Gel foam system and application thereof

Abstract

The invention relates to the technical field of oil extraction, and discloses a gel foam system and application thereof. Based on the total weight of the gel foam system, the gel foam system is prepared from the following components in percentage by weight: 0.3 to 1 percent of foaming agent, 0.25 to 0.4 percent of copolymer, 0.4 to 1 percent of cross-linking agent, 0.2 to 0.6 percent of sodium alginate, 0.01 to 0.05 percent of solubilizer, 0.01 to 0.06 percent of rice hull ash, 0.02 to 0.05 percent of deoxidant, 0.02 to 0.05 percent of stabilizer and 97.79 to 98.79 percent of water, wherein the foaming agent is a compound containing an ionic foaming agent and a nonionic foaming agent in a weight ratio of (3: 1)-(1: 3). When the gel foam system is applied to water shutoff and profile control in the oil exploitation process, good temperature resistance and salt resistance are achieved, and oil exploitation of stratums with high temperature and / or high mineralization degree is facilitated.

Description

Technical Field

[0001] The present invention relates to the technical field of oil production, and specifically relates to a gel foam system and its application. Background Art

[0002] High water cut in oil wells is a common problem during the oilfield development process (especially in the middle and late stages of development). Due to the primary and secondary heterogeneity of the formation, the difference in fluid mobility, and other reasons, preferential channels for the injected fluid are formed in the formation, resulting in coning, channeling, and fingering phenomena, which affect the economic and social benefits of oilfield development. By injecting a water plugging and profile control agent system into the formation, the water absorption profile of the formation is improved to achieve the purpose of increasing oil production and reducing water cut. Therefore, the water plugging and profile control technology has always been one of the effective means to improve the development effect of oilfields and achieve stable production of oil reservoirs.

[0003] The gel foam combines the dual advantages of weak gel and nitrogen foam. The system has strong selectivity for high-permeability layers, strong plugging performance, less liquid consumption, low price, good mechanical strength, small filtration loss, high efficiency, and low damage to the reservoir. It has the characteristics of high shear stability and thermal stability, and is widely used in water plugging and profile control in oilfield development.

[0004] The application of gel foam is not only affected by the type and concentration of foaming agent, polymer type, and crosslinking agent type, but also greatly affected by external environmental factors such as ionic strength, temperature, and pH. The existing gel foam systems have low strength under high temperature and high salinity conditions, cannot exist stably for a long time, have a short effective action time, and the action effect is not obvious.

[0005] Therefore, for high-temperature and high-salinity oil reservoirs, it is urgent to develop a gel foam system with temperature and salt resistance to achieve the purpose of water plugging and profile control. Summary of the Invention

[0006] The purpose of the present invention is to overcome the problems of low mechanical strength, poor stability, and short effective action time of the existing gel foam system when used as a profile control agent in oilfield exploitation under high-temperature and high-salt environments. A gel foam system and its application are provided. The foaming agent and polymer contained in the gel foam system both have the functions of salt and temperature resistance, and the two cooperate with each other to increase the comprehensive performance of the gel foam.

[0007] To achieve the above object, a first aspect of the present invention provides a gel foam system, which comprises a foaming agent, a copolymer, a crosslinking agent, sodium alginate, a solubilizer, rice husk ash, a deoxidizer, a stabilizer and water. Among them, based on the total weight of the gel foam system, the gel foam system contains: 0.3 - 1 wt% of the foaming agent, 0.25 - 0.4 wt% of the copolymer, 0.4 - 1 wt% of the crosslinking agent, 0.2 - 0.6 wt% of sodium alginate, 0.01 - 0.05 wt% of the solubilizer, 0.01 - 0.06 wt% of rice husk ash, 0.02 - 0.05 wt% of the deoxidizer, 0.02 - 0.05 wt% of the stabilizer and 97.79 - 98.79 wt% of water;

[0008] Among them, the foaming agent is a mixture of an ionic foaming agent and a non-ionic foaming agent; the weight ratio of the ionic foaming agent to the non-ionic foaming agent is 3:1 - 1:3.

