MX2011002754A - Compositions and methods for hindering asphaltene deposition. - Google Patents

Abstract

Methods and compositions for hindering asphaltene deposition. One method comprising: identifying an interval of the subterranean formation to be treated with a relative permeability modifier to hinder subsequent asphaltene deposition; introducing the relative permeability modifier into the subterranean formation; and allowing the relative permeability modifier to contact the interval, thereby attaching to surfaces within the subterranean formation and hindering subsequent asphaltene deposition.

Description

COMPOSITIONS AND METHODS TO PREVENT THE DEPOSIT OF ASPHALT FIELD OF THE INVENTION The present invention relates to underground treatments and more particularly, in one or more embodiments, to introduce a relative permeability modifier in an underground interval, optionally in conjunction with an asphaltene solvent system, to prevent the deposition of asphaltenes.

BACKGROUND OF THE INVENTION The formation of asphaltene deposits can be a problem in the production of crude oil. The precipitation and deposit of asphaltenes can cause problems such as loss of production due to asphaltenes plugging the pipe, perforations, and portions of the underground formation. As used in this description, the term "asphaltene" refers to organic material that can be found in hydrocarbon deposits (eg, petroleum, crude oil) and which generally comprises waxes and / or aromatic and naphthenic ring compounds. Asphaltenes can be found in crude oil in the form of colloidal, suspended, solid particles. Asphaltenes can be characterized by their insolubility in solvents of light paraffinic hydrocarbons. These compounds can typically have high molecular weights and can be polar materials due to the sulfur, nitrogen, oxygen atoms, and complex metals can be present in their structures.

The deposit of asphaltenes can occur when crude oil loses its ability to disperse and stabilize the asphaltene particles. The stability of the asphaltenes may depend on factors such as the composition of the crude oil, temperature, pressure, and the nature of the rock surface of the deposit (for example wettability of the rock). Under conditions of static deposition, asphaltenes can be maintained in a stable suspension by resins, a family of polar molecules. Changes in fluid temperature and pressure that may be associated with oil production from the reservoir may cause the asphaltenes to flocculate and precipitate from the suspension and adsorb to the rock or tube surfaces. Additionally, asphaltenes can flocculate due to the electrical charges created by the movement of the flowing hydrocarbons. The deposit of asphaltenes can occur at any time during the production life cycle.

Despite the mechanism that causes the deposition of asphaltene, the result can be a plug-in effect that inhibits or reduces oil production. Traditional methods for removing asphaltene deposits may include heat, mechanical removal, dispersants and / or solvents. The most common means of transmitting heat to the bottom of the passage is hot lubrication. While hot greasing has been a popular method for the removal of paraffin, the process can cause significant damage to the formation particularly when there are asphaltenes present in the underground formation. Mechanical removal techniques include scrapers, cutters, and jet tool deployed in spiral pipe. Mechanical removal has the limitation of not being able to remove damage to the formation outside of the perforations. Dispersing systems do not dissolve asphaltenes; rather they scatter the particles so that they can be circulated from the perforation.

The solvents most frequently used for the cleaning of asphaltenes are toluene and xylene. Cleaning with pure toluene can remove most of the asphaltenes but the surface in which the asphaltenes are adsorbed can still be covered with a layer of asphaltenes and / or remain impregnated with petroleum. Xylene or xylene mixtures may have limited effectiveness in addition to undesirable characteristics to health, safety and the environment. Other problems associated with asphaltene solvent systems are that as the solvent removes the asphaltenes, losses can occur in the rock matrix. As losses begin, several problems may arise that include, losses can be easily focused on their areas, making complete coverage of solvents difficult, losses can occur too quickly and solvent systems may not have the likelihood of completely dissolving asphaltenes of perforation, and dissolved asphaltenes can be carried beyond the matrix. In addition, even after the effective treatment of removal of asphaltenes, the deposit of asphaltenes needing a future remedy can continue.

SUMMARY OF THE INVENTION The present invention relates to underground treatments and more particularly in one or more embodiments, to introduce a relative permeability modifier in an underground interval, optionally in conjunction with a solvent system of asphaltenes, to prevent the deposition of asphaltenes.

In one embodiment, the present invention provides a method for preventing the deposition of asphaltenes comprising: identifying a range of the subterranean formation to be treated with a relative permeability modifier to prevent the subsequent deposition of asphaltenes; introduce the relative permeability modifier in the underground formation; and allowing the relative permeability modifier to make contact with the gap, thereby joining the surfaces within the underground formation and preventing the subsequent deposition of asphaltene.

In another embodiment, the present invention provides a method for removing asphaltenes and preventing the subsequent deposition of asphaltenes in an underground formation comprising: introducing a fluid comprising a relative permeability modifier and an asphaltene solvent system in the underground formation; and allowing the fluid to make contact with a portion of the underground portion, wherein the asphaltene solvent system removes at least a portion of an asphaltene in the portion of the underground formation, and wherein the relative permeability modifier prevents the deposit Subsequent asphaltene in the portion of the underground formation.

In yet another embodiment, the present invention provides a method for removing asphaltenes and preventing the subsequent deposition of asphaltenes in an underground formation comprising: introducing a permeability modifying fluid into a perforation penetrating an underground formation, wherein the permeability modifying fluid comprises a relative permeability modifier; allowing at least a portion of the permeation modifying fluid to penetrate a portion of the subterranean formation so that the relative permeability modifier present in the portion of the underground formation substantially deviates the aqueous fluids subsequently introduced to less permeable portions in the underground formation , wherein the relative permeability modifier in the portion of the underground formation prevents the subsequent deposition of asphaltenes; introducing an asphaltene solvent system into a hole to remove the asphaltenes in the underground formation where the relative permeability modifier present in the portion of the underground formation diverts the asphaltene solvent system to a less permeable portion of the underground formation.

The features and advantages of the present invention will be readily apparent to those skilled in the art. While numerous changes can be made by those skilled in the art, these changes are within the spirit of the invention.

DESCRIPTION OF THE PREFERRED MODALITIES The present invention relates to underground treatments and more particularly, in one or more embodiments, to introduce a relative permeability modifier in an underground interval, optionally in conjunction with an asphaltene solvent system, to reduce the deposit of asphaltenes.

