CN107236532B

CN107236532B - Clean fracturing fluid and preparation method thereof

Info

Publication number: CN107236532B
Application number: CN201710462583.3A
Authority: CN
Inventors: 夏佐贵; 陈学
Original assignee: Sichuan Yinyu Chemical Technology Co ltd
Current assignee: Sichuan Yinyu Chemical Technology Co ltd
Priority date: 2017-06-19
Filing date: 2017-06-19
Publication date: 2020-11-24
Anticipated expiration: 2037-06-19
Also published as: CN107236532A

Abstract

The invention belongs to the technical field of oil exploitation, and particularly relates to a clean fracturing fluid and a preparation method thereof. The invention provides a novel clean fracturing fluid, which at least comprises 0.1-0.5 part by weight of associative polymer thickening agent; 0.1-0.7 parts of a surfactant; 0.3-0.8 part of a crosslinking agent; 0.2-0.6 parts of cellulose; 0.001-0.05 parts of a capsule gel breaker; 100 parts of water; the associative polymer thickening agent is obtained by polymerizing acrylate, acrylamide, quaternary ammonium salt, trifluoroethyl methacrylate and aliphatic polyurethane hexaacrylate in an aqueous solution through an initiator.

Description

Clean fracturing fluid and preparation method thereof

Technical Field

The invention belongs to the technical field of oil exploitation, and particularly relates to a novel clean fracturing fluid and a preparation method thereof.

Background

The application of the hydraulic fracturing technology in oil fields starts in the last 40 th century, and gradually becomes one of important yield increasing measures for improving the productivity of oil and gas wells and the recovery ratio of oil reservoirs after the development of more than 70 years. The hydraulic fracturing is to inject high-viscosity sand-carrying fracturing fluid which exceeds the absorption capacity of the stratum into a shaft by utilizing ground high-pressure equipment so as to improve the stratum pressure of a near-wellbore area, and when the stratum pressure exceeds the fracture pressure, one or more cracks with certain flow conductivity can be generated, so that the purposes of increasing the production and the injection of the oil-water well are achieved. The outstanding characteristics of oil and gas resources in China are that low-permeability oil and gas reservoirs are wide in distribution and large in reserve volume, and hydraulic fracturing is objectively determined to be a first choice measure for achieving the goal of stable production and yield increase of oil fields in China.

The performance of the fracturing fluid is related to success or failure of fracturing construction, so that the improvement of the performance of the fracturing fluid is taken as a research focus at home and abroad. The fracturing fluid has the functions of pressure transmission, crack formation, sand carrying and crack purification, and the ideal fracturing fluid has the performances of high viscosity, low filtration loss, good rheological property, good thermal stability and shear stability, good compatibility, easy gel breaking and flowback, small damage, low price and the like. The water-based fracturing fluids which are widely applied to oil fields at home and abroad at present and achieve good yield increasing effect can be divided into 3 types: (1) natural and synthetic vegetable gum fracturing fluids; (2) a cellulosic fracturing fluid; (3) a polymer fracturing fluid.

The thickening agents of the systems have overlarge relative molecular mass, so the thickening agents have poor solubility, more water-insoluble substances and easy formation of fish eyes, the utilization rate of the thickening agents is greatly reduced, and the loss can be compensated only by increasing the addition of the thickening agents on site; in addition, the three fracturing fluid gel breaking solutions contain a large amount of residues capable of reducing the formation permeability, and the fracturing effect is seriously influenced.

In 1997, Schlumberger company developed a fracturing fluid without damage and pollution to the stratum by using a viscoelastic surfactant (VES), which is also called clean fracturing fluid. The clean fracturing fluid is simple in preparation, and does not need a cross-linking agent or other chemical additives; the flowing friction resistance is small and is only 25 to 40 percent of that of clear water, and the construction is safe and simple; the water-insoluble substances are not generated during liquid preparation, no residue is generated after gel breaking, and the flowback rate is high, so that the fracturing fluid has no formation damage, can keep the flow conductivity of cracks, can obtain a good fracturing effect, is widely concerned by people, and raises the heat tide of research and application of clean fracturing fluid in the world.

