A drilling fluid encapsulant and method of making same

Abstract

The application provides a drilling fluid coating agent and a preparation method thereof, and the drilling fluid coating agent is prepared by using an aqueous phase solution, an oil phase solution and an initiator as reaction raw materials through a reverse phase emulsion polymerization method; the aqueous phase solution comprises acrylamide monomers, cationic monomers, an organic silicon modifier, a tackifier, a cosolvent, an inhibitor, sodium acrylate and water; the oil phase solution comprises white oil and an emulsifier; and the inhibitor is a modified polyether amine. The drilling fluid coating agent has the advantages of temperature resistance, shear resistance, fast dissolution speed and good coating inhibition effect, and specifically, under the condition of 40,000 mineralization degrees and 230 DEG C, the plastic viscosity of the coating agent is greater than or equal to 32 mPa*s, the dynamic shear force is greater than or equal to 24 Pa, the high shear viscosity retention rate is greater than or equal to 75%, the polymer rock debris recovery rate is greater than or equal to 82%, and the dissolution speed is less than or equal to 18 s.

Description

Technical Field

[0001] This invention relates to the field of petroleum extraction technology, and in particular to a drilling fluid coating agent and its preparation method. Background Technology

[0002] Drilling fluid is the "blood" of drilling and plays a very important role in drilling operations. Coating agents, as one of the key treatment agents for drilling fluid, can coat drill cuttings to inhibit their dispersion and maintain the stability of drilling fluid performance, and adsorb onto the well wall to maintain well wall stability. This can reduce drilling accidents and drilling cycles, and lower drilling costs.

[0003] Currently, during drilling, the formation span is large, the lithology of the formation varies greatly, and the drilling fluid interacts with the formation for a long time, which can easily lead to problems such as narrowing and stuck, collapse and widening, and leakage. In related technologies, polyacrylamide-based coating agents are commonly used in oilfield drilling fluid systems. However, these coating agents cause potassium salt pollution and have problems such as slow dissolution rate, poor shear resistance, and poor cuttings suppression and dispersion.

[0004] Therefore, based on the above problems, there is an urgent need to provide a new drilling fluid coating agent and its preparation method. Summary of the Invention

[0005] This invention provides a drilling fluid coating agent that is environmentally friendly, has a fast dissolution rate, good shear resistance, and good cuttings suppression and dispersion effect.

[0006] In a first aspect, the present invention provides a drilling fluid coating agent, wherein the drilling fluid coating agent is prepared by reverse emulsion polymerization using an aqueous phase solution, an oil phase solution, and an initiator as reactants; wherein the aqueous phase solution comprises an acrylamide monomer, a cationic monomer, an organosilicon modifier, a thickener, a cosolvent, an inhibitor, sodium acrylate, and water; the oil phase solution comprises white oil and an emulsifier; and the inhibitor is a modified polyetheramine.

[0007] Preferably, the acrylamide monomer is at least one of acrylamide, methacrylamide, or ethylacrylamide;

[0008] The cationic monomer is at least one of methacryloyloxyethyltrimethylammonium chloride, acryloyloxyethyltrimethylammonium chloride, or dimethyl diallylammonium chloride;

[0009] The organosilicon modifier is at least one of dimethylvinylsilanol, methyldivinylsilanol, and methylvinylphenylsilanol;

[0010] The tackifier is at least one of perfluorooctyl ethyl acrylate, dodecafluoroheptyl acrylate, (N-methylperfluorohexylsulfonamide) ethyl acrylate or 3-perfluorooctyl-2-methacrylate.

[0011] The co-solvent is at least one of sodium dodecyl sulfate, nonylphenol polyoxyethylene ether, urea, or anhydrous sodium sulfate.

[0012] Preferably, the modified polyetheramine is prepared as follows: polyetheramine, 3-chlorostyrene and catalyst are stirred and mixed, and the modified polyetheramine is obtained after alkylation reaction; wherein the catalyst is aluminum trichloride.

[0013] Preferably, by weight, the polyetheramine is 120-140 parts, 3-chlorostyrene is 50-80 parts, and the catalyst is 2-3 parts.

[0014] More preferably, the reaction temperature is 40-50℃ and the reaction time is 1-2h.

[0015] Preferably, the emulsifier is at least one of polyglycerol oleate or N-polyoxyethylene stearamide.

[0016] Preferably, the initiator includes an oxidant, a chain extender, and a reducing agent.

[0017] Preferably, the oxidant is at least one of ammonium persulfate, hydrogen peroxide, or dicumyl peroxide; the chain extender is at least one of diethylaminoethanol, sodium formate, or dodecyl mercaptan; and the reducing agent is at least one of sulfite or metabisulfite.

[0018] More preferably, the mass ratio of the oxidant, the chain extender and the reducing agent is (1-2):(0.8-1):(0.2-0.3).