The embodiments of the present invention relate to the use of a relative permeability modifier (eg, hydrophobically modified, water-soluble polymers), and optionally an asphaltene solvent system, to treat a range of an underground formation. As used in this description, the term "relative permeability modifier" refers to a polymer that selectively reduces the effective permeability of an underground formation to water-based fluids. According to embodiments of the present invention, the relative permeability modifier can form a film on a surface of the perforation in the range of the underground formation, thereby decreasing the water permeability by indefinitely increasing the stability of the water film. It is believed that the water film should prevent the deposit of asphaltenes. Additionally, the relative permeability modifier can also be used to divert asphaltene solvent systems, for example, to less permeable portions of the formation. Otherwise, the asphaltene solvent system may preferentially introduce portions of the high permeability range at the expense of portions of the interval with lower permeability. Additionally, the relative permeability modifier and the asphaltene solvent system can be introduced simultaneously into the underground formation. As desired, the embodiments of the present invention can use relative permeability modifiers, for example, to alleviate the need to use multiple asphaltene removal treatments.

I. Example Methods.- Treatment of interval of formation A. Example treatments with Modifiers of Relative Permeability The compositions described herein can be used to treat a range of a subterranean formation penetrated by a perforation. The range may have a range that has been identified for treatment with a relative permeability modifier to prevent deposition of asphaltenes, in accordance with the present embodiments. As will be appreciated by those skilled in the art, with the benefits of this disclosure, the range can be any range of an underground formation suitable for treatment. In addition, as will be appreciated by those skilled in the art, with the benefit of this disclosure, the embodiments of the present invention may be applicable for the treatment of both production and injection wells. Additionally, the embodiments of the present invention may also be suitable for sheathed boreholes or openhole boreholes.

The range identified for treatment may comprise a range that is previously treated with a method of removing asphaltenes. For example, the interval may have been treated with an asphaltene system removal system comprising heat, mechanical removal, a dispersant, a solvent. Alternatively, the interval may have not been treated with an asphaltene removal system.

In accordance with the embodiments of the present invention, the range can be contacted with a relative permeability modifier (e.g., a hydrophobically modified, water soluble polymer). In some embodiments, for the contacting of the interval with the relative permeability modifier, the relative permeability modifier may be present in a permeation modifying fluid introduced in the range. The treatment fluids comprising the relative permeability modifier will be referred to herein as "permeability modifying fluids". In some embodiments, the near perforation portion of the gap is contacted with the relative permeability modifier. Those skilled in the art will understand that the "near perforation portion" of a formation generally refers to the portion of an underground formation surrounding a perforation. For example, the "near perforation portion" can refer to the portion of the formation surrounding a perforation and having a penetration depth of about 1 to about 3 perforation diameters. In certain embodiments, the "near perforation portion" may refer to the portion of the formation that surrounds a perforation in the range of about 9.14 meters (30 feet) to about 15.24 meters (50 feet).

In general, the relative permeability modifier can be attached to rock surfaces present in the range and should increase the stability of the water film on rock surfaces by increasing water retention. While it is not desired to be limited by theory, it is believed that a considerable reduction in the adsorbed asphaltenes is observed, because the increased stability of the water film on the rock surfaces helps to reduce the adsorption rate of asphaltenes. and the presence of the relative permeability modifier reduces the surface availability of the asphaltene particles that are adsorbed. Accordingly, it is believed that the proportion of asphaltene deposit in the range can be reduced for the most part when production begins.

In certain embodiments, the contact of the gap with the relative permeability modifier must be controlled so that the flow of fluids (eg, aqueous fluids) across the range is not substantially impeded after treatment with the relative permeability modifier. . To substantially reduce the flow of fluids through an interval after treatment, the contact of the interval can be stopped with the relative permeability modifier, if the injection pressure increases to 90% of the anticipated fracture gradient, and any subsequent fluid to be injected at the interval can be "stained" before continuing the injection in the interval. In certain embodiments, the effective permeability of the water range should be at least about 1% to about 80% of its pre-treatment injectability index (injection rate divided by injection pressure), alternatively, about 30% to approximately 40%. In certain embodiments, the interval may retain sufficient water permeability to allow injection of water at a rate of about 1/4 barrel per minute (approximately 10 gallons / minute). Examples of relative permeability modifiers suitable for use in the embodiments of the present invention are described in more detail below.

Any suitable technique can be used for the introduction of the permeation modifying fluid in the range, for example, forced pumping, spiral piping, pipe joining (for example, with mounted packers, precise injection tools, etc.) or can be used any other suitable technique. It should be noted that, in order to reduce the potential for undesired fracturing of the range, the permeability modifying fluid must be introduced in the range at flow rates of the matrix. Exemplary flow rates for the permeability modifier fluid are in the range of about 0.25 barrels to about 3 barrels per minute. However, those skilled in the art will appreciate that these flow rates are only examples, and the embodiments of the present invention are applicable at flow rates outside these ranges. Furthermore, as discussed above, in certain embodiments, the contacting of the interval with the relative permeability modifier must be controlled so that the effective patency of the interval is not undesirably reduced. For example, the pressure of the permeability modifying fluid can be monitored as it is entered into the range. As the effective water permeability of the range decreases, due to the relative permeability modifier, there must be an increase in the pressure of the permeability modifying fluid. Therefore, this pressure can be monitored so that the permeability of the interval is not undesirably reduced to allow subsequent treatment of the interval. Other suitable techniques can also be used to monitor the interval permeability.

