A selective and efficient inorganic composite plugging agent and its preparation method

Abstract

This invention discloses a selective and efficient inorganic composite plugging agent and its preparation method for oilfield development, comprising the following components by weight: 10-20 parts modified sludge, 5-15 parts inorganic gel, 4-8 parts thickener, 0.5-0.7 parts sodium citrate, and 0.1-0.3 parts aminosulfonate. Through the synergistic effect of modified sludge and inorganic gel, the plugging agent can precisely block water flow channels without excessively affecting the oil layer. The addition of inorganic gel ensures the stability of the plugging agent in underground oilfields. The gel can form a robust plugging layer in a short time, effectively blocking water flow channels and preventing further water flow. Simultaneously, the thickener and modified sludge in the plugging agent enhance its long-term stability under high temperature and high pressure environments, ensuring the long-term effectiveness of the plugging effect.

Description

Technical Field

[0001] This invention belongs to the field of oilfield development technology, specifically referring to a selective and efficient inorganic composite plugging agent and its preparation method. Background Technology

[0002] Water plugging technology is a crucial technique in oil extraction, primarily used to seal highly permeable channels or water drive channels in underground oil and gas reservoirs to improve oil recovery and extend the oilfield's production life. However, with the increasing sophistication of oilfield development, traditional water plugging and water control techniques are no longer sufficient, especially given the complex underground environment, lower oil production efficiency, and growing environmental pressures. Therefore, there is an urgent need to develop more efficient, environmentally friendly, and selective water plugging materials.

[0003] Traditional plugging agents mainly fall into two categories: organic and inorganic. Inorganic plugging agents are widely used in oilfield applications such as cement plugging and wellbore stabilization due to their advantages such as good high-temperature resistance, salt and alkali resistance, and relatively low price. However, traditional inorganic plugging agents also have some shortcomings. First, inorganic plugging agents have limited effectiveness in selectively plugging water, often making precise control difficult, resulting in poor sealing of oil-bearing formations and potentially affecting the exploitation of oil-producing formations. Second, inorganic plugging agents may lose stability under extreme conditions such as temperature and pressure, making it difficult to sustain the plugging effect and affecting the long-term effectiveness of plugging. Furthermore, traditional inorganic plugging agents often have the problem of being difficult to degrade, which may lead to secondary pollution.

[0004] To address these issues, traditional inorganic plugging agents are modified to improve their plugging performance and selectivity, enabling them to better adapt to the development needs of complex oil and gas reservoirs. The main advantage of inorganic composite plugging agents lies in adjusting their physicochemical properties by adding different additives and modifying materials, thereby improving their selective plugging ability against different permeability layers while maintaining high stability and durability. Summary of the Invention

[0005] To address the above issues and overcome the shortcomings of existing technologies, this invention provides a selective and highly efficient inorganic composite plugging agent and its preparation method. Through the synergistic effect of modified sludge and inorganic gel, the plugging agent can precisely seal water flow channels without excessively affecting the oil reservoir. The addition of inorganic gel ensures the stability of the plugging agent in underground oilfields. The gel can form a robust plugging layer in a short time, effectively sealing water flow channels and preventing further water flow. Simultaneously, the thickener and modified sludge in the plugging agent enhance its long-term stability under high temperature and high pressure environments, ensuring the long-term effectiveness of the plugging effect.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The present invention proposes a selective and efficient inorganic composite blockage regulator, wherein the inorganic composite blockage regulator comprises the following components in parts by weight: 10-20 parts modified sludge, 5-15 parts inorganic gel, 4-8 parts thickener, 0.5-0.7 parts sodium citrate, and 0.1-0.3 parts aminosulfonate.

[0007] Preferably, the method for preparing the inorganic gel specifically includes the following steps:

[0008] P1. Dissolve (3-mercaptopropyl)trimethoxysilane and tetraethoxysilane in anhydrous methanol, add DMF and mix well, then stir at 180-220 rpm for 10-15 min. Add ammonia solution and increase the stirring speed to 300-350 rpm. After reacting for 30 min, SiO2 wet gel is obtained.

[0009] Preferably, in step S1, the mass ratio between (3-mercaptopropyl)trimethoxysilane and tetraethoxysilane is 1:3-4;

[0010] Preferably, in step S1, the mass concentration of the tetraethoxysilane in anhydrous methanol is 0.1-0.2 g / mL;

[0011] Preferably, in step S1, the volume ratio between the anhydrous methanol and DMF is 1:3-4;

[0012] Preferably, in step S1, the ammonia solution is obtained by mixing concentrated ammonia and deionized water, and the mass fraction of the ammonia solution is 10%-15%; the volume of the ammonia solution added is 10%-20% of the volume of anhydrous methanol.