[0019] Preferably, the contents of each reactant are as follows, by mass: 170-200 parts of acrylamide monomer, 20-40 parts of cationic monomer, 10-15 parts of organosilicon modifier, 3-5 parts of thickener, 2-15 parts of cosolvent, 2-5 parts of inhibitor, 200-300 parts of sodium acrylate, 110-290 parts of water, 220-280 parts of white oil, 20-35 parts of emulsifier, and 0.2-2 parts of initiator.

[0020] Secondly, the present invention also provides a method for preparing the drilling fluid coating agent described in any one of the above claims, the method comprising the following steps:

[0021] (1) Add acrylamide monomers, cationic monomers, organosilicon modifiers, thickeners, cosolvents, modified polyetheramine inhibitors and sodium acrylate to water and mix well to obtain an aqueous solution; stir and emulsify white oil and emulsifier to obtain an oil solution;

[0022] (2) Add the oxidant and chain extender from the initiator to the aqueous solution, mix well, and then add the oil solution for stirring and emulsification to obtain a reverse emulsion;

[0023] (3) Add the reducing agent in the initiator to the reverse emulsion to initiate a polymerization reaction, and the drilling fluid coating agent is obtained after the reaction.

[0024] Preferably, step (2) further includes adjusting the pH of the aqueous solution to 6.5 to 6.8.

[0025] Preferably, in step (2), the stirring speed for emulsification is 300-500 r / min, and the stirring time for emulsification is 30-60 min.

[0026] Preferably, before initiating the polymerization reaction in step (3), the step further includes introducing nitrogen gas into the reaction system;

[0027] After initiating the polymerization reaction in step (3), the process further includes adding a phase inversion agent to the reaction system to obtain the drilling fluid coating agent; wherein the phase inversion agent is at least one of alkylphenol polyoxyethylene ether, nonylphenol polyoxyethylene ether or octylphenol polyoxyethylene ether.

[0028] Preferably, the mass ratio of the phase-transforming agent to the acrylamide monomer is (20-28):(170-200).

[0029] Preferably, the polymerization reaction is initiated at a temperature of 15-18°C, the polymerization temperature is 35-40°C, and the reaction time is 2-3 hours.

[0030] Compared with the prior art, the present invention has at least the following beneficial effects:

[0031] (1) In this invention, a drilling fluid coating agent is prepared by reverse emulsion polymerization of an oil-in-water system consisting of an aqueous solution containing an organosilicon modifier and a modified polyetheramine inhibitor and an oil-phase solution. The modified polyetheramine inhibitor can form a macromolecular polymer coating agent through polymerization reaction with cationic monomers, organosilicon modifiers, acrylamide monomers, etc. The addition of the modified polyetheramine inhibitor can not only effectively inhibit shale hydration and clay hydration expansion, and enhance the inhibitory properties of the coating agent, but also enhance the temperature resistance and shear resistance of the coating agent. At the same time, the modified polyetheramine inhibitor does not contain potassium ions and has good environmental friendliness. The addition of the organosilicon modifier can inhibit shale dispersion and improve the cuttings recovery rate. With the addition of the cosolvent, the coating agent in this invention has a suitable dissolution rate, good shear resistance and high cuttings recovery rate.

[0032] (2) The drilling fluid coating agent in this invention has the advantages of temperature resistance, shear resistance, fast dissolution rate and good coating inhibition effect. Specifically, the coating agent has a plastic viscosity ≥32mPa·s, dynamic shear force ≥24Pa, high shear viscosity retention rate ≥75%, polymer cuttings recovery rate ≥82% and dissolution rate ≤18s under the conditions of 40,000 mineralization degree and 230℃. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a flowchart of a method for preparing a drilling fluid coating agent provided by the present invention. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0036] This invention provides a drilling fluid coating agent, which is prepared by reverse emulsion polymerization using an aqueous phase solution, an oil phase solution, and an initiator as reactants. The aqueous phase solution comprises acrylamide monomers, cationic monomers, organosilicon modifiers, thickeners, cosolvents, inhibitors, sodium acrylate, and water; the oil phase solution comprises white oil and an emulsifier; and the inhibitor is a modified polyetheramine.

[0037] In this embodiment of the invention, a drilling fluid coating agent is prepared by reverse emulsion polymerization of an oil-in-water system consisting of an aqueous solution containing an organosilicon modifier and a modified polyetheramine inhibitor, and an oil-phase solution. The modified polyetheramine inhibitor can form a macromolecular polymer coating agent through polymerization reactions with cationic monomers, organosilicon modifiers, acrylamide monomers, etc. The addition of the modified polyetheramine inhibitor can not only effectively inhibit shale hydration and clay hydration swelling, and enhance the inhibitory effect of the coating agent, but also enhance the temperature resistance and shear resistance of the coating agent. At the same time, the modified polyetheramine inhibitor does not contain potassium ions, and has good environmental friendliness. The addition of the organosilicon modifier can inhibit shale dispersion and improve the cuttings recovery rate. With the addition of a co-solvent, the coating agent of this invention has a suitable dissolution rate, good shear resistance, and high cuttings recovery rate.

