An emulsion delayed crosslinking type plugging gel and a preparation method thereof

Abstract

The present application provides a kind of emulsion delayed crosslinking type plugging gel, the emulsion delayed crosslinking type plugging gel is oil-in-water type, including the following raw materials by weight percentage: non-ionic monomer 25wt%-40wt%, dihydroxy anthraquinone 0.5wt%-2wt%, anionic monomer 5wt%-16wt%, initiator 0.002wt%-0.2wt%, deionized water 10wt%-35wt%, non-polar solvent 15wt%-30wt%, emulsifier 2wt%-8wt%, emulsifying aid 1wt%-4wt%, phase transfer agent 0.5wt%-1.5wt%.The plugging gel is by adding modified functional monomer dihydroxy anthraquinone, dihydroxy anthraquinone and acrylamide copolymerization with other monomers oil-in-water polymer gel, not only initial viscosity is low, intensity and plugging rate is high, and gel time is controllable.

Description

Technical Field

[0001] This invention relates to the chemical industry, and in particular to an emulsion-based slow-crosslinking blockage-regulating gel and its preparation method. Background Technology

[0002] Currently, polymer-modified plugging gels are widely used in oilfield development both domestically and internationally for water shut-off in oil wells. These gels effectively block water layers in oil wells, preventing water and oil mixing and improving oil recovery. In terms of bottomhole fluid regulation, plugging gels can alter the viscosity, density, and other properties of bottomhole fluids, thereby controlling and regulating oil well production. Plugging gels are primarily used in oil and gas drilling, reservoir water injection, fracturing, and recovery to prevent blockage problems during oil and gas production.

[0003] There are currently nearly a hundred types of water shut-off and plugging agents in eight major categories, mainly including precipitated inorganic salt water shut-off and plugging agents, granular profile control and water shut-off chemicals, foam water shut-off and plugging agents, water shut-off agents that modify rock wettability, resin water shut-off agents, microbial profile control and water shut-off chemicals, cement-based profile control and water shut-off chemicals, and polymer gel profile control and water shut-off chemicals. With the development of technology, plugging gel systems are gradually shifting from traditional physical gelation methods to chemical gelation methods. Compared with traditional physical gels, chemical gels have the advantages of shorter gelation time, higher strength, and better stability. At the same time, new plugging gels have also made certain breakthroughs in water injection well conditioning processes, injection stability, and recoverability.

[0004] Currently, polymer gel-based plugging agents are widely used, with partially hydrolyzed polyacrylamide gel plugging agents being the most widely used oilfield treatment agents. Their excellent crosslinking properties, low price, and large-scale industrial production provide a foundation for their application. my country's industrialized polyacrylamide comes in various types, with molecular weights ranging from 3 million to 23 million. From a molecular structure perspective, there are non-hydrolyzed polyacrylamide, partially hydrolyzed polyacrylamide, zwitterionic polyacrylamide, and polyacrylamide copolymers. Different structures of polyacrylamide possess different properties. The degree of hydrolysis mainly affects the polymer's water solubility and crosslinking reaction performance. The introduction of zwitterions can improve the polymer's adsorption in porous media, while block copolymers can significantly improve the polymer's temperature resistance and salt resistance. The gel consists of low-concentration, high-molecular-weight polyacrylamide and a crosslinking agent. The polymer requires a molecular weight of over 9 million and a concentration range of 0.01%-0.12%. The crosslinking agent is mainly selected from polyvalent metal ions, such as aluminum citrate. Since the cross-linking reaction is easily affected by the salinity and pH of formation water, the application of this system is limited to a certain extent. Therefore, the development of new emulsion slow cross-linking plugging agents to improve the recovery rate has an urgent practical need and good application prospects.

[0005] For example, Chinese patent document CN115677923A discloses a pre-crosslinked gel particle plugging agent with a size at the micro-nano level, which can penetrate deep into the formation to achieve better profile control and water shut-off effects. It uses 2-acrylamide-2-methylpropanesulfonic acid-modified lithium saponite nanoparticles to prepare a nano-dispersion system that can stably exist in both polymer and salt solutions. After aging at 90℃ for 180 days, the plugging rate was above 94% before aging; after aging, the plugging rate could still be maintained above 80%, but the viscosity and gelation time were not mentioned.

[0006] Chinese patent document CN115466352A discloses a plugging agent that improves association performance by introducing long-chain hydrophobic monomers into the raw materials, resulting in better monomer polymerization and a more stable polymer. The tested viscosity is >11 mPa·s, and the plugging rate can reach up to 99%. However, the gelation time is not mentioned, nor is the viscosity value after gelation measured.

