to "z" because said materials are generally easier to synthesize and therefore are generally less expensive. ABA systems are shown in the Examples below, but systems can also be used ABC, BAB and BAD. Also, blocks A, B, C and D can be further substituted with the proviso that the substitution does not change much the hydrophobic or hydrophilic characteristic of the blocks in such a way that the co-gelling agent is not effective. Said substitution may affect the appropriate values of "x", "y", and, "z". Successful deviations of the basic formulas (for example the basic formula in which A and C are hydrophobic, and may be an alkyl chain (saturated or unsaturated, straight or branched chain, and may contain one or more aromatic rings); B is hydrophilic, and may be ionic, for example, it may be polyacrylate, or non-ionic, being better non-ionic for betaine systems, and is preferably as mentioned above, and "x" and "z" are preferably less than 22), substantially dependent on the concentrations of surfactant and co-gelling agent, as well as the presence and concentration of other materials (especially salts and co-surfactants). The appropriate concentrations (in the final fluid system) are from about 0.005% to about 3%, for example from about 0.01% to about 0.5%, for example from about 0.01% to about 0.1% . These are very low concentrations for agents that improve rheology or co-gelling agents. The co-gelling agents of the present invention give the desired results with any ATV system, for example those based on cationic, amphoteric and zwitterionic viscoelastic surfactant systems. It has been found that they are particularly effective with certain zwitterionic surfactants. In general, particularly suitable zwitterionic surfactants have the formula: RCONH- (CH2) a (CH2CH20) m (CH2) b-N + (CH3) 2- (CH2) a- (CH2CH20) m- (CH2) COO_ wherein R is an alkyl group containing from about 17 to about 23 carbon atoms which may be straight or branched chain and which may be saturated or unsaturated, "a", "b", "a" and "b" ' are each from 0 to 10 and "m" and "m" are each from 0 to 13, "a" and "b" are each 1 or 2 if "m" is not 0, y, (a + b ) is from 2 to 10 if m is 0; "a" 'and "b"' are each 1 or 2 when "m '" is not 0, and, (a' + b ') is from 1 to 5 if m' is 0; (m + m ') is from 0 to 14; and CH2CH20 can also be OCH2CH2. Preferred zwitterionic surfactants include the betaines. Two appropriate examples of betaines are BET-0 and BET-E. The surfactant is BET-O-30 shown below, a chemical name is oleylamidopropyl betaine. BET-O-30 is designated as obtained from the supplier (Rhodia, Inc., Cranbury, New Jersey, USA) which calls it Mirataine BET-O-30 because it contains an amide group of oleic acid (which includes a final group). of alkene Ci7H33) and contains about 30% active surfactant; the remainder is substantially water, sodium chloride and propylene glycol. An analogous material, BET-E-40, is also available from Rhodia and contains an erucic acid amide group (which includes a final group of C2 alkene H1) and is approximately 40% active ingredient; the remainder is substantially water, sodium chloride and isopropanol. ATV systems, in particular BET-E-40, optionally contain about 1% (of the original concentrate) of a condensation product of a naphthalene sulfonic acid, for example sodium polynaphthalene sulfonate, as a rheology-modifying agent, as described in the U.S. Patent Application Publication No. 2005-0134751. The surfactant in BET-E-40 is also shown below, a chemical name is erucyl amidopropyl betaine. The original BET-E-40 concentrates were used in the experiments reported below. BET surfactants, as well as other ATVs that are suitable for the present invention, are described in U.S. Patent No. 6,258,859. According to that patent, BET surfactants form viscoelastic gels when they are in the presence of certain organic acids, salts of organic acids or inorganic salts; In that patent, the inorganic salts were present in a concentration by weight of up to about 30%. Co-surfactants may be useful for extending brine tolerance as well as for increasing the gel strength and reducing the shear sensitivity of the ATV fluid, in particular for surfactants of the BET-O type. An example given in U.S. Patent No. 6,258,859 is sodium dodecylbenzene sulfonate (SDBS), which is also shown below.

