Waterproofing locking agent for drilling fluid, preparation method thereof and treatment agent for oil field exploration

Abstract

This invention relates to the field of oil and gas field drilling technology, and discloses a waterproof locking agent for drilling fluid, its preparation method, and a treatment agent for oilfield exploration. The method includes: (1) dissolving reactants A, B, and C in water to obtain mixture I; (2) contacting mixture I with reactant D and a surfactant to obtain mixture II, and then subjecting it to an irradiation polymerization reaction; (3) pulverizing, filtering, washing, extracting, and drying the obtained crude product to obtain the waterproof locking agent; reactant A is selected from at least one of methyl glucoside, chitosan, cyclodextrin, cellulose, and lignin; reactant B is an amide monomer containing an alkenyl group; reactant C is a quaternary ammonium salt monomer containing an alkenyl group; and reactant D is a hydrophobic monomer containing a phenyl group. This waterproof locking agent can effectively reduce the surface tension of the aqueous phase and the interfacial tension between oil and water, and can effectively prevent damage to core permeability caused by oil-water emulsification and water-locking effects.

Description

Technical Field

[0001] This invention relates to the field of oil and gas field drilling, specifically to a waterproof locking agent for drilling fluid, its preparation method, and a treatment agent for oil field exploration. Background Technology

[0002] Among the discovered natural gas reservoirs, medium- and low-permeability reservoirs constitute the majority, and a large portion of them are ultra-low-permeability reservoirs. Low-permeability reservoirs are characterized by high clay content, high water saturation, high capillary pressure, strong water sensitivity, small pore throats, poor permeability, complex structure, and strong heterogeneity. When the initial saturation is lower than the bound water saturation, excess capillary pressure exists in the reservoir. When external fluids enter, capillary self-absorption of the aqueous phase easily occurs, resulting in slow or even no return of the invading external fluid, leading to water-lock damage and a decrease in gas well productivity.

[0003] There are two main methods to address water-locking damage: physical and chemical methods. Physical methods include eliminating drilling fluid filter cake blockage, increasing production pressure differential, altering reservoir pore geometry, and formation heating technologies. However, physical methods suffer from drawbacks such as high energy consumption, shallow removal depth, and high recurrence rate. Chemical methods primarily involve adding water-locking agents to the external fluid to induce wetting reversal on the reservoir surface, reducing interfacial tension between immiscible phases and decreasing the initial pressure gradient of the fluid in low-permeability gas reservoirs. This technique, known as reducing the Jamin effect, mitigates water-locking damage and is currently the main research direction for reducing water-locking damage and improving reservoir productivity.

[0004] Currently, commonly used waterproofing lock-in agents are mainly surfactant-based products, such as sodium dodecyl sulfate (SDS), octylphenol polyoxyethylene ether (OP-10), sorbitan monooleate (Span 80), and sodium perfluorooctane sulfonate (PFOS). However, these products have drawbacks such as easy foaming, low efficiency in reducing surface tension and oil-water interfacial tension, and low permeability recovery rate. In recent years, various research institutions have been actively researching various surfactant-based waterproofing lock-in agents. For example, 3M provides a nonionic fluoropolymer surfactant-based waterproofing lock-in agent. This agent includes a fluoroalkyl terminal group and an olefinic head terminal group, belonging to a nonionic surfactant. It can change the wettability of rocks from strong water wettability to neutral water wettability, effectively increasing the relative gas permeability, and maintaining stability over a wide range of temperatures, pressures, permeabilities, and brine salinity.

[0005] CN102887974B discloses a polymer-type waterproofing agent, which is a hydrophobic associative polymer with tridecyl methacrylate as the hydrophobic monomer. However, it is generally believed that fluorine-containing organic compounds will have certain negative impacts on the ecological environment, and whether the product has good biodegradability is debatable.

[0006] Therefore, researching and developing a waterproofing sealant is of great significance. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of existing waterproofing agents in terms of insufficient water-locking effect, and to provide a waterproofing agent for drilling fluid, its preparation method, and a treatment agent for oilfield exploration. This waterproofing agent can effectively reduce the surface tension of the aqueous phase and the interfacial tension between oil and water, can transform hydrophilic surfaces into neutral wetting surfaces, and can effectively prevent the damage to core permeability caused by oil-water emulsification and water-locking effects.