B. Example Treatments with Relative Permeability Modifiers and Asphaltene Solvent Systems The compositions described herein can be used for the dispersion of aqueous fluids in a variety of underground operations, such as in asphaltene removal operations. In some embodiments, the methods may comprise: introducing a permeability modifying liquid into a perforation that penetrates an underground formation, wherein the permeability modifying fluid comprises a relative permeability modifier; allowing at least a portion of the permeation modifying fluid to penetrate a portion of the subterranean formation so that the relative permeability modifier present in the portion of the subterranean formation substantially deviates the aqueous fluids subsequently introduced to less permeable portions of the underground formation , where the relative permeability modifier in the portion of the underground formation prevents the subsequent deposition of asphaltenes; and introducing an asphaltene solvent system into the drilling to remove the asphaltenes in the underground formation, where the relative permeability modifier present in the underground formation portion diverts the asphaltene solvent system to a less permeable portion of the formation underground In certain embodiments, the methods may comprise: introducing a permeability modifying fluid into a perforation that penetrates an underground formation, wherein the permeability modifying fluid comprises a relative permeability modifier and an asphaltene solvent system; allowing at least a portion of the permeation modifying fluid to penetrate an underground formation portion so that the relative permeability modifier present in the portion of the underground formation substantially deviates the aqueous fluids subsequently introduced to less permeable portions of the underground formation in so much that it increases the wettability to water of the formation.

It is believed that the relative permeability modifiers bind to surfaces within the porosity of the portion of the underground formation. Among other things, the presence of the relative permeability modifier in the portion of the underground formation must reduce the permeability thereof to aqueous fluids without substantially changing their permeability to hydrocarbons. Due to the reduction in the permeability of the portion of the underground formation, any aqueous fluid subsequently introduced into the bore must be substantially diverted to another portion of the underground formation. Additionally, the relative permeability modifiers can also act to reduce the subsequent problems associated with the water flowing in the borehole from the underground formation. In some embodiments, the relative permeability modifier may be mixed with an aqueous fluid and introduced into a portion of the underground formation between the stages of a treatment or as a pretreatment. In some embodiments, the asphaltene solvent systems of the present invention can be self-diverters. For example, in some embodiments, the relative permeability modifier may be included in the asphaltene solvent system during the underground treatment. In these embodiments, the relative permeability modifier can be progressively diverted to the asphaltene solvent system to another portion of the underground formation. For example, in some embodiments, as a portion of the asphaltene solvent system penetrates a portion of the underground formation, a second portion of the asphaltene solvent system can be diverted to another portion of the underground formation.

In asphaltene removal operations, in some embodiments, a permeability modifying fluid of the present invention can be introduced into the underground formation between the steps of the asphaltene removal operation, as a pretreatment, or as a combination thereof. For example, when the asphaltene removal operation is carried out in stages, in the first step an asphaltene solvent system can be introduced into a portion of the underground formation, followed by a permeability modifying fluid of the present invention. The relative permeability modifier present in the particular permeability modifier fluid of the present invention to reduce the permeability of the portion of the underground formation to aqueous fluids. The second stage of the asphaltene removal operation can then be diverted subsequently to another portion of the underground formation. The alternating steps of the asphaltene solvent system and the permeability modifying fluid of the present invention can be continued as desired. In other embodiments, the permeability modifying fluids of the present invention can be used as a pre-treatment. For example, a permeability modifying fluid of the present invention can be introduced into a portion of the subterranean formation, wherein the relative permeability modifier present in a permeability modifying fluid of the present invention reduces the permeability of the formation portion. underground to aqueous fluids. A system of asphaltene solvent introduced into the bore after pre-treatment, such as an asphaltene solvent system, can be substantially diverted to another portion of the underground formation.

II. Example Relative Permeability Modifiers As described above, a relative permeability modifier may be introduced in at least a portion of an underground formation, according to certain modalities. In general, suitable relative permeability modifiers can be any of a variety of compounds that are capable of selectively reducing the effective permeability of a formation to water-based fluids without a comparable reduction in the effective permeability of the formation to the hydrocarbons. . Suitable relative permeability modifiers generally include water-soluble polymers that bind to surfaces within the formation, reduce water permeability without a comparable reduction in hydrocarbon permeability. As used herein, "water soluble" refers to at least about 0.0001 weight percent soluble in water. In certain embodiments, the water soluble polymer is at least about 0.45 weight percent soluble in distilled water at room temperature. In certain embodiments, the water soluble polymer is at least about 0.6 weight percent soluble in distilled water at room temperature.

Those skilled in the art, with the benefit of this disclosure, will appreciate that a variety of different water-soluble polymers may be suitable for use as the relative permeability modifiers. Examples of suitable water-soluble polymers include, but are not limited to, homo-, co-, and ter-polymers of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, N, N-dimethylacrylamide, vinyl- pyrrolidone, dimethylaminoethyl methacrylate, acrylic acid, dimethylaminopropylmethacrylamide, vinyl amine, vinyl acetate, trimethylammoniomethyl methacrylate chloride, methacrylamide, hydroxyethyl acrylate, vinyl sulphonic acid, vinyl phosphonic acid, methacrylic acid, vinyl caprolactam, N- vinylformamide,?,? - diallylacetamide, dimethyldiallylammonium halide, itaconic acid, styrene-sulfonic acid, methacrylamidoethyltrimethylammonium halide, quaternary salt derivatives of acrylamide salt of quaternary salt of acrylic acid, and combinations thereof In addition, water-soluble polymers suitable for use as relative permeability modifiers may also include hydrophobically modified polymers. As used herein, the terms "hydrophobically modified", "hydrophobic modification" and the like refer to the incorporation into the hydrophilic structure of the polymer of hydrophobic groups, wherein the length of the alkyl chain is from about 4 to about 22 carbons. While these hydrophobically modified polymers have hydrophobic groups incorporated in the hydrophilic structure of the polymer, they must remain soluble in water. In some embodiments, a molar ratio of a hydrophobic monomer to the hydrophobic compound in the hydrophobically modified polymer is in the range of about 99.98: 0.02 to about 90:10, wherein the hydrophilic monomer is a calculated amount present in the hydrophilic polymer. In certain embodiments, the hydrophobically modified polymers may comprise a polymer structure comprising polar heteroatoms. In general, polar heteroatoms present within the polymer structure of the hydrophobically modified polymers include, but are not limited to, oxygen, nitrogen, sulfur or phosphorus.

Exemplary hydrophobically modified polymers may contain a hydrophilic polymer structure and a hydrophobic branch, wherein the hydrophobic branch includes an alkyl chain of about 4 to about 22 carbons, in certain embodiments, the hydrophobic branch may have a chain length of alkyl from about 7 to about 22 carbons. In certain embodiments, the hydrophobic branch can have an alkyl chain length of about 12 to about 18 carbons.

