Emulsion slow crosslinking type plugging gel and preparation method thereof

Abstract

The invention provides an emulsion slow crosslinking type plugging control gel, which is in an oil-in-water type, and is prepared from the following raw materials in percentage by weight: 25 to 40 weight percent of nonionic monomer, 0.5 to 2 weight percent of dihydroxy anthraquinone, 5 to 16 weight percent of anionic monomer, 0.002 to 0.2 weight percent of initiator and the balance of water. The emulsion comprises the following components in percentage by weight: 10 to 35 percent of deionized water, 15 to 30 percent of non-polar solvent, 2 to 8 percent of emulsifier, 1 to 4 percent of emulsifying aid and 0.5 to 1.5 percent of phase inversion agent. According to the plugging adjusting gel, the modified functional monomer dihydroxy anthraquinone is added, and the dihydroxy anthraquinone and monomers such as acrylamide are copolymerized to form oil-in-water type polymer gel, so that the initial viscosity is low, the strength and the plugging rate are high, and the gelling time is controllable.

Description

Technical Field

[0001] The invention relates to the field of chemical industry, and in particular to an emulsion slow-crosslinking plugging regulating gel and a preparation method thereof. Background Art

[0002] At present, in the development of oil fields at home and abroad, polymer plugging gel has been widely used in oil well water plugging. The plugging gel can effectively plug the water layer in the oil well, prevent water and oil from mixing, and improve the oil field recovery rate. In terms of bottom hole fluid regulation, the plugging gel can change the viscosity, density and other properties of the bottom hole fluid, thereby achieving the purpose of controlling oil well production and regulating oil well production. The plugging gel is mainly used in oil and gas drilling, reservoir water injection, fracturing, recovery and other fields to prevent blockage problems caused by the oil and gas production process.

[0003] There are nearly 100 types of plugging and regulating agents in eight categories, mainly including precipitated inorganic salt plugging and regulating agents, granular profile-control plugging and regulating agents, foam plugging and regulating agents, plugging and regulating agents that change rock wettability, resin plugging and regulating agents, microbial profile-control plugging and regulating agents, cement profile-control plugging and regulating agents, and polymer gel profile-control plugging and regulating agents. With the development of science and technology, the plugging and regulating gel system has gradually transformed from the traditional physical gel method to the chemical gel method. Compared with the traditional physical gel, the chemical gel has the characteristics of short gelation time, high strength, and good stability; at the same time, the new plugging and regulating gel has also made certain breakthroughs in the injection process of water injection wells, injection stability, and recoverability.

[0004] At present, the most widely used plugging agent is polymer gel. Partially hydrolyzed polyacrylamide gel plugging agent is the most widely used oilfield treatment agent. Its good cross-linking performance, low price and a large number of industrialized products provide a basis for the application of this additive. There are many types of industrialized polyacrylamide in my country, with molecular weights ranging from 3 million to 23 million; from the perspective of molecular structure, there are non-hydrolyzed polyacrylamide, partially hydrolyzed polyacrylamide, zwitterionic polyacrylamide and polyacrylamide copolymers. Polyacrylamide with different structures has different characteristics. The degree of hydrolysis mainly affects the water solubility and cross-linking reaction performance of the polymer. The introduction of zwitterions can improve the adsorption of the polymer in porous media, while block copolymers can significantly improve the temperature resistance and salt resistance of the polymer. The gel is composed of low-concentration high-molecular-weight polyacrylamide and a cross-linking agent. The polymer requires a molecular weight of more than 9 million and a concentration range of 0.01%-0.12%. The cross-linking agent mainly selects multivalent metal ions, such as aluminum citrate. Since the cross-linking reaction is easily affected by the mineralization and pH value of the formation water, the application of this system is limited to a certain extent; therefore, the development of a new emulsion slow-cross-linking plugging agent to improve the recovery rate has an urgent practical need and good application prospects.

