Polyacrylonitrile slow-crosslinking deep plugging agent as well as preparation method and application thereof

Abstract

The invention discloses a polyacrylonitrile slow crosslinking deep plugging agent, which is composed of the following components: 2.0%-5.0% of a main agent, 0.2%-1.0% of a phenolic aldehyde crosslinking agent, 0.8%-3.0% of a catalyst, 0.5%-1.0% of a stabilizer, 0.3%-0.5% of a deoxidant, and the balance of water. The invention discloses a preparation method of a polyacrylonitrile slow-crosslinking deep plugging and adjusting agent, which comprises the following steps: (1) adding a formula amount of main agent into a formula amount of water under a stirring condition, and uniformly dispersing to obtain a main agent solution; and (2) under a stirring condition, adding a formula amount of phenolic aldehyde crosslinking agent, a formula amount of catalyst, a formula amount of stabilizer and a formula amount of deoxidant into the main agent solution, and uniformly stirring to obtain the polyacrylonitrile slow crosslinking deep plugging agent. The invention also discloses application of the polyacrylonitrile slow crosslinking deep plugging agent as a profile control plugging agent in medium-high temperature and high permeability fractured reservoirs.

Description

Technical Field

[0001] The invention belongs to the field of oilfield chemistry, and in particular relates to a polyacrylonitrile slow-crosslinking deep plugging and regulating agent and a preparation method and application thereof. Background Art

[0002] At present, old oil fields in eastern China have generally entered a high water content stage. Problems such as unbalanced displacement and ineffective cross-flow of injected water are becoming increasingly serious, resulting in low crude oil recovery.

[0003] Profile control and water plugging technology is an important technology for achieving balanced displacement and improving crude oil recovery. Since the 1950s, China's water plugging and profile control technology has been applied in major oil fields, forming a plugging and adjustment system dominated by polymer gel. For example, Chinese patent application CN114854381A discloses a salt-resistant and strength-adjustable weak gel profile control and water plugging agent and its preparation and application. The raw materials of the weak gel profile control and water plugging agent are: polymer containing AMPS, resorcinol, hexamethylenetetramine, hydrophilic nanoparticles and mineralized water; its preparation method is: first add the polymer to the mineralized water and stir and mature, then add cross-linking agents resorcinol and hexamethylenetetramine, and strength regulator hydrophilic nanoparticles to mix, and adjust the pH to 6.0-6.5 to obtain a gelling solution.

[0004] Water-soluble polymers form gel after cross-linking under formation conditions, which can block large channels and high-permeability pores in the formation, realize the subsequent fluid flow diversion, and then expand the swept volume and improve the recovery rate. Therefore, the thermal stability and strength of gel under reservoir conditions are important indicators that determine its plugging and regulation efficiency. In addition, with the continuous deepening of water injection development, crude oil near the wellbore area is becoming less and less. Deep plugging and regulation puts forward higher requirements on gel injectability and slow cross-linking, which have not yet been effectively solved.

[0005] Conventional water-soluble polymers are mainly partially hydrolyzed polyacrylamide or acrylamide (AM) copolymers. Lignin, tannin, xanthan gum and other biopolymers were also used in the early days. Crosslinkers can be mainly divided into metal ion crosslinkers (chromium crosslinkers, zirconium crosslinkers, aluminum crosslinkers) and organic crosslinkers (phenolic crosslinkers, polyethyleneimine crosslinkers). Under reservoir conditions, polymer molecules are prone to hydrolysis and oxidative degradation, which leads to gel dehydration and strength reduction, which is the direct cause of the deterioration of gel stability. To address this problem, increasing the amount of polymer can effectively improve gel stability. For example, conventional chrome gel dehydrates rapidly above 90°C, but chrome gel prepared by Sydansk using 5% partially hydrolyzed polyacrylamide can be stable for more than 2 years at 120°C and seawater conditions. In addition, introducing temperature-resistant and salt-resistant groups into polymer molecules, such as 2-acrylamide-2-methylpropanesulfonic acid (AMPS) and N-vinylpyrrolidone (NVP), can also effectively improve gel stability. For example, Chinese invention patent CN113025292B discloses a method for preparing a high-strength gel temporary plugging agent for plugging horizontal wellbore before thermal recovery horizontal well repair. The plugging agent is composed of 1.8% AM-AMPS-NVP copolymer (molecular weight 4 million), 0.5% partially hydrolyzed polyacrylamide (molecular weight 12 million-15 million), phenolic crosslinker, chromium crosslinker, deoxidizer, organic acid, and sodium soil. The plugging agent can achieve graded crosslinking at different temperatures, is stable for 3-5 days at 200°C, and breaks after 7 days. Chinese invention patent CN113897189B discloses a gel system suitable for high-temperature and high-salt fracture-cavity reservoirs. The system is composed of AM-AMPS copolymer, non-ionic polyacrylamide, hydroquinone and hexamethylenetetramine, which meets the plugging requirements at 130°C and 220,000 mg / L. However, the molecular weight or use concentration of the polymer in the above two types of plugging agents is too high, which will lead to excessive viscosity of the gelling liquid and difficulty in injection.