Additional examples of suitable hydrophobically modified polymers include a polymer that has been hydrophobically modified with an alkyl group present in an amino group (in the polymer structure or as a pendant group) in quaternized form. For example, an alkyl group may be present in a pendant dialkyl amino group in quaternized form. In one embodiment, the alkylamino pendant group comprises a pendant dimethylamino group. A specific example of a hydrophobically modified polymer includes a polydimethylaminoethyl methacrylate or polydimethylaminopropyl methacrylamide which has been hydrophobically modified with an alkyl group with 4 carbons at 22 carbons (eg, 4 carbons, 6 carbons, 8 carbons, 10 carbons, 12 carbons, carbons, 16 carbons, 18 carbons, 20 carbons, 22 carbons, etc.) in a dimethylamino group. An example of a suitable hydrophobically modified polymer is HPT-1MR relative permeability modifying polymer available from Halliburton Energy Services, Inc., Duncan, Oklahoma.

Examples of suitable hydrophobically modified polymers that may be used include, but are not limited to, acrylamide / octadecyldimethylammonium methyl methacrylate bromide, dimethylaminoethyl methacrylate / vinyl pyrrolidone terpolymer / hexadecyldimethylammonium methyl methacrylate bromide, and terpolymer acrylamide / 2-acrylamido-2-methyl-propan-sulphonic acid / 2-ethylhexyl methacrylate. Another example of a suitable hydrophobically modified polymer comprises an amino-methacrylate / alkyl-amino-methacrylate copolymer. An example of a suitable amino-methacrylate / alkyl-amino-methacrylate copolymer includes a copolymer of dimethylaminoethyl-methacrylate / alkyl-diethylammonium-methyl-methacrylate. An example of a suitable copolymer of dimethylaminoethyl methacrylate / alkyl-dimethylammoniomethyl-methacrylate includes a copolymer of dimethylaminoethyl methacrylate / hexadecyl-dimethylammoniomethyl-methacrylate. As discussed in more detail below, these copolymers can be formed, in embodiments, by reactions with a variety of alkyl halide. For example, in some embodiments, the hydrophobically modified polymer may comprise a copolymer of dimethylaminoethyl methacrylate / hexadecyl-dimethylammoniomethyl methacrylate bromide.

The hydrophobically modified polymers of examples can be synthesized using any suitable technique. For example, the hydrophobically modified polymers can be a reaction product of a reaction comprising a hydrophilic polymer and a hydrophobic compound. By way of further example, the hydrophobically modified polymers can be prepared from a polymerization reaction comprising a hydrophilic monomer and a hydrophobically modified hydrophilic monomer. In certain embodiments, the hydrophobically modified polymers can be pre-reacted before they are placed in the perforation. Alternatively, in some embodiments, the hydrophobically modified polymers can be prepared by an appropriate in situ reaction. Suitable hydrophobically modified polymers and methods for their preparation are described in more in more detail in U.S. Patent Nos. 6,476,169 and 7,117,942, the disclosures of which are incorporated herein by reference. Those skilled in the art, with the benefit of this disclosure, will be able to determine other suitable methods for the synthesis of hydrophobically modified polymers, suitable.

In certain embodiments, suitable hydrophobically modified polymers can be synthesized by the hydrophobic modification of a hydrophilic polymer by reaction with a hydrophobic compound. As described above, the hydrophobic modification refers to the incorporation into the hydrophilic polymer structure of hydrophobic groups, wherein the alkyl chain length is from about 4 to about 22 carbons. Suitable hydrophilic polymers for forming the hydrophobically modified polymers used in the present invention must be capable of reacting with hydrophobic compounds. Suitable hydrophilic polymers include homo-, co-, or terpolymers such as, but not limited to, polyacrylamides, polyvinylamines, poly (vinyl amines / vinyl alcohols), alkyl acrylate polymers in general, and combinations thereof. Additional examples of the alkyl acrylate polymers include polydimethylaminoethyl methacrylate, polydimethylaminopropyl methacrylamide, poly (acrylamide / dimethylaminoethyl methacrylate), poly (methacrylic acid / dimethylaminoethyl methacrylate), poly (2-acrylamido-2-methyl-propane) -sulfonic / dimethylaminoethyl methacrylate), poly (acrylamide / dimethylaminopropyl methacrylamide), poly (acrylic acid / dimethylaminopropyl-methacrylamide), poly (methacrylic acid / dimethylaminopropyl-methacrylamide), and combinations thereof. In certain embodiments, the hydrophilic polymers comprise a polymer structure and amino reactive groups in the polymer structure or as pendant groups, the amino reactive groups capable of reacting with hydrophobic compounds. In some embodiments, the hydrophilic polymers comprise pendant dialkyl amino groups. In some embodiments, the hydrophilic polymers comprise a pendant dimethylamino group and a monomer comprising dimethylaminoethyl methacrylate or dimethylaminopropyl methacrylamide. In certain embodiments, the hydrophilic polymers comprise polymer structure comprising polar heteroatoms, wherein the polar heteroatoms present within the polymer structure of the hydrophilic polymers include oxygen, nitrogen, sulfur or phosphorus. Suitable hydrophilic polymers comprising polar heteroatoms within the polymer structure include homo-, co-, or ter-polymers, such as, but not limited to, celluloses, chitosan, polyamides, polyether amines, polyethylene imines, polyhydroxy-erieteramines, polylysines, polysulfones , gums, starches, and combinations thereof. In one embodiment, the starch is a cationic starch. A suitable cationic starch can be formed by reacting a starch, such as corn, abatí, waxy maize, potato, tapioca or the like, with the reaction product of epichlorohydrin and trialkylamine.

Hydrophobic compounds that are capable of reacting with the hydrophilic polymers include alkyl halides, sulfonates, sulfates, organic acids, and organic acid derivatives. Examples of suitable organic acids and derivatives thereof include, but are not limited to, octenyl succinic acid; dodecenyl succinic acid; and anhydrides, esters, imides, and amides of octenyl-succinic acid or dodecenyl-succinic acid. In certain embodiments, the hydrophobic compounds may have an alkyl chain length of from about 4 to about 22 carbons. In another embodiment, the hydrophobic compounds may have an alkyl chain length of from about 7 to about 22 carbons. In another embodiment, the hydrophobic beads can have an alkyl chain length of about 12 to about 18 carbons. For example, where the hydrophobic compound is an alkyl halide, the reaction between the hydrophobic compound and the hydrophilic polymer can result in the quaternization of some of the amino groups of the hydrophilic polymer with an alkyl halide, wherein the alkyl chain length is from about 4 to about 22 carbons.

