Amphiphilic polymer blocking agent for drilling fluid and preparation method thereof

Abstract

The invention provides a preparation method of an amphiphilic polymer blocking agent for drilling fluid, which comprises the following steps: mixing and stirring a hydrophilic polymer, an oleophylic monomer, a pore-foaming agent, a cross-linking agent and an initiator in water to form an emulsion, heating to react, filtering, and drying to obtain the amphiphilic polymer blocking agent for drilling fluid. Compared with the prior art, the plugging agent prepared by the invention has the advantages that a framework is a cross-linked oleophylic polymer, and the plugging agent has better lipophilicity; the surface is coated with a certain amount of hydrophilic stabilizer, so that the oil-based drilling fluid has good hydrophilicity and good compatibility with oil-based drilling fluid and water-based drilling fluid; the main body is a cross-linked oleophylic monomer polymer, so that the chemical stability is good, and the requirements of high-temperature plugging, leakage prevention and collapse prevention are met; furthermore, the material is hollow rigid pellets at normal temperature, is easy to crush, and is wide in particle size selection range and wide in adaptive stratum; toughness deformation is achieved at the high temperature, and good plugging, leakage preventing and collapse preventing performance is achieved in oil-based drilling fluid and water-based drilling fluid; the blocking agent is simple in preparation process and convenient for large-scale production and application.

Description

Technical Field

[0001] The invention belongs to the technical field of oilfield chemistry, and in particular relates to an amphiphilic polymer plugging agent for drilling fluid and a preparation method thereof. Background Art

[0002] In the exploration and development of shale gas, there are generally serious problems of formation leakage and wellbore instability. In the northeastern Sichuan region, where leakage is serious, the leakage of drilling fluid in a single well can reach tens of thousands of cubic meters, and the economic losses caused by leakage are serious. In addition, with the adjustment of the development process and mode of shale gas wells, there are more and more deep wells and ultra-deep wells, and the bottom hole temperature is getting higher and higher, which puts higher requirements on the temperature resistance and universality of drilling fluid plugging materials. The shale gas strata in the Luzhou block in Sichuan are well developed with bedding fractures, and leakage is serious during the drilling of the target layer. In 2020-2021, the wells with leakage of oil-based drilling fluid in this block accounted for 45% of the total wells under construction. The burial depth of shale gas in the Longmaxi Formation in this block is generally above 4000m. The formation temperature during drilling construction is above 155°C, and the bottom hole temperature of Lu 211 well reaches 168°C. At present, there are few polymer plugging materials for oil-based drilling fluids, and the existing materials have a short working time at high temperatures of 150°C and are prone to high-temperature failure, or swelling and other reactions occur in oil-based drilling fluids, and the return materials are easily screened out by vibrating screens; while polymer plugging materials for water-based drilling fluids have insufficient temperature resistance.

[0003] At present, many scholars have developed treatment agents for oil-based drilling fluids using styrene as raw material. Wang Lijun and others from the Engineering Technology Research Institute of Great Wall Drilling Engineering Company developed an oil-based fluid loss reducer FCL, which is prepared by moderate sulfonation of α-olefin-styrene polymer prepared by emulsion polymerization with acetic anhydride and concentrated sulfuric acid. The polymer appears in the form of colloid in white oil and will not damage the performance of the drilling fluid. At the same time, this colloid with an appropriate particle size can block the pores in the filter cake, thereby achieving the purpose of reducing the filtration loss. Ji Yihui and others from the Drilling Engineering Technology Research Institute of China National Petroleum Corporation used St, MMA and HDA as raw materials and adopted the suspension polymerization method to prepare a shear-enhancing agent for oil-based drilling fluid. After the polymer was dissolved in oil, the long chains stretched out by themselves connected with each other, increasing the viscosity and shear thinning of the system. In addition, the polymer has a good rubber protection ability and can form a spatial network structure of a certain strength with the adsorbed solid particles in the system, which can greatly improve the shear force of diesel-based drilling fluid. These treatment agents also improve the oil absorption, swelling or solubility in oil-based drilling fluid by adding long-chain lipophilic monomers, thereby achieving plugging and filtration loss reduction performance or viscosity increase and shear-enhancing properties.