Other suitable co-surfactants include, for example, those having a structure similar to SDBS in which "x" is from 5 to 15; Preferred co-surfactants are those in which "x" is from 7 to 15. Even other co-surfactants suitable for BET-O-30 are certain chelating agents such as sodium hydroxyethyl ethylenediamine acetate. The gelling co-agents of the present invention can be used with viscoelastic surfactant fluid systems containing said additives such as co-surfactants, organic acids, organic acid salts and / or inorganic salts. Surfactant agent in BET-O-30 (when n is 3 and p is 1) Surfactant agent in BET-E-40 (when n is 3 and p is 1) SDBS (when x is 11 and the counter-ion is Na +) Preferred configurations of the present invention utilize betaines; the most preferred configurations use BET-E-40. Although no experiments have been conducted in this regard, it is believed that mixtures of betaines, especially BET-E-40, with other surfactants are also suitable. Said mixtures are within the scope of the configurations of the invention. Other betaines that are suitable include those in which the alkene side chain (final group) contains from 17 to 23 carbon atoms (without counting the carbon atom of the carbonyl group) which can be straight or branched chain and which can be saturated or not saturated, "n" is from 2 to 10, and "p" is from 1 to 5, as well as mixtures of these compounds. The most preferred betaines are those in which the alkene side chain contains from 17 to 21 carbon atoms (without counting the carbon atom of the carbonyl group) which may be straight or branched chain and which may be saturated or unsaturated, " n "is from 3 to 5, and" p "is from 1 to 3, as well as mixtures of these compounds. The surfactants are used at a concentration of from about 0.5 to about 10%, preferably from about 1 to about %, and much more preferably from about 1.5 to about 4.5%. Exemplary cationic surfactants include the amine salts as well as the quaternary amine salts which are disclosed in U.S. Patent Nos. 5,979,557 and 6,435,277 which have the same assignee as that of the present application and which are incorporated herein by reference. to the present as a reference. Examples of suitable cationic viscoelastic surfactants include cationic surfactants having the structure: R2N + (R2) (R3) (R4) X "wherein Rx has from about 14 to about 26 carbon atoms and can be straight or branched chain , aromatic, saturated or unsaturated, and may contain a carbonyl, an amide, a retroamide, an imine, a urea, or an amine: R2, R3 and R4 are each independently hydrogen or an aliphatic group Cx up to about C6 which may be the same or different, of straight or branched chain, saturated or unsaturated and one or more of one of them may be substituted with a group that makes the group R2, R3 and R4 more hydrophilic; , R3 and R4 can be incorporated in a 5 or 6 element heterocyclic ring structure including the nitrogen atom, the groups R2, R3 and R4 can be the same, the groups Ri, R2, R3 and / or R4 can be contain one or more units of ethylene oxide and / or propylene oxide; and X "is an anion Mixtures of these compounds are also suitable As a further example, Rx is from about 18 to 22 carbon atoms and may contain a carbonyl, an amide or an amine, and R2, R3 and R4 are the same ones and others and contain from 1 to about 3 carbon atoms Cationic surfactants having the structure RXN + (R2) (R3) (R4) X "may optionally contain amines having the structure RaN (R2) (R3). It is well known that commercially available quaternary amine cationic surfactants often contain the corresponding amines (in which R 7 R 2 and R 3 in the cationic surfactant and in the amine have the same structure). Concentrate formulations of commercially available original ATV surfactants, for example the cationic ATV surfactant formulations, may also optionally contain one or more elements from the group consisting of solvents, mutual solvents, organic acids, salts of organic acids, inorganic salts and oligomers, polymers, co-polymers, as well as the mixtures of these elements. They may also contain performance enhancing agents, such as viscosity-improving agents, for example, polysulfonates, for example polysulfonic acids, as described in U.S. Patent Application Publication No. 2003-0134751 co-pending with the same assignee that the present application and which is incorporated herein by reference. Another suitable cationic ATV is bis (2-hydroxyethyl) methyl ammonium erucyl chloride, also known as (Z) -13 docosenyl-N, N-bis (2-hydroxyethyl) methyl ammonium chloride. It is commonly obtained from the manufacturers