[0008] To achieve the above objectives, a first aspect of the present invention provides a method for preparing a waterproof locking agent for drilling fluids, wherein the preparation method includes:

[0009] (1) Dissolve reactants A, B and C in water to obtain mixture I;

[0010] (2) After contacting the mixture I with reactant D and surfactant, mixture II is obtained, and then irradiation polymerization reaction is carried out;

[0011] (3) The crude product obtained in step (2) is pulverized and then filtered, washed, extracted and dried to obtain a waterproofing agent;

[0012] Wherein, reactant A is selected from one or more of methyl glucoside, chitosan, cyclodextrin, cellulose and lignin;

[0013] Wherein, reactant B is an amide monomer containing an alkenyl group;

[0014] Wherein, reactant C is a quaternary ammonium salt monomer containing an alkenyl group;

[0015] The reactant D is a hydrophobic monomer containing a phenyl group.

[0016] A second aspect of the present invention provides a waterproof locking agent for drilling fluid prepared by the aforementioned preparation method.

[0017] A third aspect of the present invention provides a treatment agent for oilfield exploration, wherein the treatment agent for oilfield exploration includes the aforementioned waterproofing lock agent for drilling fluid.

[0018] Through the above technical solutions, the waterproofing agent of the present invention can effectively reduce surface tension, for example, to 17.99-19.85 mN / m; it can reduce oil / water interfacial tension, for example, to between 0.41 mN / m and 0.44 mN / m; and it can increase the contact angle to between 89.2° and 91.8°, indicating that it can transform hydrophilic surfaces into neutral wettable surfaces. Furthermore, drilling fluids using the waterproofing agent of the present invention exhibit significantly higher permeability recovery rates in artificial cores, all exceeding 88%, effectively preventing damage to core permeability caused by oil-water emulsification and water-locking effects. Detailed Implementation

[0019] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0020] The first aspect of this invention provides a method for preparing a waterproofing sealant for drilling fluids, wherein the preparation method includes:

[0021] (1) Dissolve reactants A, B and C in water to obtain mixture I;

[0022] (2) After contacting the mixture I with reactant D and surfactant, mixture II is obtained, and then irradiation polymerization reaction is carried out;

[0023] (3) The crude product obtained in step (2) is pulverized and then filtered, washed, extracted and dried to obtain the waterproofing agent;

[0024] Wherein, reactant A is selected from one or more of methyl glucoside, chitosan, cyclodextrin, cellulose and lignin;

[0025] Wherein, reactant B is an amide monomer containing an alkenyl group;

[0026] Wherein, reactant C is a quaternary ammonium salt monomer containing an alkenyl group;

[0027] The reactant D is a hydrophobic monomer containing a phenyl group.

[0028] According to the present invention, in step (1), reactants A, B, and C are dissolved in water to obtain a mixture. The container used for dissolution is not specifically limited; for example, a beaker may be used. Furthermore, preferably, the dissolution can be carried out under stirring conditions, for example, at room temperature, at a stirring rate of 500-1200 r / min, until dissolved.

[0029] According to the present invention, the molar ratio of reactant A, reactant B, reactant C, and reactant D is (60-160):(50-100):(5-20):(0.2-2), preferably (80-120):(60-80):(10-15):(0.5-1.5).

[0030] Considering that the polymerization of each reactant is non-selective and that the gas-gathering rates differ, the above-described ratios of reactants only indicate the molar ratio of each reactant structural unit when the monomer to which the active agent originally belongs is used as a raw material in the reactor during the synthesis process. They do not represent the ratio of the structural units of each reactant in the waterproofing agent molecule.

[0031] According to the present invention, reactant A, reactant B, reactant C and water are added sequentially to a beaker and stirred until completely dissolved. The water is not particularly limited, but is preferably deionized water.

[0032] According to the present invention, the surfactant acts as an emulsifier, and the concentration of the surfactant in mixture II is 3wt%-5wt%.

[0033] According to the present invention, reactant B is selected from one or more of acrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide, N-vinylmethylacetamide, N-vinylethylacetamide, N-isopropylacrylamide, diacetone acrylamide, and N-hydroxymethylacrylamide; preferably, reactant B is selected from one or more of acrylamide, N,N-dimethylacrylamide, N-isopropylacrylamide, N-hydroxymethylacrylamide, and N-vinylmethylacetamide. In the present invention, reactant B has adsorption groups and can undergo polymerization with reactant A, thereby adsorbing onto the rock through the amide groups in reactant B.

