Temperature-sensitive wall-fixing agent based on Pickering emulsion and preparation method of temperature-sensitive wall-fixing agent

Abstract

The invention discloses a temperature-sensitive wall fixing agent based on Pickering emulsion and a preparation method of the temperature-sensitive wall fixing agent, and relates to the cross technical field of exploration and development of carbonate oil and gas reservoirs and oilfield chemistry. The temperature-sensitive wall fixing agent is prepared from the following raw material components: a long side chain functional monomer, a temperature-resistant and salt-resistant functional monomer, an acrylamide monomer, a cationic functional monomer, a Pickering emulsifier, a stabilizer, an initiator, white oil and water. The temperature-sensitive wall fixing agent is prepared by preparing a reverse-phase water-in-oil emulsion by using a Pickering emulsifier, introducing a long-side-chain functional monomer, a temperature-resistant and salt-resistant functional monomer, an acrylamide monomer and a cationic functional monomer, and carrying out suspension polymerization by using the reverse-phase emulsion. The catalyst has the advantages of moderate molecular weight, narrow distribution range, excellent temperature resistance and compression resistance, strong rock adsorbability, timely temperature response and the like.

Description

Technical Field

[0001] This invention relates to the interdisciplinary fields of carbonate oil and gas reservoir exploration and development and oilfield chemistry, specifically to a temperature-sensitive wall-stabilizing agent based on Picking emulsion and its preparation method. Background Technology

[0002] Carbonate oil and gas reservoirs occupy a very important position in global oil and gas reservoirs. According to incomplete statistics, they account for approximately 70% of global oil and gas resources. Against the backdrop of increasingly acute international energy supply and demand contradictions and national energy security concerns, the exploration and development of carbonate oil and gas reservoirs has become one of the current research hotspots. Typical carbonate oil and gas reservoirs in my country are mainly distributed in the Erdos Basin, Tarim Basin, and Sichuan Basin. Among them, the Dengying Formation carbonate gas reservoir of the Sinian System in the central-Moxi section of the Sichuan Basin is the most typical. Oil and gas resource exploration and development is moving towards deeper strata. Multiple pressure systems, poor drillability, ultra-high temperature, ultra-high pressure, and high sulfur content pose significant challenges to drilling engineering. At the same time, wellbore collapse is extremely serious during the drilling of carbonate oil and gas reservoirs, especially in the Dengying Formation, where wellbore collapse is particularly severe, prolonging the drilling cycle and greatly threatening drilling safety.

[0003] Factors contributing to wellbore instability and collapse during the exploration and development of carbonate oil and gas reservoirs include drilling geological factors, drilling fluid process factors, and drilling technology factors. Among these, drilling geological factors are difficult to influence and can only be predicted as accurately as possible to provide guidance and reference for drilling fluid system design and drilling technology design. The hydrostatic pressure of the drilling fluid itself and the filter cake structure formed after filtration are powerful measures to ensure and enhance wellbore stability; in other words, regulating the performance of the drilling fluid system is one of the main ways to improve wellbore stability. Currently, solutions mainly focus on the following four aspects:

[0004] 1) High-viscosity gel-based treatment agents: These agents adhere to the wellbore surface through their high viscosity, increasing the wellbore's compressive strength and thus preventing instability and collapse. For example, Chinese patent CN116063991A utilizes an adhesive wall-protecting agent, a cementing wall-stabilizing agent, and an accelerator to prepare an adhesive-cementing wall-stabilizing agent for shale formations; Chinese patent CN114854379B prepares an environmentally friendly cementing wall-stabilizing agent for water-based drilling fluids by combining polymers, tannic acid, and water. While these materials are economical, environmentally friendly, and low-cost, their high viscosity properties are only fully realized at high concentrations, making them unsuitable for wall stabilization during drilling.

[0005] 2) Biomimetic Adhesion Functional Materials: These materials utilize the biomimetic principle of shellfish adsorbing onto rocks, adsorbing onto the wellbore surface to exert their inhibitory properties. For example, Chinese patent CN104177517A prepared a biomimetic polymer material that strengthens wellbore stability by grafting dopamine groups onto chitosan; Chinese patent CN106634884A synthesized a biomimetic wall-stabilizing agent using polyphenolic proteins, acrylamide, etc. The advantages of biomimetic adhesion functional materials are good biodegradability and strong environmental friendliness, but they are expensive and have limited temperature resistance.

[0006] 3) Chemical adhesives and binders: such as asphalt, epoxy resin adhesives, sodium silicate, etc. For example, Chinese patent CN113969153B prepared a micro-crosslinked emulsion wall-fixing agent based on lithium silicate and ultrafine particles by combining lithium silicate, ultrafine particles, stabilizers, dispersants, crosslinking agents, and water; Chinese patent CN115057967B prepared a water-in-oil emulsion using an aqueous phase (water-soluble olefin monomers, crosslinking agents, acids, emulsifier I) and an oil phase (macromolecule monomers, ester monomers, emulsifier II), and then added an initiator to initiate a free radical polymerization reaction to prepare a microgel chemical wall-fixing agent for high-temperature water-based drilling fluids. The above materials have problems such as incompatibility with drilling fluid systems, large particle size, and loss of binding effect in aqueous solutions.

