Fracturing fluid with imbibition oil displacement and anti-swelling functions and preparation method thereof

Abstract

The present invention discloses a fracturing fluid with imbibition oil displacement and anti-swelling functions, comprising the following components by mass percentage: 0.1% to 0.5% thickener, 0.2% to 0.6% imbibition improver, 0.5% to 1.2% oil displacement enhancer, 0.2% to 0.8% anti-swelling control agent, and the remainder being water; the imbibition improver is selected from one of nano-silicon dioxide, nano-calcium carbonate, and nano-zirconium dioxide, or a mixture of two thereof; the oil displacement enhancer is selected from one of hydrogenated styrene diene copolymer, polymethacrylate, ethylene propylene copolymer, and polyisobutylene; and the anti-swelling control agent is a Gemini surfactant. The fracturing fluid provided by the present invention has imbibition oil displacement and anti-swelling functions, avoiding the problems of imbibition oil displacement agents in the prior art causing crude oil emulsification and difficulty in demulsification after fracturing, and the anti-swelling agent affecting liquid properties; it also has the basic functions of drag reduction and sand carrying, meeting the requirements of oil production fracturing construction.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas exploitation, in particular to a fracturing fluid with imbibition oil displacement and anti-swelling functions and a preparation method thereof. Background Art

[0002] With the continuous development of onshore oil fields, mature oil fields have entered the late stage of high water content, and the focus of oil and gas exploration and development has gradually shifted to low-permeability reservoirs. Low-permeability reservoirs are reservoirs with permeabilities less than 50 mD and can be further divided into low-permeability reservoirs (10.0-50.0 mD), ultra-low permeability reservoirs (1.0-10.0 mD), and ultra-low permeability reservoirs (0.1-1.0 mD). Low-permeability reservoirs generally have the following characteristics: a single reservoir type, mainly lithologic and structural-lithologic reservoirs, and primarily elastically driven reservoirs; poor reservoir properties, low porosity and permeability; small pore throats; strong heterogeneity; fractures are usually developed, but the fracture width is small, and the reservoir sensitivity is high. Development methods for this type of low-permeability reservoir include chemical flooding, gas injection flooding, and microbial flooding.

[0003] For some water-sensitive, low-permeability reservoirs, the content and distribution of clay minerals are crucial factors influencing hydration swelling in the reservoir core. If a large amount of clay minerals are distributed on the surface of the rock pores, when incompatible water is injected, the water molecules wedge into the crystal layers, interacting with the rock and causing crystal layer swelling. This changes the mechanical properties of the rock and can even cause clay particles to fall off and migrate, leading to pore blockage and a significant increase in injection pressure, seriously impacting oil production efficiency. To address this issue of clay mineral hydration affecting reservoir production, anti-swelling agents are added to protect the reservoir and inhibit the swelling and migration of clay minerals. Anti-swelling agents come in two types: inorganic and organic.

[0004] There are two problems with existing imbibition flooding and anti-swelling technologies: (1) Imbibition flooding leads to emulsification of fracturing flowback water, which then needs to be demulsified after production; and (2) anti-swelling agents have the harmful effect of reducing the viscosity of the anionic polymer fracturing fluid system. Summary of the Invention

[0005] Aiming at the problems in the prior art that imbibition oil displacement agents cause crude oil emulsification after fracturing, making demulsification difficult, and anti-swelling agents affect the performance of fracturing fluids, the present invention provides a fracturing fluid with imbibition oil displacement and anti-swelling functions and a preparation method thereof.

[0006] The fracturing fluid with imbibition oil displacement and anti-swelling functions provided by the present invention comprises the following components in percentage by mass:

[0007] Thickener 0.1% to 0.5%, imbibition improver 0.2% to 0.6%, oil displacement enhancer 0.5% to 1.2%, anti-swelling control agent 0.2% to 0.8%, and the rest is water.

[0008] The imbibition improver is selected from one of nano silicon dioxide, nano calcium carbonate, nano zirconium dioxide or a mixture of two thereof.

[0009] The oil displacement enhancer is selected from one of hydrogenated styrene diene copolymer, polymethacrylate, ethylene propylene copolymer and polyisobutylene.