as a mixture containing about 60 weight percent surfactant in a mixture of isopropanol, ethylene glycol and water. Other suitable amine salts and quaternary amine salts include (either alone or in combination according to the invention), erucyl trimethyl ammonium chloride; N-methyl-N, N-bis (2-hydroxyethyl) rape seed of ammonium rapeseed; oleyl methyl bis (hydroxyethyl) ammonium chloride; erucilamidopropyltrimethylamine chloride, octadecyl methyl bis (hydroxyethyl) ammonium bromide; octadecyl tris (hydroxyethyl) ammonium bromide; octadecyl dimethyl hydroxyethyl ammonium bromide; cetyl dimethyl hydroxyethyl ammonium bromide; cetyl methyl bis salicylate (hydroxyethyl) ammonium; 3, 4-dichlorobenzoate of cetyl methyl bis (hydroxyethyl) ammonium; cetyl tris (hydroxyethyl) ammonium iodide; cosyl dimethyl hydroxyethyl ammonium bromide; cosyl methyl bis (hydroxyethyl) ammonium chloride; tris (hydroxyethyl) ammonium bromide; dicosyl dimethyl hydroxyethyl ammonium bromide; dicosyl methyl bis (hydroxyethyl) ammonium chloride; disocyl tris (hydroxyethyl) ammonium bromide; hexadecyl ethyl bis (hydroxyethyl) ammonium chloride; hexadecyl isopropyl bis (hydroxyethyl) ammonium iodide; and cetylamino, N-octadecyl pyridinium chloride. Amphoteric viscoelastic surfactants are also suitable. Exemplary amphoteric viscoelastic surfactant systems include those described in U.S. Patent No. 6,703,352, for example, amine oxides. Mixtures of zwitterionic surfactants and amphoteric surfactants are suitable. An example is a mixture of about 13% isopropanol, about 5% 1-butanol, about 15% ethylene glycol monobutyl ether, about 4% sodium chloride, about 30% water, about 30% cocoamidopropyl betaine , and approximately 2% cocoa oxide idopropylamine. Viscoelastic surfactant fluids, for example those used in oil fields, may also contain agents that dissolve minerals and compounds, for example in formations, crusts and filter cakes. Such agents can be, for example, acids and chelating agents, for example hydrochloric acid, formic acid, acetic acid, lactic acid, glycolic acid, sulphamic acid, malic acid, citric acid, maleic acid, methylsulfamic acid, chloroacetic acid, aminopolycarboxylic acids , 3-hydroxypropionic acid, polyamino-polycarboxylic acids, for example hydroxyethylethylenediamine trisodium triacetate, as well as the salts thereof and mixtures of these acids and / or salts. For sandstone treatment, the fluid also generally contains a source of hydrogen fluoride. The source of hydrogen fluoride can be FH itself or can be selected from ammonium fluoride and / or ammonium bifluoride or mixtures of the two; when strong acid is present the source of FH may also be one or more of polyvinylammonium fluoride, polyvinylpyridinium fluoride, pyridinium fluoride, imidazolinium fluoride, sodium tetrafluoroborate, ammonium tetrafluoroborate, hexafluoroantimony salts, fluoride-containing polymer, TEFLON ™ synthetic resinous, and blends. When the agent that dissolves the formation is a strong acid, preferably the fluid contains an agent that inhibits corrosion. The fluid optionally contains chelating agents for polyvalent cations, for example especially aluminum, calcium and iron (in which case the agents are often referred to as iron sequestering agents) to prevent their precipitation. Some of the agents that dissolve the training that have just been described are also chelating agents. The chelating agents are added at a concentration, for example, of about 0.5% (active ingredient). When ATV fluids contain strong acids, they typically do not form gels and show low viscosity; When the pH increases as the acid reacts with the mineral, the system forms gels as well as the viscosity increases. Said fluids can be referred to as viscoelastic derivative acids or ADV. The gelation coagents of the present invention can be used in viscoelastic surfactant fluid systems containing acids or other chelating agents. The preparation and use (mixing, storage, pumping, etc.) of the improved ATV fluid systems containing the co-gelling agents of the invention are the same for such fluids without the co-gelling agents. For example, the order of the mixture is not affected by the inclusion of these co-gelling agents. Optional, the co-gelling agents can be incorporated in concentrates of surfactants (with the proviso that they do not affect the solubilities of the component or the freezing points of the concentrate) so that the concentrates can be diluted with an aqueous fluid to form the ATV systems. This maintains the operational simplicity of the ATV systems. Such concentrates may contain other