[0006] Chinese invention patent CN105802598B discloses a method for preparing a polyacrylonitrile sodium salt modified alkali lignin composite gel plugging agent, the plugging agent is composed of low molecular weight polymer alkali lignin (dosage 3%-5%), polyacrylonitrile sodium salt (dosage 1.5%-2.5%) and a crosslinking agent. Among them, polyacrylonitrile sodium salt is the hydrolysis product of polyacrylonitrile under alkaline or acidic conditions, and the main component is acrylamide-acrylonitrile copolymer. Due to the high amount of polymer, the plugging agent has good toughness, applicable temperature 90℃-150℃, salt resistance 200000mg / L, and gel strength 0.048MPa-0.086MPa. However, the gelling time is short, only 2-6 hours, and it is difficult to achieve deep plugging and adjustment under medium and high permeability oil reservoir conditions. Chinese invention patent application CN1150599 also discloses a polyacrylonitrile composite crosslinked water plugging agent and its preparation method, the system is composed of polyacrylonitrile sodium aqueous solution (dosage 3%-20%) and a composite crosslinking agent. To summarize the above reports, it can be seen that small molecule polymers can be used at higher concentrations to produce plugging agents with higher strength and stability, but the gelling time is too fast, which is not conducive to deep plugging.

[0007] The reported slow cross-linking technology of gel is mainly aimed at chromium gel (such as Chinese patent application CN104910883A discloses a delayed cross-linking chromium gel profile control and water plugging agent, which belongs to the technical field of oil field profile control and water plugging. The present invention has a partially hydrolyzed polyacrylamide and Cr3+ cross-linking formed by redox reaction, and has the following weight percentage composition: partially hydrolyzed polyacrylamide 0.3-0.8%, sodium dichromate 0.02-0.20%, additives 0.15-0.50%, and the balance is water), while the phenolic gel with a higher use temperature has not yet formed a feasible solution. With the continuous deepening of the development of old oil fields and the continuous use of high-temperature and high-salt oil fields, the existing gel system gradually cannot meet the needs of deep plugging and adjustment. It is of great significance to develop a new plugging agent that takes into account high-temperature and high-salt stability and slow cross-linking characteristics. Summary of the invention

[0008] Purpose of the invention: In view of the shortcomings of the prior art, the present invention provides a polyacrylonitrile slow-crosslinking deep plugging agent and its preparation method and application. The plugging agent prepared by this method has a gelling process that can be divided into two stages: hydrolysis and crosslinking, thereby achieving the purpose of delaying gelling. The polymer in the plugging agent is carried into the formation by water, the liquid viscosity is low, the injection difficulty is low, and the plugging agent has the advantages of easy availability of materials, high stability, high strength, and environmental protection.

[0009] Technical solution: A polyacrylonitrile slow-crosslinking deep plugging agent, which is composed of the following components by mass percentage:

[0010] The main agent is 2.0%-5.0%, the phenolic cross-linking agent is 0.2%-1.0%, the catalyst is 0.8%-3.0%, the stabilizer is 0.5%-1.0%, the deoxidizer is 0.3%-0.5%, and the balance is water.

[0011] Furthermore, the main agent is polyacrylonitrile.

[0012] Furthermore, the polyacrylonitrile contains a structural unit A derived from an acrylonitrile monomer, and the content of the structural unit A is greater than 96% based on the total mass of the polyacrylonitrile.

[0013] Furthermore, the weight average molecular weight of the polyacrylonitrile is 20,000-200,000.