[0004] Wang Jianhua et al. used styrene and methyl methacrylate as raw materials and synthesized a nano-polymer plugging agent for oil-based drilling fluid by emulsion polymerization. The particle size of the plugging agent is distributed between 50 and 300 nm, with good thermal stability and a decomposition temperature of up to 393°C. The size of the plugging agent matches the microcracks well, and it can form a tight sealing layer on the surface of the microcracks, which is beneficial to the stability of the wellbore. Wanwei of Sichuan Qing Drilling used methyl methacrylate and butyl acrylate to prepare a high-temperature resistant resin particle suitable for oil-based drilling fluid with high efficiency plugging ability through emulsion polymerization. The resin particle can improve the plugging ability of the drilling fluid to the shale formation, reduce the pressure transmission caused by the liquid phase invading the formation, and prevent the wellbore from becoming unstable. Kuang Xubing of Great Wall Drilling used oil-soluble monomers such as butyl acrylate, octadecyl acrylate, acrylic acid and styrene as raw materials, oleophilic modified quartz powder as condensation nucleus, and emulsion polymerization process to synthesize an acrylic resin material with a core-shell structure. As an oil-based drilling fluid plugging agent, it has little effect on the rheological properties of the oil-based drilling fluid slurry and can greatly improve the filtration wall-building properties and emulsion stability of the oil-based drilling fluid slurry.

[0005] However, these treatment agents have small particle sizes and limited application range. Summary of the invention

[0006] In view of this, the technical problem to be solved by the present invention is to provide an amphiphilic polymer plugging agent for drilling fluid and a preparation method thereof. The amphiphilic polymer plugging agent for drilling fluid prepared by the method has excellent temperature resistance and can overcome the plugging problem of high-temperature deep well oil-based drilling fluid and water-based drilling fluid above 180°C.

[0007] The present invention provides a method for preparing an amphiphilic polymer plugging agent for drilling fluid, comprising the following steps:

[0008] The hydrophilic polymer, lipophilic monomer, porogen, crosslinking agent and initiator are mixed and stirred in water to form an emulsion, and after heating reaction, the emulsion is filtered, dried, crushed and sieved to obtain an amphiphilic polymer plugging agent for drilling fluid.

[0009] Preferably, the step S) is specifically:

[0010] The hydrophilic polymer is mixed with water, and then the oleophilic monomer, porogen, crosslinking agent and initiator are added and stirred to form an emulsion. After heating and reaction, an amphiphilic polymer plugging agent for drilling fluid is obtained.

[0011] Preferably, the hydrophilic polymer is selected from one or more of polyvinyl alcohol, polyacrylamide, sodium polyacrylate and hydroxypropyl methylcellulose; the mass of the hydrophilic polymer is 0.3% to 6% of the mass of the lipophilic monomer.

[0012] Preferably, the oleophilic monomer is selected from one or more of styrene, butyl methacrylate and methyl methacrylate; the mass of the oleophilic monomer is 5% to 40% of the mass of water.

[0013] Preferably, the porogen is selected from one or more of cyclohexane, n-heptane, cyclohexanone and dodecane; the mass of the porogen is 10% to 60% of the mass of the lipophilic monomer.

[0014] Preferably, the crosslinking agent is selected from one or more of divinylbenzene, 1,4-butylene glycol diacrylate, diisocyanate and N,N-methylenebisacrylamide; the mass of the crosslinking agent is 0.1% to 5% of the mass of the lipophilic monomer;

[0015] The initiator is selected from peroxide initiators and / or azo initiators; the mass of the initiator is 0.3% to 5% of the mass of the lipophilic monomer.

[0016] Preferably, the temperature of the heating reaction is 60° C. to 98° C.; and the time of the heating reaction is 2 to 12 hours.