[0038] According to some preferred embodiments, the acrylamide monomer is at least one of acrylamide, methacrylamide, or ethylacrylamide; the cationic monomer is at least one of methacryloyloxyethyltrimethylammonium chloride, acryloyloxyethyltrimethylammonium chloride, or dimethyldiallylammonium chloride; the organosilicon modifier is at least one of dimethylvinylsilanol, methyldivinylsilanol, or methylvinylphenylsilanol; the tackifier is at least one of perfluorooctyl ethyl acrylate, (N-methylperfluorohexylsulfonamide) ethyl acrylate, or 3-perfluorooctyl-2-hydroxypropyl methacrylate; and the cosolvent is at least one of sodium dodecyl sulfate, nonylphenol polyoxyethylene ether, urea, or anhydrous sodium sulfate.

[0039] According to some preferred embodiments, the emulsifier is at least one of polyglycerol oleate or N-polyoxyethylene stearamide.

[0040] According to some preferred embodiments, the initiator includes an oxidant, a chain extender, and a reducing agent; the oxidant is at least one of ammonium persulfate, hydrogen peroxide, or dicumyl peroxide; the chain extender is at least one of diethylaminoethanol, sodium formate, or dodecyl mercaptan; and the reducing agent is at least one of sulfite or metabisulfite; the mass ratio of the oxidant, the chain extender, and the reducing agent is (1-2):(0.8-1):(0.2-0.3) (for example, it can be 1:0.8:0.2, 1:1:0.3, or 2:1:3).

[0041] In this embodiment of the invention, acrylamide monomers, cationic monomers, organosilicon modifiers, tackifiers, polyetheramine inhibitors, and cosolvents are used as the main reactants in the polymerization reaction, and an oil-phase solution is used as the emulsion system. During the reaction, the monomers can form a macromolecular polymer coating agent through emulsion reverse polymerization under the action of an initiator. The addition of cationic monomers provides strong adsorption sites for the polymer coating agent, and the contained cationic adsorption groups can neutralize clay particles, reducing the zeta potential of the clay, decreasing electronegativity, and inhibiting hydration swelling. Furthermore, by using the aforementioned types of organosilicon... The modifier, an organosilicon modifier, contains Si-OH bonds, which allows the polymer coating agent to react with shale to form Si-O-Si bonds. This causes the organic-terminated Si-CH3 to adsorb onto the shale surface, reducing the hydrophilicity of the shale surface and converting it from hydrophilic to oleophilic. This effectively reduces the penetration of water molecules, thereby preventing the adsorption of water molecules on the shale surface and inhibiting shale dispersion. Furthermore, the synergistic effect of modified polyetheramine inhibitors, solubilizers, and cosolvents with the aforementioned reactive monomers results in a polymer coating agent that possesses excellent clay swelling inhibition properties, shear resistance, dissolution rate, and rock fragment dispersion inhibition properties.

[0042] According to some preferred embodiments, the modified polyetheramine is prepared as follows: polyetheramine, 3-chlorostyrene and catalyst are stirred and mixed, and the modified polyetheramine is obtained after alkylation reaction; wherein, the catalyst is aluminum trichloride;

[0043] The polyetheramine is 120-140 parts by weight (e.g., 120, 130 or 140 parts), 3-chlorostyrene is 50-80 parts by weight (e.g., 50, 60, 70 or 80 parts), and the catalyst is 2-3 parts by weight (e.g., 2, 2.5 or 3 parts); the reaction temperature is 40-50°C (e.g., 40°C, 42°C, 45°C, 48°C or 50°C), and the reaction time is 1-2 hours (e.g., 1 hour, 1.5 hours or 2 hours).

[0044] Unlike traditional potassium salt inhibitors, in this embodiment of the invention, polyetheramine is alkylated with 3-chlorostyrene under certain reaction conditions to form a modified polyetheramine inhibitor. This inhibitor can form a polymer coating agent through polymerization with other monomers. Since the modified polyetheramine inhibitor molecule contains amine groups, firstly, during use, the amine groups can abstract protons from water to generate two ammonium ions, which are then adsorbed onto adjacent clay sheets through electrostatic adsorption, binding the clay sheets together and increasing clay stability. Secondly, the amine groups can form a large number of hydrogen bonds with the silicon-oxygen tetrahedra of clay particles, enhancing the adsorption strength of the coating agent, thus giving the coating agent excellent clay swelling inhibition performance. Furthermore, the introduction of benzene rings into the polyetheramine during the modification process increases the rigidity of the polymer molecular chain, thereby further giving the polymer coating agent excellent shear resistance.

[0045] It should be noted that, in this embodiment, the polyetheramine is preferably polyetheramine D230.