[0014] Furthermore, the phenolic crosslinking agent is a water-soluble phenolic resin or a composite phenolic crosslinking agent, preferably a composite phenolic crosslinking agent.

[0015] Furthermore, the composite phenolic crosslinking agent is a mixture of resorcinol and urotropine, and the mass ratio of resorcinol to urotropine is 1:(0.5-2), preferably 1:1.

[0016] Furthermore, the catalyst is one of sodium hydroxide, sodium carbonate and potassium hydroxide, preferably sodium hydroxide.

[0017] Furthermore, the mass ratio of the main agent to the sodium hydroxide or the potassium hydroxide is 5:(2-3).

[0018] Furthermore, the mass ratio of the main agent to the sodium carbonate is 5:(4-5).

[0019] Furthermore, the stabilizer is silica sol.

[0020] Furthermore, the silica sol is one of alkaline silica sol JN-40, ammonium silica sol AN-30, and silica sol SW-30, preferably alkaline silica sol JN-40.

[0021] Furthermore, the median particle size of the silicon dioxide particles in the silica sol is 20nm-100nm.

[0022] Furthermore, the deoxidizer is one of thiourea and sodium sulfite, preferably thiourea.

[0023] Furthermore, the water has a mineralization of less than 4×10 4 mg / L of water.

[0024] The method for preparing any one of the above-mentioned polyacrylonitrile slow-crosslinking deep plugging and regulating agents comprises the following steps:

[0025] (1) Add the main agent in the formula amount to the water in the formula amount under stirring, and disperse evenly to obtain the main agent solution;

[0026] (2) Under stirring conditions, add a formulated amount of phenolic crosslinking agent, a formulated amount of catalyst, a formulated amount of stabilizer, and a formulated amount of deoxidizer to the main agent solution, and stir evenly to obtain a polyacrylonitrile slow-crosslinking deep plugging agent.

[0027] The above-mentioned polyacrylonitrile slow-crosslinking deep plugging and regulating agent is used as a profile control and water plugging agent in medium-high temperature and high permeability fractured oil reservoirs.

[0028] The polyacrylonitrile slow-crosslinking deep plugging agent of the present invention has a gelling time of 48-72 hours and a storage modulus greater than 180 Pa after gelling.

[0029] According to the present invention, the functions of each component are as follows:

[0030] The polyacrylonitrile used in the present invention is a type of low molecular weight polymer, slightly soluble in water, and can be dispersed in water after simple stirring, and carried into the deep formation by water, thereby achieving that the amount of polymer used in the plugging agent is not limited by the viscosity of the gelling liquid. Under certain temperature and alkaline conditions, the cyano group on the polyacrylonitrile molecule gradually undergoes multi-stage hydrolysis, and the hydrolysis products are amide groups and carboxyl groups in sequence. Among them, the amide group can be cross-linked with the composite phenolic cross-linking agent, thereby achieving the purpose of delaying cross-linking.

[0031] The preferred phenolic crosslinking agent in the present invention is a mixture of resorcinol and urotropine. Under certain conditions, urotropine slowly decomposes and releases formaldehyde molecules, which react with resorcinol to produce hydroxymethylphenol, which can react with the amide groups on the polymer molecules to form a gel. This process is also conducive to delaying the gelation time.

[0032] The catalyst described in the present invention is sodium hydroxide, which mainly plays the role of adjusting the pH of the system to adjust the hydrolysis rate of polyacrylonitrile.

[0033] The stabilizer described in the present invention is alkaline silica sol JN-40, which can form hydrogen bonds with the amide groups on the polymer molecules to increase the density of the three-dimensional network structure of the jelly. At the same time, the nanoparticles in the silica sol can form a certain steric hindrance after being adsorbed on the polymer molecules, which can delay the cross-linking reaction of the jelly on the one hand, and delay the further hydrolysis and oxidative degradation of the amide groups on the other hand, thereby enhancing the stability of the jelly.

[0034] The preferred oxygen scavenger in the present invention is thiourea, which can act as a sacrificial agent to preferentially react with dissolved oxygen in water to avoid oxidative degradation of the polymer, thereby improving the stability of the jelly.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1. The polyacrylonitrile slow-crosslinking deep plugging and adjusting agent of the present invention is suitable for water plugging and profile adjustment in medium-high permeability oil reservoirs and fractured oil reservoirs at 90°C-120°C, realizing the diversion of the subsequent injected fluid flow, expanding the sweep coefficient, and improving the crude oil recovery rate.