[0034] According to the present invention, the reactant C is selected from one or more of dimethyl diallyl ammonium chloride, diethyl diallyl ammonium chloride, 2-hydroxy-3-methacryloyloxypropyltrimethyl ammonium chloride, acryloyloxyethyl dimethyl ammonium chloride, and 2-acrylamidoethyl dimethyl ammonium chloride. In the present invention, reactant C is introduced, which can electrostatically adsorb onto negatively charged rocks, and under the conditions specified above for reactant C in the present invention, the adsorption of polymer molecular chains between rocks can be enhanced.

[0035] According to the present invention, the reactant D has the structure shown in formula (1);

[0036]

[0037] Where R1 is H or CH3; n is an integer 0 ≤ n ≤ 5.

[0038] In this invention, preferably, n is 0, 1, 2 or 5.

[0039] In this invention, more preferably, the reactant D is selected from one or more of 4,4,4-triphenyl-1-butene, 2-methyl-3,3,3-triphenylpropene, 8,8,8-triphenyl-1-octene, 3,3,3-triphenylpropene, and 5,5,5-triphenyl-1-pentene.

[0040] According to the present invention, a hydrophobic monomer (reactant D) containing phenyl is introduced as a hydrophobic group, which has low polarizability. When the polymer molecules are adsorbed on the rock surface, they can form a hydrophobic film on the rock surface, transforming the hydrophilic rock surface into a hydrophobic one, thereby increasing the relative gas permeability and ultimately reducing the degree of waterlock damage.

[0041] According to the present invention, the surfactant is selected from any one of anionic surfactants; preferably, the surfactant is selected from one or more of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, sodium dodecyl sulfonate, sodium octadecylbenzenesulfonate, sodium octadecyl sulfate, and sodium octadecyl sulfonate; more preferably, the surfactant is selected from one or more of sodium dodecyl sulfate, sodium dodecyl sulfonate, sodium octadecylbenzenesulfonate, sodium octadecyl sulfate, and sodium octadecyl sulfonate.

[0042] According to the present invention, in step (2), the contact conditions include a temperature of 40-60°C and a time of 4-6 hours; preferably, the contact further includes being carried out under stirring and in the presence of nitrogen; wherein the stirring conditions include a stirring rate of 500-1200 r / min. In the present invention, nitrogen is purged to remove oxygen dissolved in the mixture I. Preferably, under the condition of maintaining nitrogen purging, the mixture obtained in step (1) is contacted with reactant D and surfactant at a predetermined reaction temperature of 40-60°C.

[0043] According to the present invention, in step (2), the reactant mixture II after the mixture I is in contact with reactant D and surfactant is transferred to an irradiation bottle and placed in an irradiation field for co-irradiation reaction, wherein the conditions of the co-irradiation reaction include: under the irradiation of a radiation source, the irradiation dose is 4-16 kGy and the reaction time is 4-6 h; preferably, the radiation source is selected from cobalt-60.

[0044] According to the present invention, in step (3), the crude product after the reaction in step (2) is pulverized. This is achieved by first cutting the crude product into small pieces, then drying the pieces in a drying oven to constant weight, pulverizing them, adding ethanol for precipitation, filtering, washing the product with acetone 3-5 times, extracting, and then vacuum drying at 25-30°C to constant weight. In the present invention, the extractant used in the extraction is a mixed solvent containing glacial acetic acid and ethylene glycol; more preferably, the volume ratio of glacial acetic acid to ethylene glycol is 3:2.

[0045] A second aspect of the present invention provides a waterproof locking agent for drilling fluid prepared by the method described above.

[0046] According to the present invention, the viscosity-average molecular weight (Mv) of the waterproofing agent for drilling fluid provided by the present invention is 4.5 × 10⁻⁶. 5 g / mol - 7.5 × 10 5 g / mol.

[0047] A third aspect of the present invention provides a treatment agent for oilfield exploration, wherein the treatment agent for oilfield exploration includes the aforementioned waterproofing lock agent for drilling fluid.

[0048] According to the present invention, the amount of the waterproofing agent is 0.2-2% by weight, based on the total weight of the oilfield exploration treatment agent.