[0005] For example, the size of the pre-crosslinked gel particle plugging agent disclosed in Chinese patent document CN115677923A is at the micro-nano level, which can enter deep into the formation to achieve better profile control and water plugging effect. It uses 2-acrylamide-2-methylpropanesulfonic acid to modify lithium soapstone nanoparticles to prepare a nano-dispersion system that can be stably present in both polymer and salt solution. After aging at 90°C for 180 days, the plugging rate is above 94% before aging; after aging, the plugging rate can still be maintained above 80%, but the viscosity and gelation time are not mentioned.

[0006] Chinese patent document CN115466352A discloses a plugging agent, which specifically improves the associative properties by introducing a long carbon chain hydrophobic monomer into the raw material, making the monomer polymerization effect better and obtaining a more stable polymer. The tested viscosity is >11mPa·s, and the plugging rate can reach up to 99%. However, the gelation time is not mentioned, and the viscosity value after gelation is not measured.

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

[0008] In the document "Preparation and Evaluation of New Composite Gel Water Plugging and Profile Control Agent", a new composite gel water plugging and profile control agent was prepared by using plant gum modified polymer as gel skeleton, inorganic polymer as main agent, cross-linking agent and cross-linking regulator as auxiliary agents. The initial viscosity was 55.9 mPa·s; the viscosity retention rate of the gel liquid was >90%, and the plugging rate could be as high as 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 document "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 the gel system is less than 20 mPa·s, the viscosity within 10 to 40 days is less than 300 mPa·s, and the gelled viscosity is above 2500 mPa·s. It can smoothly enter the deep oil layer and effectively plug the crossflow channel. However, the initial viscosity is high, and the viscosity after gelling is low, and the plugging rate has not been evaluated.

[0010] Cao Zhengquan et al. published "Gel Formation Performance of Polyacrylamide / Water-soluble Phenolic Resin Inverse Emulsion Aqueous Dispersion", which disclosed the use of inverse emulsion polymerization technology to synthesize polyacrylamide emulsion, with phenolic resin as the cross-linking agent, and the polyacrylamide and the cross-linking agent undergo cross-linking reaction to form gel. The displacement agent is an inverse emulsion dispersed in water before reaching the formation, with low viscosity, and can reach deep positions in the formation. Under the protection of the oil phase, the polyacrylamide and cross-linking agent in the latex particles will not be adsorbed by the formation, and the ratio of the two will not change, so the cross-linking reaction can be carried out effectively, with an initial viscosity greater than 105 mPa·s, and a gelation viscosity of 5000-70000 mPa·s, but the gelation is unstable (stratification occurs within 8 weeks of placement), and no plugging rate test was conducted, and the gelation time was not mentioned. Summary of the invention

[0011] In view of the problems existing in the prior art and the direction to be improved, the present invention provides an emulsion slow cross-linking plugging control gel, which is formed by adding a modified functional monomer dihydroxyanthraquinone and copolymerizing with monomers such as acrylamide to form an oil-in-water polymer gel, which not only has low initial viscosity, high strength and plugging rate, but also has controllable gelation time. It effectively solves the problems of short gelation time, low strength and plugging rate, and high initial viscosity existing in the current polymer plugging control gel system under high mineralization.

[0012] To achieve the above object, the present invention provides the following technical solutions:

[0013] An emulsion slow cross-linking plugging control gel, the emulsion slow cross-linking plugging control gel is an oil-in-water type, and comprises the following raw materials by weight percentage:

[0014] Non-ionic monomer 25wt%-40wt%, modified functional monomer 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 inversion agent 0.5wt%-1.5wt%;

[0015] Wherein, 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-acrylamide-2-methylpropane sulfonic acid, sodium styrene sulfonate, acrylic acid and methacrylic acid.

[0018] The latex slow cross-linking plugging control gel also contains a trace amount of pH regulator, but due to the small amount, the content of the pH regulator can be ignored.

[0019] Optionally, in the emulsion slow cross-linking plugging control 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-mentioned monomers. The initiator recommended by the present invention is selected from one or more of ammonium persulfate, sodium bisulfite, azobisisobutyramidine hydrochloride, dimethyl azobisisobutyrate and azobiscyanovaleric acid.