components such as agents that reduce the freezing point; the examples are methanol, ethanol, isopropanol, ethylene glycol and propylene glycol. As is normally the case in the formulation of fluids, laboratory tests must be run to ensure that the additives do not affect, and are not affected by, other components in the fluid (such as salts, for example). In particular, the co-gelling agents of the present invention can be used with other agents that modify the rheology. The adjustment of the concentrations of the surfactant, the co-gelling agent as well as the other components of the fluid to account for the effects of the other components is within the scope of the invention. The fluid can be used, for example, in treatments for oil fields. As examples, the fluid can be used as a sliding fluid and / or as a carrier fluid as a bypass fluid in hydraulic fractures, as a carrier fluid for flow control agents, as a carrier fluid for gravel filling, and as a bypass fluid or a major fluid in acidification and acid fracture. Fluids can also be used in other industries, such as pharmaceuticals, cosmetics, printing and agriculture. The optimum concentration of an additive of the invention since it improves the rheology for a given selection of ATV surfactant fluid systems at a given concentration and temperature, and given the presence of other materials, can be determined by means of simple experiments. The total concentration of viscoelastic surfactant should be sufficient to form a viscoelastic gel under conditions at which the surfactants have sufficient tendency to aggregation. The appropriate amounts of surfactant and co-gelling agent are those necessary to achieve the viscosity as well as the desired shear recovery time as determined by the experiment. Again, the tolerance as well as the optimum quantities of other additives can also be determined by means of simple experiments. In general, the amount of surfactant (as active ingredient) is from about 1 to about 10%. Commercially available surfactant concentrates may contain some materials which are themselves rheology improving agents, although they are present for example to reduce the freezing point of the concentrate, so that the amount of surfactant and co-agent of Gelation is determined by the specific concentrate used. Mixtures of surfactants and / or mixtures of co-gelling agents (including mixtures of more than one co-gelling agent of the invention, as well as mixtures of one or more co-gelling agents of the invention can be used. invention with one or more different co-gelling agents). Mixtures of surfactants may include surfactants that are not viscoelastic surfactants when they are not part of a viscoelastic surfactant system. All samples are tested and optimized; For example, too much co-agent total gelling can decrease the beneficial effects. Example 1: After the addition of a co-gelling agent to an ATV BET-O-40 system, a new fluid system was formed which proved to have good viscosity profiles even at a concentration of 2 to 3% ATV . (Results with ATV BET-O-40 at 3% are shown in Figure 1, although no experiments were conducted, it is believed that lower concentrations can be used). The original BET-O-40 ATV that was used in the experiments contained approximately 1% of a sodium polynaphthalene sulfonate (see below). The co-gelling agent used was an ABA type material of the formula 2 mentioned above with "x" and "z" being 12, and "y" being 32 as an example to demonstrate the effect. As shown in Figure 1, this BET-O-40 system formed a good fluid at a concentration of 6%. The decrease in the concentration of surfactant to 3% without a co-gelling agent caused the reduction of the viscosity of the fluid to a very low value at some temperatures. It is not shown that decreasing the concentration of the surfactant without a co-gelling agent also resulted in unacceptably long restoration times after severe shear stress. When very small amounts of the co-gelling agent were added to form a new fluid formulation, the new fluids had good viscosity profiles at an ATV concentration of 3%. It is not shown, either, that the viscosity was adequate at a concentration of 2%. Their shear recovery times were as good as those of an otherwise identical fluid made with 6% ATV and no co-gelling agent. Figure 1 gives the temperature and viscosity profiles of a series of fluids using varying concentrations of this ABA co-gelling agent. Fluids with the gelation coagent also contained approximately 0.12% of DAXAD 19, a high molecular weight sodium polynaphthalene sulfonate available from Hampshire Chemical