[0010] The anti-swelling control agent is a cationic surfactant, preferably a Gemini surfactant, and more preferably didodecyldimethylammonium chloride.

[0011] The thickener is polyacrylamide. The thickener is preferably any one of anionic polyacrylamide and its derivatives. The molecular weight of anionic polyacrylamide is 16 million, and it is a copolymer of AMPS and AM.

[0012] Preferably, the components and mass percentages of the fracturing fluid are as follows:

[0013] Anionic polyacrylamide 0.15% to 0.3%; nano calcium carbonate 0.4% to 0.6%; polymethacrylate 0.8% to 1.0%; didodecyldimethylammonium chloride 0.4% to 0.6%; the rest is water.

[0014] The preparation method of the fracturing fluid with imbibition oil displacement and anti-swelling functions comprises the following steps:

[0015] S1. Add an imbibition improver, water, and an oil displacement enhancer to a reaction vessel, start stirring, and heat to 70° C. at a stirring rate of 50 to 150 r / min. React for 3 to 4 hours, and then allow to cool for 1 to 2 hours.

[0016] S2. Add an anti-swelling control agent to the reaction vessel, stir for 1.5 to 3 hours at a stirring rate of 50 to 150 r / min, and then let it stand for 0.5 to 1 hour;

[0017] S3. Add a thickener to the reaction container, stir at a rate of 600 r / min to 1000 r / min, and stir evenly to obtain a fracturing fluid.

[0018] Compared with the prior art, the present invention is beneficial in that:

[0019] (1) The fracturing fluid provided by the present invention has a cationic surfactant (didodecyldimethylammonium chloride) with an ammonium polar group at one end, which can be adsorbed to the surface of the imbibition improver due to van der Waals forces; and a long-chain alkyl group at the other end, whose structure has good compatibility with the alkyl hydrophobic segment of polyacrylamide, forming a hydrophobic interaction point. This allows more cationic surfactant and oil displacement enhancer to be adsorbed on the surface of the imbibition improver. Due to the adsorption of the cationic surfactant on the surface of the imbibition improver, the positive charge concentration of the cationic surfactant is reduced, which not only ensures the efficient anti-swelling effect of the dicationic acid, but also reduces the effect of the cationic charge on the viscosity of the anionic polyacrylamide solution.

[0020] (2) The carbonyl groups in the oil displacement enhancer segments in the fracturing fluid system provided by the present invention form intermolecular forces with the hydroxyl functional groups on the surface of the imbibition improver, thereby increasing the adsorption effect. The imbibition improver has a large specific surface area and more active adsorption sites, which can effectively adsorb oily molecules. The hydrophobic interaction points formed by the cationic surfactant and the imbibition improver enhance the adsorption effect, forming a gel structure that fixes more oily components on the surface of the imbibition improver.

[0021] (3) Since the oil displacement enhancer is an oil-soluble polymer compound, the imbibition improver adsorbed with the oil displacement enhancer can selectively adsorb asphaltene, inhibit the self-association of asphaltene and colloid, reduce crude oil viscosity, reduce crude oil flow resistance, and improve displacement effect. The oil-soluble polymer chemical chain segments on the surface of the imbibition improver (nano-calcium carbonate) contain carbonyl groups, which interact with the amide groups in the polyacrylamide structure to achieve the composite oil displacement effect of polymer-nano-calcium carbonate. It not only utilizes the small size of nano-calcium carbonate to enter the pore throat of the low permeability reservoir, but also achieves the imbibition displacement effect of the polymer-oil-soluble polymer chemical composite system. At the same time, it solves the problem of the need to demulsify the return water due to the influence of conventional surfactant systems on crude oil emulsification.