[0007] 4) Various types of plugging materials: The research focuses on the synergistic enhancement of drilling fluid plugging performance through the compounding of plugging agents with different particle sizes, aiming to minimize drilling fluid filtration loss, reduce formation damage, and inhibit formation clay hydration swelling and migration. Chinese patent CN115093837B describes a wall-stabilizing agent prepared by combining redispersible latex powder, rubber, thermosetting resin, epoxy resin, chloroprene latex, and nano-silica. Chinese patent 112239655A discloses a layer-by-layer deposition wall-stabilizing agent dispersion, comprising a base fluid, wall-stabilizing particles, a main dispersant, and a co-dispersant. Improving drilling fluid filtration performance and enhancing wellbore stability through plugging agents is a relatively ideal and widely used construction method; however, it is difficult for drilling fluid to achieve zero water loss under differential pressure.

[0008] In summary, it is evident that existing wall-stabilizing agents cannot respond promptly to formation temperature in a water environment, and their adsorption on the wellbore surface is difficult to adjust according to temperature, hindering their efficient wall-stabilizing effect. Therefore, addressing the issues of wall-stabilizing agents' inability to respond promptly to formation temperature, their large polymer molecular weight and wide molecular weight distribution, poor performance controllability, and incompatibility with drilling fluid systems, there is an urgent need to develop high-performance water-based drilling fluid wall-stabilizing agents using novel preparation methods. This will provide technical support for improving wellbore stability in carbonate oil and gas reservoirs. Summary of the Invention

[0009] Addressing the limitations of current wall-stabilizing agents in responding promptly to formation temperatures and their large polymer molecular weights, this invention aims to provide a temperature-sensitive wall-stabilizing agent based on Picking emulsions and its preparation method. The method involves formulating a reverse-phase water-in-oil emulsion using Picking emulsifier, introducing long-side-chain functional monomers, temperature- and salt-resistant functional monomers, acrylamide monomers, and cationic functional monomers, followed by reverse-phase emulsion suspension polymerization. This method offers advantages such as moderate molecular weight, narrow distribution range, excellent temperature and pressure resistance, strong rock adsorption, and timely temperature response.

[0010] This invention is achieved through the following technical solution:

[0011] In a first aspect, this application provides a temperature-sensitive wall-fixing agent based on Picking emulsion. The raw material components for preparing the temperature-sensitive wall-fixing agent include long side-chain functional monomers, temperature-resistant and salt-resistant functional monomers, acrylamide monomers, cationic functional monomers, Picking emulsifiers, stabilizers, initiators, white oil, and water.

[0012] Furthermore, by weight, the raw material components for preparing the temperature-sensitive wall-fixing agent include: 4 to 8 parts of long side-chain functional monomers, 3 to 5 parts of temperature-resistant and salt-resistant functional monomers, 1.5 to 3.5 parts of cationic functional monomers, 1.5 to 2.5 parts of Pickering emulsifier, 0.3 to 0.7 parts of system stabilizer, 0.8 to 1.6 parts of initiator, 110 to 130 parts of white oil, and 80 to 100 parts of water.

[0013] Furthermore, the long side-chain functional monomer includes at least one of methyl allyl alcohol polyoxyethylene ether, polyethylene glycol monomethyl ether, and allyl polyoxyethylene ether.

[0014] Furthermore, the temperature- and salt-resistant functional monomer includes at least one of 2-acrylamido-2-methylpropanesulfonic acid, sodium p-styrenesulfonate, and sodium vinylsulfonate.

[0015] Furthermore, the acrylate monomers include at least one of acrylamide, isobutoxymethacrylamide, and isopropylacrylamide.

[0016] Furthermore, the cationic functional monomer includes at least one of dimethyl diallyl ammonium chloride, methacryloyloxyethyl trimethyl ammonium chloride, and acryloyloxyethyl trimethyl ammonium chloride.

[0017] Furthermore, the Pickering emulsifier includes at least one of ultrafine calcium carbonate, nano-graphene oxide, and dichlorodimethylsilane-grafted silica.

[0018] Furthermore, the system stabilizer includes at least one of the following: Scripset SMA 520, a copolymer of styrene and maleic anhydride; sodium dodecylbenzenesulfonate; and nonylphenol polyoxyethylene ether TX-10.

[0019] Furthermore, the initiator includes at least one of ammonium persulfate, potassium persulfate, and benzoyl peroxide.

[0020] Secondly, this application provides a method for preparing a temperature-sensitive wall-fixing agent based on Picking emulsion, comprising the following steps:

[0021] Add 4 to 8 parts of long side-chain functional monomers, 3 to 5 parts of temperature-resistant and salt-resistant functional monomers, 3 to 7 parts of acrylamide monomers, and 1.5 to 3.5 parts of cationic functional monomers to 77 to 97 parts of water, stir at a constant temperature of 40 to 50°C for 20 to 30 minutes to dissolve or disperse evenly, adjust the pH of the system to 6 to 8 using a 40% sodium hydroxide solution, and then add 0.3 to 0.7 parts of system stabilizer to obtain an aqueous solution of functional monomers.