[0046] According to some preferred embodiments, the contents of each reactant, by mass parts, are as follows: 170-200 parts of acrylamide monomer (e.g., 170, 180, 190, or 200 parts), 20-40 parts of cationic monomer (e.g., 20, 30, 35, or 40 parts), 10-15 parts of organosilicon modifier (e.g., 10, 12, 14, or 15 parts), 3-5 parts of tackifier (e.g., 3, 4, or 5 parts), 2-15 parts of cosolvent (e.g., 2, 5, 10, or 15 parts), and 2-5 parts of inhibitor (…). For example, the following components may be used: 3 parts, 4 parts, or 5 parts; 200-300 parts of sodium acrylate (e.g., 200 parts, 2200 parts, 250 parts, 280 parts, or 300 parts); 110-290 parts of water (e.g., 110 parts, 150 parts, 200 parts, 250 parts, or 290 parts); 220-280 parts of white oil (e.g., 220 parts, 240 parts, 250 parts, or 280 parts); 20-35 parts of emulsifier (e.g., 20 parts, 25 parts, 30 parts, or 35 parts); and 0.2-2 parts of initiator (e.g., 0.2 parts, 0.5 parts, 1 part, or 2 parts).

[0047] In this embodiment, experiments have confirmed that using an oil-phase solution as the reaction system and an initiator to initiate polymerization reactions of appropriate amounts of acrylamide monomers, cationic monomers, organosilicon modifiers, thickeners, cosolvents, inhibitors, and sodium acrylate under certain conditions is beneficial for preparing environmentally friendly, fast-dissolving polymer coating agents with excellent shear resistance and rock fragment dispersion inhibition. Adding an appropriate amount of cosolvent can improve the dissolution rate of the polymer coating agent, but excessive cosolvent content is detrimental to the polymerization between reactants and reduces the viscosity of the polymer coating agent. The inhibitor contains amine ions, which have low hydration energy and are close to the mesh size between oxygen atoms in adjacent crystal layers. They can be embedded in the mesh and are not easily exchanged by other cations, effectively inhibiting shale hydration, suppressing clay hydration swelling, and enhancing the inhibitory effect of the coating agent. If the inhibitor content is too low, it will not be conducive to ensuring the good shear resistance and clay swelling inhibition performance of the polymer coating agent. If the inhibitor content is too high, it will inhibit the effect of other active monomers, which will also be detrimental to ensuring the good overall performance of the polymer coating agent. At the same time, a suitable organosilicon modifier can cooperate with other reactive monomers to ensure that the polymer coating agent has a good effect on inhibiting rock fragment dispersion. If the content of organosilicon modifier is too high, it will not only be detrimental to significantly improving the rock fragment dispersion inhibition effect of the polymer coating agent, but will also increase the cost of reaction preparation.

[0048] This invention also provides a method for preparing the drilling fluid coating agent described in any one of the above claims, the method comprising the following steps:

[0049] (1) Add acrylamide monomers, cationic monomers, organosilicon modifiers, thickeners, cosolvents, modified polyetheramine inhibitors and sodium acrylate to water and mix well to obtain an aqueous solution; stir and emulsify white oil and emulsifier to obtain an oil solution;

[0050] (2) Add the oxidant and chain extender from the initiator to the aqueous solution, mix well, and then add the oil solution for stirring and emulsification to obtain a reverse emulsion;

[0051] (3) Add the reducing agent in the initiator to the reverse emulsion to initiate a polymerization reaction, and the drilling fluid coating agent is obtained after the reaction.

[0052] In this embodiment, an aqueous phase is first prepared by dissolving components such as acrylamide monomers, cationic monomers, thickeners, cosolvents, polyetheramine modification inhibitors, and sodium acrylate in water. White oil and emulsifier are used as the oil phase. After stirring and emulsifying, the mixture undergoes a reverse emulsification polymerization reaction initiated by an initiator, thereby preparing a drilling fluid coating agent with fast dissolution rate, good coating inhibition effect, and high temperature and shear resistance. Under the conditions of 40,000 salinity and 230℃, the plastic viscosity of this coating agent is ≥32mPa·s, dynamic shear force is ≥24Pa, high shear viscosity retention rate is ≥75%, polymer cuttings recovery rate is ≥82%, and dissolution rate is ≤18s.

[0053] According to some preferred embodiments, step (2) further includes adjusting the pH value of the aqueous solution to 6.5 to 6.8; in step (2), the stirring and emulsification speed is 300 to 500 r / min (for example, it can be 300 r / min, 400 r / min or 500 r / min), and the stirring and emulsification time is 30 to 60 min (for example, it can be 30 min, 40 min, 50 min or 60 min).

[0054] To ensure a good initiation rate for the polymerization reaction, this embodiment includes a step of adjusting the pH of the mixed solution to 6.5-6.8 using a pH adjuster after adding the oxidant and chain extender to the aqueous solution. Specifically, this embodiment does not limit the type of pH adjuster, such as sodium hydroxide or potassium hydroxide.

[0055] According to some preferred embodiments, before initiating the polymerization reaction in step (3), a step of introducing nitrogen gas into the reaction system is also included.

[0056] In this embodiment, because oxygen acts as a polymerization inhibitor and can affect the polymerization reaction of the monomers, nitrogen gas needs to be introduced into the reaction system to remove oxygen before adding the reducing agent to initiate the polymerization reaction, in order to ensure the normal progress of the polymerization reaction. The nitrogen introduction time can be, for example, 20-40 minutes.