[0049] This invention polymerizes a reactive monomer containing an adsorption group (i.e., an amide group containing an alkenyl group) with reactant A (methyl glucoside), which facilitates the adsorption of molecular chains onto the surface of clay particles. The grafted quaternary ammonium salt monomer containing an alkenyl group can electrostatically adsorb with negatively charged clay, thereby enhancing the adsorption of polymer molecular chains between clay particles. In addition, the introduction of a hydrophobic monomer containing a phenyl group into the molecule provides low polarizability. When the polymer molecules are adsorbed onto the rock surface, they can form a hydrophobic film on the rock surface, transforming the hydrophilic rock surface into a hydrophobic one, thereby increasing the relative gas permeability and ultimately preventing waterlock damage.

[0050] The present invention will be described in detail below through embodiments.

[0051] In the following examples and comparative examples:

[0052] (1) Surface tension was measured using a KRUSS surface tension meter (KRUSS GmbH, Germany) at room temperature (25℃) (ring method);

[0053] (2) The interfacial tension of the TX500 rotating drop interfacial tensiometer (Kno Industries, Inc., USA) was determined with respect to 0. # Interfacial tension of diesel fuel sample;

[0054] (3) The contact angle on the glass plate surface was measured using an SL200L contact angle meter (Shanghai Solon Information Technology Co., Ltd.).

[0055] (4) The viscosity-average molecular weight was determined by LC-10A high performance liquid chromatograph (Shimadzu Corporation, Japan) at room temperature (25°C) using gel permeation chromatography.

[0056] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0057] Example 1

[0058] This embodiment illustrates the waterproofing sealant prepared using the method of the present invention.

[0059] (1) Add 194.18g of methyl glucoside, 42.648g of acrylamide, 16.167g of dimethyl diallyl ammonium chloride and 2900mL of water to a beaker in sequence, and stir at a stirring speed of 800rpm until completely dissolved to obtain a mixture.

[0060] (2) Under a stirring speed of 800 rpm, the mixture obtained in step (1) was contacted with 2.844 g of 4,4,4-triphenyl-1-butene and 131.5 g of sodium octadecylbenzenesulfonate. The stirring was continued to solubilize 4,4,4-triphenyl-1-butene in the sodium octadecylbenzenesulfonate micelles. Nitrogen gas was purged for at least 30 min to remove dissolved oxygen in the liquid. The stirring was stopped, and the mixture was heated to the predetermined reaction temperature of 50 °C while maintaining nitrogen purging. The mixture was then transferred to an irradiation bottle and placed in an irradiation field for co-irradiation reaction. The irradiation dose was 10 kGy and the reaction time was 5.5 h, thus obtaining the crude product of the waterproofing lock.

[0061] (3) The crude yellow gelatinous waterproofing agent was cut into small pieces and dried in a drying oven to constant weight. After precipitation with 2000 mL of ethanol, the product was filtered. The product was washed three times with acetone each time. Then, the product was extracted with a Soxhlet extractor for 24 hours using a 3:2 (v / v) glacial acetic acid-ethylene glycol mixture. The product was then vacuum dried at 25°C to constant weight to obtain the target waterproofing agent, with a molecular weight (Mv) of 6.14 × 10⁻⁶. 5 g / mol.

[0062] Example 2

[0063] This embodiment illustrates the waterproofing sealant prepared using the method of the present invention.

[0064] (1) Add 233.016g of methyl glucoside, 59.478g of N,N-dimethylacrylamide, 23.77g of 2-hydroxy-3-methacryloyloxypropyltrimethylammonium chloride and 2846.376mL of water to a beaker in sequence, and stir at a stirring speed of 500rpm until completely dissolved to obtain a mixture;

[0065] (2) Under a stirring speed of 500 rpm, the mixture obtained in step (1) was contacted with 1.422 g of 2-methyl-3,3,3-triphenylpropene and 97.8576 g of sodium octadecyl sulfate. The mixture was stirred continuously to solubilize 2-methyl-3,3,3-triphenylpropene in sodium octadecyl sulfate micelles. Nitrogen gas was purged for more than 30 min to remove dissolved oxygen in the liquid. While maintaining nitrogen purging and raising the temperature to the predetermined reaction temperature of 60 °C, the mixture was transferred to an irradiation bottle and placed in an irradiation field for co-irradiation reaction. The irradiation dose was 16 kGy and the reaction time was 4 h, thus obtaining the crude product of the waterproofing lock.