[0022] Add 1.5 to 2.5 parts of Pickering emulsifier to 110 to 130 parts of white oil, and stir at room temperature for 20 to 30 minutes to disperse it evenly to obtain the oil phase;

[0023] An initiator aqueous solution can be obtained by dissolving 0.8 to 1.6 parts of the initiator in 1 to 3 parts of water under stirring.

[0024] Add the obtained functional monomer aqueous solution to the obtained oil phase, and after the mixed system is heated to 60-80℃, shear emulsify it at 9000-12000r / min for 20-30min to obtain Pickering emulsion;

[0025] The obtained Pickering emulsion is deoxygenated by purging with nitrogen for 5-15 minutes, and then the obtained initiator aqueous solution is added. The reaction is carried out at a constant temperature of 60-80℃ for 3-4 hours to obtain a temperature-sensitive wall-solidifying agent based on Pickering emulsion.

[0026] The above-mentioned temperature-sensitive wall-stabilizing agent and the temperature-sensitive wall-stabilizing agent prepared by the above preparation method can be applied to the exploration and development of carbonate oil and gas reservoirs.

[0027] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0028] (1) The molecular conformation of the temperature-sensitive wall-fixing agent based on Pickering emulsion of the present invention is temperature-responsive. That is, in a low-temperature environment, the molecular chains are coiled and the adsorption groups are in a bound state, reducing the adsorption on the well wall of carbonate oil and gas reservoirs. More wall-fixing agent molecules exist in the drilling fluid system. In a high-temperature environment, the molecular chains are stretched and more adsorption groups are exposed, and more wall-fixing agent molecules are adsorbed on the well wall of carbonate oil and gas reservoirs, which can play a more efficient role in wall-fixing.

[0029] (2) The temperature-sensitive wall-fixing agent based on Pickering emulsion of the present invention is prepared by reverse emulsion suspension polymerization. The wall-fixing agent molecules have advantages such as moderate molecular weight, narrow distribution range, excellent temperature and salt resistance, and strong rock adsorption.

[0030] (3) The preparation method and process of the temperature-sensitive wall-solidifying agent based on Pickering emulsion of the present invention are simple, easy to operate, and have low cost, making them suitable for large-scale industrial production. Attached Figure Description

[0031] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings:

[0032] Figure 1 The adsorption amount of the wall-solidifying agent for drilling fluid prepared in Examples 1-3 and Comparative Examples 1-2 on the surface of clay particles at different temperatures. Detailed Implementation

[0033] 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.

[0034] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0035] Example 1

[0036] This embodiment provides a method for preparing a temperature-sensitive wall-solidifying agent for Pickering emulsions, using the following raw material formulation:

[0037] 6 parts long side-chain functional monomers, 5 parts temperature-resistant and salt-resistant functional monomers, 3 parts acrylamide monomers, 3.5 parts cationic functional monomers, 1.5 parts Pickering emulsifier, 0.3 parts system stabilizer, 1.2 parts initiator, 120 parts white oil, and 90 parts water.

[0038] Among them, the long side-chain functional monomer is allyl polyoxyethylene ether, the temperature-resistant and salt-resistant functional monomer is sodium vinyl sulfonate, the acrylamide monomer is isobutoxymethacrylamide, the cationic functional monomer is acryloyloxyethyltrimethylammonium chloride, the Pickering emulsifier is ultrafine calcium carbonate, the system stabilizer is nonylphenol polyoxyethylene ether TX-10, and the initiator is benzoyl peroxide.

[0039] The specific preparation method is as follows:

[0040] S1. Add 6 parts allyl polyoxyethylene ether, 5 parts sodium vinyl sulfonate, 3 parts isobutoxymethacrylamide, and 3.5 parts acryloyloxyethyltrimethylammonium chloride to 87 parts water, stir at a constant temperature of 40°C for 25 minutes to dissolve or disperse evenly, adjust the pH of the system to 6 using a 40% sodium hydroxide solution, and then add 0.3 parts nonylphenol polyoxyethylene ether TX-10 to obtain the functional monomer aqueous solution.

[0041] S2. Add 1.5 parts of ultrafine calcium carbonate to 120 parts of white oil and stir at room temperature for 25 minutes to disperse it evenly to obtain the oil phase.

[0042] S3. Dissolve 1.2 parts of benzoyl peroxide in 3 parts of water under stirring to obtain an initiator aqueous solution.

[0043] S4. Add the aqueous solution of the functional monomer obtained in step S1 to the oil phase obtained in step S2. After the mixed system is heated to 70°C, perform shear emulsification at 9000 r / min for 30 min to obtain Pickering emulsion.

[0044] S5. The Pickering emulsion obtained in step S4 is deoxygenated by passing nitrogen gas through it for 5 minutes. Then, the initiator aqueous solution obtained in step S3 is added, and the mixture is reacted at a constant temperature of 70°C for 4 hours to obtain a temperature-sensitive wall-solidifying agent based on the Pickering emulsion.