[0013] P2. Dissolve aluminum sec-butoxide in anhydrous ethanol and mix it with the SiO2 wet gel prepared in step S1. Stir at 100-120 rpm for 20-30 min, add ammonia solution, continue stirring and react for 2-3 h, centrifuge at 2000-3000 rpm for 5-10 min, remove the supernatant to obtain inorganic gel.

[0014] Preferably, in step S2, the mass-to-volume ratio of the tetraethoxysilane to aluminum sec-butoxide is 4-5 g / mL;

[0015] Preferably, in step S2, the volume fraction of aluminum sec-butoxide in anhydrous ethanol is 1.3-2.0%;

[0016] Preferably, in step S2, the ammonia solution is obtained by mixing concentrated ammonia and deionized water, and the mass fraction of the ammonia solution is 10%-15%; the volume of the ammonia solution added is 20%-30% of the volume of anhydrous ethanol.

[0017] Preferably, the method for preparing the modified sludge specifically includes the following steps:

[0018] P3. Place the oily sludge in a constant temperature drying oven and dry it at 100-110℃ for 6-8 hours. After grinding, pass it through a 20-40 mesh sieve and add it to petroleum ether. Stir at 150-180 rpm and react for 1-2 hours. Filter and collect the solid. Place it in a 1 mol / L hydrochloric acid solution, raise the temperature to 60-80℃, and stir at 200-300 rpm for 1-2 hours. Filter and collect the solid. Wash it repeatedly with acetone and deionized water, and then dry it to obtain de-oiled sludge.

[0019] Preferably, in step P3, the mass-to-volume ratio between the oily sludge and petroleum ether is 0.05-0.1 g / mL;

[0020] P4. Dissolve the silane coupling reagent KH550 in anhydrous ethanol, add the degreased sludge prepared in step P3, raise the temperature to 60-80℃, stir the reaction at 150-180 rpm, react for 2-4 hours, cool, filter, wash with anhydrous ethanol and deionized water, and dry to obtain pretreated sludge.

[0021] Preferably, in step P4, the mass concentration of the silane coupling reagent KH550 in anhydrous ethanol is 10-50 g / L;

[0022] Preferably, in step P4, the mass ratio of the silane coupling reagent KH550 to the degreased sludge is 1:3-5;

[0023] P5. Dissolve cysteine ​​in an ethanol-water solution, add EDC and NHS, stir at 120-150 rpm for 20-40 min, adjust the pH to 2-3, add the pretreated sludge prepared in step P4 to the reaction system, introduce nitrogen gas, heat to 40-60℃ under nitrogen atmosphere, stir at 200-250 rpm for 4-6 h, cool, wash with anhydrous ethanol and deionized water, and dry to obtain modified sludge;

[0024] Preferably, in step P5, the mass concentration of cysteine ​​in the ethanol aqueous solution is 20-30 g / L;

[0025] Preferably, in step P5, the mass ratio of cysteine, EDC, and NHS is 1-1.2:1.5-1.8:1.8-2.1;

[0026] Preferably, in step P5, the mass ratio of pretreated sludge to cysteine ​​is 4-6:1;

[0027] Preferably, the method for preparing the tackifier specifically includes the following steps:

[0028] P6. Dissolve thioctic acid in DMAC, add CDI, mix well, then purge with nitrogen. Under nitrogen atmosphere, raise the temperature to 40-50℃ and activate the reaction for 8-10 hours. Add N-(2-hydroxyethyl)acrylamide and continue stirring at 150-180 rpm. Raise the reaction temperature to 80-90℃ and react for 12-16 hours. Cool, concentrate under reduced pressure to remove the reaction solvent, add deionized water for washing, and freeze-dry to obtain acrylamide-thioctic ester.

[0029] Preferably, in step P6, the mass concentration of lipoic acid in DMAC is 20-40 g / L;

[0030] Preferably, in step P6, the mass ratio of CDI to lipoic acid is 1:1.2-1.5;

[0031] Preferably, in step P6, the mass ratio of N-(2-hydroxyethyl)acrylamide to thioctic acid is 0.5-0.7:1;

[0032] P7. Dissolve the acrylamide-thioclate and methacrylamide prepared in step P6 in DMAC, place them under a nitrogen atmosphere, add azobisisobutyronitrile, raise the temperature to 80-90℃, react for 2-3 hours, remove excess reaction solvent, and dry to obtain the thickener.

[0033] Preferably, in step P7, the mass ratio between acrylamide-thioclate and methacrylamide is 1:4-6;

[0034] Preferably, in step P7, the mass concentration of the methacrylamide in DMAC is 0.12-0.2 g / mL;

[0035] Preferably, in step P7, the mass of azobisisobutyronitrile added is 0.5%-1% of the mass of methacrylamide.

[0036] This invention also provides a method for preparing a selective and efficient inorganic composite blockage regulator, specifically comprising the following steps:

[0037] S1. Dissolve the inorganic gel in deionized water, stir at 500-700 rpm, add the thickener, continue stirring and mixing for 1-2 hours, and after mixing evenly, obtain the mixture.