[0017] Preferably, after the emulsion is formed, the temperature is first raised to 60° C. to 85° C. for reaction for 1 to 8 hours, and then continued to be raised to 90° C. to 98° C. for reaction for 1 to 4 hours to obtain an amphiphilic polymer plugging agent for drilling fluid.

[0018] The present invention also provides an amphiphilic polymer plugging agent for drilling fluid prepared by the above preparation method.

[0019] The present invention also provides a drilling fluid, comprising the amphiphilic polymer plugging agent for drilling fluid prepared by the above preparation method.

[0020] The present invention provides a method for preparing an amphiphilic polymer plugging agent for drilling fluid, comprising the following steps: mixing a hydrophilic polymer, an oleophilic monomer, a porogen, a crosslinking agent and an initiator in water to form an emulsion, heating the reaction, filtering, drying, crushing and screening to obtain an amphiphilic polymer plugging agent for drilling fluid. Compared with the prior art, the plugging agent prepared by the present invention has a crosslinked oleophilic polymer skeleton with good oleophilicity; a certain amount of hydrophilic stabilizer is coated on the surface, which has good hydrophilicity and good compatibility with oil-based drilling fluid and water-based drilling fluid; and because the main body is a crosslinked oleophilic monomer polymer, the chemical stability is good, so that the plugging agent is temperature-resistant up to 180°C, meeting the high-temperature plugging, leak-proof and collapse-proof requirements; furthermore, it is a hollow rigid sphere at room temperature, easy to crush, with a wide range of particle size selection, and adaptable to a wide range of formations; it is ductile and deformed at high temperature, and has good plugging, leak-proof and collapse-proof properties in both oil-based drilling fluid and water-based drilling fluid; the preparation process of the plugging agent is simple, and it is convenient for large-scale production and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1The structural formula of the lipophilic part of the amphiphilic polymer plugging agent for drilling fluid provided by the present invention;

[0022] Figure 2 is the infrared spectrum of the amphiphilic polymer plugging agent obtained in Example 1 of the present invention;

[0023] Figure 3 This is a particle size distribution diagram of the amphiphilic polymer plugging agent obtained in Example 1 of the present invention. DETAILED DESCRIPTION

[0024] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0025] The invention provides a method for preparing an amphiphilic polymer plugging agent for drilling fluid, comprising the following steps: mixing a hydrophilic polymer, an oleophilic monomer, a porogen, a crosslinking agent and an initiator in water to form an emulsion, and heating the mixture for reaction to obtain the amphiphilic polymer plugging agent for drilling fluid.

[0026] The plugging agent prepared by the invention uses a hydrophilic polymer as a stabilizer and is formed by polymerizing an oleophilic monomer and the like through a sedimentation polymerization method under the action of a porogen.

[0027] The present invention has no particular limitation on the sources of all raw materials, and any raw materials available on the market can be used.

[0028] According to the present invention, the hydrophilic polymer is a hydrophilic polymer well known to those skilled in the art without any special limitation. In the present invention, it preferably includes but is not limited to one or more of polyvinyl alcohol, polyacrylamide, sodium polyacrylate and hydroxypropyl methylcellulose; the mass of the hydrophilic polymer is preferably 0.3% to 6% of the mass of the lipophilic monomer, more preferably 0.5% to 6%, more preferably 0.3% to 3.5%, more preferably 0.5% to 3.5%, preferably 1% to 3%; in some embodiments provided by the present invention, the mass of the hydrophilic polymer is specifically 2.7% or 1.4% of the mass of the lipophilic monomer; the degree of polymerization of the hydrophilic polymer is preferably 500 to 5000, more preferably 500 to 3000, more preferably 800 to 2500, more preferably 1000 to 2000, more preferably 1400 to 1800, and most preferably 1600 to 1700.