[0007] Chinese patent document CN107699219A discloses a high-temperature resistant and high-strength gel plugging system. This plugging system contains both elastic gel and solid microparticles, which have a good plugging effect on crossflow channels. The core plugging rate in indoor experiments can reach up to 98%, but the viscosity and gelation time are not mentioned.

[0008] The literature "Preparation and Evaluation of Novel Composite Gel Water-Plugling and Profile Control Agent" describes the preparation of a novel composite gel water-plugging and profile control agent using plant gum-modified polymer as the gel skeleton, inorganic polymer as the main agent, and crosslinking agent and crosslinking regulator as auxiliary agents. The initial viscosity was 55.9 mPa·s; the viscosity retention rate of the gel solution was >90%, and the plugging rate could reach 98.87%. However, the initial viscosity was slightly high, the viscosity after gelation was not mentioned, and the controllable range of gelation time was narrow.

[0009] The paper "Experimental Study on Oil Displacement Effect of Low Initial Viscosity Gel Plugging System" published by Zhang Weisen et al. discloses a low initial viscosity gel plugging system. The initial viscosity of this gel system is less than 20 mPa·s, the viscosity within 10 to 40 days is less than 300 mPa·s, and the gel viscosity is above 2500 mPa·s. It can smoothly enter the deep oil layer and effectively plug the channeling. However, the initial viscosity is high and the viscosity after gelation is low. The plugging rate was not evaluated.

[0010] The paper "Gel-forming Properties of Polyacrylamide / Water-soluble Phenolic Resin Reverse Emulsion Aqueous Dispersion" published by Cao Zhengquan et al. discloses the synthesis of polyacrylamide emulsions using reverse emulsion polymerization technology, with phenolic resin as a crosslinking agent. The polyacrylamide and crosslinking agent undergo a crosslinking reaction to form a gel. This reflooding agent is a reverse emulsion dispersed in water before reaching the formation, exhibiting low viscosity and enabling it to reach deep formation locations. Under the protection of the oil phase, the polyacrylamide and crosslinking agent in the latex particles are not adsorbed by the formation, their ratio remains unchanged, and the crosslinking reaction proceeds effectively. The initial viscosity is greater than 105 mPa·s, and the gel viscosity is between 5000 and 70000 mPa·s. However, the gel formation is unstable (stratification occurs within 8 weeks), and no plugging rate test was conducted. The gel formation time was not mentioned. Summary of the Invention

[0011] To address the problems and areas for improvement in existing technologies, this invention provides an emulsion-based slow-crosslinking plugging gel. This water-in-oil polymer gel, formed by copolymerizing the modified functional monomer dihydroxyanthraquinone with monomers such as acrylamide, not only exhibits low initial viscosity, high strength and plugging efficiency, but also offers controllable gelation time. This effectively solves the problems of short gelation time, low strength and plugging efficiency, and high initial viscosity inherent in current polymer plugging gel systems at high salinity.

[0012] To achieve the above objectives, the present invention provides the following technical solution:

[0013] An emulsion-based slow-crosslinking blockage-regulating gel, wherein the emulsion-based slow-crosslinking blockage-regulating gel is an oil-in-water type, and comprises the following raw materials by weight percentage:

[0014] Nonionic monomers 25wt%–40wt%, modified functional monomers 0.5wt%–2wt%, anionic monomers 5wt%–16wt%, initiator 0.002wt%–0.2wt%, deionized water 10wt%–35wt%, nonpolar solvent 15wt%–30wt%, emulsifier 2wt%–8wt%, emulsification aid 1wt%–4wt%, phase inversion agent 0.5wt%–1.5wt%;

[0015] The nonionic monomer is selected from one or more of acrylamide, N,N-methylenebisacrylamide, N,N-dimethylacrylamide and methyl methacrylate;

[0016] The modified functional monomer is dihydroxyanthraquinone; preferably 1,4-dihydroxyanthraquinone.

[0017] The anionic monomer is one or more of 2-acrylamido-2-methylpropanesulfonic acid, sodium styrene sulfonate, acrylic acid, and methacrylic acid.

[0018] This emulsion-based slow-crosslinking blockage-regulating gel also contains trace amounts of pH adjusters; however, due to the small amount, the pH adjuster content is negligible.

[0019] Optionally, in the emulsion slow-crosslinking blockage-regulating gel provided by the present invention, the initiator can be any conventional one in the industry, as long as it can initiate the polymerization of the above monomers. The initiator recommended by the present invention is selected from one or more of ammonium persulfate, sodium bisulfite, azobisisobutyramidine hydrochloride, dimethyl azobisisobutyrate, and azodicyanovalerate.

[0020] Optionally, in the emulsion slow crosslinking type blockage regulating gel provided by the present invention, the non-polar solvent is any one of biodiesel, No. 3 white oil and No. 5 white oil.