[0038] Preferably, in step S1, the inorganic gel has a mass concentration of 80-100 g / L in deionized water;

[0039] S2. Add modified sludge to the mixture prepared in step S2, stir until the reaction system is homogeneous, add sodium citrate and aminosulfonate, raise the temperature to 40-50℃, use a high-speed mixer to stir at a speed of 10000-12000 rpm, and after cooling and drying, obtain the inorganic blockage regulator.

[0040] The beneficial effects achieved by this invention are as follows:

[0041] This invention provides a selective and highly efficient inorganic composite plugging agent. Through the synergistic effect of modified sludge and inorganic gel, the plugging agent can precisely seal water flow channels without excessively affecting the oil layer. The addition of inorganic gel ensures the stability of the plugging agent in underground oilfields. The gel can form a robust plugging layer in a short time, effectively sealing water flow channels and preventing further water flow. Simultaneously, the thickener and modified sludge in the plugging agent enhance its long-term stability under high temperature and high pressure environments, ensuring the long-term effectiveness of the plugging effect. The modified sludge, a key component of this invention, is mainly derived from oily sludge. After multi-step modification, it exhibits good physicochemical stability and strong selective plugging ability. Through acid washing, degreasing, and surface modification (such as treatment with silane coupling agent KH550 and cysteine ​​modification), the modified sludge significantly improves its compatibility with the inorganic gel and enhances its plugging effect in high-permeability layers. Through these treatments, the modified sludge can not only effectively improve the adhesion of the plugging agent, but also continuously play a sealing role in the complex underground environment of the oilfield, reducing the formation of water-drive layers. The inorganic gel can rapidly form a stable gel structure in highly permeable channels through a gelation reaction, blocking water flow channels, preventing water from entering the oil layer, and maintaining the crude oil production of the oilfield. Specifically, the preparation process described in steps P1 and P2 generates SiO2 wet gel through the reaction of (3-mercaptopropyl)trimethoxysilane and tetraethoxysilane, which is then mixed with aluminum sec-butoxide and treated with ammonia to form an inorganic gel, ensuring that it has good gel strength and stability. When the inorganic gel is mixed with other components, it can quickly solidify in the underground environment and form a solid sealing layer. The high stability of the inorganic gel ensures that it will not fail under high temperature and high pressure environments and can maintain the sealing effect for a long time. The addition of the thickener to the plugging agent is to enhance its rheological properties and adhesion, so that it can be more evenly distributed in the complex underground oil reservoir. The viscosity improver (a copolymer of acrylamide-thioclate and methacrylamide) described in steps P6 and P7 increases the viscosity of the plugging agent, ensuring its stability during oilfield injection and preventing stratification or sedimentation. This enhanced rheological property allows the plugging agent to precisely seal water flow channels in underground oil reservoirs while maintaining good permeability, avoiding negative impacts on crude oil production. The selective and efficient inorganic composite plugging agent prepared in this invention can effectively improve plugging efficiency, prolong the sealing effect, reduce the impact of waterflooding on the oil reservoir, and ultimately improve oilfield recovery. Furthermore, the use of modified sludge, inorganic gel, and other raw materials not only enhances the performance of the plugging agent but also reduces costs, exhibiting good economic and environmental benefits. These technical advantages give this invention broad application prospects and practical value in oilfield development. Attached Figure Description

[0042] Figure 1The suspension performance results of the inorganic composite profile control agents prepared in Examples 1-3 and Comparative Examples 1-3 of this invention are shown in the figure.

[0043] Figure 2 The graph shows the results of the consolidated clay properties of the inorganic composite profile control agents prepared in Examples 1-3 and Comparative Examples 1-3 of this invention.

[0044] Figure 3 The graph shows the erosion resistance results of the inorganic composite profile control agents prepared in Examples 1-3 and Comparative Examples 1-3 of this invention.

[0045] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof. Detailed Implementation

[0046] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0047] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those familiar to those skilled in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to this invention. The preferred embodiments and materials described herein are for illustrative purposes only and do not limit the scope of this application.

[0048] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; unless otherwise specified, the experimental materials and test strains used in the following examples were purchased from commercial channels.

[0049] Example 1

[0050] This embodiment provides a selective and efficient inorganic composite blockage regulator, which comprises the following components in parts by weight: 10 parts modified sludge, 15 parts inorganic gel, 4 parts thickener, 0.7 parts sodium citrate, and 0.3 parts aminosulfonate.

[0051] The preparation method of inorganic gels specifically includes the following steps:

[0052] P1. Accurately weigh 1g of (3-mercaptopropyl)trimethoxysilane and 4g of tetraethoxysilane into a flask, add 40mL of anhydrous methanol to dissolve the reactants, add 120mL of DMF and mix well, then place the flask on a magnetic stirrer and stir at 200rpm for 10min. Prepare a 15wt% ammonia solution using concentrated ammonia and deionized water, take 4mL and add it to the reaction system, increase the stirring speed to 300rpm, and stir for 30min to obtain SiO2 wet gel.