[0020] Optionally, in the emulsion slow-crosslinking plugging control gel provided by the present invention, the non-polar solvent is any one of biodiesel, 3# white oil and 5# white oil.

[0021] Optionally, in the emulsion slow-crosslinking plugging gel provided by the present invention, the emulsifier can be any 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 plugging control 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 plugging control gel provided by the present invention, the phase transition 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 cross-linking plugging regulating gel, comprising the following steps:

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

[0026] Oil phase: evenly mix the non-polar solvent, emulsifier, emulsifying aid and phase inversion agent to obtain a uniform and stable oil phase;

[0027] Inverse emulsion polymerization: under stirring conditions, the water phase is added to the oil phase to form a stable emulsion, and then inverse emulsion polymerization is carried out in an oxygen-free atmosphere to obtain the emulsion slow cross-linking plugging control gel.

[0028] Optionally, in the method for preparing the emulsion slow-crosslinking plugging control gel provided by the present invention, during the process of adding the water phase to the oil phase, the specific addition rate is not limited, as long as the system temperature is controlled at 10-30° C. during the addition process.

[0029] Optionally, in the method for preparing the emulsion slow-crosslinking plugging control gel provided by the present invention, the temperature of the inverse emulsion polymerization is 35 to 70° C., and the time is 5 to 14 hours.

[0030] Optionally, in the method for preparing the emulsion slow-crosslinking plugging regulating gel provided by the present invention, the inverse emulsion polymerization is carried out in a closed container.

[0031] In the preparation method of the emulsion slow-crosslinking plugging control gel provided by the present invention, the oxygen-free environment can be achieved by conventional operations in the industry, such as introducing nitrogen after the water phase is added to the oil phase to replace the oxygen-containing air atmosphere in the system with nitrogen.

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

[0033] Beneficial effect 1: The emulsion slow-crosslinking plugging gel provided by the present invention introduces a modified functional monomer dihydroxyanthraquinone, which is polymerized with an acrylamide non-ionic monomer and an organic acid anionic monomer containing a carbon-carbon double bond to form a polymer with low viscosity and good stability, thereby forming an oil-in-water plugging gel. The plugging gel has the advantages of low initial viscosity, controllable gelation time, and high plugging rate, and has a very broad application prospect.

[0034] 2. The emulsion slow cross-linking plugging gel provided by the present invention can form a pre-crosslinking structure through free radical polymerization between anthraquinone functional groups and acrylamide monomers, increase the cross-linking degree of acrylamide monomers, and make the plugging system have higher cross-linking density and compressive strength. Dihydroxyanthraquinone is highly dispersible and can make the plugging agent disperse evenly. The hydroxyl functional group can delay the cross-linking time in the polymerization reaction. The hydrophilic group gives it good fluidity and electron affinity, and can adsorb on the oil-water interface or solid-liquid interface, increase the interaction force between the polymer gel and the oil phase or the water phase, and improve the plugging performance of the plugging agent. The emulsion slow cross-linking plugging agent has good stability and no stratification after being placed for 8 weeks; the initial viscosity is as low as 4mPa·s, and it will gel in 30 days and the viscosity after gelation can reach 20000mPa·s, and the plugging rate can reach up to 99.6%.

[0035] 3. The preparation method of the emulsion slow-crosslinking plugging regulating gel provided by the present invention is simple to operate and easy to control. DETAILED DESCRIPTION

[0036] The present invention is described in detail below by way of examples. It is necessary to point out that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Those skilled in the art in this field can make some non-essential improvements and adjustments to the present invention based on the above content of the present invention.

[0037] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially.