As mentioned above, in certain embodiments, suitable hydrophobically modified polymers can also be prepared from a polymerization reaction comprising a hydrophilic monomer and a hydrophobically modified hydrophilic monomer. The hydrophobically modified polymers synthesized from the polymerization reactions can have molecular weights estimated in the range of about 100,000 to about 10,000,000 and molar ratios of the hydrophilic monomers to the hydrophobicly modified hydrophilic monomers in the range of about 99.98: 0.02 to about 90. -.10.

A variety of hydrophilic monomers can be used to form the hydrophobically modified polymers useful in the present invention. Examples of suitable hydrophilic monomers include, but are not limited to, acrylamide, 2-acrylamido-2-metpropanesulfonic acid, N, -dimetcrylamide, vinyl-pyrrolidone, dimetminoetmethacrylate, acrylic acid, dimetminopropylmethacrylamide, vinyl-amine , vinyl acetate, trimetmmoniometmethacrylate chloride, methacrylamide, hydroxyetacrylate, vinyl sulphonic acid, vinyl phosphonic acid, methacrylic acid, vinyl caprolactam, N-vinylformamide, N, N-diallylacetamide, dimetiallylammonium halide, itaconic acid, styrene-sulfonic acid, methacrylamidoetrimetammonium halide, quaternary acrylamide salt derivatives, quaternary salt of acrylic acid derivatives, and combinations thereof.

A variety of hydrophilic, hydrophobically modified monomers can also be used to form the hydrophobically modified polymers useful in certain embodiments. Examples of suitable hydrophilic, hydrophobically modified monomers include, but are not limited to, alkyl acrylates, alkyl methacrylates, alkyl-acrylamides, alkyl-methacrylamides, alkyl-dimetmmonium-etmethacrylate halides, and alkyl-dimetmmonium propyl halides. -methacrylamide, wherein the alkyl groups have from about 4 to about 22 carbon atoms. In another embodiment, the alkyl groups have from about 7 to about 22 carbons. In another embodiment, the alkyl groups have from about 12 to about 18 carbons. In certain embodiments, the hydrophobic, hydrophobically modified hydrophilic monomer comprises octadecyldimetmmoniometmethacrylate bromide, hexadecyldimetmmoniometmethacrylate bromide, hexadecyldimetmmonium propyl methacrylamide bromide, 2-etexyl methacrylate, or hexadecyl-methacrylamide.

In addition, water-soluble polymers suitable for use as relative permeability modifiers may also include hydrophilically modified polymers. As used in this description, the terms "hydrophilic modification", "hydrophilically modified", and the like refer to the incorporation in the hydrophilic polymer structure of hydrophilic groups, such as introducing branching or increasing the degree of branching in the hydrophilic polymer. The hydrophilically modified polymers of certain embodiments typically have molecular weights in the range of about 100,000 to about 10,000,000. In certain embodiments, the hydrophilically modified polymers comprise a polymer structure, the polymer structure comprising polar heteroatoms. In general, polar heteroatoms present within the polymer structure of the hydrophilically modified polymers include, but are not limited to, oxygen, nitrogen, sulfur or phosphorus.

The hydrophilically modified polymers can be synthesized using any suitable method. In one example, the hydrophilically modified polymers can be a reaction product of a hydrophilic polymer and a hydrophilic compound. In certain embodiments, suitable hydrophilically modified polymers can be formed by additional hydrophilic modification, for example, to introduce branching or to increase the degree of branching, of a hydrophilic polymer. Those skilled in the art, with the benefit of this disclosure, will be able to determine other suitable methods for the preparation of suitable hydrophilically modified polymers.

Suitable hydrophilic polymers for forming the hydrophilically modified polymers used in certain embodiments must be capable of reacting with hydrophilic compounds. In certain embodiments, suitable hydrophilic polymers include, homo-, co-, or ter-polymers, such as, but not limited to, polyacrylamides, polyvinylamines, poly (vinylamines / vinyl alcohols), and in general alkyl acrylate polymers . Additional examples of alkyl acrylate polymers include, but are not limited to, polydimethylaminoethyl-methacrylate, polydimethylaminopropyl-methacrylamide, poly (acrylamide / dimethylaminoethyl-methacrylate), poly (methacrylic acid / dimethylaminoethyl-methacrylate), poly (2-acrylamido- 2-methyl-propanesulfonic acid / dimethylaminoethyl methacrylate), poly (acrylamide / dimethylaminopropyl-methacrylamide), poly (acrylic acid / dimethylaminopropyl-methacrylamide), and poly (methacrylic acid / dimethylaminopropyl-methacrylamide). In certain embodiments, the hydrophilic polymers comprise a polymer structure and amino reactive groups in the polymer structure or as pendant groups, the amino reactive groups capable of reacting with hydrophilic compounds. In some embodiments, the hydrophilic polymers comprise pendant dialkylamino groups. In some embodiments, the hydrophilic polymers comprise a pendant dimethylamino group and at least one monomer comprising dimethylaminoethyl methacrylate or dimethylaminopropyl methacrylamide. In other embodiments, the hydrophilic polymers comprise a polymer structure comprising polar heteroatoms, wherein the polar heteroatoms present within the polymer structure of the hydrophilic polymers include, but are not limited to, oxygen, nitrogen, sulfur or phosphorus. Suitable hydrophilic polymers comprising polar heteroatoms within the polymer structure include homo-, co-, or ter-polymers, such as, but not limited to, celluloses, chitosans, polyamides, polyetheramines, polyethyleneimines, polyhydroxyetheramines, polylysines, polysulfones, gums, starches, and derivatives thereof. In one embodiment, the starch is a cationic starch. A suitable cationic starch can be formed by reacting a starch, such as corn, abatí, waxy maize, potato, tapioca and the like, with the reaction product of epichlorohydrin and trialkylamine.