[0057] According to some preferred embodiments, after initiating the polymerization reaction in step (3), the step further includes adding a phase inversion agent to the reaction system to obtain the drilling fluid coating agent; wherein the phase inversion agent is at least one of alkylphenol polyoxyethylene ether, nonylphenol polyoxyethylene ether or octylphenol polyoxyethylene ether; the mass ratio of the phase inversion agent to the acrylamide monomer is (20-28):(170-200) (for example, it can be 20:170, 25:170, 28:170, 20:180, 28:180, 20:200 or 28:200).

[0058] According to some preferred embodiments, the initiation temperature of the polymerization reaction is 15-18°C (e.g., 15°C, 16°C, 17°C or 18°C), the polymerization reaction temperature is 35-40°C (e.g., 35°C, 38°C or 40°C), and the reaction time is 2-3 hours (e.g., 2 hours, 2.5 hours or 3 hours).

[0059] In this embodiment, after mixing the aqueous and oil phase solutions, because the content of effective components in the reaction system is high, in order to prevent explosive polymerization, the temperature of the reaction system needs to be controlled at 15-18°C before adding the reducing agent to initiate the reaction. After reaching the reaction temperature, the reaction is further carried out at a constant temperature for 2-3 hours, which helps to ensure sufficient reaction between the reactants.

[0060] Meanwhile, in order to ensure the uniform reaction of the reactants, a micro-injection pump is used in this embodiment to inject the reducing agent aqueous solution into the reaction system to initiate the reaction. The mass concentration of the reducing agent solution can be 1-2%.

[0061] The present invention also provides a drilling fluid coating agent, which is prepared by the preparation method provided in the present invention.

[0062] To more clearly illustrate the technical solution and advantages of the present invention, the following examples provide a detailed description of a drilling fluid coating agent and its preparation method.

[0063] In the following examples, the mass of acrylamide monomers, cationic monomers, silicone modifiers, thickeners, cosolvents, modified polyetheramine inhibitors, sodium acrylate, deionized water, white oil, emulsifiers, and initiators are expressed in parts by mass.

[0064] Example 1:

[0065] (1) Preparation of modified polyetheramine inhibitors:

[0066] After stirring and mixing 130 parts of polyetheramine D230 and 60 parts of 3-chlorostyrene, 2 parts of catalyst (aluminum trichloride) were added, and the mixture was reacted at 45°C for 2 hours to obtain modified polyetheramine.

[0067] 190 parts of acrylamide monomer (acrylamide), 40 parts of cationic monomer (acryloyloxyethyltrimethylammonium chloride), 12 parts of organosilicon modifier (dimethylvinylsilanol), 15 parts of cosolvent (urea), 3 parts of thickener (ethyl acrylate (N-methylperfluorohexylsulfonamide), 3 parts of the above-mentioned modified polyetheramine inhibitor, and 250 parts of sodium acrylate were added to 173 parts of deionized water and stirred to obtain an aqueous solution.

[0068] A solution of oil phase was obtained by mixing 250 parts of white oil and 24 parts of emulsifier (18 parts of polyglycerol oleate and 6 parts of N-polyoxyethylene stearamide).

[0069] (2) Add 0.2 parts of oxidant (ammonium persulfate) and 0.1 parts of chain extender (sodium formate) to the aqueous phase solution, stir and mix well, add the pH adjuster acrylic acid to adjust the pH value of the mixed solution to 6.6, add the oil phase solution and stir and emulsify at 400 r / min for 2 h to obtain a reverse emulsion;

[0070] (3) Transfer the reverse emulsion to the reactor, purge with nitrogen for 40 min, adjust the temperature of the reaction system to 16℃, add 0.3 parts of reducing agent aqueous solution (1% sodium metabisulfite by mass) with a micro-injection pump under stirring at 280 r / min to initiate the polymerization reaction, raise the temperature to 40℃ and keep the reaction at a constant temperature for 2.5 h; after the temperature of the reaction system drops to room temperature (25℃), add 21 parts of phase inversion agent (octylphenol polyoxyethylene ether), stir and mix well to obtain drilling fluid coating agent.

[0071] Example 2:

[0072] (1) Preparation of modified polyetheramine inhibitors:

[0073] After stirring and mixing 130 parts of polyetheramine D230 and 60 parts of 3-chlorostyrene, 2 parts of catalyst (aluminum trichloride) were added, and the mixture was reacted at 45°C for 2 hours to obtain modified polyetheramine.

[0074] 199 parts of acrylamide monomer (acrylamide), 35 parts of cationic monomer (acryloyloxyethyltrimethylammonium chloride), 12.5 parts of organosilicon modifier (methylvinylphenylsilanol), 18 parts of cosolvent (urea), 2 parts of thickener (perfluorooctyl ethyl dodecafluoroheptyl acrylate), 4 parts of the above modified polyetheramine inhibitor, and 260 parts of sodium acrylate were added to 173 parts of deionized water and stirred to obtain an aqueous solution.