[0066] (3) The crude yellow gelatinous waterproofing agent was cut into small pieces and dried in a drying oven to constant weight. After precipitation with 2000 mL of ethanol, the product was filtered. The product was washed three times with acetone each time. Then, it was extracted with a Soxhlet extractor for 24 hours using a 3:2 (v / v) glacial acetic acid-ethylene glycol mixture. The product was then vacuum dried at 25°C to constant weight to obtain the target waterproofing agent, with an Mv of 5.77 × 10⁻⁶. 5 g / mol.

[0067] Example 3

[0068] This embodiment illustrates the waterproofing sealant prepared using the method of the present invention.

[0069] (1) Add 233.016g of methyl glucoside, 90.528g of N-isopropylacrylamide, 26.805g of 2-acrylamidoethyldimethylammonium chloride and 6656.631mL of water to a beaker in sequence, and stir at a stirring speed of 1200rpm until completely dissolved to obtain a mixture.

[0070] (2) Under a stirring speed of 1200 rpm, the mixture obtained in step (1) was contacted with 1.7025 g of 8,8,8-triphenyl-1-octene and 368.8781 g of sodium dodecyl sulfate. The mixture was stirred continuously to solubilize 8,8,8-triphenyl-1-octene in sodium dodecyl sulfate micelles. Nitrogen gas was purged for more than 30 min to remove dissolved oxygen in the liquid. While maintaining nitrogen purging and raising the temperature to the predetermined reaction temperature of 40 °C, the mixture was transferred to an irradiation bottle and placed in an irradiation field for co-irradiation reaction. The irradiation dose was 16 kGy and the reaction time was 6 h, thus obtaining the crude product of the waterproofing lock.

[0071] (3) The crude yellow gelatinous waterproofing agent was cut into small pieces and dried in a drying oven to constant weight. After precipitation with 3600 mL of ethanol, the product was filtered. The product was washed three times with acetone each time. Then, it was extracted with a Soxhlet extractor for 24 hours using a 3:2 (v / v) glacial acetic acid-ethylene glycol mixture. The product was then vacuum dried at 25°C to constant weight to obtain the target waterproofing agent, with a molecular weight (Mv) of 7.5 × 10⁻⁶. 5 g / mol.

[0072] Example 4

[0073] This embodiment illustrates the waterproofing sealant prepared using the method of the present invention.

[0074] (1) Add 155.344g of methyl glucoside, 92.104g of N-hydroxymethylacrylamide, 17.96g of acryloyloxyethyl dimethylammonium chloride and 1503.9787mL of water to a beaker in sequence, and stir at a stirring speed of 1000rpm until completely dissolved to obtain a mixture.

[0075] (2) Under a stirring speed of 1000 rpm, the mixture obtained in step (1) was contacted with 4.056 g of 3,3,3-triphenylpropylene and 93.339 g of sodium dodecyl sulfonate. The mixture was stirred continuously to solubilize 3,3,3-triphenylpropylene in sodium dodecyl sulfonate micelles. Nitrogen gas was purged for more than 30 min to remove dissolved oxygen in the liquid. While maintaining nitrogen purging and raising the temperature to the predetermined reaction temperature of 52°C, the mixture was transferred to an irradiation bottle and placed in an irradiation field for co-irradiation reaction. The irradiation dose was 12 kGy and the reaction time was 5.0 h, thus obtaining the crude product of the waterproofing lock.

[0076] (3) The crude yellow gelatinous waterproofing agent was cut into small pieces and dried in a drying oven to constant weight. After precipitation with 1800 mL of ethanol, the product was filtered. The product was washed three times with acetone each time. Then, it was extracted with a Soxhlet extractor for 24 hours using a 3:2 mixture of glacial acetic acid and ethylene glycol as the extraction solvent. The product was then vacuum dried at 25°C to constant weight to obtain the target waterproofing agent, with a molecular weight (Mv) of 6.14 × 10⁻⁶. 5 g / mol.

[0077] Example 5

[0078] This embodiment illustrates the waterproofing sealant prepared using the method of the present invention.

[0079] (1) Add 194.18g of methyl glucoside, 69.39g of N-vinylmethylacetamide, 22.76g of diethyldiallyl ammonium chloride and 2000mL of water to a beaker in sequence, and stir at a stirring speed of 720rpm until completely dissolved to obtain a mixture.