[0021] Optionally, in the emulsion slow crosslinking type plugging gel provided by the present invention, the emulsifier can be a conventional one in the industry. The emulsifier recommended by the present invention is selected from at least two of Span-40, Span-60, Span-80, Tween-85 and OP-10. Preferably, the HLB value of the emulsifier is 4-8.

[0022] Optionally, in the emulsion slow-crosslinking blockage-regulating gel provided by the present invention, the emulsifying aid is selected from one or more of methanol, n-butanol, ethylene glycol and n-hexanol.

[0023] Optionally, in the emulsion slow-crosslinking blockage-regulating gel provided by the present invention, the phase inversion agent is selected from one or more of fatty alcohol polyoxyethylene ether, nonylphenol polyoxyethylene ether, octylphenol polyoxyethylene ether and benzylphenol polyoxyethylene ether.

[0024] The present invention also provides a method for preparing the above-mentioned emulsion slow crosslinking type blockage regulating gel, comprising the following steps:

[0025] Aqueous phase: After the nonionic monomer, modified functional monomer and anionic monomer are mixed evenly in deionized water, the pH of the system is adjusted to neutral using a pH adjuster, and then the initiator is added and mixed evenly to obtain the aqueous phase;

[0026] Oil phase: The non-polar solvent, emulsifier, emulsifying aid and phase-transfer agent are mixed evenly to obtain a homogeneous and stable oil phase;

[0027] Reverse emulsion polymerization: Under stirring conditions, the aqueous phase is added to the oil phase to form a stable emulsion, and then reverse emulsion polymerization is carried out in an anaerobic atmosphere to obtain the emulsion slow crosslinking type blockage regulating gel.

[0028] Optionally, in the preparation method of the emulsion slow crosslinking type blockage regulating gel provided by the present invention, the specific addition rate of the aqueous phase to the oil phase is not limited, as long as the system temperature is controlled at 10-30°C during the addition process.

[0029] Optionally, in the preparation method of the emulsion slow crosslinking type blockage regulating gel provided by the present invention, the temperature of the reverse emulsion polymerization is 35-70°C and the time is 5-14h.

[0030] Optionally, in the preparation method of the emulsion slow crosslinking type blockage regulating gel provided by the present invention, the reverse emulsion polymerization is carried out in a closed container.

[0031] In the preparation method of the emulsion slow crosslinking type blockage regulating gel provided by the present invention, the anaerobic environment can be achieved by conventional operation in the industry, such as after adding the oil phase to the aqueous phase, nitrogen gas is introduced to replace the oxygen-containing air atmosphere in the system with nitrogen gas.

[0032] Compared with the prior art, the present invention has the following advantages:

[0033] Beneficial Effect 1: The emulsion slow crosslinking type plugging gel provided by the present invention introduces the modified functional monomer dihydroxyanthraquinone, which is polymerized with acrylamide nonionic monomers and organic acid anionic monomers containing carbon-carbon double bonds to form a polymer with low viscosity and good stability, thereby forming an oil-in-water plugging gel. This plugging gel has advantages such as low initial viscosity, controllable gelation time, and high plugging rate, and has a very wide range of application prospects.

[0034] 2. The emulsion-based slow-crosslinking plugging gel provided by this invention allows anthraquinone functional groups to form a pre-crosslinked structure with acrylamide monomers through free radical polymerization, increasing the degree of crosslinking of acrylamide monomers and giving the plugging system higher crosslinking density and compressive strength. Dihydroxyanthraquinone exhibits high dispersibility, ensuring uniform dispersion of the plugging agent. The hydroxyl functional groups can delay crosslinking time during polymerization, while the hydrophilic groups provide good fluidity and electron affinity, allowing adsorption at oil-water or solid-liquid interfaces, increasing the interaction between the polymer gel and the oil or aqueous phase, and improving the plugging performance of the plugging agent. This emulsion-based slow-crosslinking plugging agent demonstrates good stability, showing no stratification after 8 weeks of storage; its initial viscosity is as low as 4 mPa·s, gelling after 30 days with a viscosity reaching 20,000 mPa·s, and the plugging rate reaches a maximum of 99.6%.

[0035] 3. The preparation method of the emulsion slow crosslinking type blockage regulating gel provided by the present invention is simple to operate and easy to control. Detailed Implementation

[0036] The present invention will now be described in detail through embodiments. It should be noted that the following embodiments are only for further illustration of the present invention and should not be construed as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above description.

[0037] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0038] The specifications and manufacturers of the raw materials involved in the following embodiments and comparative examples are shown in the table below.