[0009] A second aspect of the present invention provides the application of the gel foam system described in the first aspect in water plugging and profile control during oil exploitation.

[0010] Through the above technical solutions, the foaming agent contained in the gel foam system of the present invention is a mixture of an ionic foaming agent and a non-ionic foaming agent. The foaming agent has two hydrophilic groups and combines the advantages of non-ionic and anionic surfactants, making it have good salt tolerance and high temperature resistance, excellent anti-decomposition ability and dispersion performance, as well as good compatibility performance; secondly, the present invention introduces structural units from functional monomers into the molecular structure of the copolymer in the gel foam system, improving the thickening property and salt tolerance of the polymer; in addition, the gel foam system of the present invention also contains a solubilizer, rice husk ash and sodium alginate, and the addition of the three improves the performance of the gel foam from different aspects, which is beneficial to improving the stability of the gel foam. The foaming agent containing an ionic surfactant and a non-ionic surfactant of the present invention can significantly improve the gelation viscosity of the gel foam. Under high temperature and high salinity conditions, the foaming agent still has high foaming performance; in the present invention, the copolymer is not easily decomposed in a high temperature and high salinity environment, has good viscosity and elasticity, improves the mechanical strength and stability of the gel foam, effectively improves the water plugging and profile control effect of the gel foam in oilfield development, extends the action time of the gel foam, and is beneficial to oil exploitation in formations with higher temperature and / or higher salinity. Detailed Embodiments

[0011] The endpoints and any values in the ranges disclosed herein are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of each range, between the endpoint values of each range, between the endpoint values and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0012] The following is a detailed description of the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only for the purpose of illustrating and explaining the present invention, and are not used to limit the present invention.

[0013] The first aspect of the present invention provides a gel foam system, which comprises a foaming agent, a copolymer, a crosslinking agent, sodium alginate, a solubilizer, rice husk ash, a deoxidizer, a stabilizer and water. Among them, based on the total weight of the gel foam system, the gel foam system contains: 0.3 - 1 wt% of the foaming agent, 0.25 - 0.4 wt% of the copolymer, 0.4 - 1 wt% of the crosslinking agent, 0.2 - 0.6 wt% of sodium alginate, 0.01 - 0.05 wt% of the solubilizer, 0.01 - 0.06 wt% of rice husk ash, 0.02 - 0.05 wt% of the deoxidizer, 0.02 - 0.05 wt% of the stabilizer and 97.79 - 98.79 wt% of water;

[0014] Among them, the foaming agent is a compound of an ionic foaming agent and a non-ionic foaming agent; the weight ratio of the ionic foaming agent to the non-ionic foaming agent is 3:1 - 1:3.

[0015] According to the present invention, the foaming agent contained in the gel foam system is a compound of an ionic foaming agent and a non-ionic foaming agent. Preferably, the ionic foaming agent is an anionic foaming agent. The ionic foaming agent and the non-ionic foaming agent can be selected from anionic surfactants and non-ionic surfactants respectively. The foaming agent has two hydrophilic groups, and at the same time has the advantages of non-ionic and anionic surfactants, making it have good salt tolerance and high temperature resistance, excellent anti-decomposition ability and dispersion performance, and good compatibility performance; secondly, the present invention introduces structural units from functional monomers into the molecular structure of the copolymer contained in the gel foam system, improving the thickening property and salt tolerance of the polymer; in addition, the gel foam system of the present invention also contains a solubilizer, rice husk ash and sodium alginate, and the addition of the three improves the performance of the gel foam from different aspects, which is beneficial to improving the stability of the gel foam. The gel foam system of the present invention has good salt tolerance and high temperature resistance in oilfield exploitation, which is beneficial to the exploitation of high-temperature and high-salinity reservoirs.