[0045] Example 2

[0046] This embodiment provides a method for preparing a temperature-sensitive wall-solidifying agent for Pickering emulsions, using the following raw material formulation:

[0047] 4 parts long side-chain functional monomers, 4 parts temperature-resistant and salt-resistant functional monomers, 7 parts acrylamide monomers, 2.5 parts cationic functional monomers, 1.0 part Pickering emulsifier, 0.5 parts system stabilizer, 1.6 parts initiator, 130 parts white oil, and 80 parts water.

[0048] Among them, the long side-chain functional monomer is polyethylene glycol monomethyl ether, the temperature-resistant and salt-resistant functional monomer is sodium p-styrene sulfonate, the acrylamide monomer is acrylamide, the cationic functional monomer is methacryloyloxyethyltrimethylammonium chloride, the Pickering emulsifier is nano-graphene oxide, the system stabilizer is sodium dodecylbenzene sulfonate, and the initiator is potassium persulfate.

[0049] The specific preparation method is as follows:

[0050] S1. Add 4 parts of polyethylene glycol monomethyl ether, 4 parts of sodium p-styrene sulfonate, 7 parts of acrylamide, and 2.5 parts of methacryloyloxyethyltrimethylammonium chloride to 77 parts of water, and stir at a constant temperature of 50°C for 20 minutes to dissolve or disperse evenly. Adjust the pH of the system to 8 using a 40% sodium hydroxide solution, and then add 0.5 parts of sodium dodecylbenzene sulfonate to obtain an aqueous solution of the functional monomer.

[0051] S2. Add 1.0 part of nano-graphene oxide to 130 parts of white oil and stir at room temperature for 20 minutes to disperse it evenly to obtain the oil phase.

[0052] S3. Dissolve 1.6 parts of potassium persulfate in 3 parts of water under stirring to obtain an initiator aqueous solution.

[0053] S4. Add the aqueous solution of the functional monomer obtained in step S1 to the oil phase obtained in step S2. After the mixed system is heated to 80°C, shear emulsify it at 11000 r / min for 20 min to obtain Pickering emulsion.

[0054] S5. The Pickering emulsion obtained in step S4 is deoxygenated by passing nitrogen gas for 10 min, and then the initiator aqueous solution obtained in step S3 is added. The reaction is carried out at a constant temperature of 80°C for 3 h to obtain a temperature-sensitive wall-solidifying agent based on Pickering emulsion.

[0055] Example 3

[0056] This embodiment provides a method for preparing a temperature-sensitive wall-solidifying agent for Pickering emulsions, using the following raw material formulation:

[0057] 8 parts long side-chain functional monomers, 3 parts temperature-resistant and salt-resistant functional monomers, 5 parts acrylamide monomers, 1.5 parts cationic functional monomers, 2.5 parts Pickering emulsifier, 0.7 parts system stabilizer, 1.2 parts initiator, 110 parts white oil, and 100 parts water.

[0058] Among them, the long side-chain functional monomer is methyl allyl alcohol polyoxyethylene ether, the temperature-resistant and salt-resistant functional monomer is 2-acrylamido-2-methylpropanesulfonic acid, the acrylamide monomer is isopropylacrylamide, the cationic functional monomer is dimethyl diallyl ammonium chloride, the Pickering emulsifier is dichlorodimethylsilane-grafted silica, the system stabilizer is Scripset SMA 520 copolymer of styrene and maleic anhydride, and the initiator is ammonium persulfate.

[0059] The specific preparation method is as follows:

[0060] S1. Add 8 parts of methyl allyl alcohol polyoxyethylene ether, 3 parts of 2-acrylamide-2-methylpropanesulfonic acid, 5 parts of isopropylacrylamide, and 1.5 parts of dimethyl diallyl ammonium chloride to 97 parts of water. Stir at a constant temperature of 45°C for 30 minutes to dissolve or disperse evenly. Adjust the pH of the system to 7 using a 40% sodium hydroxide solution. Then add 0.7 parts of styrene-maleic anhydride copolymer Scripset SMA 520 to obtain the functional monomer aqueous solution.

[0061] S2. Add 2.5 parts of dichlorodimethylsilane-grafted silica to 110 parts of white oil and stir at room temperature for 30 minutes to disperse it evenly to obtain the oil phase.

[0062] S3. Dissolve 1.2 parts of ammonium persulfate in 3 parts of water under stirring to obtain an initiator aqueous solution.

[0063] S4. Add the aqueous solution of the functional monomer obtained in step S1 to the oil phase obtained in step S2. After the mixed system is heated to 60°C, shear emulsify it at 12000 r / min for 25 min to obtain the Pickering emulsion.

[0064] S5. The Pickering emulsion obtained in step S4 is deoxygenated by passing nitrogen gas for 15 minutes, and then the initiator aqueous solution obtained in step S3 is added. The reaction is carried out at a constant temperature of 60°C for 3.5 hours to obtain a temperature-sensitive wall-forming agent based on Pickering emulsion.