[0053] P2. Add 0.8 mL of aluminum sec-butoxide to 40 mL of anhydrous ethanol and mix until the reaction system is homogeneous. Transfer the mixture to the SiO2 wet gel prepared in step S1 and mix. Stir at 100 rpm for 20 min. Then, take 10 mL of the ammonia solution prepared in step S1 and continue stirring for 2 h. After centrifugation at 3000 rpm for 5 min, remove the supernatant and wash the precipitate repeatedly with deionized water until neutral to obtain the organic gel.

[0054] The method for preparing modified sludge specifically includes the following steps:

[0055] P3. Place 20g of oily sludge in a constant temperature drying oven and dry it at 100℃ for 8 hours. After grinding, pass it through a 40-mesh sieve and add it to 400mL of petroleum ether. Stir at 180rpm and react for 1 hour. Filter and collect the solid. Place it in a 1mol / L hydrochloric acid solution, raise the temperature to 80℃, and stir at 200rpm for 2 hours. Filter and collect the solid. Wash it repeatedly with acetone and deionized water, and dry it to obtain degreased sludge.

[0056] P4. Dissolve 3g of silane coupling reagent KH550 in 100mL of anhydrous ethanol, add 15g of the degreased sludge prepared in step P3, raise the temperature to 80℃, stir the reaction at 150rpm, react for 2h, cool, filter, wash with anhydrous ethanol and deionized water, and dry to obtain pretreated sludge.

[0057] P5. Dissolve 3g of cysteine ​​in 100mL of 75vol% ethanol aqueous solution, add 4.5g of EDC and 5.25g of NHS, stir at 150rpm for 20min, adjust the pH to 3, add 12g of the pretreated sludge prepared in step P4 to the reaction system, introduce nitrogen gas, heat to 50℃ under nitrogen atmosphere, stir at 220rpm for 5h, cool, wash with anhydrous ethanol and deionized water, and dry to obtain modified sludge;

[0058] The preparation method of the thickener specifically includes the following steps:

[0059] P6. Dissolve 3.0g of thioctic acid in 100mL of DMAC, add 2.5g of CDI, mix well, purge with nitrogen, and then raise the temperature to 40℃ under a nitrogen atmosphere to activate the reaction for 10h. Then add 1.8g of N-(2-hydroxyethyl)acrylamide, continue stirring at 180rpm, raise the reaction temperature to 80℃, and react for 16h. After cooling, concentrate under reduced pressure to remove the dissolved reaction, add deionized water for washing, and freeze-dry to obtain acrylamide-thioctic ester.

[0060] P7. Take 3.5g of acrylamide-thioctic ester and 14g of methacrylamide prepared in step P6 and dissolve them in 100mL LMAC. Place the solution in a nitrogen atmosphere, add 70mg of azobisisobutyronitrile, raise the temperature to 80℃, react for 3h, remove excess reaction solvent, and dry to obtain the thickener.

[0061] This embodiment also provides a method for preparing a selective and efficient inorganic composite blockage regulator, specifically including the following steps:

[0062] S1. Dissolve the inorganic gel in deionized water at a mass concentration of 90 g / L, stir at 700 rpm, add the thickener, and continue stirring and mixing for 1.5 h. After mixing evenly, a mixture is obtained.

[0063] S2. Add modified sludge to the mixture prepared in step S2, stir until the reaction system is homogeneous, add sodium citrate and aminosulfonate, raise the temperature to 45°C, use a high-speed mixer to stir at a speed of 11000 rpm, and after cooling and drying, obtain the inorganic blockage regulator.

[0064] Example 2

[0065] This embodiment provides a selective and efficient inorganic composite blockage regulator, which comprises the following components in parts by weight: 20 parts modified sludge, 10 parts inorganic gel, 8 parts thickener, 0.5 parts sodium citrate, and 0.1 parts aminosulfonate.

[0066] The preparation method of inorganic gels specifically includes the following steps:

[0067] P1. Accurately weigh 1g of (3-mercaptopropyl)trimethoxysilane and 3g of tetraethoxysilane into a flask, add 15mL of anhydrous methanol to dissolve the reactants, add 60mL of DMF and mix well, then place the flask on a magnetic stirrer and stir at 220rpm for 15min. Prepare a 10wt% ammonia solution using concentrated ammonia and deionized water, take 3mL and add it to the reaction system, increase the stirring speed to 300rpm, and stir for 30min to obtain SiO2 wet gel.