[0016] According to the present invention, preferably, when the content of the foaming agent is 0.6 - 0.9 wt% based on the total weight of the gel foam system, the foaming agent has better foaming performance.

[0017] According to the present invention, preferably, when the weight ratio of the ionic foaming agent to the non-ionic foaming agent is 1.5:1 - 1:2, the gel foaming agent of the present invention has good salt tolerance and high temperature resistance, excellent anti-decomposition ability and dispersion performance, and good compatibility performance.

[0018] According to the present invention, in order to make the foaming agent have excellent foaming performance, preferably, the ionic foaming agent is selected from one or more of sodium α-olefin sulfonate, sodium dodecyl sulfate, sodium dodecyl benzene sulfonate, coconut diethanolamide, sodium fatty alcohol polyoxyethylene ether sulfate, fatty acid methyl ester sulfonate, cetyl trimethyl ammonium chloride, coconut amide propyl betaine; preferably selected from one or more of sodium α-olefin sulfonate, sodium dodecyl sulfate, sodium dodecyl benzene sulfonate, coconut amide propyl betaine; more preferably coconut amide propyl betaine and sodium dodecyl benzene sulfonate.

[0019] According to the present invention, in the ionic foaming agent, the weight ratio of coconut amide propyl betaine to sodium dodecyl benzene sulfonate can be any ratio, preferably 1 - 3:1 - 2.

[0020] The non-ionic foaming agent is selected from one or more of monoethanolamine, polyglycerol ether, and polypropylene glycol.

[0021] According to the present invention, in order to reduce the decomposition of the polymer under high temperature and high salinity conditions and further improve the salt and temperature resistance performance of the gel foam system of the present invention, preferably, the copolymer contains structural unit A from a water-soluble monomer and structural unit B from a functional monomer.

[0022] Preferably, the weight average molecular weight of the copolymer is 2 million - 10 million g / mol, preferably 3 million - 9 million g / mol.

[0023] According to the present invention, in order to improve the strength during the application of the gel foam system, preferably, the water-soluble monomer is selected from one or more of acrylamide, acrylic acid, and acrylonitrile; more preferably selected from acrylamide and / or acrylic acid.

[0024] According to the present invention, in order to improve the temperature and salt tolerance of the gel foam system, preferably, the functional monomer is selected from one or more of 2-acrylamide-2-methylpropanesulfonic acid, vinylsulfonic acid, allylsulfonic acid, N-vinylpyrrolidone, and N,N-dimethylacrylamide; preferably selected from one or more of 2-acrylamide-2-methylpropanesulfonic acid, vinylsulfonic acid, allylsulfonic acid, and N,N-dimethylacrylamide, and more preferably 2-acrylamide-2-methylpropanesulfonic acid, vinylsulfonic acid, and allylsulfonic acid.

[0025] According to the present invention, preferably, the copolymer of the present invention is a five-component copolymer, and further preferably an acrylamide-acrylic acid-2-acrylamide-2-methylpropanesulfonic acid-vinylsulfonic acid-allylsulfonic acid copolymer.

[0026] According to the present invention, preferably, in the gel foam system of the present invention, the weight ratio of the structural unit A to the structural unit B is 5:1 - 1:5, preferably 1:1 - 1:1.5. Each utilizes the carbon-carbon double bond in the monomer to form the copolymer through addition polymerization.

[0027] According to the present invention, among the water-soluble monomers providing the structural unit A, the weight ratio of acrylamide to acrylic acid can be any ratio, preferably 1:1 - 3:1; among the functional monomers providing the structural unit B, the weight ratio of 2-acrylamide-2-methylpropanesulfonic acid, vinylsulfonic acid, and allylsulfonic acid is 1 - 2:1 - 3:1 - 2.