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

[0039] Table 1

[0040]

[0041]

[0042] Example 1

[0043] This embodiment provides an emulsion slow cross-linking plugging control gel, the preparation method of which includes the following steps:

[0044] Preparation of aqueous phase: Use a precision balance to weigh 40 g of a mixture of acrylamide, N,N-methylenebisacrylamide and methyl methacrylate (the mass ratio of acrylamide, N,N-methylenebisacrylamide and methyl methacrylate is 1:1:1), 0.7 g of 1,4-dihydroxyanthraquinone, and 12 g of sodium styrene sulfonate and acrylic acid (the mass ratio of sodium styrene sulfonate to acrylic acid is 1:2), add to 24 g of deionized water, stir until completely dissolved and clarified, adjust the pH of the system to 7 with NaOH, add a mixed initiator of ammonium persulfate and sodium bisulfite in a mass ratio of 1:1 (total 0.1 g), and after complete dissolution, obtain an aqueous phase;

[0045] Preparation of oil phase: weigh 18g of biodiesel and put it in a three-necked flask, add 2g of emulsifier (the mass ratio of Span-40, Span-80 and Tween-85 is 2:2:1), 2g of emulsifier ethylene glycol, 1.2g of phase transition agent (the mass ratio of fatty alcohol polyoxyethylene ether and benzylphenol polyoxyethylene ether is 1:2)) while stirring, stir until completely dissolved to obtain a uniform and stable oil phase;

[0046] Inverse emulsion polymerization: add the above-mentioned water phase to the oil phase, control the system temperature at 15°C during the addition process, and after the water phase is added, quickly stir and emulsify for 30 minutes to form a stable emulsion; then maintain a closed environment and introduce nitrogen for 30 minutes for deoxygenation. After deoxygenation, heat to 45°C and react at this temperature for 5 hours to obtain an emulsion slow cross-linking plugging gel.

[0047] Example 2

[0048] This embodiment provides an emulsion slow cross-linking plugging control gel, the preparation method of which includes the following steps:

[0049] Preparation of aqueous phase: Use a precision balance to weigh 35 g of acrylamide and N,N-methylenebisacrylamide (the mass ratio of acrylamide and N,N-methylenebisacrylamide is 1:1), 1.6 g of 1,4-dihydroxyanthraquinone, and 16 g of 2-acrylamide-2-methylpropanesulfonic acid and methacrylic acid (the mass ratio of 2-acrylamide-2-methylpropanesulfonic acid and methacrylic acid is 1:1), add to 18.85 g of deionized water, stir until completely dissolved and clarified, adjust the pH of the system to 7 with NaOH, add a mixed initiator of azobisisobutyramidine hydrochloride and dimethyl azobisisobutyrate in a mass ratio of 2:1 (a total of 0.05 g), and after complete dissolution, obtain the aqueous phase;

[0050] Preparation of oil phase: weigh 20g of biodiesel and put it in a three-necked flask, add 4g of emulsifier (the mass ratio of Span-60, Tween-85, and OP-10 is 2:1:1), 3g of emulsifier (the mass ratio of n-butanol to ethylene glycol is 1:2), and 1.5g of phase transition agent (the mass ratio of nonylphenol polyoxyethylene ether to octylphenol polyoxyethylene ether is 1:1) while stirring, and stir until completely dissolved to obtain a uniform and stable oil phase;

[0051] Inverse emulsion polymerization: add the above-mentioned water phase to the oil phase, control the system temperature at 20°C during the addition process, and after the water phase is added, quickly stir and emulsify for 30 minutes to form a stable emulsion; then maintain a closed environment and introduce nitrogen for 30 minutes for deoxygenation. After deoxygenation, heat to 60°C and react at this temperature for 8 hours to obtain an emulsion slow cross-linking plugging gel.

[0052] Example 3

[0053] This embodiment provides an emulsion slow cross-linking plugging control gel, the preparation method of which includes the following steps:

[0054] Preparation of aqueous phase: Use a precision balance to weigh 30 g of a mixture of N,N-methylenebisacrylamide and N,N-dimethylacrylamide (mass ratio 1:1), 1.6 g of 1,4-dihydroxyanthraquinone, and 10 g of 2-acrylamide-2-methylpropanesulfonic acid and sodium styrenesulfonate (mass ratio of 2-acrylamide-2-methylpropanesulfonic acid to sodium styrenesulfonate 2:1), add 19.59 g of deionized water, stir until completely dissolved and clarified, adjust the pH to 7 with NaOH, add 0.01 g of initiator dimethyl azobisisobutyrate, and wait until completely dissolved to obtain an aqueous phase.