[0075] A solution of oil phase was obtained by mixing 250 parts of white oil and 24 parts of emulsifier (18 parts of polyglycerol oleate and 6 parts of N-polyoxyethylene stearamide).

[0076] (2) Add 0.2 parts of oxidant (ammonium persulfate) and 0.08 parts of chain extender (sodium formate) to the aqueous phase solution, stir and mix well, add the pH adjuster acrylic acid to adjust the pH value of the mixed solution to 6.6, then add the oil phase solution and stir and emulsify at 400 r / min for 2 h to obtain a reverse emulsion;

[0077] (3) Transfer the reverse emulsion to the reactor, purge with nitrogen for 40 min, adjust the temperature of the reaction system to 16℃, add 0.3 parts of reducing agent aqueous solution (1% sodium metabisulfite by mass) with a micro-injection pump under stirring at 280 r / min to initiate the polymerization reaction, raise the temperature to 40℃ and keep the reaction at a constant temperature for 2.5 h; after the temperature of the reaction system drops to room temperature (25℃), add 21 parts of phase inversion agent (octylphenol polyoxyethylene ether), stir and mix well to obtain drilling fluid coating agent.

[0078] Example 3

[0079] (1) Preparation of modified polyetheramine inhibitors:

[0080] After stirring and mixing 130 parts of polyetheramine D230 and 60 parts of 3-chlorostyrene, 2 parts of catalyst (aluminum trichloride) were added, and the mixture was reacted at 45°C for 2 hours to obtain modified polyetheramine.

[0081] 188 parts of acrylamide monomer (acrylamide), 38 parts of cationic monomer (acryloyloxyethyltrimethylammonium chloride), 12 parts of organosilicon modifier (dimethylvinylsilanol), 2 parts of cosolvent (sodium dodecyl sulfate), 3 parts of tackifier (ethyl acrylate (N-methylperfluorohexylsulfonamide)), 4 parts of the above-mentioned modified polyetheramine inhibitor, and 260 parts of sodium acrylate were added to 175 parts of deionized water and stirred to obtain an aqueous solution.

[0082] 250 parts of white oil and 24 parts of emulsifier (18 parts of polyglycerol polyoleate and 6 parts of N-polyoxyethylene stearamide) were mixed and emulsified by stirring at 500 r / min for 40 min to obtain an oil phase solution.

[0083] (2) Add 0.2 parts of oxidant (ammonium persulfate) and 0.1 parts of chain extender (sodium formate) to the aqueous phase solution, stir and mix well, add the pH adjuster acrylic acid to adjust the pH value of the mixed solution to 6.6, add the oil phase solution and stir and emulsify at 400 r / min for 2 h to obtain a reverse emulsion;

[0084] (3) Transfer the reverse emulsion to the reactor, purge with nitrogen for 40 min, adjust the temperature of the reaction system to 16℃, add 0.3 parts of reducing agent aqueous solution (1% sodium metabisulfite by mass) with a micro-injection pump under stirring at 280 r / min to initiate the polymerization reaction, raise the temperature to 40℃ and keep the reaction at a constant temperature for 2.5 h; after the temperature of the reaction system drops to room temperature (25℃), add 21 parts of phase inversion agent (octylphenol polyoxyethylene ether), stir and mix well to obtain drilling fluid coating agent.

[0085] Example 4

[0086] (1) Preparation of modified polyetheramine inhibitors:

[0087] After stirring and mixing 130 parts of polyetheramine D230 and 60 parts of 3-chlorostyrene, 2 parts of catalyst (aluminum trichloride) were added, and the mixture was reacted at 45°C for 2 hours to obtain modified polyetheramine.

[0088] 193 parts of acrylamide monomer (acrylamide), 30 parts of cationic monomer (acryloyloxyethyltrimethylammonium chloride), 11 parts of organosilicon modifier (methylvinylphenylsilanol), 2.5 parts of cosolvent (sodium dodecyl sulfate), 3.5 parts of tackifier (ethyl acrylate (N-methylperfluorohexylsulfonamide)), 4 parts of the above-mentioned modified polyetheramine inhibitor, and 245 parts of sodium acrylate were added to 180 parts of deionized water and stirred to obtain an aqueous solution.

[0089] A solution of oil phase was obtained by mixing 250 parts of white oil and 24 parts of emulsifier (18 parts of polyglycerol oleate and 6 parts of N-polyoxyethylene stearamide).

[0090] (2) Add 0.2 parts of oxidant (ammonium persulfate) and 0.1 parts of chain extender (sodium formate) to the aqueous phase solution, stir and mix well, add the pH adjuster acrylic acid to adjust the pH value of the mixed solution to 6.6, add the oil phase solution and stir and emulsify at 500 r / min for 2 h to obtain a reverse emulsion;

[0091] (3) Transfer the reverse emulsion to the reactor, purge with nitrogen for 40 min, adjust the temperature of the reaction system to 16℃, add 0.3 parts of reducing agent aqueous solution (1% sodium metabisulfite by mass) with a micro-injection pump under stirring at 280 r / min to initiate the polymerization reaction, raise the temperature to 40℃ and keep the reaction at a constant temperature for 2.5 h; after the temperature of the reaction system drops to room temperature (25℃), add 21 parts of phase inversion agent (octylphenol polyoxyethylene ether), stir and mix well to obtain drilling fluid coating agent.