Therefore, it is necessary to develop a new clean fracturing fluid through research and development.

Disclosure of Invention

In order to solve the technical problems, the first aspect of the invention provides a novel clean fracturing fluid, which at least comprises the following components in parts by weight

The associative polymer thickening agent is obtained by polymerizing acrylate, acrylamide, quaternary ammonium salt, trifluoroethyl methacrylate and aliphatic polyurethane hexaacrylate in an aqueous solution through an initiator.

In a preferred embodiment of the present invention, in the associative polymer thickener, the weight ratio of the acrylate, the acrylamide, the quaternary ammonium salt, the trifluoroethyl methacrylate, and the aliphatic polyurethane hexaacrylate is: 10: (10-30): 20: 12: 5.

as a preferred embodiment of the present invention, the surfactant is selected from: any one or combination of several of cationic surfactant, anionic surfactant, nonionic surfactant, gemini surfactant and biosurfactant.

As a preferred embodiment of the present invention, the crosslinking agent is selected from: any one or combination of a plurality of boric acid, sodium borate, organic boron crosslinking agent and organic boron zirconium crosslinking agent.

As a preferred embodiment of the present invention, the cellulose is selected from: any one or combination of several of carboxymethyl cellulose, hydroxypropyl methyl cellulose, carboxymethyl hydroxyethyl cellulose and carboxymethyl hydroxypropyl cellulose.

As a preferable technical scheme, the cellulose is modified cellulose, and the modified cellulose is sodium dodecyl benzene sulfonate modified cellulose.

As a preferable technical scheme of the present invention, in the modified cellulose, in the sodium dodecylbenzenesulfonate modified cellulose, a weight ratio of sodium dodecylbenzenesulfonate to cellulose is: 1: 5.

as a preferable technical scheme of the invention, the capsule gel breaker is a mixed core material of potassium persulfate, ammonium persulfate, chloroform, hexadecyl trimethyl ammonium chloride, polyethylene glycol 600 and cyclodextrin, and a mixed capsule coat of ethyl methacrylate, chitosan, polyethylene glycol, vinyl triethoxysilane, vinyl acetate and n-butanol.

As a preferred technical scheme of the invention, the preparation method of the capsule gel breaker comprises the following steps:

(1) uniformly mixing potassium sulfate, ammonium persulfate, chloroform, hexadecyl trimethyl ammonium chloride and polyethylene glycol 600 to obtain a first mixed solution;

(2) uniformly mixing ethyl methacrylate, chitosan, polyethylene glycol, vinyl triethoxysilane, vinyl acetate and n-butanol to obtain a second mixed solution;

(3) and (3) adding the second mixed solution obtained in the step (2) into the first mixed solution, heating the reaction temperature to 60 ℃, stirring, reacting for 3-5 h, washing for 3 times by using ethanol, and drying to obtain the microcapsule gel breaker.

In a second aspect, the present invention provides a method for preparing a novel clean fracturing fluid, comprising at least the following steps:

(1) adding an associative polymer thickener, cellulose and a surfactant into water, uniformly stirring, and obtaining a novel clean fracturing fluid;

(2) and (3) in the process of fracturing operation, sequentially adding a cross-linking agent and a capsule gel breaker into the novel clean fracturing fluid obtained in the step (1) to obtain the jelly-like novel clean fracturing fluid.

The foregoing and other features, aspects, and advantages of the present invention will become more apparent with reference to the following detailed description.

Detailed Description

The disclosure may be understood more readily by reference to the following detailed description of preferred embodiments of the invention and the examples included therein. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In case of conflict, the present specification, including definitions, will control.

The term "prepared from …" as used herein is synonymous with "comprising". The terms "comprises," "comprising," "includes," "including," "has," "having," "contains," "containing," or any other variation thereof, as used herein, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.