[0068] P2. Add 0.65 mL of aluminum sec-butoxide to 50 mL of anhydrous ethanol and mix until the reaction system is homogeneous. Transfer the mixture to the SiO2 wet gel prepared in step S1 and mix. Stir at 120 rpm for 30 min. Then, take 15 mL of the ammonia solution prepared in step S1 and continue stirring for 3 h. After centrifugation at 2000 rpm for 10 min, remove the supernatant and wash the precipitate repeatedly with deionized water until neutral to obtain the inorganic gel.

[0069] The method for preparing modified sludge specifically includes the following steps:

[0070] P3. Place 50g of oily sludge in a constant temperature drying oven and dry it at 110℃ for 6 hours. After grinding, pass it through a 40-mesh sieve and add it to 500mL of petroleum ether. Stir at 180rpm and react for 2 hours. Filter and collect the solid. Place it in a 1mol / L hydrochloric acid solution, raise the temperature to 60℃, and stir at 300rpm for 1 hour. Filter and collect the solid. Wash it repeatedly with acetone and deionized water, and dry it to obtain degreased sludge.

[0071] P4. Dissolve 5g of silane coupling reagent KH550 in 100mL of anhydrous ethanol, add 15g of the degreased sludge prepared in step P3, raise the temperature to 80℃, stir the reaction at 180rpm, and after reacting for 3h, cool, filter, wash with anhydrous ethanol and deionized water, and dry to obtain pretreated sludge.

[0072] P5. Dissolve 2g of cysteine ​​in 100mL of 75vol% ethanol aqueous solution, add 3g of EDC and 3.6g of NHS, stir at 150rpm for 40min, adjust the pH to 2, add 10g of the pretreated sludge prepared in step P4 to the reaction system, introduce nitrogen gas, heat to 40℃ under nitrogen atmosphere, stir at 250rpm for 4h, cool, wash with anhydrous ethanol and deionized water, and dry to obtain modified sludge;

[0073] The preparation method of the thickener specifically includes the following steps:

[0074] P6. Dissolve 4.0 g of thioctic acid in 100 mL of DMAC, add 3.0 g of CDI, mix well, purge with nitrogen, and then raise the temperature to 60 °C under a nitrogen atmosphere to activate the reaction for 8 h. Add 2.8 g of N-(2-hydroxyethyl)acrylamide, continue stirring at 160 rpm, raise the reaction temperature to 85 °C, and react for 14 h. Cool, concentrate under reduced pressure to remove the dissolved reaction, add deionized water for washing, and freeze dry to obtain acrylamide-thioctic ester.

[0075] P7. Take 4g of acrylamide-thioctic ester and 20g of methacrylamide prepared in step P6 and dissolve them in 100mL LDMAC. Place the mixture under a nitrogen atmosphere, add 0.16g of azobisisobutyronitrile, raise the temperature to 90℃, react for 2 hours, remove excess reaction solvent, and dry to obtain the thickener.

[0076] This embodiment also provides a method for preparing a selective and efficient inorganic composite blockage regulator, specifically including the following steps:

[0077] S1. Dissolve the inorganic gel in deionized water at a mass concentration of 80 g / L, stir at 600 rpm, add the thickener, and continue stirring and mixing for 2 hours until the mixture is homogeneous to obtain the final mixture.

[0078] S2. Add modified sludge to the mixture prepared in step S2, stir until the reaction system is homogeneous, add sodium citrate and aminosulfonate, raise the temperature to 40°C, use a high-speed mixer to stir at a speed of 12000 rpm, and after cooling and drying, obtain the inorganic blockage regulator.

[0079] Example 3

[0080] This embodiment provides a selective and efficient inorganic composite blockage regulator, which comprises the following components in parts by weight: 15 parts modified sludge, 5 parts inorganic gel, 6 parts thickener, 0.6 parts sodium citrate, and 0.2 parts aminosulfonate.

[0081] The preparation method of inorganic gels specifically includes the following steps:

[0082] P1. Accurately weigh 1g of (3-mercaptopropyl)trimethoxysilane and 4g of tetraethoxysilane into a flask, add 20mL of anhydrous methanol to dissolve the reactants, add 60mL of DMF and mix well, then place the flask on a magnetic stirrer and stir at 180rpm for 10min. Prepare a 15wt% ammonia solution using concentrated ammonia and deionized water, take 2mL and add it to the reaction system, increase the stirring speed to 300rpm, and stir for 30min to obtain SiO2 wet gel.

[0083] P2. Take 1 mL of aluminum sec-butoxide and add it to 50 mL of anhydrous ethanol. Mix until the reaction system is homogeneous. Transfer it to the SiO2 wet gel prepared in step S1 and mix. Stir at 120 rpm for 20 min. Take 10 mL of the ammonia solution prepared in step S1 and continue stirring for 2 h. After centrifugation at 2500 rpm for 5 min, remove the supernatant and wash the precipitate repeatedly with deionized water until neutral to obtain the inorganic gel.