Suitable hydrophilic compounds for reaction with hydrophilic polymers include, but are not limited to: polyethers comprising halogens, sulphonates sulfates; organic acids; and derivatives of organic acids. Examples of suitable polyethers include, but are not limited to, polyoxyethylene oxides, polypropylene oxides, and polybutylene oxides, and copolymers, terpolymers, and mixtures thereof. In some embodiments, the polyether comprises a methyl ether of polyethylene oxide terminated with epichlorohydrin.

The hydrophilically modified polymers formed from the reaction of a hydrophilic polymer with a hydrophilic compound can have molecular weights estimated in the range of about 100,000 to about 10,000,000 and can have weight ratios of the hydrophilic polymers to the polyethers in the range of about 1. : 1 to about 10: 1. Examples of suitable hydrophilically modified ones having molecular weights and weight ratios in the ranges set forth above include, but are not limited to, the reaction product of polydimethylaminoethyl methacrylate and polyethylene methyl ether terminated with epichlorohydrin; the reaction product of polydimethylaminopropyl-methacrylamide and methyl ether of polyethylene oxide terminated with epichlorohydrin; and the reaction product of poly (acrylamide / dimethylaminopropyl-methacrylamide) and methyl ether of polyethylene oxide terminated with epichlorohydrin. In some embodiments, the hydrophilically modified polymer comprises the reaction product of a polydimethylaminoethyl methacrylate and polyethylene ether methyl ether terminated with epichlorohydrin having a weight ratio of polydimethylaminoethyl methacrylate to methyl ether of polyethylene oxide terminated with epichlorohydrin of about 3: 1 III. Fluids Example Permeability Modifiers According to some embodiments, the relative permeability modifier may be present in a permeation modifying fluid introduced in the underground formation. Sufficient concentrations of the relative permeability modifier in these permeability modifying fluids must be present to provide the desired level of permeability modification. In some embodiments, the relative permeability modifier may be present in these permeability modifying fluids in an amount in the range of about 0.02% to about 10% by weight of the permeability modifying fluid. In another embodiment, the relative permeability modifier may be present in these permeability modifying fluids in an amount in the range of about 0.05% to about 1.0% by weight of the permeability modifying fluid. In certain embodiments, the relative permeability modifier may be provided in a concentrated aqueous solution prior to its combination with the other components necessary to form the permeability modifying fluids.

In addition to the relative permeability modifier, the permeability modifying fluids also generally comprise water. The water included in the permeation modifier fluid may include fresh water, salt water (eg, water containing one or more salts dissolved therein), brines (eg, natural or produced brines), sea water, or other aqueous fluid that does not undesirably affect the other components in the permeability modifying fluid.

IV. Example Asphaltene Solvent Systems As described above, an asphaltene solvent system can be introduced into a portion of an underground formation, according to certain modalities. In general, suitable asphaltene solvent systems can include any solvent system capable of removing asphaltene from an underground formation. In some embodiments, the asphaltene solvent system may comprise water, an organic solvent, and a surfactant. In certain embodiments, the asphaltene solvent system may be a weak emulsion or dispersion.

The water included in the asphaltene solvent system may include fresh water, water (eg, water containing one or more salts dissolved therein) brines (eg, natural or produced brines), sea water, or other aqueous fluid that does not undesirably affect the other components in the permeability modifying fluid. In some embodiments, the water may comprise an acid. Preferably, the water may comprise a water soluble salt. In certain embodiments, water is present in the asphaltene solvent system in an amount in the range of about 50% to about 100% by volume of the asphaltene solvent system. In certain embodiments, water is present in the asphaltene solvent system in the range of about 65% to about 85% by volume of the asphaltene solvent system. In certain embodiments, water is present in the asphaltene solvent system in the range of about 70% to about 80% by volume of the asphaltene solvent system. One skilled in the art with the benefit of this disclosure will recognize the appropriate amount of water for a chosen application. In addition, in certain embodiments, the water may comprise a permeability modifying fluid.

The organic solvent used in the embodiments of the asphaltene solvent systems of the present invention may comprise any non-polar organic solvent or polar organic solvent. In certain embodiments, the organic solvent may be present in the asphaltene solvent system in an amount in the range of about 30% to about 90% by volume of the asphaltene solvent system. In certain modalities, the organic solvent may be present in the asphaltene solvent system in an amount in the range of about 30% to about 70% by volume of the asphaltene solvent system. In certain embodiments, the organic solvent may be present in the asphaltene solvent system in an amount in the range of about 40% to about 60% by volume of the asphaltene solvent system.

Suitable examples of non-polar organic solvents include aromatic solvents, terpenes, kerosene, diesel, and any combination thereof. Examples of suitable aromatic solvents include heavy aromatics, light aromatics, xylene, toluene and naphtha. Other examples of polar organic solvents include N-methyl-pyrrolidone and cyclohexanone.

Solvents must be selected to be effective in substantially dissolving asphaltenes. Another consideration when choosing a solvent is that the components should not be incompatible with the formation fluids to avoid the formation of undesirable precipitates or residues. Other considerations include that the solvent should not tend to impurify any catalyst used in the refining of hydrocarbon produced from the well.

In some embodiments, the organic solvent may comprise a mixture of organic solvents. In some embodiments, the mixture of organic solvents may comprise a non-polar organic solvent and a polar organic solvent. In certain embodiments, the mixture of organic solvents comprises the non-polar organic solvent in an amount of about 90% to about 99.9% by volume of the organic solvent mixture, and the polar organic solvent in an amount of about 0.1% to about 10%. % by volume of the organic solvent mixture. In certain embodiments, the mixture of organic solvents comprises the non-polar organic solvent in an amount of about 95% to about 99% by volume of the mixture of organic solvents and the polar organic solvent in an amount of about 1% to about 5%. in volume of the mixture of organic solvents.

The specific mixture of organic solvents can be selected to be effective in substantially dissolving the asphaltenes. As is well known in the art, the exact composition in the nature of asphaltenes can vary widely depending on the source, and it may be desirable to adjust or modify the exact mixture of solvents and water-solvent emulsion compositions depending on the source of the asphaltenes. For example, a composition according to the invention can be adapted more particularly for asphaltenes of the types found in Italy or North Africa.