The conjunction "consisting of …" excludes any unspecified elements, steps or components. If used in a claim, the phrase is intended to claim as closed, meaning that it does not contain materials other than those described, except for the conventional impurities associated therewith. When the phrase "consisting of …" appears in a clause of the subject matter of the claims rather than immediately after the subject matter, it defines only the elements described in the clause; other elements are not excluded from the claims as a whole.

When an amount, concentration, or other value or parameter is expressed as a range, preferred range, or as a range of upper preferable values and lower preferable values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether ranges are separately disclosed. For example, when a range of "1 to 5" is disclosed, the described range should be interpreted to include the ranges "1 to 4", "1 to 3", "1 to 2 and 4 to 5", "1 to 3 and 5", and the like. When a range of values is described herein, unless otherwise stated, the range is intended to include the endpoints thereof and all integers and fractions within the range.

The singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. "optional" or "any" means that the subsequently described event or events may or may not occur, and that the description includes instances where the event occurs and instances where it does not.

Approximating language, as used herein throughout the specification and claims, is intended to modify a quantity, such that the invention is not limited to the specific quantity, but includes portions that are literally received for modification without substantial change in the basic function to which the invention is related. Accordingly, the use of "about" to modify a numerical value means that the invention is not limited to the precise value. In some instances, the approximating language may correspond to the precision of an instrument for measuring the value. In the present description and claims, range limitations may be combined and/or interchanged, including all sub-ranges contained therein if not otherwise stated.

In addition, the indefinite articles "a" and "an" preceding an element or component of the invention are not intended to limit the number requirement (i.e., the number of occurrences) of the element or component. Thus, "a" or "an" should be read to include one or at least one, and the singular form of an element or component also includes the plural unless the stated number clearly indicates that the singular form is intended.

Associative polymer thickener

In the application, the associative polymer thickener is obtained by polymerizing acrylate, acrylamide, quaternary ammonium salt, trifluoroethyl methacrylate and aliphatic polyurethane hexaacrylate in an aqueous solution through an initiator.

As the acrylic acid salt, there may be mentioned: sodium acrylate, calcium acrylate, magnesium acrylate, and the like; most preferably sodium acrylate.

The quaternary ammonium salts include: acryloyloxyethyltrimethylammonium chloride, methacryloyloxyethyltrimethylammonium chloride, acryloyloxyethyltrimethylammonium bromide, methacryloyloxyethyltrimethylammonium bromide, dodecyldimethylallylammonium chloride, dodecyldimethylallylammonium bromide, tetradecyldimethylallyl ammonium chloride, tetradecyldimethylallyl ammonium bromide, hexadecyldimethylallylammonium chloride, hexadecyldimethylallylammonium bromide, octadecyldimethylallyl ammonium chloride, octadecyldimethylallyl ammonium bromide, etc.; most preferred is acryloyloxyethyltrimethyl ammonium chloride.

The trifluoroethyl methacrylate is purchased from new chemical industries, ltd, Weihai.

The aliphatic polyurethane hexaacrylate is purchased from Guangzhou Liqian trade company, and the product trade mark is as follows: and RJ 424.

In a preferred embodiment, the associative polymer thickener is prepared by the following specific steps:

adding 500ml of water into a 1000ml beaker, and sequentially adding sodium acrylate, acrylamide, acryloyloxyethyl trimethyl ammonium chloride, trifluoroethyl methacrylate and aliphatic polyurethane hexaacrylate under stirring, wherein the weight ratio of the sodium acrylate to the acrylamide to the acryloyloxyethyl trimethyl ammonium chloride to the trifluoroethyl methacrylate to the aliphatic polyurethane hexaacrylate is as follows: 10: 20: 20: 12: 5; after the monomers are completely dissolved, respectively adding ammonium persulfate and sodium bisulfite of which the total amount is 5 ten thousandth of the total amount of the monomers, then adding 2 per thousand of dimethylaminobutyronitrile, starting polymerization, reacting for 2 hours to obtain a reaction polymerization product, hydrolyzing for 4 hours at 90 ℃, cutting into 3mm particles, drying at 85 ℃, and crushing for later use.