[0084] The method for preparing modified sludge specifically includes the following steps:

[0085] P3. Place 20g of oily sludge in a constant temperature drying oven and dry it at 100℃ for 7h. After grinding, pass it through a 30-mesh sieve and add it to 250mL of petroleum ether. Stir at 150rpm and react for 1.5h. Filter and collect the solid. Place it in a 1mol / L hydrochloric acid solution, raise the temperature to 70℃, and stir at 250rpm for 1.5h. Filter and collect the solid. Wash it repeatedly with acetone and deionized water, and dry it to obtain degreased sludge.

[0086] P4. Dissolve 3g of silane coupling reagent KH550 in 300mL of anhydrous ethanol, add 12g of the degreased sludge prepared in step P3, raise the temperature to 70℃, stir the reaction at 150rpm, react for 3h, cool, filter, wash with anhydrous ethanol and deionized water, and dry to obtain pretreated sludge.

[0087] P5. Dissolve 2.5g of cysteine ​​in 100mL of 75vol% ethanol aqueous solution, add 3.8g of EDC and 4.5g of NHS, stir at 150rpm for 20min, adjust the pH to 2.5, add 12.5g of the pretreated sludge prepared in step P4 to the reaction system, introduce nitrogen gas, heat to 50℃ under nitrogen atmosphere, stir at 220rpm for 5h, cool, wash with anhydrous ethanol and deionized water, and dry to obtain modified sludge;

[0088] The preparation method of the thickener specifically includes the following steps:

[0089] P6. Dissolve 2.0g of thioctic acid in 100mL of DMAC, add 1.3g of CDI, mix well, purge with nitrogen, and then raise the temperature to 50℃ under a nitrogen atmosphere to activate the reaction for 9h. Then add 1.0g of N-(2-hydroxyethyl)acrylamide, continue stirring at 150rpm, raise the reaction temperature to 90℃, and react for 12h. After cooling, concentrate under reduced pressure to remove the dissolved reaction mixture, add deionized water for washing, and freeze-dry to obtain acrylamide-thioctic ester.

[0090] P7. Take 2g of acrylamide-thioctic ester and 12g of methacrylamide prepared in step P6 and dissolve them in 100mL LMAC. Place the solution in a nitrogen atmosphere, add 0.12g of azobisisobutyronitrile, raise the temperature to 85℃, react for 2.5h, remove excess reaction solvent, and dry to obtain the thickener.

[0091] This embodiment also provides a method for preparing a selective and efficient inorganic composite blockage regulator, specifically including the following steps:

[0092] S1. Dissolve the inorganic gel in deionized water at a mass concentration of 100 g / L, stir at 500 rpm, add the thickener, continue stirring and mixing for 1 hour, and after mixing evenly, obtain the mixture.

[0093] S2. Add modified sludge to the mixture prepared in step S2, stir until the reaction system is homogeneous, add sodium citrate and aminosulfonate, raise the temperature to 50°C, use a high-speed mixer to stir at a speed of 10,000 rpm, and after cooling and drying, obtain the inorganic blockage regulator.

[0094] Comparative Example 1

[0095] This comparative example provides an inorganic profile control agent and its preparation method. The only difference between this example and Example 1 is that the modified sludge is replaced with the same weight parts of oily sludge, while the other components and their contents are the same as in Example 1.

[0096] Comparative Example 2

[0097] This comparative example provides an inorganic profile control agent and its preparation method. The only difference between this and Example 1 is that in the preparation method of the inorganic gel, step P1 is replaced with the same weight parts of tetraethoxysilane instead of (3-mercaptopropyl)trimethoxysilane. The remaining components and their contents are the same as in Example 1.

[0098] Comparative Example 3

[0099] This comparative example provides an inorganic profile modifier and its preparation method. The only difference between this example and Example 1 is that the preparation method of the modifier does not include P6, that is, N-(2-hydroxyethyl)acrylamide is not modified with thioctic acid. The other components and their contents are the same as in the example.

[0100] Experimental Example 1

[0101] This experiment tested the suspension properties of the inorganic profile control agents prepared in Examples 1-3 and Comparative Examples 1-3. The inorganic composite profile control agents prepared in Examples 1-3 and Comparative Examples 1-3 were diluted with deionized water at 30 wt%, stirred and mixed at 2000 rpm, placed in a graduated cylinder, and allowed to stand at room temperature. The sedimentation was observed, and the water separation rate was calculated according to the following formula.

[0102] Water separation rate (%) = (Vs - Vg) / Vs × 100%;

[0103] Where Vs is the total volume of the inorganic composite blockage agent dilution before settling, in mL; and Vg is the volume of the inorganic composite blockage agent after settling, in mL.