[0037] 2. The polyacrylonitrile slow-crosslinking deep plugging and regulating agent in the present invention has a gelling time of 48 hours to 72 hours. The polymer is carried into the deep formation by the injected water and is not limited by the viscosity of the gelling liquid, thus meeting the demand for large-dose deep plugging and regulating.

[0038] 3. The polyacrylonitrile slow-crosslinking deep plugging and regulating agent of the present invention has high strength, and the storage modulus after gelation is greater than 180Pa. It does not dehydrate after aging for 120 days at a temperature of 90°C-120°C, and there is no phenomenon of strength reduction, and the plugging and regulating effect period is long. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 The present invention discloses a flow chart of a method for preparing the polyacrylonitrile slow-crosslinking deep plugging agent. DETAILED DESCRIPTION

[0040] The present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited to the following embodiments.

[0041] Unless otherwise specified, the methods are conventional methods. Unless otherwise specified, the raw materials can be obtained from public commercial channels.

[0042] Example 1

[0043] A polyacrylonitrile slow-crosslinking deep plugging agent, composed of the following components by mass percentage:

[0044] Main agent 2.0%, phenolic cross-linking agent 0.2%, catalyst 0.8%, stabilizer 0.5%, deoxidizer 0.3%, and the balance is water.

[0045] Furthermore, the main agent is polyacrylonitrile.

[0046] Furthermore, the polyacrylonitrile contains a structural unit A derived from an acrylonitrile monomer, and the content of the structural unit A is greater than 96% based on the total mass of the polyacrylonitrile.

[0047] Furthermore, the weight average molecular weight of the polyacrylonitrile is 20,000.

[0048] Furthermore, the phenolic crosslinking agent is a composite phenolic crosslinking agent, which is a mixture of resorcinol and urotropine in a mass ratio of 1:1. In another embodiment, the phenolic crosslinking agent is a water-soluble phenolic resin.

[0049] Further, the catalyst is sodium hydroxide. In another embodiment, the content of the main agent polyacrylonitrile is 2%, and the content of the catalyst sodium hydroxide is 1.2%. In another embodiment, the content of the main agent polyacrylonitrile is 2%, and the content of the catalyst sodium hydroxide is 1%.

[0050] Furthermore, the stabilizer is silica sol.

[0051] In a further embodiment, the silica sol is alkaline silica sol JN-40. In another embodiment, the silica sol is ammonium silica sol AN-30. In another embodiment, the silica sol is silica sol SW-30.

[0052] Furthermore, the median particle size of the silicon dioxide particles in the silica sol is 20 nm.

[0053] Furthermore, the deoxidizer is thiourea.

[0054] Furthermore, the water has a mineralization of less than 4×10 4 mg / L of water.

[0055] The preparation method of the above-mentioned polyacrylonitrile slow-crosslinking deep plugging agent comprises the following steps:

[0056] (1) Add the main agent in the formula amount to the water in the formula amount under stirring, and disperse evenly to obtain the main agent solution;

[0057] (2) Under stirring conditions, add a formulated amount of phenolic crosslinking agent, a formulated amount of catalyst, a formulated amount of stabilizer, and a formulated amount of deoxidizer to the main agent solution, and stir evenly to obtain a polyacrylonitrile slow-crosslinking deep plugging agent.

[0058] The above-mentioned polyacrylonitrile slow-crosslinking deep plugging and regulating agent is used as a profile control and water plugging agent in medium-high temperature and high permeability fractured oil reservoirs.

[0059] Example 2

[0060] A polyacrylonitrile slow-crosslinking deep plugging agent, composed of the following components by mass percentage:

[0061] The main agent is 3%, the phenolic cross-linking agent is 0.5%, the catalyst is 3%, the stabilizer is 0.7%, the deoxidizer is 0.4%, and the balance is water.

[0062] Furthermore, the main agent is polyacrylonitrile.

[0063] Furthermore, the polyacrylonitrile contains a structural unit A derived from an acrylonitrile monomer, and the content of the structural unit A is greater than 96% based on the total mass of the polyacrylonitrile.

[0064] Furthermore, the weight average molecular weight of the polyacrylonitrile is 89,000.