[0039] Table 1

[0040]

[0041]

[0042] Example 1

[0043] This embodiment provides an emulsion-based slow-crosslinking blockage-regulating gel, the preparation method of which includes the following steps:

[0044] Preparation of the aqueous phase: Weigh 40g of a mixture of acrylamide, N,N-methylenebisacrylamide and methyl methacrylate (mass ratio of acrylamide, N,N-methylenebisacrylamide and methyl methacrylate is 1:1:1), 0.7g of 1,4-dihydroxyanthraquinone, and 12g of sodium styrene sulfonate and acrylic acid (mass ratio of sodium styrene sulfonate to acrylic acid is 1:2) using a precision balance. Add the mixture to 24g of deionized water and stir until completely dissolved and clear. Adjust the pH of the system to 7 with NaOH. Then add 0.1g of a mixed initiator of ammonium persulfate and sodium bisulfite (mass ratio of 1:1). After complete dissolution, the aqueous phase is obtained.

[0045] Preparation of the oil phase: Weigh 18g of biodiesel into a three-necked flask, and while stirring, add 2g of emulsifier (Span-40, Span-80 and Tween-85 in a mass ratio of 2:2:1), 2g of emulsifying aid ethylene glycol, and 1.2g of phase inversion agent (fatty alcohol polyoxyethylene ether and benzylphenol polyoxyethylene ether in a mass ratio of 1:2). Stir until completely dissolved to obtain a homogeneous and stable oil phase.

[0046] Reverse emulsion polymerization: The above aqueous phase is added to the oil phase. During the addition process, the system temperature is controlled at 15°C. After the aqueous phase is added, the mixture is rapidly stirred and emulsified for 30 minutes to form a stable emulsion. Then, nitrogen gas is introduced into a sealed environment for 30 minutes to remove oxygen. After the oxygen removal is completed, the temperature is raised to 45°C and reacted at this temperature for 5 hours to obtain an emulsion slow crosslinking type plugging gel.

[0047] Example 2

[0048] This embodiment provides an emulsion-based slow-crosslinking blockage-regulating gel, the preparation method of which includes the following steps:

[0049] Preparation of the aqueous phase: Weigh out 35g of acrylamide and N,N-methylenebisacrylamide (mass ratio of acrylamide to N,N-methylenebisacrylamide is 1:1), 1.6g of 1,4-dihydroxyanthraquinone, and 16g of 2-acrylamido-2-methylpropanesulfonic acid and methacrylic acid (mass ratio of 2-acrylamido-2-methylpropanesulfonic acid and methacrylic acid is 1:1) using a precision balance. Add them to 18.85g of deionized water and stir until completely dissolved and clear. Adjust the pH of the system to 7 with NaOH. Then add 0.05g of a mixture of azobisisobutyramidine hydrochloride and dimethyl azobisisobutyrate initiator (mass ratio of 2:1). After complete dissolution, the aqueous phase is obtained.

[0050] Preparation of the oil phase: Weigh 20g of biodiesel into a three-necked flask, and while stirring, add 4g of emulsifier (Span-60, Tween-85, and OP-10 in a mass ratio of 2:1:1), 3g of emulsifying aid (butanol and ethylene glycol in a mass ratio of 1:2), and 1.5g of phase inversion agent (nonylphenol polyoxyethylene ether and octylphenol polyoxyethylene ether in a mass ratio of 1:1). Stir until completely dissolved to obtain a homogeneous and stable oil phase.

[0051] Reverse emulsion polymerization: The above aqueous phase is added to the oil phase. During the addition process, the system temperature is controlled at 20°C. After the aqueous phase is added, the mixture is rapidly stirred and emulsified for 30 minutes to form a stable emulsion. Then, nitrogen gas is introduced into a sealed environment for 30 minutes to remove oxygen. After the oxygen removal is completed, the temperature is raised to 60°C and reacted at this temperature for 8 hours to obtain the emulsion slow crosslinking type plugging gel.

[0052] Example 3

[0053] This embodiment provides an emulsion-based slow-crosslinking blockage-regulating gel, the preparation method of which includes the following steps:

[0054] Preparation of the aqueous phase: Weigh 30g of a mixture of N,N-methylenebisacrylamide and N,N-dimethylacrylamide (mass ratio 1:1), 1.6g of 1,4-dihydroxyanthraquinone, and 10g of a mixture of 2-acrylamido-2-methylpropanesulfonic acid and sodium styrene sulfonate (mass ratio of 2-acrylamido-2-methylpropanesulfonic acid to sodium styrene sulfonate 2:1) using a precision balance. Add 19.59g of deionized water and stir until completely dissolved and clear. Adjust the pH to 7 with NaOH, add 0.01g of the initiator dimethyl azobisisobutyrate, and wait for complete dissolution to obtain the aqueous phase.