[0080] (2) Under a stirring speed of 720 rpm, the mixture obtained in step (1) was contacted with 3.58 g of 5,5,5-triphenyl-1-pentene and 100 g of sodium octadecyl sulfonate. The mixture was stirred continuously to solubilize 5,5,5-triphenyl-1-pentene in the sodium octadecyl sulfonate micelles. Nitrogen gas was purged for more than 30 min to remove oxygen dissolved in the liquid. While maintaining nitrogen purging and raising the temperature to the predetermined reaction temperature of 55 °C, the mixture was transferred to an irradiation bottle and placed in an irradiation field for co-irradiation reaction. The irradiation dose was 12 kGy and the reaction time was 6.0 h, thus obtaining the crude product of the waterproofing lock.

[0081] (3) The crude yellow gelatinous waterproofing agent was cut into small pieces and dried in a drying oven to constant weight. After precipitation with 2000 mL of ethanol, the product was filtered. The product was washed three times with acetone each time. Then, it was extracted with a Soxhlet extractor for 24 hours using a 3:2 (v / v) glacial acetic acid-ethylene glycol mixture. The product was then vacuum dried at 25°C to constant weight to obtain the target waterproofing agent, with an Mv of 4.5 × 10⁻⁶. 5 g / mol.

[0082] Comparative Example 1

[0083] The waterproofing sealant was prepared using the same method as in the examples, except that 4,4,4-triphenyl-1-butene was not added.

[0084] Comparative Example 2

[0085] The waterproofing agent was prepared using the same method as in the examples, except that the added hydrophobic monomer was p-methylstyrene, that is, "4,4,4-triphenyl-1-butene" in Example 1 was replaced with "p-methylstyrene", and the molar amount of p-methylstyrene was the same as the molar amount of 4,4,4-triphenyl-1-butene in Example 1.

[0086] Comparative Example 3

[0087] The waterproofing agent was prepared using the same method as in the examples, except that the added hydrophobic monomer was N-hexadecylacrylamide, that is, "4,4,4-triphenyl-1-butene" in Example 1 was replaced with "N-hexadecylacrylamide", and the molar amount of N-hexadecylacrylamide was the same as the molar amount of 4,4,4-triphenyl-1-butene in Example 1.

[0088] Comparative Example 4

[0089] The waterproofing agent was prepared using the same method as in the examples, except that the added hydrophobic monomer was tridecylfluorooctyl methacrylate, that is, "4,4,4-triphenyl-1-butene" in Example 1 was replaced with "tridecylfluorooctyl methacrylate", and the molar amount of tridecylfluorooctyl methacrylate was the same as the molar amount of 4,4,4-triphenyl-1-butene in Example 1.

[0090] Test Example 1

[0091] Sodium dodecyl sulfate (SDS), octylphenol polyoxyethylene ether (OP-10), sorbitan monooleate (Span 80), sodium perfluorooctane sulfonate (PFOS), the waterproofing lock-in agents prepared in Examples 1-5, and the waterproofing lock-in agents in Comparative Examples 1-4 were formulated into a 0.6% (w / w) solution. The surface tension and its relationship with 0.05% (w / w) were measured at room temperature (25°C). #The interfacial tension of the diesel fuel sample was measured, as well as its contact angle on the glass plate surface. The test results are shown in Table 1, which shows the surface tension (mN / m), oil / water interfacial tension (mN / m), and contact angle (°) of the waterproofing sealant.

[0092] Table 1

[0093]

[0094]

[0095] As can be seen from Table 1, compared with the waterproofing lockers prepared in Comparative Examples 1-4 and the commonly used waterproofing lockers SDS, OP-10, Span 80 and PFOS in drilling fluids, the waterproofing lockers prepared in Examples 1-5 can effectively reduce surface tension and oil / water interfacial tension and can transform hydrophilic surfaces into neutral wetting surfaces. According to the Young-Laplace equation, a decrease in surface tension can significantly reduce capillary pressure, thereby reducing the likelihood of water-locking damage. A decrease in oil / water interfacial tension can effectively reduce excess capillary pressure in the reservoir, reducing the driving force for the inhalation of foreign liquid phases into porous media. This effectively reduces the amount of foreign liquid phase intrusion near the wellbore or fracture surface, lowers the liquid saturation in tight reservoirs, increases oil and gas flow space, improves near-wellbore oil and gas flow conditions, and reduces the degree of water-locking. The transition from a water-wetted surface to a neutral water-wetted surface weakens the hydrophilicity of the core surface, reduces liquid phase adhesion on the core surface, facilitates gas phase flow, improves the flow capacity of the oil phase in the core pores, reduces capillary pressure, and prevents water-locking damage. Furthermore, the large contact angles in Examples 1-5 indicate a stronger oleophilicity, meaning a greater ability to change the glass surface from hydrophilic to oleophilic, which is more beneficial for reservoir protection.