[0065] Comparative Example 1

[0066] This comparative example provides a wall-building agent based on Pickering emulsion. The difference between this and Example 3 is that this comparative example does not contain long-side-chain functional monomers, and the raw material formulation used is as follows:

[0067] 6 parts of temperature- and salt-resistant functional monomers, 8 parts of acrylamide monomers, 3.5 parts of cationic functional monomers, 2.5 parts of Pickering emulsifier, 0.7 parts of system stabilizer, 1.2 parts of initiator, 110 parts of white oil, and 100 parts of water.

[0068] Among them, the temperature-resistant and salt-resistant functional monomer is 2-acrylamido-2-methylpropanesulfonic acid, the acrylamide monomer is isopropylacrylamide, the cationic functional monomer is dimethyldiallylammonium chloride, the Pickering emulsifier is dichlorodimethylsilane-grafted silica, the system stabilizer is Scripset SMA 520, a copolymer of styrene and maleic anhydride, and the initiator is ammonium persulfate.

[0069] The specific preparation method is as follows:

[0070] S1. Add 6 parts of 2-acrylamido-2-methylpropanesulfonic acid, 8 parts of isopropylacrylamide, and 3.5 parts of dimethyldiallylammonium chloride to 97 parts of water, and stir at a constant temperature of 45°C for 30 minutes to dissolve or disperse evenly. Adjust the pH of the system to 7 using a 40% sodium hydroxide solution. Then add 0.7 parts of styrene-maleic anhydride copolymer Scripset SMA520 to obtain an aqueous solution of the functional monomer.

[0071] S2. Add 2.5 parts of dichlorodimethylsilane-grafted silica to 110 parts of white oil and stir at room temperature for 30 minutes to disperse it evenly to obtain the oil phase.

[0072] S3. Dissolve 1.2 parts of ammonium persulfate in 3 parts of water under stirring to obtain an initiator aqueous solution.

[0073] S4. Add the aqueous solution of the functional monomer obtained in step S1 to the oil phase obtained in step S2. After the mixed system is heated to 60°C, shear emulsify it at 12000 r / min for 25 min to obtain the Pickering emulsion.

[0074] S5. The Pickering emulsion obtained in step S4 is deoxygenated by passing nitrogen gas for 15 minutes, and then the initiator aqueous solution obtained in step S3 is added. The mixture is reacted at a constant temperature of 60°C for 3.5 hours to obtain a wall-fixing agent based on the Pickering emulsion.

[0075] Comparative Example 2

[0076] This comparative example provides a wall-fixing agent based on Pickering emulsion. The difference between this and Example 3 is that this comparative example does not contain long-side-chain functional monomers or temperature- and salt-resistant functional monomers. The raw material formulation used is as follows:

[0077] 11 parts acrylamide monomers, 6.5 parts cationic functional monomers, 2.5 parts Pickering emulsifier, 0.7 parts system stabilizer, 1.2 parts initiator, 110 parts white oil, and 100 parts water.

[0078] The acrylamide monomer is isopropylacrylamide, the cationic functional monomer is dimethyldiallylammonium chloride, the Pickering emulsifier is dichlorodimethylsilane-grafted silica, the system stabilizer is Scripset SMA 520, a copolymer of styrene and maleic anhydride, and the initiator is ammonium persulfate.

[0079] The specific preparation method is as follows:

[0080] S1. Add 11 parts isopropylacrylamide and 6.5 parts dimethyldiallylammonium chloride to 97 parts water, stir at a constant temperature of 45°C for 30 minutes to dissolve or disperse evenly, adjust the pH of the system to 7 using a 40% sodium hydroxide solution, and then add 0.7 parts of styrene-maleic anhydride copolymer Scripset SMA 520 to obtain the functional monomer aqueous solution.

[0081] S2. Add 2.5 parts of dichlorodimethylsilane-grafted silica to 110 parts of white oil and stir at room temperature for 30 minutes to disperse it evenly to obtain the oil phase.

[0082] S3. Dissolve 1.2 parts of ammonium persulfate in 3 parts of water under stirring to obtain an initiator aqueous solution.

[0083] S4. Add the aqueous solution of the functional monomer obtained in step S1 to the oil phase obtained in step S2. After the mixed system is heated to 60°C, shear emulsify it at 12000 r / min for 25 min to obtain the Pickering emulsion.

[0084] S5. The Pickering emulsion obtained in step S4 is deoxygenated by passing nitrogen gas for 15 minutes, and then the initiator aqueous solution obtained in step S3 is added. The mixture is reacted at a constant temperature of 60°C for 3.5 hours to obtain a wall-fixing agent based on the Pickering emulsion.

[0085] Test Example 1

[0086] In this test example, 30g of 10-mesh shale and coal rock cuttings were placed in a molding press (D=15mm), 3mL of distilled water was added, and the core was pressed under a hydraulic pressure of 10MPa for 5min to obtain a simulated carbonate oil and gas reservoir core. The drilling fluids prepared in Examples 1-3 and Comparative Examples 1-2 were prepared into aqueous solutions with a wall-stabilizing agent with a mass fraction of 0.5%. The cores were immersed in different wall-stabilizing agent solutions for 24h, and the integrity of the cores was observed. The test results are shown in Table 1.