[0055] Preparation of the oil phase: Weigh 28g of No. 3 white oil into a three-necked flask, and while stirring, add 6g of emulsifier (Span 40, Span-60, and Tween-85 in a mass ratio of 1:1:1), 4g of emulsifying aid (methanol and ethylene glycol in a mass ratio of 1:1), and 0.8g of phase inversion agent (fatty alcohol polyoxyethylene ether and nonylphenol polyoxyethylene ether in a mass ratio of 1:1) until completely dissolved to obtain a homogeneous and stable oil phase;

[0056] Reverse emulsion polymerization: The aqueous solution is added to the oil phase while the system temperature is controlled at 30°C during the addition process. After the aqueous phase is added, the mixture is rapidly stirred and emulsified for 30 minutes to form a stable emulsion. Then, nitrogen gas is introduced into the sealed environment for 30 minutes to remove oxygen. After the oxygen removal is completed, the temperature is raised to 70°C and reacted at this temperature for 12 hours to obtain the emulsion slow crosslinking type plugging gel.

[0057] Example 4

[0058] This embodiment provides an emulsion-based slow-crosslinking blockage-regulating gel, the preparation method of which includes the following steps:

[0059] Preparation of the aqueous phase: Weigh 32g of a mixture of acrylamide, N,N-methylenebisacrylamide, and methyl methacrylate (mass ratio of 1:1:2), 1.8g of 1,4-dihydroxyanthraquinone, and 16g of a mixture of 2-acrylamido-2-methylpropanesulfonic acid and acrylic acid (mass ratio of 3:1) using a precision balance. Add 18.19g of deionized water and stir until completely dissolved and clear. Adjust the pH to 7 with NaOH, add 0.01g of mixed initiator (mass ratio of dimethyl azobisisobutyrate to azodicyanovalerate 2:1), and wait for complete dissolution to obtain the aqueous phase.

[0060] Preparation of the oil phase: Weigh 25g of No. 3 white oil into a three-necked flask, and while stirring, add 3.5g of emulsifier (Span-80, Tween-85, OP-10 in a mass ratio of 1:1:1), 3g of emulsifying aid (ethylene glycol, n-hexanol in a mass ratio of 2:1), and 0.5g of phase inversion agent nonylphenol polyoxyethylene ether until completely dissolved to obtain a homogeneous and stable oil phase;

[0061] Reverse emulsion polymerization: The aqueous phase solution is added to the oil phase. During the addition process, the system temperature is controlled at 30°C. After the aqueous phase is added, the mixture is rapidly stirred and emulsified for 30 minutes to form a stable emulsion. Then, nitrogen gas is introduced into the sealed environment for 30 minutes to remove oxygen. After the oxygen removal is completed, the temperature is raised to 55°C and reacted at this temperature for 10 hours to obtain the emulsion slow crosslinking type plugging gel.

[0062] Example 5

[0063] This embodiment provides an emulsion-based slow-crosslinking blockage-regulating gel, the preparation method of which includes the following steps:

[0064] Preparation of the aqueous phase: Weigh 40g of a mixture of acrylamide and N,N-dimethylacrylamide (acrylamide to N,N-dimethylacrylamide mass ratio 1:2), 0.6g of 1,4-dihydroxyanthraquinone, and 14g of a mixture of sodium styrene sulfonate and acrylic acid (sodium styrene sulfonate to acrylic acid mass ratio 1:1) using a precision balance. Add 12.2g of deionized water and stir until completely dissolved and clear. Adjust the pH to 7 with NaOH, add 0.2g of mixed initiator (ammonium persulfate to sodium bisulfite mass ratio 1:1), and wait for complete dissolution to obtain the aqueous phase.

[0065] Preparation of the oil phase: Weigh 22g of No. 5 white oil into a three-necked flask, and while stirring, add 6g of emulsifier (Span-60 and Tween-85 in a mass ratio of 1:1), 4g of emulsifying aid (methanol and n-hexanol in a mass ratio of 1:1), and 1g of phase inversion agent (nonylphenol polyoxyethylene ether and benzylphenol polyoxyethylene ether in a mass ratio of 1:2) until completely dissolved to obtain a homogeneous and stable oil phase;

[0066] Reverse emulsion polymerization: The aqueous phase solution is added to the oil phase. During the addition process, the system temperature is controlled at 30°C. After the aqueous phase is added, the mixture is rapidly stirred and emulsified for 30 minutes to form a stable emulsion. Then, nitrogen gas is introduced into a sealed environment for 30 minutes to remove oxygen. After deoxygenation, the temperature is raised to 50°C and reacted at this temperature for 12 hours to obtain the emulsion slow crosslinking type plugging gel.