[0092] Example 5

[0093] Example 5 is basically the same as Example 1, except that in step (1), the amount of organosilicon modifier (dimethylvinylsilane) added is 20 parts.

[0094] Example 6

[0095] Example 6 is basically the same as Example 1, except that in step (1), the amount of modified polyetheramine inhibitor added is 8 parts.

[0096] Example 7

[0097] Example 7 is basically the same as Example 1, except that in step (1), the amount of modified polyetheramine inhibitor added is 1 part.

[0098] Example 8

[0099] Example 8 is basically the same as Example 1, except that in step (1), the amount of cosolvent (urea) added is 20 parts.

[0100] Example 9

[0101] Example 9 is basically the same as Example 1, except that in step (1), the amount of tackifier (ethyl acrylate (N-methylperfluorohexylsulfonamide)) added is 10 parts.

[0102] Comparative Example 1

[0103] Comparative Example 1 is basically the same as Example 1, except that the cosolvent in step (1) is replaced with the same amount of deionized water.

[0104] Comparative Example 2

[0105] Comparative Example 2 is basically the same as Example 1, except that the thickener in step (1) is replaced with the same amount of deionized water.

[0106] Comparative Example 3

[0107] Comparative Example 3 is basically the same as Example 1, except that the organosilicon modifier (dimethylvinylsilane) in step (1) is replaced with the same amount of deionized water.

[0108] Comparative Example 4

[0109] Comparative Example 4 is basically the same as Example 1, except that the modified polyetheramine inhibitor in step (1) is replaced with the same amount of deionized water.

[0110] Comparative Example 5

[0111] Comparative Example 5 is basically the same as Example 1, except that the modified polyetheramine inhibitor in step (1) is replaced with the same amount of polyetheramine.

[0112] Comparative Example 6

[0113] Comparative Example 6 is basically the same as Example 1, except that the modified polyetheramine inhibitor in step (1) is replaced with the same amount of potassium acrylate.

[0114] The coating agents (hereinafter referred to as samples) prepared in Examples 1 to 9 and Comparative Examples 1 to 6 were subjected to performance index tests. The specific test methods are as follows, and the test results are shown in Table 1.

[0115] The coating agents prepared in the examples and comparative examples were compared and evaluated according to the method in SY / T 5696-2017;

[0116] Preparation of brine-based slurry: Add 2g of anhydrous sodium carbonate to 1000mL of brine (30% NaCl, 10% KCl), and add 40g of bentonite while stirring. Stir at high speed for a total of 20min, stopping at least twice during the process to scrape off the bentonite adhering to the cup wall. After curing in a sealed environment at 25℃±1℃ for 24h, a bentonite-based slurry with a mass fraction of 4% is obtained.

[0117] Drilling fluid rheology: The cured brine-based slurry was stirred at high speed for 5 minutes, and the apparent viscosity, plastic viscosity and dynamic shear force were measured in accordance with GB / T 16783.1.

[0118] Rock cuttings recovery rate test: Prepare sample solutions with a concentration of 2‰ using brine (30% NaCl, 10% KCl). Place 20g of shale rock cuttings (8-10 mesh) in an aging tank, add 350mL of sample solution, and then place the aging tank in a roller heating furnace at 230℃ for 16h. After cooling, pour out the solution and drill cuttings, pass them through a 40-mesh sieve, and place the drill cuttings remaining on the sieve in an oven at 110℃ to dry to constant weight. Calculate the rolling recovery rate by the ratio of the obtained drill cuttings mass to the initial drill cuttings mass.

[0119] Dissolution time test: At room temperature (25℃), 4g of the above sample was added to 400g of deionized water and dissolved. The stirring speed was 800-900r / min. The dissolution time of the above sample was measured when the liquid surface became flat and the stirring rod showed signs of climbing.

[0120] Shear resistance test: The high shear viscosity retention rate of the above samples was determined using a six-speed viscometer at φ100, concentration of 0.5%, and high-speed stirring at 8000 r / min.

[0121] Table 1

[0122]

[0123]

[0124] As shown in Table 1, compared with the comparative examples, the drilling fluid coating agent prepared in the embodiments of the present invention has the advantages of fast dissolution speed, high temperature resistance, strong salt resistance, high high shear viscosity retention rate, and high cuttings recovery rate. It has a good adsorption and coating effect on cuttings and can effectively inhibit dispersion. As can be seen from Comparative Examples 1 to 4, when no co-solvent is added during the polymerization reaction, the dissolution of the coating agent is poor, the dissolution time is longer, and the cuttings recovery rate is significantly reduced. When no organosilicon modifier is added, the cuttings recovery rate is significantly reduced. At the same time, when no modified polyetheramine inhibitor is added, the clay swelling inhibition performance and shear resistance of the coating agent are poor, the high shear viscosity retention rate is low, and the cuttings recovery rate is significantly reduced.