[0104] Figure 1The figures show the suspension performance results of the inorganic composite profile control agents prepared in Examples 1-3 and Comparative Examples 1-3 of this invention. As shown in the figures, the water separation rates of the inorganic composite profile control agents prepared in Examples 1-3 were 2.6%, 3.5%, and 3.2% within 10 minutes, and 25.0%, 23.1%, and 22.7% within 1 hour. Compared with the comparative examples, this invention enhances the crosslinking ability of the inorganic composite profile control agent in the oil displacement system by removing and modifying the oily sludge, selecting silanes containing mercapto groups, and utilizing the activity of disulfide bonds. In the thickener, the oil-containing thioctic acid branch chain also enhances the stability of the inorganic composite profile control agent in the oil displacement system through the regulating performance of disulfide bonds.

[0105] Experiment Example 2

[0106] This experiment tested the consolidation properties of the inorganic composite profile control agents prepared in Examples 1-3 and Comparative Examples 1-3. The inorganic composite profile control agents prepared in Examples 1-3 and Comparative Examples 1-3 were diluted with deionized water at 30 wt%. A certain amount of mudstone sample was taken, ground and passed through a 40-mesh sieve. The mudstone sample was then thoroughly dried to remove moisture and added to a high-temperature and high-pressure consolidation device. The temperature was typically set to 80°C and the pressure to 30 MPa. 100 mL of inorganic profile control agent was injected. After consolidation for 48 h, the compressive strength was measured, and the consolidation properties of the mudstone were expressed.

[0107] Figure 2 The figures show the results of the consolidation properties of the inorganic composite profile control agents prepared in Examples 1-3 and Comparative Examples 1-3 of this invention. As shown in the figures, the compressive strength of the inorganic composite profile control agent reaches 11.4 MPa under the condition of no clay. As the proportion of clay increases, the compressive strength after consolidation decreases. When the proportion of clay reaches 90% of the inorganic composite profile control agent, the compressive strength of the treatment in Examples 1-3 can reach more than 5.0 MPa, while the compressive strength of the inorganic composite profile control agent prepared in Comparative Example 1 is close to 1 MPa. The inorganic composite profile control agent prepared in Comparative Example 2 has a higher compressive strength at the beginning, but the compressive strength decreases significantly with the increase of the proportion of clay.

[0108] Experimental Example 3

[0109] This experiment tested the erosion resistance of the inorganic composite profile control agents prepared in Examples 1-3 and Comparative Examples 1-3. A single-tube experimental model was used for the test. The experimental steps included filling a sand-filled tube, diluting the inorganic composite profile control agents prepared in Examples 1-3 and Comparative Examples 1-3 at 30 wt% with deionized water, injecting them into a 1 / 2 PV oil displacement system, placing them in a constant temperature chamber at the experimental temperature to achieve gelation, switching to water displacement at a pressure of 2 PV, and observing the injection pressure.

[0110] Figure 3The figure shows the scour resistance results of the inorganic composite profile control agent prepared in Examples 1-3 and Comparative Examples 1-3 of this invention. As shown in the figure, after switching to water flooding, the subsequent displacement pressure gradually increased and stabilized at 8.4 MPa, indicating that the plugging agent effectively blocked the core. No significant change was observed in the subsequent 2PV water flooding pressure, indicating good scour resistance.

[0111] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention.

[0112] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention. The actual application is not limited to this. In conclusion, if those skilled in the art are inspired by this description and design similar methods and embodiments without departing from the spirit of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A selective and highly efficient inorganic composite plugging agent, characterized in that: The inorganic composite blockage regulator comprises the following components in parts by weight: 10-20 parts modified sludge, 5-15 parts inorganic gel, 4-8 parts thickener, 0.5-0.7 parts sodium citrate, and 0.1-0.3 parts aminosulfonate. The preparation method of the inorganic gel specifically includes the following steps: P1. Dissolve (3-mercaptopropyl)trimethoxysilane and tetraethoxysilane in anhydrous methanol, add DMF and mix well, then stir at 180-220 rpm for 10-15 min. Add ammonia solution and increase the stirring speed to 300-350 rpm. After reacting for 30 min, SiO2 wet gel is obtained. P2. Dissolve aluminum sec-butoxide in anhydrous ethanol and mix it with the SiO2 wet gel prepared in step S1. Stir at 100-120 rpm for 20-30 min, add ammonia solution, continue stirring and react for 2-3 h, centrifuge at 2000-3000 rpm for 5-10 min, remove the supernatant to obtain inorganic gel. The method for preparing the modified oily sludge specifically includes the following steps: P3. Place the oily sludge in a constant temperature drying oven and dry it at 100-110℃ for 6-8 hours. After grinding, pass it through a 20-40 mesh sieve and add it to petroleum ether. Stir at 150-180 rpm and react for 1-2 hours. Filter and collect the solid. Place it in a 1 mol / L hydrochloric acid solution, raise the temperature to 60-80℃, and stir at 200-300 rpm for 1-2 hours. Filter and collect the solid. Wash it repeatedly with acetone and deionized water, and then dry it to obtain de-oiled sludge. P4. Dissolve the silane coupling reagent KH550 in anhydrous ethanol, add the degreased sludge prepared in step P3, raise the temperature to 60-80℃, stir the reaction at 150-180 rpm, react for 2-4 hours, cool, filter, wash with anhydrous ethanol and deionized water, and dry to obtain pretreated sludge. P5. Dissolve cysteine ​​in an ethanol-water solution, add EDC and NHS, stir at 120-150 rpm for 20-40 min, adjust the pH to 2-3, add the pretreated sludge prepared in step P4 to the reaction system, introduce nitrogen gas, heat to 40-60℃ under nitrogen atmosphere, stir at 200-250 rpm for 4-6 h, cool, wash with anhydrous ethanol and deionized water, and dry to obtain modified sludge; The preparation method of the thickener specifically includes the following steps: P6. Dissolve thioctic acid in DMAC, add CDI, mix well, then purge with nitrogen. Under nitrogen atmosphere, raise the temperature to 40-50℃ and activate the reaction for 8-10 hours. Add N-(2-hydroxyethyl)acrylamide and continue stirring at 150-180 rpm. Raise the reaction temperature to 80-90℃ and react for 12-16 hours. Cool, concentrate under reduced pressure to remove the dissolved reaction mixture, add deionized water for washing, and freeze-dry to obtain acrylamide-thioctic ester. P7. Dissolve the acrylamide-thioclate and methacrylamide prepared in step P6 in DMAC, place under a nitrogen atmosphere, add azobisisobutyronitrile, raise the temperature to 80-90℃, react for 2-3 hours, remove excess reaction solvent, and dry to obtain the thickener.