[0087] Table 1 Integrity of carbonate oil and gas reservoir cores after immersion in different wall-stabilizing agent solutions for 24 hours

[0088]

[0089] The temperature-sensitive wall-stabilizing agent based on Pickering emulsion of the present invention can be effectively adsorbed onto core samples from carbonate oil and gas reservoirs. Simultaneously, it possesses a certain cementing effect, thus stabilizing the wellbore. Test results show that the core samples obtained in Examples 1-3 exhibit good stability and structural integrity in solutions of the temperature-sensitive wall-stabilizing agent based on Pickering emulsion under different ambient temperatures. However, in the wall-stabilizing agent solutions obtained in Comparative Examples 1-2, the stability and structural integrity are good after soaking at a lower temperature of 25°C for 24 hours, but the stability decreases and the structure collapses after soaking at higher temperatures of 90°C and 150°C for 24 hours.

[0090] Test Example 2

[0091] This test example compares and analyzes the adsorption amount of drilling fluid wall-stabilizing agents prepared in Examples 1-3 and Comparative Examples 1-2 on the surface of clay particles at different temperatures. The method used is the organic oxygen demand (COD) method. Specifically, according to GB11914-1989 "Determination of Chemical Oxygen Demand in Water - Dichromate Method", first, a 4% bentonite aqueous solution was prepared, and then 2% of the drilling fluid wall-stabilizing agents prepared in Examples 1-3 and Comparative Examples 1-2 were added to it respectively. The mixture was stirred and mixed evenly at different temperatures, and after centrifugation at 4000 rpm for 10 min, the supernatant was collected to obtain the bentonite filtrate. Then, dichromate standard solution and ferrous ammonium sulfate standard solution were prepared, and the samples were measured according to the standard method. The adsorption amount of wall-stabilizing agents on the surface of clay particles at different temperatures was obtained. The results are as follows. Figure 1 As shown.

[0092] The temperature-sensitive wall-stabilizing agent based on Pickering emulsion of this invention exhibits temperature-responsive characteristics. Test results show that the wall-stabilizing agents for drilling fluids prepared in Examples 1-3 adsorb significantly less on the surface of bentonite particles at lower temperatures than at higher temperatures. In contrast, the wall-stabilizing agents for drilling fluids prepared in Comparative Examples 1-2 show an inverse relationship with temperature on the surface of bentonite particles. The wall-stabilizing agents for drilling fluids prepared in Examples 1-3 incorporate long-side-chain functional monomers, giving them temperature-responsive characteristics. At lower temperatures, the hydration and expansion of components such as shale and mudstone in carbonate oil and gas reservoirs are minimal, requiring little wall-stabilizing agent action. The wall-stabilizing agent molecular chains are coiled, and the adsorption groups are in a bound state, reducing adsorption on the carbonate oil and gas reservoir core. When drilling reaches high-temperature blocks, the high-temperature environment causes the wall-stabilizing agent molecular chains to expand, exposing more adsorption groups. Consequently, more wall-stabilizing agent molecules adsorb onto the well wall of the carbonate oil and gas reservoir, resulting in more efficient wall-stabilizing action.

[0093] Test Example 3

[0094] In this test example, the drilling fluid wall-stabilizing agent solutions prepared in Examples 1-3 and Comparative Examples 1-2 were compared with distilled water for inhibition. 10g of bentonite was placed in the core column and compacted under a pressure of 2.8MPa for 5min. The compacted core was suspended on the instrument and after returning to zero, a wall-stabilizing agent solution with a mass concentration of 2% and distilled water were added respectively. The expansion of the core was observed at different times.

[0095] Table 2. Swelling tests of carbonate oil and gas reservoir cores in different solvents.

[0096] sample 1h / mm 2h / mm 4h / mm 8h / mm Example 1 0.30 0.51 0.68 0.98 Example 2 0.28 0.47 0.61 0.87 Example 3 0.25 0.44 0.52 0.81 Comparative Example 1 0.39 0.53 0.79 1.24 Comparative Example 2 0.44 0.69 0.93 1.68 distilled water 0.68 1.20 1.85 2.96

[0097] The test data show that the temperature-sensitive wall-stabilizing agent based on Pickering emulsion of the present invention has a good inhibitory effect on bentonite cores. The degree of expansion at various different expansion test ages is less than that under distilled water conditions, indicating good inhibitory performance.

[0098] Test Example 4

[0099] This test example compares the rheological properties of drilling fluid base slurry before and after aging using the wall-stabilizing agents prepared in Examples 1-3 and Comparative Examples 1-2. 16g of bentonite and 0.56g of sodium carbonate were added to 400mL of water, and the mixture was sheared and stirred at 8000r / min for 20min at room temperature, then sealed and allowed to stand for 16h to hydrate, resulting in a 4% base slurry. 2% (by mass) of the wall-stabilizing agent prepared in Examples 1-3 and Comparative Examples 1-2 was taken, and the mixture was sheared and stirred at 5000r / min for 20min at room temperature. The rheological and filtration properties of the drilling fluid were tested according to the American Petroleum Institute (API) standard (API RP 13B 1, 2009). The above drilling fluid samples were placed in a roller furnace, aged at 150℃ for 16h, and their rheological and filtration properties were measured again after aging.