[0029] According to the present invention, the lipophilic monomer is a polymerizable lipophilic monomer well known to those skilled in the art, and there is no special limitation. In the present invention, it preferably includes but is not limited to lipophilic vinyl monomers and / or lipophilic acrylic monomers, and more preferably includes but is not limited to one or more of styrene, butyl methacrylate and methyl methacrylate; the mass of the lipophilic monomer is preferably 5% to 40% of the mass of water, more preferably 8% to 35%, more preferably 10% to 30%, more preferably 15% to 25%, and most preferably 15% to 20%; in some embodiments provided by the present invention, the mass of the lipophilic monomer is specifically 18% of the mass of water.

[0030] According to the present invention, the porogen preferably includes but is not limited to one or more of cyclohexane, n-heptane, cyclohexanone and dodecane; the mass of the porogen is preferably 10% to 60% of the mass of the oleophilic monomer, more preferably 10% to 50%, more preferably 10% to 40%, more preferably 15% to 30%, and most preferably 20% to 25%; in some embodiments provided by the present invention, the mass of the porogen is specifically 21.6% of the mass of the oleophilic monomer.

[0031] According to the present invention, the crosslinking agent is preferably one or more of divinylbenzene, 1,4-butylene glycol diacrylate, diisocyanate and N,N-methylenebisacrylamide; the mass of the crosslinking agent is preferably 0.1% to 5% of the mass of the lipophilic monomer, more preferably 0.3% to 4%, further preferably 0.5% to 3.5%, and most preferably 1.0% to 3.0%; in some embodiments provided by the present invention, the mass of the crosslinking agent is specifically 1.75% or 2.5% of the mass of the lipophilic monomer.

[0032] According to the present invention, the initiator is preferably a peroxide initiator and / or an azo initiator; the peroxide initiator is any peroxide initiator well known to those skilled in the art, and may be an inorganic peroxide initiator or an organic peroxide initiator, without any special restrictions, and preferably includes but is not limited to one or more of sodium persulfate, potassium persulfate, ammonium persulfate, benzoyl peroxide, and lauroyl peroxide; the azo initiator is any azo initiator well known to those skilled in the art, without any special restrictions, and preferably includes but is not limited to azobisisobutyronitrile and / or azobisisoheptanenitrile; the mass of the initiator is preferably 0.3% to 5% of the mass of the lipophilic monomer, more preferably 0.5% to 5%, more preferably 1% to 5%, and most preferably 1.5% to 4%; in some embodiments provided by the present invention, the mass of the initiator is specifically 1.4% or 2.7% of the mass of the lipophilic monomer.

[0033] In the present invention, preferably, the hydrophilic polymer is first mixed with water, and then the oleophilic monomer, porogen, crosslinking agent and initiator are added and stirred to form an emulsion, and after heating and reaction, an amphiphilic polymer plugging agent for drilling fluid is obtained.

[0034] Mix the hydrophilic polymer with water; if there is a water-soluble substance in the initiator, add it here; the mixing is preferably carried out under heating conditions, and the heating temperature is preferably 35°C to 45°C, more preferably 40°C; after mixing until completely dissolved, the aqueous phase can be obtained.

[0035] Then add lipophilic monomer, porogen, crosslinking agent and initiator and stir to disperse the monomer into uniform small liquid droplets to form an emulsion.

[0036] The emulsion is heated for reaction; the heating reaction is preferably carried out in a protective atmosphere; the protective atmosphere is any protective atmosphere known to those skilled in the art and is not particularly limited, and is preferably nitrogen in the present invention; the temperature of the heating reaction is preferably 60°C to 98°C, more preferably 70°C to 98°C, and more preferably 80°C to 95°C; the heating reaction time is preferably 2 to 12 hours, more preferably 4 to 12 hours, more preferably 6 to 12 hours, and most preferably 8 to 10 hours; in the present invention, after the emulsion is formed, it is preferably heated to 60°C to 85°C for reaction for 1 ~8h, after the microspheres are shaped and cured, the temperature is continued to rise to 90℃~98℃ for reaction for 1~4h to further harden the microspheres; more preferably, the temperature is first raised to 70℃~85℃ for reaction for 3~8h, after the microspheres are shaped and cured, the temperature is continued to rise to 90℃~98℃ for reaction for 1~3h; more preferably, the temperature is first raised to 80℃~85℃ for reaction for 5~7h, after the microspheres are shaped and cured, the temperature is continued to rise to 90℃~95℃ for reaction for 1~3h; most preferably, the temperature is first raised to 80℃~83℃ for reaction for 6h, after the microspheres are shaped and cured, the temperature is continued to rise to 95℃ for reaction for 2h. The preparation method provided by the present invention can be convenient for crushing by adjusting the amount of porogen and the sedimentation polymerization conditions, which is helpful for drilling plugging.