[0055] Preparation of oil phase: weigh 28g of 3# white oil and put it in a three-necked flask, add 6g of emulsifier (mass ratio of Span 40, Span-60, Tween-85 is 1:1:1), 4g of emulsifying aid (mass ratio of methanol to ethylene glycol is 1:1), and 0.8g of phase transfer agent (mass ratio of fatty alcohol polyoxyethylene ether and nonylphenol polyoxyethylene ether is 1:1) while stirring until it is completely dissolved to obtain a uniform and stable oil phase;

[0056] Inverse emulsion polymerization: add the aqueous phase solution to the oil phase, control the system temperature at 30°C during the addition process, and after the aqueous phase is added, quickly stir and emulsify for 30 minutes to form a stable emulsion, and then maintain a closed environment and introduce nitrogen for 30 minutes for deoxygenation. After deoxygenation, heat to 70°C and react at this temperature for 12 hours to obtain an emulsion slow cross-linking plugging gel.

[0057] Example 4

[0058] This embodiment provides an emulsion slow cross-linking plugging control gel, the preparation method of which includes the following steps:

[0059] Preparation of aqueous phase: Use a precision balance to weigh 32 g of acrylamide, N,N-methylenebisacrylamide, and methyl methacrylate mixture (the mass ratio of the three is 1:1:2), 1.8 g of 1,4-dihydroxyanthraquinone, and 16 g of a mixture of 2-acrylamido-2-methylpropanesulfonic acid and acrylic acid (the mass ratio of the two is 3:1), add 18.19 g of deionized water, stir until completely dissolved and clarified, adjust the pH to 7 with NaOH, add 0.01 g of mixed initiator (the mass ratio of dimethyl azobisisobutyrate to azobiscyanovaleric acid is 2:1), and after complete dissolution, obtain the aqueous phase.

[0060] Preparation of oil phase: weigh 25g of 3# white oil and put it in a three-necked flask, add 3.5g of emulsifier (mass ratio of Span-80, Tween-85, OP-10 is 1:1:1), 3g of emulsifier (mass ratio of ethylene glycol and n-hexanol is 2:1), and 0.5g of phase transition agent nonylphenol polyoxyethylene ether while stirring until it is completely dissolved to obtain a uniform and stable oil phase;

[0061] Inverse emulsion polymerization: add the aqueous phase solution to the oil phase, control the system temperature at 30°C during the addition process, and after the aqueous phase is added, quickly stir and emulsify for 30 minutes to form a stable emulsion, and then maintain a closed environment and introduce nitrogen for 30 minutes for deoxygenation. After deoxygenation, heat to 55°C and react at this temperature for 10 hours to obtain an emulsion slow cross-linking plugging gel.

[0062] Example 5

[0063] This embodiment provides an emulsion slow cross-linking plugging control gel, the preparation method of which includes the following steps:

[0064] Preparation of aqueous phase: Use a precision balance to weigh 40 g of a mixture of acrylamide and N,N-dimethylacrylamide (mass ratio of acrylamide to N,N-dimethylacrylamide is 1:2), 0.6 g of 1,4-dihydroxyanthraquinone, and 14 g of a mixture of sodium styrene sulfonate and acrylic acid (mass ratio of sodium styrene sulfonate to acrylic acid is 1:1), add 12.2 g of deionized water, stir until completely dissolved and clarified, adjust the pH to 7 with NaOH, add 0.2 g of a mixed initiator (mass ratio of ammonium persulfate to sodium bisulfite is 1:1), and after complete dissolution, obtain an aqueous phase;

[0065] Preparation of oil phase: weigh 22g of 5# white oil and put it in a three-necked flask, add 6g of emulsifier (Span-60, Tween-85 mass ratio 1:1), 4g of emulsifying aid (methanol, n-hexanol mass ratio 1:1), 1g of phase transition agent (nonylphenol polyoxyethylene ether, benzylphenol polyoxyethylene ether mass ratio 1:2) while stirring until completely dissolved to obtain a uniform and stable oil phase;

[0066] Inverse emulsion polymerization: add the aqueous phase solution to the oil phase, and control the system temperature at 30°C during the addition process. After the aqueous phase is added, quickly stir and emulsify for 30 minutes to form a stable emulsion, and then maintain a closed environment and introduce nitrogen for 30 minutes for deoxygenation. After deoxygenation, heat to 50°C and react at this temperature for 12 hours to obtain an emulsion slow cross-linking plugging gel.