[0022] Other advantages, objectives and features of the present invention will be reflected in part from the following description and will be understood by those skilled in the art through study and practice of the present invention. DETAILED DESCRIPTION

[0023] The preferred embodiments of the present invention are described below. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0024] Example 1

[0025] A fracturing fluid with imbibition oil displacement and anti-swelling functions, wherein the raw materials are expressed in parts by weight as shown in Table 1 below:

[0026] Table 1, Example 1 raw materials

[0027]

[0028] Preparation method:

[0029] S1: Add imbibition improver, water and oil displacement enhancer to the reaction vessel, start stirring and heat to 70°C, react for 3-4 hours, and let it stand for 1 hour;

[0030] S2: Add anti-swelling control agent to the reaction vessel, stir for 2 hours, and let it stand for 1 hour;

[0031] S3: Add a thickener to the reaction container and stir evenly to obtain a multifunctional fracturing fluid.

[0032] Example 2

[0033] A fracturing fluid with imbibition oil displacement and anti-swelling functions, wherein the raw materials are expressed in parts by weight as shown in Table 2 below:

[0034] Table 2, Example 2 raw materials

[0035]

[0036] The preparation method is the same as that of Example 1.

[0037] Example 3

[0038] A fracturing fluid with imbibition oil displacement and anti-swelling functions, wherein the raw materials are expressed in parts by weight as shown in Table 3 below:

[0039] Table 3, Example 3 raw materials

[0040]

[0041] The preparation method is the same as that of Example 1.

[0042] Example 4

[0043] A fracturing fluid with imbibition oil displacement and anti-swelling functions, wherein the raw materials are expressed in parts by weight as shown in Table 4 below:

[0044] Table 4, Example 4 raw materials

[0045]

[0046] The preparation method is the same as that of Example 1.

[0047] Example 5

[0048] A fracturing fluid with imbibition oil displacement and anti-swelling functions, wherein the raw materials are expressed in parts by weight as shown in Table 5 below:

[0049] Table 5, Example 5 raw materials

[0050]

[0051] The preparation method is the same as that of Example 1.

[0052] Example 6

[0053] A fracturing fluid with imbibition oil displacement and anti-swelling functions, wherein the raw materials are expressed in parts by weight as shown in Table 6 below:

[0054] Table 6, Example 6 raw materials

[0055]

[0056]

[0057] Example 7

[0058] A fracturing fluid with imbibition oil displacement and anti-swelling functions, wherein the raw materials are expressed in parts by weight as shown in Table 7 below:

[0059] Table 7, Example 7 raw materials

[0060]

[0061] The preparation method is the same as that of Example 1.

[0062] Example 8

[0063] A fracturing fluid with imbibition oil displacement and anti-swelling functions, wherein the raw materials are expressed in parts by weight as shown in Table 8 below:

[0064] Table 8, Example 8 raw materials

[0065]

[0066] The preparation method is the same as that of Example 1.

[0067] Example 9

[0068] A fracturing fluid with imbibition oil displacement and anti-swelling functions, wherein the raw materials are expressed in parts by weight as shown in Table 9 below:

[0069] Table 9, Example 9 raw materials

[0070]

[0071] The preparation method is the same as that of Example 1.

[0072] Example 10

[0073] A fracturing fluid with imbibition oil displacement and anti-swelling functions, wherein the raw materials are expressed in parts by weight as shown in Table 10 below:

[0074] Table 10, Example 10 Raw Materials

[0075]

[0076] The preparation method is the same as that of Example 1.

[0077] Example 11

[0078] A fracturing fluid with imbibition oil displacement and anti-swelling functions, wherein the raw materials are expressed in parts by weight as shown in Table 11 below:

[0079] Table 11, Example 11 raw materials

[0080]

[0081] The preparation method is the same as that of Example 1.

[0082] Example 12

[0083] A fracturing fluid with imbibition oil displacement and anti-swelling functions, wherein the raw materials are expressed in parts by weight as shown in Table 12 below:

[0084] Table 12, Example 12 Raw Materials

[0085]

[0086] The preparation method is the same as that of Example 1.

[0087] Comparative Example 1

[0088] A fracturing fluid, wherein the raw materials are expressed in parts by weight as shown in Table 13 below:

[0089] Table 13, Raw materials

[0090]

[0091] The preparation method is the same as that of Example 1.