[0037] After the heating reaction, the mixture is preferably filtered, dried, crushed and sieved to obtain an amphiphilic polymer plugging agent for drilling fluid.

[0038] The plugging agent prepared by the present invention has a skeleton of a cross-linked oleophilic polymer and good oleophilicity; a certain amount of hydrophilic stabilizer is coated on the surface, has good hydrophilicity, and has good compatibility with oil-based drilling fluid and water-based drilling fluid; and because the main body is a cross-linked oleophilic monomer polymer, the chemical stability is good, so that the plugging agent can resist a temperature of 180°C, meeting the requirements of high-temperature plugging, leakage prevention and collapse prevention; furthermore, the plugging agent is a hollow rigid sphere at room temperature, is easy to crush, has a wide range of particle size selection, and is suitable for a wide range of formations; it is ductilely deformed at high temperature, and has good plugging, leakage prevention and collapse prevention in both oil-based drilling fluid and water-based drilling fluid; the plugging agent has a simple preparation process and is convenient for large-scale production and application.

[0039] The present invention also provides an amphiphilic polymer plugging agent for drilling fluid prepared by the above preparation method; 50 The particle size is preferably 1 to 300 μm.

[0040] See also Figure 1 , Figure 1 The structural formula of the oleophilic part of the amphiphilic polymer plugging agent for drilling fluid prepared by the present invention is shown in FIG. wherein m and n are the degree of polymerization, preferably in the range of 0 to 100,000 respectively; R1 is a C1 to C10 alkyl group, preferably a C1 to C8 alkyl group, more preferably a C1 to C5 alkyl group, still more preferably a C1 to C4 alkyl group, and most preferably a methyl group or a butyl group; and R2 is H or a methyl group.

[0041] The amphiphilic polymer plugging agent for drilling fluid provided by the present invention can be screened as required, can participate in the formation of mud cake, improve the quality of mud cake, and has a good plugging effect while drilling.

[0042] The present invention also provides a drilling fluid, comprising the amphiphilic polymer plugging agent for drilling fluid prepared by the above preparation method; the drilling fluid is preferably a water-based drilling fluid or an oil-based drilling fluid; the drilling fluid is preferably used for high-temperature formations above 150°C.

[0043] The mass of the amphiphilic polymer plugging agent for drilling fluid is preferably 1.5% to 4.0% of the mass of the drilling fluid.

[0044] When the drilling fluid is an oil-based drilling fluid, the liquid phase of the drilling fluid preferably includes an oil phase and an aqueous phase; the volume ratio of the oil phase to the aqueous phase is preferably (7-9):(1-3), more preferably (8-8.5):(2-1.5); the oil phase is preferably diesel and / or white oil; the aqueous phase is preferably a calcium chloride aqueous solution and / or a potassium sulfate aqueous solution; the mass concentration of the calcium chloride aqueous solution and / or the potassium sulfate aqueous solution is preferably 15% to 35%, more preferably 20% to 25%.

[0045] According to the present invention, the oil-based drilling fluid preferably also includes an emulsifier; the mass of the emulsifier is preferably 1% to 10% of the mass of the drilling fluid, more preferably 3% to 6%, and even more preferably 4% to 6%; the emulsifier can be an emulsifier well known to those skilled in the art, and there is no special limitation; in the embodiments provided by the present invention, polyamide emulsifiers are specifically used as an example for illustration.