[0125] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A drilling fluid coating agent, characterized in that, The drilling fluid coating agent is prepared by reverse emulsion polymerization using an aqueous phase solution, an oil phase solution, and an initiator as reactants. The aqueous phase solution comprises acrylamide monomers, cationic monomers, organosilicon modifiers, thickeners, cosolvents, inhibitors, sodium acrylate, and water; the oil phase solution comprises white oil and an emulsifier; and the inhibitor is a modified polyetheramine. The cationic monomer is at least one of methacryloyloxyethyltrimethylammonium chloride, acryloyloxyethyltrimethylammonium chloride, or dimethyl diallylammonium chloride; The organosilicon modifier is at least one of dimethylvinylsilanol, methyldivinylsilanol, and methylvinylphenylsilanol; The tackifier is at least one of perfluorooctyl ethyl acrylate, dodecafluoroheptyl acrylate, (N-methylperfluorohexylsulfonamide) ethyl acrylate or 3-perfluorooctyl-2-methacrylate. The modified polyetheramine is prepared as follows: polyetheramine, 3-chlorostyrene and catalyst are stirred and mixed, and the modified polyetheramine is obtained after alkylation reaction; wherein the catalyst is aluminum trichloride.

2. The drilling fluid coating agent according to claim 1, characterized in that, The acrylamide monomer is at least one of acrylamide, methacrylamide, or ethylacrylamide; The co-solvent is at least one of sodium dodecyl sulfate, nonylphenol polyoxyethylene ether, urea, or anhydrous sodium sulfate.

3. The drilling fluid coating agent according to claim 1, characterized in that, By weight, the polyetheramine is 120-140 parts, 3-chlorostyrene is 50-80 parts, and the catalyst is 2-3 parts; The reaction temperature is 40-50℃, and the reaction time is 1-2 hours.

4. The drilling fluid coating agent according to claim 1, characterized in that, The emulsifier is at least one of polyglycerol oleate or N-polyoxyethylene stearamide.

5. The drilling fluid coating agent according to claim 1, characterized in that, The initiator includes an oxidant, a chain extender, and a reducing agent; The oxidant is at least one of ammonium persulfate, hydrogen peroxide, or dicumyl peroxide; the chain extender is at least one of diethylaminoethanol, sodium formate, or dodecyl mercaptan; and the reducing agent is at least one of sulfite or metabisulfite.

6. The drilling fluid coating agent according to claim 5, characterized in that, The mass ratio of the oxidant, the chain extender and the reducing agent is (1-2):(0.8-1):(0.2-0.3).

7. The drilling fluid coating agent according to claim 1, characterized in that, The contents of each reactant, by mass, are as follows: The composition includes 170-200 parts of acrylamide monomers, 20-40 parts of cationic monomers, 10-15 parts of organosilicon modifiers, 3-5 parts of thickeners, 2-15 parts of cosolvents, 2-5 parts of inhibitors, 200-300 parts of sodium acrylate, 110-290 parts of water, 220-280 parts of white oil, 20-35 parts of emulsifiers, and 0.2-2 parts of initiators.

8. A method for preparing a drilling fluid coating agent according to any one of claims 1 to 7, characterized in that, The preparation method includes the following steps: (1) Add acrylamide monomers, cationic monomers, organosilicon modifiers, thickeners, cosolvents, modified polyetheramine inhibitors and sodium acrylate to water and mix well to obtain an aqueous solution; stir and emulsify white oil and emulsifier to obtain an oil solution; (2) Add the oxidant and chain extender from the initiator to the aqueous solution, mix well, and then add the oil solution for stirring and emulsification to obtain a reverse emulsion; (3) Add the reducing agent in the initiator to the reverse emulsion to initiate a polymerization reaction, and the drilling fluid coating agent is obtained after the reaction.

9. The preparation method according to claim 8, characterized in that, Step (2) further includes adjusting the pH of the aqueous solution to 6.5-6.8; and / or In step (2), the stirring speed for emulsification is 300~500 r / min, and the stirring time for emulsification is 30~60 min.

10. The preparation method according to claim 8, characterized in that, Before initiating the polymerization reaction in step (3), the process also includes the step of introducing nitrogen gas into the reaction system; After initiating the polymerization reaction in step (3), the process further includes adding a phase inversion agent to the reaction system to obtain the drilling fluid coating agent; wherein the phase inversion agent is at least one of alkylphenol polyoxyethylene ether, nonylphenol polyoxyethylene ether or octylphenol polyoxyethylene ether.

11. The preparation method according to claim 10, characterized in that, The mass ratio of the phase-transforming agent to the acrylamide monomer is (20~28):(170~200); and / or The polymerization reaction is initiated at a temperature of 15-18°C, and the polymerization reaction is carried out at a temperature of 35-40°C for 2-3 hours.

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