Surface active agent

In the present application, the surfactant may be: cationic surfactants, anionic surfactants, nonionic surfactants, gemini surfactants, biosurfactants, and the like.

The cationic surfactants include, for example: dodecyl trimethyl ammonium chloride, hexadecyl trimethyl ammonium chloride, octadecyl trimethyl ammonium chloride, dicocoyl dimethyl ammonium chloride, etc.;

the anionic surfactants include: sodium dodecyl benzene sulfonate, sodium lauryl alcohol polyoxyethylene ether sulfate, ammonium dodecyl sulfate, lauryl phosphate triethanolamine, sodium dodecyl sulfate and the like.

The nonionic surfactants include, for example: polyoxyethylene alkylphenol ethers, sorbitan tristearate, sucrose fatty acid esters, dodecyl glucoside, and the like.

The gemini surfactants may be exemplified by: propylidene bis (octadecyl dimethyl ammonium chloride), hydroxypropylidene bis (oleamide propyl dimethyl quaternary ammonium salt), and the like.

The biosurfactant may be exemplified by: sophorolipid, rhamnolipid, and the like.

Crosslinking agent

In the present application, the crosslinking agent is selected from: any one or combination of a plurality of boric acid, sodium borate, organic boron crosslinking agent and organic boron zirconium crosslinking agent.

Cellulose, process for producing the same, and process for producing the same

In the present application, the cellulose is selected from: any one or more of carboxymethyl cellulose, hydroxypropyl methyl cellulose, carboxymethyl hydroxyethyl cellulose and carboxymethyl hydroxypropyl cellulose.

In a preferred embodiment, the cellulose is modified cellulose, and the modified cellulose is sodium dodecylbenzenesulfonate modified cellulose.

In a preferred embodiment, in the modified cellulose, the sodium dodecylbenzenesulfonate modified cellulose has a weight ratio of sodium dodecylbenzenesulfonate to cellulose of: 1: 5.

in a preferred embodiment, the modified cellulose is prepared by the following method:

dissolving sodium dodecyl benzene sulfonate in an ethanol solution with the mass fraction of 80%, adding carboxymethyl cellulose, heating the reaction temperature to 80 ℃, reacting for 3-10 h, cooling to room temperature, pouring into acetone, fully washing, filtering, and drying in a vacuum oven at 120 ℃ for 10h to obtain the modified cellulose.

Capsule gel breaker

In the application, the capsule gel breaker is prepared by taking potassium persulfate, ammonium persulfate, chloroform, hexadecyl trimethyl ammonium chloride, polyethylene glycol 600 and cyclodextrin as mixed core materials and taking ethyl methacrylate, chitosan, polyethylene glycol 400, vinyl triethoxysilane, vinyl acetate and n-butyl alcohol as mixed capsule coats.

In a preferred embodiment, the capsule breaker is prepared by a process comprising:

(2) uniformly mixing ethyl methacrylate, chitosan, polyethylene glycol 400, vinyl triethoxysilane, vinyl acetate and n-butanol to obtain a second mixed solution;

In a preferred embodiment, the weight ratio of the potassium sulfate, the ammonium persulfate, the chloroform, the hexadecyl trimethyl ammonium chloride and the polyethylene glycol 600 is as follows: 5: 2: 10: 1: 5.

in a preferred embodiment, the weight ratio of the ethyl methacrylate, the chitosan, the polyethylene glycol 400, the vinyl triethoxysilane, the vinyl acetate and the n-butanol is as follows: 8: 5: 10: 4: 3: 8.

The present invention will be specifically described below by way of examples. It should be noted that the following examples are only for illustrating the present invention and should not be construed as limiting the scope of the present invention, and that the insubstantial modifications and adaptations of the present invention by those skilled in the art based on the above disclosure are still within the scope of the present invention.

In addition, all the starting materials are commercially available unless otherwise specified.