Another consideration in selecting the mixture of organic solvents is that the components should not be incompatible with the formation fluids to avoid the formation of undesirable precipitates or residues. Other considerations include that the mixture of solvents should not tend to impurify the catalysts used in the refining of the hydrocarbon produced from the well.

The flash point of the organic solvent mixture can be another consideration. For example, the point of inflammation of each of the organic solvents, whether polar or non-polar, in the organic solvent mixture can be greater than 40 ° C, and alternatively, it can be higher than 50 ° C. The flash point of xylene, for example, is only 27 ° C. The non-polar organic solvent in the organic solvent mixture may comprise, for example, a mixture of D-limonene and dipentene, for which some mixtures have a flash point of about 47 ° C. An example of a non-polar solvent suitable for use in the solvent mixture is a mixture of terpenes having a flash point greater than 50 ° C. In certain embodiments, a "heavy aromatic solvent" may be used, which is a distillation cut of a crude oil from which light aromatic solvents, such as xylene and toluene, have been previously distilled.

According to one embodiment of the present invention, the polar organic solvent can comprise at least two different polar organic solvents. The polar organic solvent can be selected for its ability to improve the solubility of the asphaltenes in the organic solvent mixture relative to the solubility of the asphaltenes in the non-polar organic solvent alone. A suitable polar organic solvent can be selected from the group consisting of N-methyl-pyrrolidone, which has a high flash point of 92 ° C, and cyclohexanone, which has an adequately high flashpoint of 44 ° C, and any combination thereof at any ratio. Without being limited by theory, it is believed that the combination of two different polar organic solvents helps to dissolve asphaltenes better than the use of either of these two solvents alone. Toluene has a reported Snyder polarity index of only about 2.3, and toluene is usually considered to be a non-polar organic solvent. Cyclohexanone has a reported Snyder polarity index of 4.5, and N-methyl-pyrrolidone has a reported Snyder polarity index of approximately 6.5. These polarity indices provide two different intermediate steps in polarity between non-polar solvents such as toluene and water, which has a Snyder polarity index of 9. It is believed that the use of at least two polar organic solvents having substantially different polarities is contributor to the unexpectedly improved results in the dissolution of asphaltenes. Accordingly, it is believed that other combinations of polar organic solvents will be suitable, especially if the polar organic solvents have substantially different polarities. Accordingly, in certain embodiments, two different polar organic solvents can be used with each solvent having a Snyder polarity index between about 3 and about 7. By way of example, one of the polar organic solvents can have a Snyder polarity index in the range of about 3 to about 5 and one of the polar organic solvents may have a Snyder polarity index in the range of about 5 to about 7. In certain embodiments, at least two of the polar organic solvents may have polarity indices Snyder that are at least separated by approximately 1.5 units of polarity index.

The surfactant included in the asphaltene solvent system can be any surfactant that is capable of forming a weak emulsion (preferably an external emulsion to water) a dispersion of the water and the solvent. For example, the surfactant may comprise a water soluble surfactant. The surfactant may be present in the asphaltene solvent system in an amount of about 0.1% to about 10% by volume of the asphaltene solvent system. In certain embodiments, the surfactant may be present in the asphaltene solvent system in an amount of about 0.3% to about 6% by volume of the asphaltene solvent system. In certain embodiments, the surfactant may be present in the asphaltene solvent system in an amount of about 0.3% to about 0.4% by volume of the asphaltene solvent system. Suitable surfactants may include ethoxylated alcohols, ethoxylated nonylphenol, and any combination thereof.

In certain embodiments, the flash point of the surfactant may be greater than about 40 ° C, and alternatively, greater than about 50 ° C. "Baraklean" is a suitable example of a mixture of water soluble surfactants and has a flash point above about 93 ° C (about 200 ° F), which is commercially available from Baroid Fluid Services. "Baraklean NS" or "Baraklean NS plus" are also suitable, which are a mixture of water-soluble surfactants with a complexing agent.

To facilitate a better understanding of the present invention, the following examples of certain aspects of some modalities are given. In no way should the following examples be read to limit, or define, the full scope of the invention.

Example 1 The solubility of asphaltene was measured in several crude samples obtained from Australia. A portion of each test (Sample No. 1, Sample No. 2, and Sample No. 3) was treated with either prescription 1 or prescription 2 in six separate tests. Recipe 1 comprised 35% volume / volume of Paragon 100E + (heavy aromatic naphtha, 5% volume / volume of Targon II methyl-pyrrolidone, 5% volume / volume of Paragon 1 (terpenes), 0.4% volume / volume S-36M, and 54.6% volume / volume of Fe-Acid Recipe 2 comprised 35% volume / volume of Paragon 100E +, 5% volume / volume of Targon II, 5% of Paragon 1, 0.4% volume / volume of WS-36M, and 54.6% volume / volume of a mixture comprising 93.3% volume / volume of FE-Acid and 6.7% volume / volume of a relative permeability modifier A known quantity of asphaltene was added to a test flask. was added After a predetermined amount of time and temperature Undissolved asphaltene was determined using a gravimetric test method The results of the tests are also set forth in Table 1 below.

Table 1 As can be seen from Table 1, the use of a relative permeability modifier and solvent mixture can improve the dissolution nature of an asphaltene solvent system.

Therefore, the present invention is well adapted to achieve the purposes and advantages mentioned as well as those that are inherent in the present. The particular embodiments described above are illustrative only, since the present invention can be modified and practiced in different but equivalent ways, apparent to those skilled in the art having the benefit of the teachings herein. Additionally, no limitations are proposed to the construction or design details shown herein, other than as described in the subsequent claims. Therefore, it is evident that the particular illustrative modalities described above can be altered or modified and all these variations are considered within the scope and spirit of the present invention. All numbers and ranges described above may vary by some amount. Whenever you want to describe a numerical range with a lower limit and an upper limit, any number and any included range that falls within the range is specifically described. In particular, each range of values (or the form, "of about a to about b", or equivalent, "of about aab", or equivalent, "of about ab") described herein will be understood to expose each number or range covered within the widest range of values. In addition, the indefinite articles "a" or "an", as used in the claims, are defined herein to mean one or more than one of the element that is introduced. Also, the terms in the claims have their simple and ordinary meaning unless otherwise explicitly and clearly defined by the patent assignee.