[0065] Furthermore, the phenolic cross-linking agent is a composite phenolic cross-linking agent, which is a mixture of resorcinol and urotropine, and the mass ratio of resorcinol to urotropine is 1:0.5.

[0066] Further, the catalyst is sodium carbonate. In another embodiment, the content of the main agent polyacrylonitrile is 3%, and the content of the catalyst sodium carbonate is 2.4%. In another embodiment, the content of the main agent polyacrylonitrile is 3%, and the content of the catalyst sodium carbonate is 2.7%.

[0067] Furthermore, the stabilizer is silica sol.

[0068] Furthermore, the silica sol is ammonium silica sol AN-30.

[0069] Furthermore, the median particle size of the silicon dioxide particles in the silica sol is 50 nm.

[0070] Furthermore, the deoxidizer is sodium sulfite.

[0071] Furthermore, the water has a mineralization of less than 4×10 4 mg / L of water.

[0072] The preparation method of the above-mentioned polyacrylonitrile slow-crosslinking deep plugging agent comprises the following steps:

[0073] (1) Add the main agent in the formula amount to the water in the formula amount under stirring, and disperse evenly to obtain the main agent solution;

[0074] (2) Under stirring conditions, add a formulated amount of phenolic crosslinking agent, a formulated amount of catalyst, a formulated amount of stabilizer, and a formulated amount of deoxidizer to the main agent solution, and stir evenly to obtain a polyacrylonitrile slow-crosslinking deep plugging agent.

[0075] The above-mentioned polyacrylonitrile slow-crosslinking deep plugging and regulating agent is used as a profile control and water plugging agent in medium-high temperature and high permeability fractured oil reservoirs.

[0076] Example 3

[0077] A polyacrylonitrile slow-crosslinking deep plugging agent, composed of the following components by mass percentage:

[0078] Main agent 5.0%, phenolic cross-linking agent 1.0%, catalyst 2.5%, stabilizer 1.0%, deoxidizer 0.5%, and the balance is water.

[0079] Furthermore, the main agent is polyacrylonitrile.

[0080] Furthermore, the polyacrylonitrile contains a structural unit A derived from an acrylonitrile monomer, and the content of the structural unit A is greater than 96% based on the total mass of the polyacrylonitrile.

[0081] Furthermore, the weight average molecular weight of the polyacrylonitrile is 200,000.

[0082] Furthermore, the phenolic cross-linking agent is a composite phenolic cross-linking agent, which is a mixture of resorcinol and urotropine, and the mass ratio of resorcinol to urotropine is 1:2.

[0083] Further, the catalyst is potassium hydroxide. In another embodiment, the content of the main agent polyacrylonitrile is 5%, and the mass of the catalyst potassium hydroxide is 2%. In another embodiment, the content of the main agent polyacrylonitrile is 5%, and the mass of the catalyst potassium hydroxide is 3%.

[0084] Furthermore, the stabilizer is silica sol.

[0085] Furthermore, the silica sol is silica sol SW-30.

[0086] Furthermore, the median particle size of the silicon dioxide particles in the silica sol is 100 nm.

[0087] Furthermore, the deoxidizer is thiourea.

[0088] Furthermore, the water has a mineralization of less than 4×10 4 mg / L of water.

[0089] The method for preparing any one of the above-mentioned polyacrylonitrile slow-crosslinking deep plugging and regulating agents comprises the following steps:

[0090] (1) Add the main agent in the formula amount to the water in the formula amount under stirring, and disperse evenly to obtain the main agent solution;

[0091] (2) Under stirring conditions, add a formulated amount of phenolic crosslinking agent, a formulated amount of catalyst, a formulated amount of stabilizer, and a formulated amount of deoxidizer to the main agent solution, and stir evenly to obtain a polyacrylonitrile slow-crosslinking deep plugging agent.

[0092] The above-mentioned polyacrylonitrile slow-crosslinking deep plugging and regulating agent is used as a profile control and water plugging agent in medium-high temperature and high permeability fractured oil reservoirs.

[0093] Comparative Example 1

[0094] To 97.6 g of water, 1.0 g of polyacrylonitrile powder, 0.1 g of resorcinol, 0.1 g of urotropine, 0.4 g of sodium hydroxide, 0.5 g of alkaline silica sol JN-40, and 0.3 g of thiourea were added respectively. After stirring evenly, the polyacrylonitrile was evenly dispersed in the water, and the other chemicals were fully dissolved to obtain a plugging agent.