[0067] Example 6

[0068] This embodiment provides an emulsion-based slow-crosslinking blockage-regulating gel, the preparation method of which includes the following steps:

[0069] Preparation of the aqueous phase: Weigh 32g of a mixture of acrylamide, N,N-methylenebisacrylamide, and methyl methacrylate (mass ratio of acrylamide, N,N-methylenebisacrylamide, and methyl methacrylate 1:1:1), 0.5g of 1,4-dihydroxyanthraquinone, and 8g of a mixture of 2-acrylamido-2-methylpropanesulfonic acid, sodium styrene sulfonate, and acrylic acid (mass ratio of 2-acrylamido-2-methylpropanesulfonic acid, sodium styrene sulfonate, and acrylic acid 2:1:1) using a precision balance. Add 33.89g of deionized water and stir until completely dissolved and clear. Adjust the pH to 7 with NaOH, add 0.01g of mixed initiator (mass ratio of ammonium persulfate to sodium bisulfite 1:1), and wait for complete dissolution to obtain the aqueous phase.

[0070] Preparation of the oil phase: Weigh 20g of biodiesel into a three-necked flask, and while stirring, add 4g of emulsifier (Span-40 and Span-60 in a mass ratio of 1:1), 1g of emulsifying aid n-hexanol, and 0.6g of phase inversion agent benzylphenol polyoxyethylene ether until completely dissolved to obtain a homogeneous and stable oil phase.

[0071] Reverse emulsion polymerization: The aqueous solution is added to the oil phase while the system temperature is controlled at 25°C. After the aqueous phase is added, the mixture is rapidly stirred and emulsified for 30 minutes to form a stable emulsion. Then, nitrogen gas is introduced into a sealed environment for 30 minutes to remove oxygen. After deoxygenation, the temperature is raised to 60°C and reacted at this temperature for 9 hours to obtain the emulsion slow crosslinking type plugging gel.

[0072] Example 7

[0073] This embodiment provides an emulsion-based slow-crosslinking blockage-regulating gel, the preparation method of which includes the following steps:

[0074] Preparation of the aqueous phase: Weigh 28g of N,N-methylenebisacrylamide, 1.3g of 1,4-dihydroxyanthraquinone, and 6g of 2-acrylamido-2-methylpropanesulfonic acid using a precision balance. Add 31.1g of deionized water and stir until completely dissolved and clear. Adjust the pH to 7 with NaOH, and add 0.1g of initiator (azobisisobutyramidine hydrochloride and azodicyanovalerate in a mass ratio of 1:2). After complete dissolution, the aqueous phase is obtained.

[0075] Preparation of the oil phase: Weigh 26g of No. 5 white oil into a three-necked flask, and while stirring, add 5g of emulsifier (Span 60, Span 80, OP 10 in a mass ratio of 1:2:1), 2g of emulsifying aid methanol, and 0.5g of phase inversion agent (octylphenol polyoxyethylene ether, benzylphenol polyoxyethylene ether in a mass ratio of 2:1) until completely dissolved to obtain a homogeneous and stable oil phase;

[0076] Reverse emulsion polymerization: The aqueous phase solution is added to the oil phase while the system temperature is controlled at 30°C during the addition process. After the aqueous phase is added, the mixture is rapidly stirred and emulsified for 30 minutes to form a stable emulsion. Then, nitrogen gas is introduced into a sealed environment for 30 minutes to remove oxygen. After the oxygen removal is completed, the temperature is raised to 65°C and reacted at this temperature for 10 hours to obtain the emulsion slow crosslinking type plugging gel.

[0077] Example 8

[0078] This embodiment provides an emulsion-based slow-crosslinking blockage-regulating gel, the preparation method of which includes the following steps:

[0079] Preparation of the aqueous phase: Weigh 30g of a mixture of acrylamide and methyl methacrylate (acrylamide to methyl methacrylate mass ratio 2:1), 1.7g of 1,4-dihydroxyanthraquinone, and 15g of a mixture of 2-acrylamido-2-methylpropanesulfonic acid and methacrylic acid (2:1 mass ratio) using a precision balance. Add 23.75g of deionized water and stir until completely dissolved and clear. Adjust the pH to 7 with NaOH, add 0.15g of initiator (dimethyl azobisisobutyrate to azodicyanovalerate mass ratio 2:1), and wait for complete dissolution to obtain the aqueous phase.

[0080] Preparation of the oil phase: Weigh 18g of biodiesel into a three-necked flask, and while stirring, add 8g of emulsifier (Span-80 and Tween-85 in a mass ratio of 1:1), 2.5g of emulsifying aid (methanol, n-butanol, and ethylene glycol in a mass ratio of 1:1:2), and 0.9g of phase inversion agent (fatty alcohol polyoxyethylene ether and nonylphenol polyoxyethylene ether in a mass ratio of 1:2). After complete dissolution, a homogeneous and stable oil phase is obtained.