[0092] Comparative Example 2

[0093] A fracturing fluid, wherein the raw materials are expressed in parts by weight as shown in Table 14 below:

[0094] Table 14, Raw materials

[0095]

[0096] The preparation method is the same as that of Example 1.

[0097] Comparative Example 3

[0098] A fracturing fluid, wherein the raw materials are expressed in parts by weight as shown in Table 15 below:

[0099] Table 15, Raw materials

[0100]

[0101] The preparation method is the same as that of Example 1.

[0102] Comparative Example 4

[0103] A fracturing fluid, wherein the raw materials are expressed in parts by weight as shown in Table 16 below:

[0104] Table 16, Raw Materials

[0105]

[0106]

[0107] Preparation method:

[0108] S1: Add the absorption improver and water to the reaction vessel, start stirring and heat to 70°C, react for 3-4 hours, and let it stand for 1 hour;

[0109] S2: Add anti-swelling control agent to the reaction vessel, stir for 2 hours, and let it stand for 1 hour;

[0110] S3: Add a thickener to the reaction container and stir evenly to obtain a multifunctional fracturing fluid.

[0111] Comparative Example 5

[0112] A fracturing fluid, wherein the raw materials are expressed in parts by weight as shown in Table 17 below:

[0113] Table 17, Raw Materials

[0114]

[0115] Preparation method:

[0116] S1: Add oil displacement enhancer and water to the reaction vessel, start stirring and heat to 70°C, react for 3h~4h, and let it stand for 1h;

[0117] S2: Add anti-swelling control agent to the reaction vessel, stir for 2 hours, and let it stand for 1 hour;

[0118] S3: Add a thickener to the reaction container and stir evenly to obtain a multifunctional fracturing fluid.

[0119] Comparative Example 6

[0120] A fracturing fluid, wherein the raw materials are expressed in parts by weight as shown in Table 18 below:

[0121] Table 18, Raw Materials

[0122]

[0123] Preparation method:

[0124] Add water and anti-swelling control agent to the reaction container, stir for 2 hours, and let it stand for 1 hour; then add thickener to the reaction container and stir evenly to obtain the multifunctional fracturing fluid.

[0125] Comparative Example 7

[0126] Based on Example 1, only the reaction temperature in step S1 was changed to 65°C.

[0127] Comparative Example 8

[0128] Based on Example 1, only the reaction temperature in step S1 was changed to 75°C.

[0129] Performance test experiment:

[0130] The performance of the fracturing fluids prepared in Examples 1 to 12 and Comparative Examples 1 to 8 was tested.

[0131] 1) Liquid viscosity

[0132] Test method: Take the fracturing fluids prepared in Examples 1 to 12 and Comparative Examples 1 to 8, respectively, and measure the viscosity of the fracturing fluids using a capillary viscometer or a six-speed viscometer for 170 seconds. -1 Lower viscosity.

[0133] 2) Drag reduction rate

[0134] Determination method: Take the fracturing fluid samples prepared in Examples 1 to 12 and Comparative Examples 1 to 8 respectively, and determine the drag reduction rate according to the provisions of Chapter 7.13.1.1 of SY / T6376-2008.

[0135] 3) Surface tension of the breaker liquid and interfacial tension between the breaker liquid and kerosene

[0136] Determination method: Take the fracturing fluid samples prepared in Examples 1 to 12 and Comparative Examples 1 to 8, respectively, and prepare them into breaking fluids according to 7.9.1 of SY / T 5107-2016. The breaking fluids are tested for surface tension and interfacial tension with kerosene according to 3.1 of SY / T 5370-1999.

[0137] 4) Demulsification rate

[0138] Determination method: Take the fracturing fluid samples prepared in Examples 1 to 12 and Comparative Examples 1 to 8 respectively, prepare demulsification liquids according to the provisions of 7.9.1 of SY / T 5107-2016, and test the demulsification rate of the demulsification liquids according to the provisions of 7.11.1 of SY / T 5107-2016.

[0139] 5) CST ratio

[0140] Determination method: Take the fracturing fluid samples prepared in Examples 1 to 12 and Comparative Examples 1 to 8, respectively, and prepare them into breaking fluids according to the provisions of 7.9.1 of SY / T5107-2016. The breaking fluids are tested for CST ratio according to the provisions of 7.10 of NB / T 14003.1-2015.