Corporation, Nashua, NH, USA, and fluids without co-gelling agent contained approximately 0.03% (for the 3% ATV) and approximately 0.06% (for the 6% ATV) of DAXAD 17, a low molecular weight sodium polynaphthalene sulfonate available from Hampshire Chemical Corporation,? Ashua,? H , USA. Performance of the 3% ATV system without co-gelling agent was not acceptable for typical oilfield treatment fluids once the temperature rose to approximately above 66 ° C, while with the addition of 0.025%, 0.05% and 0.075 of the co-gelation agent ABA, the performance of the ATV fluid at 3% was greatly improved. In addition, if the 3% ATV system without co-gelling agent was subjected to shear under severe conditions, it took a long time (approximately 1 minute) for the fluid to restore its viscoelasticity. It is shown that sodium polynaphthalene sulfonate increased recovery times to shear, in some cases up to more than 10 minutes to recover. With the addition of 0.025% of the ABA chemical, the shear recovery times were reduced to only a few seconds. Example 2: Table 1 below shows the shear recovery times that were observed when various amounts of the ABA gelling agent of Example 1 were added to the ATV surfactant system of Example 1. In these experiments, approximately 200 mL of the ready mixed ATV fluid was subjected to shear stress at not less than 10,000 rpm for not less than 30 seconds and no more than 1 minute in a Waring 1 L mixer. The shear test was stopped and started to be taken time. The fluid was poured from one side to the other between a picudo glass and the cup of the mixer and the recovery of the fluid was characterized by the recovery time estimated by the visual observation. The recovery time of the fluid was the time at which the "formation of a flange" of fluid occurred. The fluid "forms a ridge" when the inclination of the upper part of the weighted vessel or cup containing the fluid does not result in the flow of fluid to the container below, but rather in the formation of a "ridge" and pulling back the container to a vertical apposition returns the "flange" to its position. In the practice of fracture fluids, "flange formation" is used to estimate when the fluid reaches its elasticity close to equilibrium. The fluids also contained examples of clay control agents that could be used in treatment fluids for oilfields; (CTMA is tetramethyl ammonium chloride).

Table 1 the Table shows that with the addition of very small amounts of an ABA three-block oligomer, the shear recovery of a 3% ATV fluid system can be as fast or faster than the shear recovery of a solution to 6% of the same ATV. Without the ABA three-block oligomer, the shear recovery of the 3% solution is at least 25 times slower than the shear recovery of the 6% ATV. The co-gelling agent used in these examples is sufficiently hydrophilic in that a concentrate can easily be made by adding sufficient co-surfactant to the original BET-40-E concentrate described above containing sodium polynaphthalene sulfonate, so that the concentrate can be diluted with an aqueous fluid to make the ATV systems similar to those of the example. This maintains the operational simplicity of the ATV systems.

Claims (11)

1. Claims: 1. An aqueous composition for the treatment of oilfields comprising a viscoelastic surfactant and a co-gelling agent characterized in that the co-gelling agent has the structure ABC or BAD, characterized in that A and B are linked by a ether bond or an ester bond, B and C are linked by an ether bond or an ester bond, A and D are linked by an ether bond or an ester bond, the two bonds in the co-agent of The gelling can be the same or different, A and C are linear or branched alkyl, saturated or unsaturated hydrophobic and can comprise one or more aromatic rings and can be the same or different and can contain amine, amide and ester groups, and B and D are hydrophilic and can be the same or different.
2. 2. The composition according to claim 1, characterized in that the co-gelling agent is H (CH2) x (0CH2CH2) and O (CH2) ZH, H (CH2) xCO (0CH2CH2) and OCO (CH2) ZH, HO (CH2CH20) ) x, CO (CH2) CO (OCH2CH2) zOH, or H0 (CH2CH20) x. (CH2) and. (OCH2CH2) ZOH # characterized in that "y" is from about 10 to about 50, preferably from about 24 to about 36; "y '" is from about 4 to about 50, preferably from about 6 to about 24; "x" and "z" are from about 6 to about 22, preferably from about 8 to about 16, "x" and "z" 'are from about 1 to about 50, preferably from about 3 to about 40 and further characterized in that the values of "x" and "z", as well as "x" 'and "z"', can be the same.