Claims (25)

NOVELTY OF THE INVENTION Having described the present invention as above, it is considered as a novelty and, therefore, the content of the following is claimed as property: CLAIMS

1. A method to prevent the deposit of asphaltenes, characterized in that it comprises: identify a range of the underground formation to be treated with a relative permeability modifier to prevent the subsequent deposition of asphaltenes; introduce the relative permeability modifier in the underground formation; Y allow the relative permeability modifier to make contact with the interval, thereby joining surfaces within the underground formation and preventing subsequent deposition of asphaltenes.

2. The method in accordance with the claim 1, characterized in that the relative permeability modifier comprises a hydrophobically modified polymer, soluble in water.

3. The method in accordance with the claim 2, characterized in that the hydrophobically modified polymer comprises a hydrophilic polymer structure and a hydrophobic branch, the hydrophobic branch comprising from about 7 to about 22 carbons.

4. The method according to claim 2, characterized in that the hydrophobically modified polymer comprises an alkyl group present in an amino group in quaternized form.

5. The method according to claim 2, characterized in that the hydrophobically modified polymer comprises polydimethylaminoethylmethacrylate or polydimethylaminopropylmethacrylamide which have been hydrophobically modified with a group to the quilo of about 12 to about 22 carbons.

6. A method for removing asphaltenes and preventing the subsequent deposition of asphaltenes in an underground formation, characterized in that it comprises: introducing a fluid comprising a relative permeability modifier and an asphaltene solvent system in the underground formation; Y allowing the fluid to make contact with a portion of the underground formation, wherein the asphaltene solvent system removes at least a portion of an asphaltene in the portion of the underground formation, and wherein the relative permeability modifier prevents subsequent deposition of asphaltene in the portion of the underground formation.

7. The method according to claim 6, characterized in that it comprises identifying a range of the underground formation to be treated with the relative permeability modifier to prevent the subsequent deposition of asphaltene.

8. The method according to claim 6, characterized in that the relative permeability modifier comprises a hydrophobically modified polymer, soluble in water.

9. The method according to claim 8, characterized in that the hydrophobically modified polymer comprises a hydrophilic polymer structure and a hydrophobic branch, the hydrophobic branch comprising from about 7 to about 22 carbons.

10. The method according to claim 8, characterized in that the hydrophobically modified polymer comprises an alkyl group present in an amino group in quaternized form.

11. The method according to claim 8, characterized in that the hydrophobically modified polymer comprises polydimethylaminoethylmethacrylate or polydimethylaminopropylmethacrylamide which have been hydrophobically modified with an alkyl group of about 12 to about 22 carbons.

12. The method according to claim 6, characterized in that the asphaltene solvent system comprises water, an organic solvent, a surfactant.

13. The method in accordance with the claim 12, characterized in that the organic solvent comprises at least one non-polar organic solvent selected from the group consisting of an aromatic solvent, a terpene, kerosene, diesel, xylene, toluene, cyclohexanone, D-limonene, and dipentene.

14. The method according to claim 12, characterized in that the organic solvent comprises at least one polar organic solvent selected from the group consisting of N-methyl-pyrrolidone and cyclohexanone.

15. The method in accordance with the claim 6, characterized in that the asphaltene solvent system comprises at least two polar organic solvents, wherein one of the polar organic solvents has a Snyder polarity index in the range of about 3 to about 5, and wherein the other of the solvents polar organic has a Snyder polarity index in the range of about 5 to about 7.

16. A method for removing asphaltenes and preventing the subsequent deposition of asphaltenes in an underground formation, characterized in that it comprises: introducing a permeability modifying fluid into a perforation penetrating an underground formation, wherein the permeability modifying fluid comprises a relative permeability modifier; allowing at least a portion of the permeation modifying fluid to penetrate a portion of the subterranean formation so that the relative permeability modifier present in the portion of the subterranean formation substantially deviates the aqueous fluids subsequently introduced to less permeable portions of the underground formation , where the relative permeability modifier in the portion of the underground formation prevents the subsequent deposition of asphaltenes; and introducing an asphaltene solvent system into the drilling to remove the asphaltenes in the underground formation, where the relative permeability modifier present in the underground formation portion diverts the asphaltene solvent system to a less permeable portion of the formation underground

17. The method according to claim 16, characterized in that it comprises identifying a range of the underground formation to be treated with the permeability modifying fluid to prevent the subsequent deposition of asphaltenes.

18. The method according to claim 16, characterized in that the relative permeability modifier comprises a water-soluble hydrophobically modified polymer.

19. The method according to claim 18, characterized in that the hydrophobically modified polymer comprises a hydrophilic polymer structure and a hydrophobic branch, the hydrophobic branch comprising from about 7 to about 22 carbons.

20. The method according to claim 18, characterized in that the hydrophobically modified polymer comprises an alkyl group present in an amino group in quaternized form.

21. The method in accordance with the claim 18, 'characterized in that the hydrophobically modified polymer comprises polydimethylaminoethylmethacrylate or polydimethylaminopropylmethacrylamide which has been hydrophobically modified with an alkyl group of about 12 to about 22 carbons.

22. The method according to claim 16, characterized in that the asphaltene solvent system comprises water, an organic solvent, a surfactant agent.

23. The method according to claim 22, characterized in that the organic solvent comprises at least one non-polar organic solvent selected from the group consisting of an aromatic solvent, a terpene, kerosene, diesel, xylene, toluene, cyclohexanone, D-limonene, and dipenteno.

24. The method according to claim 22, characterized in that the organic solvent comprises at least one polar organic solvent selected from the group consisting of N-methyl-pyrrolidone and cyclohexanone.

25. The method according to claim 16, characterized in that the asphaltene solvent system comprises at least two polar organic solvents, wherein one of the polar organic solvents has a Snyder polarity index in the range of about 3 to about 5, and wherein the other of the polar organic solvents has a Snyder polarity index in the range of about 5 to about 7.