[0046] According to the present invention, the oil-based drilling fluid preferably further comprises calcium oxide; the mass of the calcium oxide is preferably 1% to 5% of the mass of the drilling fluid, more preferably 2% to 4%.

[0047] According to the present invention, the oil-based drilling fluid preferably further comprises organic soil; the mass of the organic soil is preferably 1% to 5% of the mass of the drilling fluid, more preferably 2% to 3%.

[0048] According to the present invention, the oil-based drilling fluid preferably also includes a fluid loss reducer; the mass of the fluid loss reducer is preferably 1% to 5% of the mass of the drilling fluid, and more preferably 2% to 4%; the type of the fluid loss reducer can be any fluid loss reducer well known to those skilled in the art, and there is no special limitation. In the present invention, an asphalt resin fluid loss reducer is preferred, and an oxidized asphalt fluid loss reducer is more preferred.

[0049] When the drilling fluid is a water-based drilling fluid, the water-based drilling fluid preferably further comprises bentonite; the mass of the bentonite is preferably 2% to 10% of the mass of the water-based drilling fluid, more preferably 3% to 6%, and even more preferably 4% to 5%.

[0050] According to the present invention, the water-based drilling fluid preferably also includes an alkaline compound; the mass of the alkaline compound is preferably 0.1% to 0.5% of the mass of the water-based drilling fluid, and more preferably 0.2% to 0.3%; the alkaline compound can be an alkaline compound well known to those skilled in the art without any special restrictions, and is preferably sodium carbonate in the present invention.

[0051] In order to further illustrate the present invention, the following describes in detail the amphiphilic polymer plugging agent for drilling fluid and the preparation method thereof in combination with the embodiments.

[0052] The reagents used in the following examples are all commercially available; the molecular weight of the polyvinyl alcohol used in the examples is PVA-1788 (degree of polymerization of about 1700, degree of alcoholysis of about 88%, molecular weight of 120,000 to 150,000).

[0053] Example 1

[0054] The preparation method of the amphiphilic polymer plugging agent of the present invention comprises the following steps:

[0055] In a 500mL three-necked flask equipped with a mechanical stirrer, a reflux condenser and a thermometer, add 200mL of distilled water, add 1g of polyvinyl alcohol (PVA-1788), 1.5g of sodium persulfate, stir and slowly heat to 40°C to completely dissolve it. Add 40mL of styrene, 0.7mL of divinylbenzene, 0.5g of benzoyl peroxide and 10mL of cyclohexane, adjust the stirring speed to disperse the monomer into uniform small liquid droplets, continue to heat to 80°C, react for 6h, keep the stirring speed unchanged, after the microspheres are shaped and cured, heat to 95°C, continue to react for 2h to further harden the microspheres. Stop stirring, filter, dry, crush with a small swinging mill, sieve 140-200 mesh, and after sieving, obtain the material with the required particle size, which is the amphiphilic polymer plugging agent. The infrared spectrum is as shown in Figure 2 shown.

[0056] Example 2

[0057] The preparation method of the amphiphilic polymer plugging agent of the present invention comprises the following steps:

[0058] Add 200mL of distilled water to a 500mL three-necked flask equipped with a mechanical stirrer, a reflux condenser and a thermometer, add 0.5g of polyvinyl alcohol (PVA-1788), stir and slowly heat to 40°C to completely dissolve it. Add 20mL of styrene, 20mL of methyl methacrylate, 1.0mL of divinylbenzene, 1.0g of azobisisobutyronitrile and 10mL of dodecane, adjust the stirring speed to disperse the monomer into uniform small liquid beads, continue to heat to 83°C, react for 6h, keep the stirring speed unchanged, after the microspheres are shaped and cured, heat to 95°C, continue to react for 2h, and further harden the microspheres. Stop stirring, filter, dry, crush with a small swing mill, sieve 140-200 mesh, and after sieving, obtain the material with the required particle size, which is the amphiphilic polymer plugging agent.