[0096] Test Example 2

[0097] Core permeability recovery rate test

[0098] Commonly used drilling fluid waterproofing agents such as SDS, OP-10, Span 80, PFOS, and the waterproofing agents prepared in Examples 1-5 and Comparative Examples 1-4 were prepared into solutions with a mass percentage concentration of 0.6%. The experimental water was simulated formation water (mineralization 20000 mg / L, formula: 1000 mL water + 1.73 g CaCl2 + 1.17 g MgCl2 + 5.27 g Na2SO4 + 11.83 g NaCl) for later use.

[0099] After drying the artificial core, the relative permeability (K0) was measured by gas. At a temperature of 70℃ and a displacement pressure of 0.3 MPa, formation water with a pore volume of 10 times its normal volume and formation water containing a water-locking agent were injected in reverse. The formation water and water-locking agent were then in contact with the core for 24 hours each to simulate the water-locking damage process. For the core damaged by forward gas-driven water-locking, the displaced filtrate was collected, and the gas permeability (K0) of the core after water-locking damage was measured by gas. d The test results are shown in Table 2, which shows the permeability recovery rate of the core samples.

[0100] Table 2

[0101]

[0102] As can be seen from Table 2, compared with the waterproofing agents prepared in Comparative Examples 1-4 and commonly used waterproofing agents in drilling fluids such as SDS, OP-10, Span 80 and PFOS, the waterproofing agents prepared in Examples 1-5 have significantly higher permeability recovery rates, all greater than 88.24%, which can effectively prevent the damage to core permeability caused by oil-water emulsification and water-locking effects.

[0103] Test Example 3

[0104] Biotoxicity and biodegradability evaluation

[0105] The main testing methods for drilling fluid biotoxicity include: mysid shrimp bioassay, microbial toxicity assay, and cumulative biofluorescence assay. Among these, the mysid shrimp bioassay is the only method officially approved by the U.S. Environmental Protection Agency (EPA) for evaluating the biotoxicity of drilling fluids. According to the EPA's biotoxicity and organic pollutant biodegradability classification standards and testing methods (Biotoxicity classification standards: EC...), 50 ≤1, highly toxic; 1 < EC 50 ≤100, highly toxic; 100 < EC 50 ≤1000, moderately toxic; 1000 < EC 50 ≤10000, slightly toxic; 10000 < EC 50 ≤30000, non-toxic; EC 50 >30,000, recommended emission standards; Biodegradability evaluation index (Y) = (Biochemical Oxygen Demand (BOD) / Chemical Oxygen Demand (COD)) × 100, Y ≥ 25.0, easily degradable; 15.0 ≤ Y < 25.0, relatively easily degradable; 5 ≤ Y < 15.0, degradable; Y < 5.0, difficult to degrade.

[0106] The biotoxicity and biodegradability of Examples 1-5 and Comparative Examples 1-4 were evaluated, and the test results are shown in Table 3, which shows the biotoxicity and biodegradability of the waterproofing lock.

[0107] Table 3

[0108] sample <![CDATA[EC 50 (mg / L)]]> Y Example 1 33100 18.36 Example 2 33200 19.56 Example 3 34700 17.23 Example 4 33400 17.70 Example 5 33800 17.24 Comparative Example 1 32400 16.87 Comparative Example 2 32500 17.10 Comparative Example 3 33100 17.05 Comparative Example 4 9500 8.75

[0109] As can be seen from Table 3, the EC samples from Examples 1-5 and Comparative Examples 1-3... 50 All were above 30,000 mg / L, meeting the emission standards, while the EC in comparison ratio 4... 50 Values ​​in the range of 1000 < EC 50 ≤10000, meeting the microtoxicity standard; in addition, Comparative Example 4, which uses long fluorocarbon chains as hydrophobic groups, has an EC... 50 The concentration was 9500 mg / L, and the Y value was 8.75, indicating that its biotoxicity and biodegradability were significantly weaker than other samples. Experimental results show that the waterproofing agents prepared in Examples 1-5 have good environmental performance. The environmental performance of the waterproofing agent with benzene ring structures as hydrophobic groups in the molecular chain is superior to that using long fluorocarbon chains as hydrophobic groups.