Example 1

Example 1 provides a novel clean fracturing fluid comprising, in parts by weight, at least

The specific preparation method of the associative polymer thickener comprises the following steps:

The surfactant is propylene bis (octadecyl dimethyl ammonium chloride);

the cross-linking agent is sodium borate;

the cellulose is carboxymethyl cellulose;

the capsule gel breaker is a product with the brand number of BSA-405 and is purchased from Shida Alder (Kaifeng) science and technology Limited;

the preparation method of the novel clean fracturing fluid at least comprises the following steps:

Example 2

Example 2 provides a novel clean fracturing fluid comprising, in parts by weight, at least

The surfactant is propylene bis (octadecyl dimethyl ammonium chloride);

the cross-linking agent is sodium borate;

the cellulose is carboxymethyl cellulose;

the preparation method of the novel clean fracturing fluid at least comprises the following steps：

Example 3

Example 3 provides a novel clean fracturing fluid comprising, in parts by weight, at least

The surfactant is propylene bis (octadecyl dimethyl ammonium chloride);

the cross-linking agent is sodium borate;

the cellulose is carboxymethyl cellulose;

Example 4

Example 4 provides a novel clean fracturing fluid comprising, in parts by weight, at least

The surfactant is propylene bis (octadecyl dimethyl ammonium chloride);

the cross-linking agent is sodium borate;

the cellulose is sodium dodecyl benzene sulfonate modified cellulose;

in a preferred embodiment, the preparation method of the sodium dodecyl benzene sulfonate modified cellulose comprises the following steps: dissolving sodium dodecyl benzene sulfonate in an ethanol solution with the mass fraction of 80%, adding carboxymethyl cellulose, heating the reaction temperature to 80 ℃, reacting for 5 hours, cooling to room temperature, pouring into acetone, fully washing, filtering, and drying in a vacuum oven at 120 ℃ for 10 hours to obtain the modified cellulose. Wherein, the weight ratio of the sodium dodecyl benzene sulfonate to the cellulose is as follows: 1: 5.

Example 5

Example 5 provides a novel clean fracturing fluid comprising, in parts by weight, at least

The surfactant is propylene bis (octadecyl dimethyl ammonium chloride);

the cross-linking agent is sodium borate;

the cellulose is sodium dodecyl benzene sulfonate modified cellulose;

Comparative example 1

Comparative example 1 is the same as example 5 except that the raw materials for preparing the associative polymer thickener were changed to sodium acrylate, acrylamide, acryloyloxyethyltrimethyl ammonium chloride, and aliphatic urethane hexaacrylate.

Comparative example 2

Comparative example 2 is the same as example 5 except that the raw materials for preparing the associative polymer thickener were changed to sodium acrylate, acrylamide, acryloyloxyethyltrimethyl ammonium chloride, and trifluoroethyl methacrylate.

Comparative example 3

Comparative example 3 is the same as example 5 except that the raw materials for preparing the associative polymer thickener were changed to sodium acrylate, acrylamide, acryloyloxyethyltrimethyl ammonium chloride.

Comparative example 4

Comparative example 4 is the same as example 5 except that no cellulose was added.

Comparative example 5

Comparative example 5 is the same as example 5 except that no capsule breaker was added.

Comparative example 6

Comparative example 6 is the same as example 5, except that the capsule breaker was replaced with potassium persulfate, ammonium persulfate, chloroform, cetyltrimethylammonium chloride, and polyethylene glycol 600 as the mixed core material, and ethyl methacrylate, chitosan, polyethylene glycol 400, vinyltriethoxysilane, vinyl acetate, and n-butanol as the mixed coating.

Comparative example 7

Comparative example 7 is the same as example 5 except that the capsule breaker was replaced with potassium persulfate, ammonium persulfate, chloroform, cetyltrimethylammonium chloride, polyethylene glycol 600, cyclodextrin as the mixed core material, and ethyl methacrylate, polyethylene glycol 400, vinyltriethoxysilane, vinyl acetate, n-butanol as the mixed coating.