[0081] Reverse emulsion polymerization: The aqueous phase solution is added to the oil phase while the system temperature is controlled at 20°C during the addition process. After the aqueous phase is added, the mixture is rapidly stirred and emulsified for 30 minutes to form a stable emulsion. Then, nitrogen gas is introduced into a sealed environment for 30 minutes to remove oxygen. After the oxygen removal is completed, the temperature is raised to 65°C and reacted at this temperature for 12 hours to obtain the emulsion slow crosslinking type plugging gel.

[0082] Comparative Example 1

[0083] This comparative example provides an emulsion-based slow-crosslinking blockage-regulating gel, the preparation method of which includes the following steps:

[0084] Preparation of the aqueous phase: Weigh 35g of acrylamide and N,N-methylenebisacrylamide (acrylamide and N,N-methylenebisacrylamide in a mass ratio of 1:1), 1.6g of anthrone, and 16g of 2-acrylamido-2-methylpropanesulfonic acid and methacrylic acid (2-acrylamido-2-methylpropanesulfonic acid and methacrylic acid in a mass ratio of 1:1) using a precision balance. Add them to 18.85g of deionized water and stir until completely dissolved and clear. Adjust the pH of the system to 7 with NaOH. Then add 0.05g of a mixture of azobisisobutyramidine hydrochloride and dimethyl azobisisobutyrate initiator (mass ratio of 2:1). After complete dissolution, the aqueous phase is obtained.

[0085] Preparation of the oil phase: Weigh 20g of biodiesel into a three-necked flask, and while stirring, add 4g of emulsifier (Span-60, Tween-85, and OP-10 in a mass ratio of 2:1:1), 3g of emulsifying aid (butanol and ethylene glycol in a mass ratio of 1:2), and 1.5g of phase inversion agent (nonylphenol polyoxyethylene ether and octylphenol polyoxyethylene ether in a mass ratio of 1:1). Stir until completely dissolved to obtain a homogeneous and stable oil phase.

[0086] Reverse emulsion polymerization: The above aqueous phase is added to the oil phase. During the addition process, the system temperature is controlled at 20°C. After the aqueous phase is added, the mixture is rapidly stirred and emulsified for 30 minutes to form a stable emulsion. Then, nitrogen gas is introduced into a sealed environment for 30 minutes to remove oxygen. After the oxygen removal is completed, the temperature is raised to 60°C and reacted at this temperature for 8 hours to obtain the emulsion slow crosslinking type plugging gel.

[0087] Comparative Example 2

[0088] This comparative example provides an emulsion-based slow-crosslinking blockage-regulating gel, the preparation method of which includes the following steps:

[0089] Preparation of the aqueous phase: Weigh 22g of a mixture of acrylamide and N,N-methylenebisacrylamide (acrylamide to N,N-methylenebisacrylamide mass ratio 1:1), 2.5g of 1,4-dihydroxyanthraquinone, and 20g of a mixture of 2-acrylamido-2-methylpropanesulfonic acid and methacrylic acid (2-acrylamido-2-methylpropanesulfonic acid to methacrylic acid mass ratio 1:1) using a precision balance. Add 26.498g of deionized water and stir until completely dissolved and clear. Adjust the pH to 7 with NaOH, add 0.002g of initiator (dimethyl azobisisobutyrate to azobisisobutyramidine hydrochloride mass ratio 1:2), and wait for complete dissolution to obtain the aqueous phase.

[0090] Preparation of the oil phase: Weigh 20g of biodiesel into a three-necked flask, and while stirring, add 4g of emulsifier (Tween-85, Span-60, OP-10 in a mass ratio of 1:2:1), 3g of emulsifying aid (n-butanol and ethylene glycol in a mass ratio of 1:2), and 2g of phase inversion agent (nonylphenol polyoxyethylene ether and octylphenol polyoxyethylene ether in a mass ratio of 1:1) until completely dissolved to obtain a homogeneous and stable oil phase.

[0091] Reverse emulsion polymerization: The aqueous phase solution is added to the oil phase while the system temperature is controlled at 20°C during the addition process. After the aqueous phase is added, the mixture is rapidly stirred and emulsified for 30 minutes to form a stable emulsion. Then, nitrogen gas is introduced into a sealed environment for 30 minutes to remove oxygen. After the oxygen removal is completed, the temperature is raised to 60°C and reacted at this temperature for 8 hours to obtain the emulsion slow crosslinking type plugging gel.

[0092] The blockage-regulating gels prepared in the above embodiments and comparative examples were tested according to the following methods, and the specific test results are shown in the table below.