[0110] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing a waterproof locking agent for drilling fluid, characterized in that, The preparation method includes: (1) Dissolve reactants A, B and C in water to obtain mixture I; (2) After contacting the mixture I with reactant D and surfactant, mixture II is obtained, and then irradiation polymerization reaction is carried out; (3) The crude product obtained in step (2) is pulverized and then filtered, washed, extracted and dried to obtain a waterproofing agent; Wherein, reactant A is selected from one or more of methyl glucoside, chitosan, cyclodextrin, cellulose and lignin; Wherein, reactant B is an amide monomer containing an alkenyl group; Wherein, reactant C is a quaternary ammonium salt monomer containing an alkenyl group; The reactant D is a hydrophobic monomer containing a phenyl group.

2. The preparation method according to claim 1, wherein, The reactant D has the structure shown in formula (1); Where R1 is H or CH3; n is an integer 0 ≤ n ≤ 5; Preferably, n is 0, 1, 2 or 5; More preferably, the reactant D is selected from one or more of 4,4,4-triphenyl-1-butene, 2-methyl-3,3,3-triphenylpropene, 8,8,8-triphenyl-1-octene, 3,3,3-triphenylpropene, and 5,5,5-triphenyl-1-pentene.

3. The preparation method according to claim 1 or 2, wherein, The reactant B is selected from one or more of acrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide, N-vinylmethylacetamide, N-vinylethylacetamide, N-isopropylacrylamide, diacetone acrylamide, and N-hydroxymethylacrylamide; Preferably, reactant B is selected from one or more of acrylamide, N,N-dimethylacrylamide, N-isopropylacrylamide, N-hydroxymethylacrylamide, and N-vinylmethylacetamide.

4. The preparation method according to claim 1 or 2, wherein, The reactant C is selected from one or more of dimethyl diallyl ammonium chloride, diethyl diallyl ammonium chloride, 2-hydroxy-3-methacryloyloxypropyltrimethyl ammonium chloride, acryloyloxyethyl dimethyl ammonium chloride, and 2-acrylamidoethyl dimethyl ammonium chloride.

5. The preparation method according to claim 1 or 2, wherein, The surfactant is selected from anionic surfactants; preferably, the surfactant is selected from one or more of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, sodium dodecyl sulfonate, sodium octadecylbenzenesulfonate, sodium octadecyl sulfate, and sodium octadecyl sulfonate; more preferably, the surfactant is selected from one or more of sodium dodecyl sulfate, sodium dodecyl sulfonate, sodium octadecylbenzenesulfonate, sodium octadecyl sulfate, and sodium octadecyl sulfonate.

6. The preparation method according to any one of claims 1-5, wherein, The molar ratio of reactant A, reactant B, reactant C and reactant D is (60-160):(50-100):(5-20):(0.2-2); Preferably, the molar ratio of reactant A, reactant B, reactant C and reactant D is (80-120):(60-80):(10-15):(0.5-1.5); And / or, the concentration of the surfactant in mixture II is 3wt%-5wt%.

7. The preparation method according to claim 1, wherein, In step (2), the contact conditions include: a temperature of 40-60°C and a time of 4-6 hours; Preferably, the contact is further carried out under stirring and in the presence of nitrogen.

8. The preparation method according to claim 1 or 7, wherein, In step (3), the extraction agent used is a mixed solvent containing glacial acetic acid and ethylene glycol.

9. A waterproof locking agent for drilling fluid prepared by the preparation method according to any one of claims 1-8.

10. The waterproofing sealant for drilling fluid according to claim 9, wherein, The viscosity-average molecular weight (Mv) of the waterproofing agent is 4.5 × 10⁻⁶. 5 g / mol - 7.5 × 10 5 g / mol.

11. A treatment agent for oilfield exploration, characterized in that, The oilfield exploration treatment agent includes the drilling fluid waterproofing agent as described in claim 9 or 10.

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