[0100] Table 3. Rheological and filtration loss tests of drilling fluids prepared by the wall-stabilizing agents in Examples 1-3 and Comparative Examples 1-2.

[0101]

[0102] This invention discloses a temperature-sensitive wall-stabilizing agent based on Pickering emulsion that improves the rheological properties of drilling fluid base slurry, including apparent viscosity (AV), plastic viscosity (PV), and dynamic shear force (YP), while reducing the filtration loss of the drilling fluid base slurry. Test results show that the drilling fluid system with 2 wt% of the wall-stabilizing agent in Example 3 exhibits moderate viscosity and minimal filtration loss. After aging at 150°C for 16 hours, the viscosity of the drilling fluid base slurry decreases, while the filtration loss increases. The drilling fluid system with 2 wt% of the wall-stabilizing agent in Example 3 exhibits the lowest filtration loss. In contrast, the drilling fluid system with 2 wt% of the wall-stabilizing agent in Comparative Example 2 exhibits the highest filtration loss, with filtration losses of 26 mL before and 41 mL after aging. Furthermore, compared to Examples 1-3, the wall-stabilizing agents prepared in Comparative Examples 1-2 demonstrate a more significant viscosity-enhancing effect.

[0103] Test Example 5

[0104] This test example compares the lap shear strength of the drilling fluid wall-stabilizing agents prepared in Examples 1-3 and Comparative Examples 1-2 against the rock. Specifically, according to the "Method for Determination of Tensile Shear Strength of Adhesives" (GB7124-2008), a 2wt% aqueous solution of the wall-stabilizing agents from Examples 1-3 and Comparative Examples 1-2 was uniformly applied to the single lap surface of the artificially lapped specimen (rock sheet) (water treatment served as a blank control group). The lapped specimen was pressed under 10 MPa for 2 hours, then placed in air and water at 50°C for 24 hours. Tensile force was then applied parallel to the lap surface and along the main axis of the specimen to test the maximum load that the specimen could withstand in air and water.

[0105] Table 4. Tests of the overlap shear strength of the wall-stabilizing agents prepared in Examples 1-3 and Comparative Examples 1-2 on rocks.

[0106]

[0107]

[0108] Compared to water, the temperature-sensitive wall-stabilizing agent based on Pickering emulsion of this invention significantly improves the lap shear strength of rocks after treatment. The test results show that the wall-stabilizing agent obtained in Example 3 provides the greatest improvement in the lap shear strength of rocks, with an lap shear strength of 2.125 MPa in air and 1.814 MPa in water. In contrast, the wall-stabilizing agents in Comparative Examples 1 and 2 do not incorporate long-side-chain functional monomers or temperature- and salt-resistant functional monomers. The large side-chain groups of the long-side-chain functional monomers reduce the destructive effect of free water molecules on the rock cementation force, while the sulfonic acid groups and other strongly adsorbing groups of the temperature- and salt-resistant functional monomers allow the wall-stabilizing agent to be more and more firmly adsorbed onto the surface of rock particles, thus stabilizing the wellbore. Therefore, the wall-stabilizing agents in Comparative Examples 1 and 2 show a smaller improvement in the lap shear strength of rocks.

[0109] Comparative Example 3

[0110] The comparative example is a micro-crosslinked emulsion wall-solidifying agent based on lithium silicate-ultrafine particles and its preparation method, which is described in patent number CN202010710328.8. The method involves preparing a micro-crosslinked emulsion wall-solidifying agent based on lithium silicate and ultrafine particles by combining lithium silicate, ultrafine particles, stabilizer, dispersant, crosslinking agent and water. First, the emulsifier is dispersed to obtain a uniform emulsion, and then the sealing material, lithium silicate and crosslinking agent are added in sequence to obtain a water-in-oil chemical wall-solidifying agent.

[0111] Comparative Example 4

[0112] The comparative example is a microgel chemical wall-stabilizing agent for high-temperature water-based drilling fluid, patent number CN202210824948.3, and its preparation method and application. The microgel chemical wall-stabilizing agent for high-temperature water-based drilling fluid is prepared by using olefin water-soluble monomers, crosslinking agents, acids, emulsifier I, macromolecular monomers, ester monomers, and emulsifier II. First, an aqueous phase and an oil phase are prepared separately. Then, the prepared aqueous phase is added to the oil phase, and an initiator and oxygen are added to carry out a shear polymerization emulsification reaction to obtain a water-in-oil microgel chemical wall-stabilizing agent. The water-in-oil emulsion system has problems such as large particle size and easy loss of cementing effect in aqueous solution.

[0113] Compared with Comparative Examples 3 and 4, the present invention adds the prepared aqueous phase to the oil phase, and then treats the mixture with nitrogen to remove oxygen and with an initiator to obtain a water-in-oil type Pickering emulsion water-based drilling fluid temperature-sensitive wall-stabilizing agent, which avoids problems such as large particle size in the system and easy loss of cementing effect in aqueous solution.