3. 3. The composition according to Claim 1 or Claim 2 characterized in that said surfactant comprises a zwitterionic surfactant or mixture of zwitterionic surfactants having the formula: RCONH- (CH2) a (CH2CH20) m (CH2) b-N + ( CH3) 2- (CH2) a- (CH2CH20) m, (CH2) b.C00"characterized in that R is an alkyl group containing from about 17 to about 23 carbon atoms which may be straight or branched chain and which may be be saturated or unsaturated, "a", "b", "a" 'and "b"' are each from 0 to 10 and "m" and "m" are each from 0 to 13, "a" and "b" are each 1 or 2 if "m" is not 0, and, (a + b) is from 2 to 10 if m is 0; "a" 'and "b"' are each 1 or 2 when "m '" is not 0, y, (a' + b ') is from 1 to 5 if m' is 0; (m + m ') is from 0 to 14, and CH2CH20 can also be 0CH2CH2. composition according to claim 3 characterized in that said zwitterionic surfactant It has the structure of betaine: characterized in that R is a hydrocarbyl group which may be straight or branched chain, aromatic, aliphatic or olefinic and has from about 14 to about 26 carbon atoms and may contain an amine; "n" is from about 2 to about 4; and "P" is from 1 to about 5, as well as mixtures of these compounds. The composition according to Claim 1 or Claim 2 characterized in that said surfactant comprises a cationic surfactant or mixture of surfactants having the structure: RXNAR2) (RS) (R4) X "characterized in that 2 has from about 14 to about 26 carbon atoms and can be straight or branched chain, aromatic, saturated or unsaturated, and can comprise a carbonyl, an amide, a retroamide, an imine, a urea, or an amine; R2, R3 and R4 are each independently hydrogen or an aliphatic Ca group up to about C6 which may be the same or different, straight or branched chain, saturated or unsaturated and one or more of one of them can be substituted with a group that makes that the group R2, R3 and R4 are more hydrophilic, the R2, R-3 and R-4 groups can be incorporated into a 5- or 6-membered heterocyclic ring structure that includes the nitrogen atom; the groups R2, R3 and R4 may be the same different; the groups Rlf R2, R3 and / or R4 may contain one or more units of ethylene oxide and / or propylene oxide; and X "is an anion, as well as mixtures of these compounds 6. The composition according to Claim 5 characterized in that said surfactant further comprises an amine having the structure: R? N (R2) (R3) characterized in that Ri, R2 and R3 are as defined in Claim 5. The composition according to any of the preceding Claims further comprising an acid selected from the group consisting of hydrochloric acid, hydrofluoric acid, formic acid, acetic acid, lactic acid, glycolic acid, sulphamic acid, malic acid, citric acid, tartaric acid, maleic acid, methylsulfamic acid, chloroacetic acid, as well as mixtures of these acids 8. A concentrate for addition to an aqueous fluid to form a fluid viscoelastic, the concentrate comprises an agent that reduces the freezing point, less than about 60% water, a co-gelling agent as described in Claim 1, and a viscoelastic surfactant. 9. The composition according to any of the preceding Claims further comprising a polynaphthalene sulfonate. 10. A method for shortening the recovery time to the shear stress of a viscoelastic surfactant based on a fluid comprising: a. providing a fluid comprising a viscoelastic surfactant, and b. mixing with said fluid a co-gelling agent in a sufficient concentration to shorten the recovery time to shear of said fluid, said co-gelling agent has an ABC or BAD structure, characterized in that A and B are linked by a bond of ether or an ester bond, B and C are linked by an ether bond or an ester bond, A and D are linked by an ether bond or an ester bond, the two bonds in the co-gelling agent they may be the same or different, A and C are straight or branched chain alkyl, saturated or unsaturated, hydrophobic and may comprise one or more aromatic rings and may be the same or different and may contain amine, amide and ester groups, and B and D are hydrophilic and can be the same or different. 11. A method for the treatment of oilfields that includes: a. providing a fluid containing a viscoelastic surfactant and a co-gelling agent having an ABC or BAD structure, characterized in that A and B are linked by an ether bond or an ester bond, B and C are linked by a bond of ether or an ester bond, A and D are linked by an ether bond or an ester bond, the two bonds in the co-gelling agent may be the same or different, A and C are straight chain alkyl or branched, saturated or unsaturated, hydrophobic and may comprise one or more aromatic rings and may be the same or different and may contain amine, amide and ester groups, and B and D are hydrophilic and may be the same or different, and b. Inject the fluid into a well.