[0059] Comparative Example 1

[0060] Add 200mL of distilled water to a 500mL three-necked flask equipped with a mechanical stirrer, a reflux condenser and a thermometer, add 1g of sodium dodecylbenzene sulfonate and 1.5g of sodium persulfate, stir and slowly heat to 40°C to dissolve it completely. Add 40mL of styrene, 0.7mL of divinylbenzene, 0.5g of benzoyl peroxide and 10mL of cyclohexane, adjust the stirring speed, disperse the monomer into uniform small liquid beads, continue to heat to 80°C, react for 6h, keep the stirring speed unchanged, after the microspheres are shaped and cured, heat to 95°C, continue to react for 2h, and further harden the microspheres. Stop stirring, filter, wash with clean water, dry, crush with a small swing mill, sieve 140-200 mesh, and obtain the material with the required particle size, which is an oleophilic polymer, as comparative example 1.

[0061] Comparative Example 2

[0062] The hydrophilic polymer PVA-1788 is used as comparative example 2.

[0063] The products prepared in the examples of the present invention were evaluated, and the results were as follows:

[0064] (1) Particle size analysis

[0065] The amphiphilic polymer plugging agent obtained in Example 1 was measured using a laser particle size analyzer. The results are as follows: Figure 3 As shown. Figure 3 It can be seen that the particle size D of the amphiphilic polymer plugging agent for drilling fluid obtained by the present invention is 50The diameter is 27.45μm, which is micron level. It can be used for plugging while drilling and is suitable for plugging micro cracks and pores.

[0066] (2) Plugging evaluation

[0067] ①Oil-based drilling fluid

[0068] The amphiphilic polymer plugging agent for drilling fluid obtained by the reaction of the embodiment is added to the oil-based drilling fluid, and after high-temperature aging at 180°C for 16 hours, the rheological properties of the drilling fluid are measured by a six-speed rotary viscometer at 65°C, and the high-temperature and high-pressure filtration loss of the drilling fluid and the sealing filtration loss of 380-830 μm river sand (normal temperature, 0.69 MPa) are measured. The results are shown in Table 1. As can be seen from Table 1, when the product of the present invention is added to the oil-based drilling fluid, the rheological properties of the drilling fluid system do not change much; the high-temperature and high-pressure filtration loss is reduced. It shows that the amphiphilic polymer plugging agent has good compatibility with the oil-based drilling fluid and has good filtration loss reduction and plugging performance. Comparative Example 1, as an oleophilic polymer, has a lower plugging property in the oil-based drilling fluid than the embodiment; Comparative Example 2, as a hydrophilic polymer, has a poor plugging effect and is only accumulated as solid phase particles.

[0069] Table 1 Evaluation of compatibility of product dosage and oil-based drilling fluid in the example

[0070]

[0071]

[0072] Note: Diesel oil + 20% calcium chloride aqueous solution (0 # Diesel: 20% calcium chloride aqueous solution = 80:20) + 4% emulsifier + 2% calcium oxide + 2% organic soil + 2% fluid loss reducer (density 2.2g / cm 3 ); emulsifier, Zhongyuan Petroleum Engineering Co., Ltd. (patent No. ZL.201711027059.X, Example 6); organic soil, Zhejiang Fenghong New Materials Co., Ltd. (BS-1C); fluid loss reducer is an oxidized asphalt fluid loss reducer, Shandong Deshunyuan Petroleum Technology Co., Ltd. (OFC).

[0073] ② Water-based drilling fluid

[0074] The amphiphilic polymer plugging agent for drilling fluid obtained by the reaction of the embodiment was added to the water-based slurry, and after high-temperature aging at 180°C for 16 hours, the sealed filtration loss in 250-380 mesh river sand was measured using a 71-type high-temperature and high-pressure water loss instrument. The results are shown in Table 2. As can be seen from Table 2, the product of the present invention greatly reduces the plugging filtration loss in the water-based drilling fluid and has good plugging performance; Comparative Example 1 has poor hydrophilicity, cannot be evenly distributed in the water-based drilling fluid, and has poor plugging effect; Comparative Example 2 can be dissolved in clear water, has good hydrophilicity, but does not contain high-temperature resistant skeletons such as anti-styrene, has poor temperature resistance, and has poor plugging effect after aging. The water-based slurry formula is: water + 4% bentonite + 0.2% NaCO3, cured at room temperature for 16 hours, and ready for use.