[0067] Example 6

[0068] This embodiment provides an emulsion slow cross-linking plugging control gel, the preparation method of which includes the following steps:

[0069] Preparation of aqueous phase: Use a precision balance to weigh 32 g of a mixture of acrylamide, N,N-methylenebisacrylamide, and methyl methacrylate (the mass ratio of acrylamide, N,N-methylenebisacrylamide, and methyl methacrylate is 1:1:1), 0.5 g of 1,4-dihydroxyanthraquinone, 8 g of a mixture of 2-acrylamide-2-methylpropanesulfonic acid, sodium styrenesulfonate, and acrylic acid (the mass ratio of 2-acrylamide-2-methylpropanesulfonic acid, sodium styrenesulfonate, and acrylic acid is 2:1:1), add 33.89 g of deionized water, stir until completely dissolved and clarified, adjust the pH to 7 with NaOH, add 0.01 g of a mixed initiator (the mass ratio of ammonium persulfate to sodium bisulfite is 1:1), and after complete dissolution, obtain the aqueous phase.

[0070] Preparation of oil phase: weigh 20g of biodiesel and put it in a three-necked flask, add 4g of emulsifier (Span-40, Span-60 mass ratio 1:1), 1g of emulsifier n-hexanol, and 0.6g of phase transition agent benzylphenol polyoxyethylene ether while stirring until completely dissolved to obtain a uniform and stable oil phase;

[0071] Inverse emulsion polymerization: add the aqueous phase solution to the oil phase, and control the system temperature at 25°C during the addition process. After the aqueous phase is added, quickly stir and emulsify for 30 minutes to form a stable emulsion, and then maintain a closed environment and introduce nitrogen for 30 minutes for deoxygenation. After deoxygenation, heat to 60°C and react at this temperature for 9 hours to obtain an emulsion slow cross-linking plugging gel.

[0072] Example 7

[0073] This embodiment provides an emulsion slow cross-linking plugging control gel, the preparation method of which includes the following steps:

[0074] Preparation of aqueous phase: Use a precision balance to weigh 28 g of N,N-methylenebisacrylamide, 1.3 g of 1,4-dihydroxyanthraquinone, and 6 g of 2-acrylamido-2-methylpropanesulfonic acid, add 31.1 g of deionized water, stir until completely dissolved and clarified, adjust the pH to 7 with NaOH, add 0.1 g of initiator (azobisisobutyramidine hydrochloride, azobiscyanovaleric acid mass ratio of 1:2), and after complete dissolution, obtain the aqueous phase.

[0075] Preparation of oil phase: weigh 26g of 5# white oil and put it in a three-necked flask, add 5g of emulsifier (Span 60, Span 80, OP 10 in a mass ratio of 1:2:1), 2g of emulsifier methanol, and 0.5g of phase transition agent (octylphenol polyoxyethylene ether, benzylphenol polyoxyethylene ether in a mass ratio of 2:1) while stirring until they are completely dissolved to obtain a uniform and stable oil phase;

[0076] Inverse emulsion polymerization: add the aqueous phase solution to the oil phase, control the system temperature at 30°C during the addition process, and after the aqueous phase is added, quickly stir and emulsify for 30 minutes to form a stable emulsion; then maintain a closed environment and introduce nitrogen for 30 minutes for deoxygenation. After deoxygenation, heat to 65°C and react at this temperature for 10 hours to obtain an emulsion slow cross-linking plugging gel.