2. The selective and efficient inorganic composite plugging agent according to claim 1, characterized in that: In step P1, the mass ratio between (3-mercaptopropyl)trimethoxysilane and tetraethoxysilane is 1:3-4; the mass concentration of tetraethoxysilane in anhydrous methanol is 0.1-0.2 g / mL; the volume ratio between anhydrous methanol and DMF is 1:3-4; the ammonia solution is obtained by mixing concentrated ammonia and deionized water, and the mass fraction of the ammonia solution is 10%-15%; the volume of the ammonia solution added is 10%-20% of the volume of anhydrous methanol.

3. The selective and efficient inorganic composite plugging agent according to claim 2, characterized in that: In step P2, the mass-to-volume ratio of the tetraethoxysilane to aluminum sec-butoxide is 4-5 g / mL; the volume fraction of aluminum sec-butoxide in anhydrous ethanol is 1.3-2.0%; the ammonia solution is obtained by mixing concentrated ammonia and deionized water, and the mass fraction of the ammonia solution is 10%-15%; the volume of the ammonia solution added is 20%-30% of the volume of anhydrous ethanol.

4. The selective and efficient inorganic composite plugging agent according to claim 3, characterized in that: In step P3, the mass-to-volume ratio of the oily sludge and petroleum ether is 0.05-0.1 g / mL; in step P4, the mass concentration of the silane coupling reagent KH550 in anhydrous ethanol is 10-50 g / L; in step P4, the mass ratio of the silane coupling reagent KH550 to the de-oiled sludge is 1:3-5; in step P5, the mass concentration of cysteine ​​in the ethanol aqueous solution is 20-30 g / L; in step P5, the mass ratio of cysteine, EDC, and NHS is 1-1.2:1.5-1.8:1.8-2.1; in step P5, the mass ratio of the pretreated sludge to cysteine ​​is 4-6:

1.

5. The selective and efficient inorganic composite plugging agent according to claim 4, characterized in that: In step P6, the mass concentration of lipoic acid in DMAC is 20-40 g / L; the mass ratio of CDI to lipoic acid is 1:1.2-1.5; and the mass ratio of N-(2-hydroxyethyl)acrylamide to lipoic acid is 1-1.2:

2.

6. The selective and efficient inorganic composite plugging agent according to claim 5, characterized in that: In step P7, the mass ratio between acrylamide-thioclate and methacrylamide is 1:4-6; the mass concentration of methacrylamide in DMAC is 0.12-0.2 g / mL; and the mass of azobisisobutyronitrile added is 0.5%-1% of the mass of methacrylamide.

7. A method for preparing a selective and efficient inorganic composite blockage regulator according to any one of claims 1-6, characterized in that: Specifically, the steps include the following: S1. Dissolve the inorganic gel in deionized water, stir at 500-700 rpm, add the thickener, continue stirring and mixing for 1-2 hours, and after mixing evenly, obtain the mixture. In step S1, the inorganic gel has a mass concentration of 80-100 g / L in deionized water; S2. Add modified sludge to the mixture prepared in step S2, stir until the reaction system is homogeneous, add sodium citrate and aminosulfonate, raise the temperature to 40-50℃, use a high-speed mixer to stir at a speed of 10000-12000 rpm, and after cooling and drying, obtain the inorganic blockage regulator.

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