[0075] Table 2 Example product dosage and water-based drilling fluid performance evaluation

[0076] Amphiphilic polymer plugging agent / % 250~380μm river sand sealing filtration loss / mL Base slurry 350 Base slurry + 2% Example 1 41 Base slurry + 2% Example 2 38 Base slurry + 2% Comparative Example 1 260 Base slurry + 2% Comparative Example 2 180

[0077] From the experimental results, it can be seen that the characteristics of this product include: temperature resistance up to 180°C, good compatibility with oil-based drilling fluids and water-based drilling fluids, obvious filtration reduction and plugging effects, and can be used for plugging high-temperature formations.

[0078] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention, but the present invention is not limited thereto. Those skilled in the art can understand that within the technical concept of the present invention, the technical solution of the present invention can be modified, or some technical features can be combined in any other way. These modifications or combinations do not make the essence of the corresponding technical solution deviate from the spirit and scope of each implementation of the technical solution of the present invention, and should be regarded as the contents disclosed by the present invention, which belong to the protection scope of the present invention.

Claims

1. A method for preparing an amphiphilic polymer plugging agent for drilling fluid, characterized in that: The following steps are involved: The hydrophilic polymer, lipophilic monomer, porogen, crosslinking agent and initiator are mixed and stirred in water to form an emulsion, and after heating reaction, the emulsion is filtered, dried, crushed and sieved to obtain an amphiphilic polymer plugging agent for drilling fluid.

2. The preparation method according to claim 1, characterized in that: The step S) is specifically: The hydrophilic polymer is mixed with water, and then the oleophilic monomer, porogen, crosslinking agent and initiator are added and stirred to form an emulsion. After heating and reaction, an amphiphilic polymer plugging agent for drilling fluid is obtained.

3. The preparation method according to claim 1, characterized in that: The hydrophilic polymer is selected from one or more of polyvinyl alcohol, polyacrylamide, sodium polyacrylate and hydroxypropyl methylcellulose; the mass of the hydrophilic polymer is 0.3% to 6% of the mass of the lipophilic monomer.

4. The preparation method according to claim 1, characterized in that: The oleophilic monomer is selected from one or more of styrene, butyl methacrylate and methyl methacrylate; the mass of the oleophilic monomer is 5% to 40% of the mass of water.

5. The preparation method according to claim 1, characterized in that: The porogen is selected from one or more of cyclohexane, n-heptane, cyclohexanone and dodecane; the mass of the porogen is 10% to 60% of the mass of the lipophilic monomer.

6. The preparation method according to claim 1, characterized in that: The crosslinking agent is selected from one or more of divinylbenzene, 1,4-butylene glycol diacrylate, diisocyanate and N,N-methylenebisacrylamide; the mass of the crosslinking agent is 0.1% to 5% of the mass of the lipophilic monomer; The initiator is selected from peroxide initiators and / or azo initiators; the mass of the initiator is 0.3% to 5% of the mass of the lipophilic monomer.

7. The preparation method according to claim 1, characterized in that: The temperature of the heating reaction is 60° C. to 98° C.; the time of the heating reaction is 2 to 12 hours.

8. The preparation method according to claim 1, characterized in that: After the emulsion is formed, the temperature is first raised to 60°C-85°C for reaction for 1-8 hours, and then continued to be raised to 90°C-98°C for reaction for 1-4 hours to obtain an amphiphilic polymer plugging agent for drilling fluid.

9. An amphiphilic polymer plugging agent for drilling fluid prepared by the preparation method according to any one of claims 1 to 8.

10. A drilling fluid, characterized in that: The invention relates to an amphiphilic polymer plugging agent for drilling fluid prepared by the preparation method according to any one of claims 1 to 8.

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