[0095] Comparative Example 2

[0096] To 90 g of water, 5.0 g of polyacrylonitrile powder, 0.1 g of resorcinol, 0.1 g of urotropine, 4.0 g of sodium hydroxide, 0.5 g of alkaline silica sol JN-40, and 0.3 g of thiourea were added respectively. After stirring evenly, the polyacrylonitrile was evenly dispersed in the water, and the other chemicals were fully dissolved to obtain a plugging agent.

[0097] Comparative Example 3

[0098] To 96.3 g of water, 2.0 g of polyacrylonitrile powder, 0.05 g of resorcinol, 0.05 g of urotropine, 0.8 g of sodium hydroxide, 0.5 g of alkaline silica sol JN-40, and 0.3 g of thiourea were added respectively. After stirring evenly, the polyacrylonitrile was evenly dispersed in the water, and the other chemicals were fully dissolved to obtain a plugging agent.

[0099] Comparative Example 4

[0100] To 96.6 g of water, 2.0 g of polyacrylonitrile powder, 0.1 g of resorcinol, 0.1 g of urotropine, 0.8 g of sodium hydroxide, 0.1 g of alkaline silica sol JN-40, and 0.3 g of thiourea were added respectively. After stirring evenly, the polyacrylonitrile was evenly dispersed in the water, and the other chemicals were fully dissolved to obtain a plugging agent.

[0101] Comparative Example 5

[0102] To 96.45 g of water, 2.0 g of polyacrylonitrile powder, 0.1 g of resorcinol, 0.1 g of urotropine, 0.8 g of sodium hydroxide, 0.5 g of alkaline silica sol JN-40, and 0.05 g of thiourea were added respectively. After stirring evenly, the polyacrylonitrile was evenly dispersed in the water, and the other chemicals were fully dissolved to obtain a plugging agent.

[0103] The polyacrylonitrile slow-crosslinked deep plugging agent prepared in Examples 1-3 and the plugging agent prepared in Comparative Examples 1-5 were respectively poured into a stoppered pressure-resistant glass tube and placed in an oven for aging, i.e., the corresponding test samples, wherein:

[0104] The aging temperature of Examples 1-2 and Comparative Examples 2-5 is 90°C;

[0105] The aging temperatures of Example 3 and Comparative Example 1 are both 120°C.

[0106] Verification of gelling performance:

[0107] The polyacrylonitrile slow-crosslinked deep plugging agent obtained in Examples 1-3 and the plugging agent prepared in Comparative Examples 1-5 were taken as research objects, and the performance of the polyacrylonitrile slow-crosslinked deep plugging agent provided by the present invention was investigated, including gelation time, storage modulus after gelation, and stability after aging for 120 days. The experimental results are shown in Table 1.

[0108] Table 1 Experimental results of gelling performance

[0109]

[0110] It can be seen from the experimental results in Table 1 that Examples 1 to 3 can be gelled at 90°C-120°C; the gelling time is 48 hours-72 hours, and decreases with increasing temperature and increasing system dosage; the storage modulus after gelling is 182Pa-503Pa, and increases with increasing system dosage; there is no dehydration phenomenon after aging for 120 days, and the storage modulus is slightly increased.

[0111] In Comparative Example 1, the amount of polyacrylonitrile was reduced to 1%, and the system did not form gel at 120°C.

[0112] In Comparative Example 2, the amount of sodium hydroxide was increased to 4%, and the ratio of polyacrylonitrile to sodium hydroxide was 5:4. The system could not form gel at 90°C.

[0113] In Comparative Example 3, the amount of phenolic crosslinker was reduced, and the amounts of resorcinol and urotropine were both 0.05%. The gelling time of the prepared deep plugging agent was extended to 106 hours at 90°C, but the storage modulus after gelling was reduced to 46Pa, and the storage modulus was further reduced to 32Pa after aging for 120 days.

[0114] In Comparative Example 4, the dosage of alkaline silica sol JN-40 was reduced, and the modulus of the deep plugging agent prepared was reduced to 125 Pa. After aging for 120 days, it was further reduced to 65 Pa, and the stability was poor.