The products of examples 1 to 5 and comparative examples 1 to 7 are colorless viscous liquids, and the technical standards thereof adopt SY/T6376-2008 'fracturing fluid general technical conditions' Table 4 (general technical index of viscoelastic surfactant fracturing fluid), SY/5107-.

TABLE 1 test results

The novel clean fracturing fluid has the advantages of no residue content, good gel breaking capacity, good sand carrying performance and the like, and in addition, the novel clean fracturing fluid can be recycled, the construction pressure is reduced, and the large discharge capacity can be realized; the embodiments 1-5 of the application can be suitable for construction at the formation temperature of 0-200 ℃; can be simultaneously suitable for construction at high temperature and low temperature.

The foregoing examples are illustrative only, and serve to explain some of the features of the present disclosure. The appended claims are intended to claim as broad a scope as is contemplated, and the examples presented herein are merely illustrative of selected implementations in accordance with all possible combinations of examples. Accordingly, it is applicants' intention that the appended claims are not to be limited by the choice of examples illustrating features of the invention. And that advances in science and technology will result in possible equivalents or sub-substitutes not currently contemplated for reasons of inaccuracy in language representation, and such changes should also be construed where possible to be covered by the appended claims.

Claims

1. The clean fracturing fluid is characterized by at least comprising the following components in parts by weight

The associative polymer thickening agent is obtained by polymerizing acrylate, acrylamide, quaternary ammonium salt, trifluoroethyl methacrylate and aliphatic polyurethane hexaacrylate in an aqueous solution through an initiator, and the preparation method of the capsule gel breaker comprises the following steps:

(1) uniformly mixing potassium persulfate, ammonium persulfate, chloroform, hexadecyltrimethylammonium chloride and polyethylene glycol 600 to obtain a first mixed solution;

(3) adding the second mixed solution obtained in the step (2) into the first mixed solution, heating the reaction temperature to 60 ℃, stirring, reacting for 3-5 h, washing for 3 times by using ethanol, and drying to obtain the microcapsule gel breaker; the weight ratio of the potassium persulfate to the ammonium persulfate to the chloroform to the cetyltrimethylammonium chloride to the polyethylene glycol 600 is as follows: 5: 2: 10: 1: 5, the weight ratio of the ethyl methacrylate to the chitosan to the polyethylene glycol 400 to the vinyl triethoxysilane, the vinyl acetate to the n-butanol is as follows: 8: 5: 10: 4: 3: 8, the cellulose is modified cellulose, the modified cellulose is sodium dodecyl benzene sulfonate modified cellulose, and in the sodium dodecyl benzene sulfonate modified cellulose, the weight ratio of sodium dodecyl benzene sulfonate to cellulose is 1: 5, the cellulose is selected from carboxymethyl cellulose.

2. The clean fracturing fluid of claim 1, wherein the associative polymer thickener comprises acrylate, acrylamide, quaternary ammonium salt, trifluoroethyl methacrylate and aliphatic polyurethane hexaacrylate in a weight ratio of: 10: (10-30): 20: 12: 5.

3. the clean fracturing fluid of claim 1, wherein the surfactant is selected from the group consisting of: any one or combination of several of cationic surfactant, anionic surfactant, nonionic surfactant, gemini surfactant and biosurfactant.

4. The clean fracturing fluid of claim 1, wherein the crosslinking agent is selected from the group consisting of: any one or combination of a plurality of boric acid, sodium borate, organic boron crosslinking agent and organic boron zirconium crosslinking agent.

5. The method for preparing the clean fracturing fluid of any one of claims 1 to 4, comprising at least the following steps:

(1) adding an associative polymer thickener, cellulose and a surfactant into water, uniformly stirring, and obtaining a clean fracturing fluid;

(2) and (3) in the process of fracturing operation, sequentially adding a cross-linking agent and a capsule gel breaker into the clean fracturing fluid obtained in the step (1) to obtain the jelly clean fracturing fluid.