[0077] Example 8

[0078] This embodiment provides an emulsion slow cross-linking plugging control gel, the preparation method of which includes the following steps:

[0079] Preparation of aqueous phase: Use a precision balance to weigh 30 g of a mixture of acrylamide and methyl methacrylate (mass ratio of acrylamide to methyl methacrylate is 2:1), 1.7 g of 1,4-dihydroxyanthraquinone, and 15 g of a mixture of 2-acrylamide-2-methylpropanesulfonic acid and methacrylic acid (mass ratio of 2-acrylamide-2-methylpropanesulfonic acid and methacrylic acid is 2:1), add 23.75 g of deionized water, stir until completely dissolved and clarified, adjust the pH to 7 with NaOH, add 0.15 g of initiator (mass ratio of dimethyl azobisisobutyrate to azobiscyanovaleric acid is 2:1), and after complete dissolution, obtain the aqueous phase.

[0080] Preparation of oil phase: Weigh 18g of biodiesel and place it in a three-necked flask. 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 transfer agent (fatty alcohol polyoxyethylene ether and nonylphenol polyoxyethylene ether in a mass ratio of 1:2) while stirring until completely dissolved to obtain a uniform and stable oil phase.

[0081] Inverse emulsion polymerization: add the aqueous phase solution to the oil phase, control the system temperature at 20°C during the addition process, and after the aqueous phase is added, quickly stir and emulsify for 30 minutes to form a stable emulsion; then maintain a closed environment and introduce nitrogen for 30 minutes for deoxygenation. After deoxygenation, heat to 65°C and react at this temperature for 12 hours to obtain an emulsion slow cross-linking plugging gel.

[0082] Comparative Example 1

[0083] This comparative example provides an emulsion slow cross-linking plugging regulating gel, the preparation method of which comprises the following steps:

[0084] Preparation of aqueous phase: Use a precision balance to weigh a total of 35 g of acrylamide and N,N-methylenebisacrylamide (the mass ratio of acrylamide to N,N-methylenebisacrylamide is 1:1), 1.6 g of anthrone, and a total of 16 g of 2-acrylamide-2-methylpropanesulfonic acid and methacrylic acid (the mass ratio of 2-acrylamide-2-methylpropanesulfonic acid to methacrylic acid is 1:1), add to 18.85 g of deionized water, stir until completely dissolved and clarified, adjust the pH of the system to 7 with NaOH, add a mixed initiator of azobisisobutyramidine hydrochloride and dimethyl azobisisobutyrate in a mass ratio of 2:1 (a total of 0.05 g), and after complete dissolution, obtain the aqueous phase;

[0085] Preparation of oil phase: weigh 20g of biodiesel and put it in a three-necked flask, add 4g of emulsifier (the mass ratio of Span-60, Tween-85, and OP-10 is 2:1:1), 3g of emulsifier (the mass ratio of n-butanol to ethylene glycol is 1:2), and 1.5g of phase transition agent (the mass ratio of nonylphenol polyoxyethylene ether to octylphenol polyoxyethylene ether is 1:1) while stirring, and stir until completely dissolved to obtain a uniform and stable oil phase;

[0086] Inverse emulsion polymerization: add the above-mentioned water phase to the oil phase, control the system temperature at 20°C during the addition process, and after the water phase is added, quickly stir and emulsify for 30 minutes to form a stable emulsion; then maintain a closed environment and introduce nitrogen for 30 minutes for deoxygenation. After deoxygenation, heat to 60°C and react at this temperature for 8 hours to obtain an emulsion slow cross-linking plugging gel.

[0087] Comparative Example 2

[0088] This comparative example provides an emulsion slow cross-linking plugging regulating gel, the preparation method of which comprises the following steps:

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

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

[0091] Inverse emulsion polymerization: add the aqueous phase solution to the oil phase, control the system temperature at 20°C during the addition process, and after the aqueous phase is added, quickly stir and emulsify for 30 minutes to form a stable emulsion; then maintain a closed environment and introduce nitrogen for 30 minutes for deoxygenation. After deoxygenation, heat to 60°C and react at this temperature for 8 hours to obtain an emulsion slow cross-linking plugging gel.