[0114] The microgel chemical wall-stabilizing agent for high-temperature water-based drilling fluid of Comparative Example 4 and its preparation method, along with the microgel chemical wall-stabilizing agents for high-temperature water-based drilling fluid prepared in Examples 1-5 of the present invention, were subjected to lap shear strength tests according to the "Method for Determination of Tensile Shear Strength of Adhesives" (GB7124-1986). The test results are shown in Table 5. The temperature-sensitive wall-stabilizing agent for water-based drilling fluid based on Pickering emulsion prepared in this invention was also subjected to lap shear strength tests according to the "Method for Determination of Tensile Shear Strength of Adhesives" (GB7124-2008). The test results are shown in Table 6. The results show that the chemical wall-stabilizing agent prepared by this patent has a higher lap shear strength value.

[0115] Table 5 shows the test results of the lap shear strength of the reported patents.

[0116]

[0117] Table 6. Test results of the lap joint shear strength of the present invention.

[0118]

[0119] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A temperature-sensitive wall-forming agent based on Picking emulsion, characterized in that, The raw materials for preparing temperature-sensitive wall-fixing agents include long-side-chain functional monomers, temperature-resistant and salt-resistant functional monomers, acrylamide monomers, cationic functional monomers, Pickering emulsifiers, stabilizers, initiators, white oil, and water.

2. The temperature-sensitive wall-forming agent based on Picking emulsion according to claim 1, characterized in that, The raw material components for preparing the temperature-sensitive wall-fixing agent, by weight, include: 4 to 8 parts of long side-chain functional monomers, 3 to 5 parts of temperature-resistant and salt-resistant functional monomers, 1.5 to 3.5 parts of cationic functional monomers, 1.5 to 2.5 parts of Pickering emulsifier, 0.3 to 0.7 parts of system stabilizer, 0.8 to 1.6 parts of initiator, 110 to 130 parts of white oil, and 80 to 100 parts of water.

3. The temperature-sensitive wall-forming agent based on Picking emulsion according to claim 1, characterized in that, The long side-chain functional monomers include at least one of methyl allyl alcohol polyoxyethylene ether, polyethylene glycol monomethyl ether, and allyl polyoxyethylene ether.

4. The temperature-sensitive wall-forming agent based on Picking emulsion according to claim 1, characterized in that, The temperature- and salt-resistant functional monomers include at least one of 2-acrylamide-2-methylpropanesulfonic acid, sodium p-styrenesulfonate, and sodium vinylsulfonate.

5. A temperature-sensitive wall-forming agent based on Picking emulsion according to claim 1, characterized in that, The acrylate monomers include at least one of acrylamide, isobutoxymethylacrylamide, and isopropylacrylamide.

6. A temperature-sensitive wall-forming agent based on Picking emulsion according to claim 1, characterized in that, The cationic functional monomer includes at least one of dimethyl diallyl ammonium chloride, methacryloyloxyethyl trimethyl ammonium chloride, and acryloyloxyethyl trimethyl ammonium chloride.

7. A temperature-sensitive wall-forming agent based on Picking emulsion according to claim 1, characterized in that, The Pickering emulsifier includes at least one of ultrafine calcium carbonate, nano-graphene oxide, and dichlorodimethylsilane-grafted silica.

8. A temperature-sensitive wall-forming agent based on Picking emulsion according to claim 1, characterized in that, The system stabilizer includes at least one of the following: Scripset SMA 520, a copolymer of styrene and maleic anhydride; sodium dodecylbenzenesulfonate; and nonylphenol polyoxyethylene ether TX-10.

9. A temperature-sensitive wall-forming agent based on Picking emulsion according to claim 1, characterized in that, The initiator includes at least one of ammonium persulfate, potassium persulfate, and benzoyl peroxide.

10. A method for preparing a temperature-sensitive wall-consolidating agent based on a Picking emulsion as described in any one of claims 1 to 9, characterized in that, Includes the following steps: Long-side-chain functional monomers, temperature-resistant and salt-resistant functional monomers, acrylamide monomers, and cationic functional monomers are added to water and kept at a constant temperature to dissolve or disperse them evenly. The pH of the system is adjusted to 6-8 using sodium hydroxide solution, and then a system stabilizer is added to obtain an aqueous solution of functional monomers. Add Pickering emulsifier to white oil and stir at room temperature to disperse it evenly to obtain the oil phase; An initiator aqueous solution can be obtained by dissolving the initiator in water under stirring conditions; Add the aqueous solution of the functional monomer to the obtained oil phase, and after the mixture is heated to 60-80°C, shear emulsification is performed to obtain the Pickering emulsion. The obtained Pickering emulsion is deoxygenated by passing nitrogen gas through it, and then an initiator aqueous solution is added. The reaction is carried out at a constant temperature of 60-80℃ for 3-4 hours to obtain a temperature-sensitive wall-solidifying agent based on the Pickering emulsion.

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