[0093] The initial viscosity and the viscosity after gelation were measured using a Brookfield rotational viscometer with a #2 rotor. The temperature was set between 20 and 25°C. The test liquid was added to the measuring cylinder, kept at this temperature for 10 minutes, and then the rotation speed was set for viscosity testing (specifically referring to standard GB / T 10247). The plugging rate was determined using a sand-filled core with a 2.5cm inner diameter and 20cm length. The sand-filled core was evacuated and saturated with water for 4 hours. The initial permeability K0 of the aqueous phase in the sand-filled core was measured. The gel solution was then injected, and the core was displaced with water in the reverse direction. The permeability K1 of the sand-filled core after plugging was measured. The plugging rate (E) is calculated using the following formula:

[0094]

[0095] Table 2

[0096]

[0097] Note: The gelation time was measured at 40℃.

[0098] As shown in the table above, the plugging gel provided by this invention has a better plugging effect: the plugging rate is above 94%, the gelation time is relatively long and adjustable (15-30 days), and the initial viscosity is low while the viscosity after gelation is high, indicating that the plugging gel provided by this invention has excellent comprehensive performance. Specifically, comparing Example 2 with Comparative Example 1, it can be seen that the addition of dihydroxyanthraquinone effectively prolongs the gelation time, and the initial viscosity is low, the strength after gelation is high, and the plugging rate is high, thus improving the comprehensive performance of the system. Comparing Example 2 with Comparative Example 2, it can be seen that when the amount of raw materials such as dihydroxyanthraquinone, nonionic monomers, and anionic monomers is not within the limited range, the comprehensive performance of the final plugging gel decreases significantly.

[0099] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the claims of the present invention.

Claims

1. A slow-crosslinking emulsion-based clogging-regulating gel, characterized in that, The emulsion-based slow-crosslinking blockage-regulating gel is an oil-in-water emulsion, and by weight percentage comprises the following raw materials: Nonionic monomers 25wt%~40wt%, modified functional monomers 0.5wt%~2wt%, anionic monomers 5wt%~16wt%, initiator 0.002wt%~0.2wt%, deionized water 10wt%~35wt%, nonpolar solvent 15wt%~30wt%, emulsifier 2wt%~8wt%, emulsification aid 1wt%~4wt%, phase inversion agent 0.5wt%~1.5wt%; The nonionic monomer is selected from one or more of acrylamide, N,N-methylenebisacrylamide, N,N-dimethylacrylamide and methyl methacrylate; The modified functional monomer is dihydroxyanthraquinone; The anionic monomer is one or more of 2-acrylamido-2-methylpropanesulfonic acid, sodium styrene sulfonate, acrylic acid, and methacrylic acid.

2. The emulsion-based slow-crosslinking clog-regulating gel as described in claim 1, characterized in that, The initiator is selected from one or more of ammonium persulfate, sodium bisulfite, azobisisobutyramidine hydrochloride, dimethyl azobisisobutyrate, and azobiscyanopentanoic acid.

3. The emulsion-based slow-crosslinking clog-regulating gel as described in claim 1, characterized in that, The non-polar solvent is selected from any one of biodiesel, No. 3 white oil, and No. 5 white oil.

4. The emulsion-based slow-crosslinking clog-regulating gel as described in claim 1, characterized in that, The emulsifier is selected from at least two of Span-40, Span-60, Span-80, Tween-85 and OP-10.

5. The emulsion-based slow-crosslinking clog-regulating gel as described in claim 1, characterized in that, The emulsifying agent is selected from one or more of methanol, n-butanol, ethylene glycol, and n-hexanol.

6. The emulsion-based slow-crosslinking clog-regulating gel as described in claim 1, characterized in that, The phase inversion agent is selected from one or more of fatty alcohol polyoxyethylene ether, nonylphenol polyoxyethylene ether, octylphenol polyoxyethylene ether, and benzylphenol polyoxyethylene ether.

7. The emulsion-based slow-crosslinking clog-regulating gel as described in claim 4, characterized in that, The emulsifier has an HLB value of 4-8.

8. A method for preparing an emulsion-based slow-crosslinking clog-regulating gel according to any one of claims 1-7, characterized in that, Includes the following steps: Aqueous phase: After the nonionic monomer, modified functional monomer and anionic monomer are mixed evenly in deionized water, the pH of the system is adjusted to neutral using a pH adjuster, and then the initiator is added and mixed evenly to obtain the aqueous phase; Oil phase: The non-polar solvent, emulsifier, emulsifying aid and phase-transfer agent are mixed evenly to obtain the oil phase; Reverse emulsion polymerization: Under stirring conditions, the aqueous phase is added to the oil phase, and then reverse emulsion polymerization is carried out in an anaerobic atmosphere to obtain the emulsion slow crosslinking type blockage regulating gel.

9. The preparation method according to claim 8, characterized in that, During the process of adding the aqueous phase to the oil phase, the system temperature is controlled at 10~30℃.

10. The preparation method according to claim 8, characterized in that, The reverse emulsion polymerization is carried out at a temperature of 35~70℃ for 5~14h.

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