[0141] The experimental test results are shown in Table 19 below.

[0142] Table 19. Performance test results of various fracturing fluid samples

[0143]

[0144] Examples 1-12 are all examples of the fracturing fluid of the present invention. Experimental test results show that various properties of these fracturing fluids meet the standards.

[0145] From Example 1 and Comparative Example 1, it can be seen that, based on the fracturing fluid components of the present invention, if the anti-swelling control agent, didodecyldimethylammonium chloride, is replaced with didodecyldimethylammonium chloride, the viscosity of the fracturing fluid decreases. This demonstrates that only by using the gemini didodecyldimethylammonium chloride in the present invention can the performance of the fracturing fluid be significantly improved.

[0146] Comparative Examples 2 and 3 are based on Example 1, except that the anti-swelling control agent is replaced with two other surfactants (cetyltrimethylammonium chloride and palmitamidopropyltrimethylammonium chloride). Comparative test data show that when these other surfactants are used as anti-swelling control agents, the viscosity of the fracturing fluid decreases, significantly lower than that of the fracturing fluid using didodecyldimethylammonium chloride as the anti-swelling control agent of the present invention.

[0147] Comparative Examples 4, 5, and 6 are fracturing fluids obtained by removing the oil displacement enhancer, removing the imbibition improver, and removing both the oil displacement enhancer and the imbibition improver, respectively, based on Example 1. Performance test data indicate that the oil displacement enhancer and the imbibition improver must be used simultaneously in the fracturing fluid of the present invention to achieve optimal performance. Using either or neither of the two fracturing fluids significantly reduces the performance of the resulting fracturing fluids, failing to meet the requirements of fracturing operations.

[0148] Comparative Examples 7 and 8 are based on Example 1, but with the reaction temperature of step S1 in the preparation method changed. It can be seen that by lowering (65°C) or raising (75°C) the temperature of step S1, the properties of the obtained fracturing fluids are lower than those of the fracturing fluid in Example 1. That is, only by carrying out step S1 at a temperature of 70°C can the fracturing fluid with imbibition displacement and anti-swelling functions of the present invention be prepared.

[0149] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with this profession can make some changes or modifications to equivalent embodiments of the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A fracturing fluid with imbibition oil displacement and anti-swelling functions, characterized in that: The following components are included in mass percentage: Thickener 0.1% to 0.5%, imbibition improver 0.2% to 0.6%, oil displacement enhancer 0.5% to 1.2%, anti-swelling control agent 0.2% to 0.8%, and the rest is water; The imbibition improver is selected from one or a mixture of nano-silicon dioxide, nano-calcium carbonate, and nano-zirconium dioxide; The oil displacement enhancer is selected from one of hydrogenated styrene diene copolymer, polymethacrylate, ethylene propylene copolymer, and polyisobutylene; The anti-swelling control agent is didodecyl dimethyl ammonium chloride; The thickener is any one of anionic polyacrylamide and its derivatives; the molecular weight of the anionic polyacrylamide is 16 million, and it is a copolymer of AMPS and AM.

2. A method for preparing a fracturing fluid having imbibition oil displacement and anti-swelling functions according to claim 1, characterized in that: Here are the steps: S1. Add an imbibition improver, water, and an oil displacement enhancer to a reaction vessel, start stirring, and heat to 70°C. React for 3 to 4 hours, and allow to cool for 1 to 2 hours. S2. Add an anti-swelling control agent to the reaction vessel, stir for 1.5 to 3 hours, and let it stand for 0.5 to 1 hour; S3. Add a thickener to the reaction container and stir evenly to obtain a fracturing fluid.

3. The method for preparing a fracturing fluid having imbibition displacement and anti-swelling functions according to claim 2, wherein: In the steps S1 and S2, the stirring rate is 50 r / min to 150 r / min.

4. The method for preparing a fracturing fluid having imbibition oil displacement and anti-swelling functions according to claim 2, wherein: In step S3, the stirring rate is 600 r / min to 1000 r / min.

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