[0115] In Comparative Example 5, the amount of thiourea used was reduced, and the storage modulus of the prepared deep plugging agent decreased after aging for 120 days, and the stability was weaker than that of Examples 1 to 3.

[0116] The above describes the embodiments of the present invention in detail. However, the present invention is not limited to the above embodiments, and various changes can be made within the knowledge of ordinary technicians in the relevant technical field without departing from the purpose of the present invention.

Claims

1. A polyacrylonitrile slow cross-linking deep plugging agent, It is characterized in that In terms of mass percentage, it is composed of the following components: The main agent is 2.0%-5.0%, the phenolic cross-linking agent is 0.2%-1.0%, the catalyst is 0.8%-3.0%, the stabilizer is 0.5%-1.0%, the deoxidizer is 0.3%-0.5%, and the balance is water.

2. A polyacrylonitrile slow cross-linking deep plugging agent as claimed in claim 1, It is characterized in that The main agent is polyacrylonitrile.

3. A polyacrylonitrile slow cross-linking deep plugging agent as claimed in claim 2, It is characterized in that The polyacrylonitrile contains a structural unit A derived from an acrylonitrile monomer, and the content of the structural unit A is greater than 96% based on the total mass of the polyacrylonitrile.

4. A polyacrylonitrile slow cross-linking deep plugging agent as claimed in claim 2, It is characterized in that The weight average molecular weight of the polyacrylonitrile is 20,000-200,000.

5. The polyacrylonitrile slow cross-linking deep plugging agent according to claim 1, It is characterized in that The phenolic crosslinking agent is a water-soluble phenolic resin or a composite phenolic crosslinking agent, preferably a composite phenolic crosslinking agent.

6. A polyacrylonitrile slow cross-linking deep plugging agent as claimed in claim 5, It is characterized in that The composite phenolic crosslinking agent is a mixture of resorcinol and urotropine, and the mass ratio of resorcinol to urotropine is 1:(0.5-2), preferably 1:

1.

7. The polyacrylonitrile slow cross-linking deep plugging agent according to claim 1, It is characterized in that The catalyst is one of sodium hydroxide, sodium carbonate and potassium hydroxide, preferably sodium hydroxide.

8. A polyacrylonitrile slow cross-linking deep plugging agent as claimed in claim 7, It is characterized in that The mass ratio of the main agent to the sodium hydroxide or the potassium hydroxide is 5:(2-3); The mass ratio of the main agent to the sodium carbonate is 5:(4-5).

9. The polyacrylonitrile slow cross-linking deep plugging agent according to claim 1, It is characterized in that The stabilizer is silica sol.

10. A polyacrylonitrile slow cross-linking deep plugging agent as claimed in claim 9, It is characterized in that The silica sol is one of alkaline silica sol JN-40, ammonium silica sol AN-30 and silica sol SW-30, preferably alkaline silica sol JN-40.

11. A polyacrylonitrile slow cross-linking deep plugging agent as claimed in claim 9, It is characterized in that The median particle size of the silicon dioxide particles in the silica sol is 20nm-100nm.

12. The polyacrylonitrile slow cross-linking deep plugging agent according to claim 1, It is characterized in that The deoxidizer is one of thiourea and sodium sulfite, preferably thiourea.

13. The polyacrylonitrile slow cross-linking deep plugging agent according to claim 1, It is characterized in that The water has a mineralization of less than 4×10 4 mg / L of water.

14. The method for preparing the polyacrylonitrile slow-crosslinking deep plugging agent according to any one of claims 1 to 13, comprising the following steps: (1) Add the main agent in the formula amount to the water in the formula amount under stirring, and disperse evenly to obtain the main agent solution; (2) Under stirring conditions, add a formulated amount of phenolic crosslinking agent, a formulated amount of catalyst, a formulated amount of stabilizer, and a formulated amount of deoxidizer to the main agent solution, and stir evenly to obtain a polyacrylonitrile slow-crosslinking deep plugging agent.

15. A polyacrylonitrile slow cross-linking deep plugging agent, It is characterized in that Prepared by the preparation method described in claim 14.

16. Use of the polyacrylonitrile slow-crosslinking deep plugging and regulating agent according to any one of claims 1 to 13 and 15 as a profile control and water plugging agent in medium-high-temperature and high-permeability fractured oil reservoirs.

Images