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

[0093] The initial viscosity and the viscosity after gelation are measured by a Brookfield rotation viscometer, 2# rotor, in the range of 20-25°C. The liquid to be tested is added to the measuring tube, the temperature is kept constant for 10 minutes, and then the speed is set to perform the viscosity test (refer to the standard GB / T 10247 for details). The plugging rate is measured by filling the sand core with a sand filling tube with an inner diameter of 2.5 cm and a length of 20 cm. The sand filling tube is evacuated and saturated with clean water for 4 hours to measure the initial permeability K0 of the water phase of the sand filling tube; the gel liquid is injected and reversely displaced with clean water to measure the permeability K1 of the sand filling tube after plugging. The plugging rate (E) is calculated as follows:

[0094]

[0095] Table 2

[0096]

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

[0098] It can be seen from the data in the above table that the plugging gel provided by the present invention has a better plugging effect: the plugging rate is above 94%, the gelling time is long and adjustable (15-30 days), and the initial viscosity is low and the viscosity after gelling is high, indicating that the plugging gel provided by the present invention has excellent comprehensive performance. Specifically, by comparing Example 2 with Comparative Example 1, it can be seen that the addition of dihydroxyanthraquinone effectively prolongs the gelling time, and has low initial viscosity, high strength after gelling, and a high plugging rate, thereby improving the comprehensive performance of the system; by 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 specified range, the comprehensive performance of the final plugging gel is significantly reduced.

[0099] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, technicians familiar with the field may make various corresponding changes and deformations based on the present invention, but these corresponding changes and deformations should all fall within the scope of protection of the claims of the present invention.

Claims

1. An emulsion slow cross-linking plugging control gel, characterized in that: The emulsion slow cross-linking plugging control gel is an oil-in-water type, and comprises the following raw materials by weight percentage: Non-ionic monomer 25wt%-40wt%, modified functional monomer 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 inversion agent 0.5wt%-1.5wt%; Wherein, 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-acrylamide-2-methylpropane sulfonic acid, sodium styrene sulfonate, acrylic acid and methacrylic acid.

2. The emulsion slow cross-linking plugging control gel according to claim 1, characterized in that: The initiator is selected from one or more of ammonium persulfate, sodium bisulfite, azobisisobutyramidine hydrochloride, dimethyl azobisisobutyrate and azobiscyanovaleric acid.

3. The emulsion slow cross-linking plugging control gel according to claim 1, characterized in that: The non-polar solvent is selected from any one of biodiesel, 3# white oil and 5# white oil.

4. The emulsion slow cross-linking plugging control gel according to 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. Preferably, the HLB value of the emulsifier is 4-8.

5. The emulsion slow cross-linking plugging control gel according to claim 1, characterized in that: The emulsifying aid is selected from one or more of methanol, n-butanol, ethylene glycol and n-hexanol.

6. The emulsion slow cross-linking plugging control gel according to claim 1, characterized in that: The phase transfer agent is selected from one or more of fatty alcohol polyoxyethylene ether, nonylphenol polyoxyethylene ether, octylphenol polyoxyethylene ether and benzylphenol polyoxyethylene ether.

7. A method for preparing the emulsion slow cross-linking plugging control gel according to any one of claims 1 to 6, characterized in that: The steps include: Aqueous phase: after the nonionic monomer, the modified functional monomer and the anionic monomer are uniformly mixed in deionized water, the pH of the system is adjusted to neutral using a pH adjuster, and then the initiator is added and mixed to obtain an aqueous phase; Oil phase: evenly mix the non-polar solvent, emulsifier, emulsifying aid and phase inversion agent to obtain the oil phase; Inverse emulsion polymerization: under stirring conditions, the water phase is added to the oil phase, and then inverse emulsion polymerization is carried out in an oxygen-free atmosphere to obtain the emulsion slow cross-linking plugging control gel.

8. The preparation method according to claim 7, characterized in that: During the process of adding the water phase into the oil phase, the system temperature is controlled at 10-30°C.

9. The preparation method according to claim 7, characterized in that: The temperature of the inverse emulsion polymerization is 35-70° C. and the time is 5-14 hours.

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