[0028] According to the present invention, by adjusting the ratio between the water-soluble monomers and the functional monomers for preparing the copolymer, a modified copolymer with salt and temperature tolerance properties is obtained; by adjusting the ratio between different water-soluble monomers and the ratio between different functional monomers, the requirements for oilfield exploitation under different salinity and different temperature conditions are met, and the purpose of water shutoff and profile control under different environments is truly achieved.

[0029] According to the present invention, preferably, the copolymer can be obtained by copolymerization of water-soluble monomers and functional monomers. According to a preferred embodiment of the present invention, the polymerization reaction includes the following steps:

[0030] (S1) Dissolve the water-soluble monomers and the functional monomers in deionized water, and control the pH value of the solution between 7 - 8 with a NaOH solution to obtain an aqueous reactant solution;

[0031] (S2) Under stirring conditions, add an initiator, an accelerator, and a surfactant to the aqueous reactant solution obtained in (S1), and carry out a polymerization reaction under nitrogen protection to obtain an aqueous gel copolymer solution;

[0032] (S3) Cool the aqueous solution of the gel copolymer obtained in (S2) to room temperature, filter it, soak it repeatedly in a large amount of distilled water, wash it with absolute ethanol, and dry it; place it in a Soxhlet extractor and extract it with an organic solvent to obtain a purified product;

[0033] (S4) Soak the purified product obtained in (S3) in deionized water, dry and grind it to obtain a temperature- and salt-resistant polymer powder.

[0034] Preferably, in (S1), the dissolution process further includes a magnetic stirring step, and the conditions of the magnetic stirring include: at a temperature of 20-40 °C and a rotation speed of 200-800 rpm, the stirring time is 15-20 min.

[0035] Preferably, in (S2), the initiator is selected from one or more of ammonium persulfate (APS), potassium persulfate (KPS), sodium persulfate (NaPS), azobisisobutyronitrile (AIBN), and azobisisoheptonitrile (ABVN).

[0036] Preferably, the accelerator is tetramethylethylenediamine (TEMED).

[0037] In (S2), there is no particular limitation on the surfactant. Preferably, the surfactant is sodium dodecyl sulfate (SDS). In the present invention, under the action of SDS, according to the principle of micellar polymerization, the hydrophobic monomer is solubilized in the micelles formed by the surfactant and is incorporated into the main chain of the polymer by chain radical initiation, and can participate in the construction of the micelles. Therefore, the structural units of the monomer can be distributed on the polymer molecular chain and can also be incorporated into the microblock structure, enhancing the stability of the gel.

[0038] Preferably, in (S2), the conditions of the polymerization reaction are: at a temperature of 60-80 °C for 6-8 h.

[0039] Preferably, in (S3), wash with absolute ethanol 3-5 times to remove unreacted monomers; the drying temperature is 60-80 °C; the organic solvent is acetone.

[0040] Preferably, in (S4), the drying temperature is 60-80 °C.

[0041] According to the present invention, preferably, the crosslinking agent in the gel foam is selected from one or more of phenolic resin crosslinking agents, polyethyleneimine, and organic chromium crosslinking agents; preferably selected from phenolic resin crosslinking agents and / or organic chromium crosslinking agents.

[0042] According to the present invention, preferably, the solubilizer is selected from one or more of benzyl alcohol, ethanol, propylene glycol, polysorbate 80, and cyclodextrin. The addition of the solubilizer promotes the formation of microemulsion, reduces the electrostatic repulsion, and helps the formation of micelles.

[0043] According to the present invention, preferably, the deoxidizer is selected from one or several of thiourea, sodium sulfite, and sodium thiosulfate.

[0044] According to the present invention, preferably, the stabilizer is selected from one or several of ethanol, ethylene glycol, glycerol, sorbitol, sucrose, and polyethylene glycol. The stabilizer can improve the stability of the gel foam after crosslinking.

[0045] According to the present invention, preferably, the average particle size of the rice husk ash is 10 - 40 μm. The micron-sized rice husk ash adsorbed on the foam surface can effectively increase the specific surface area and the number of oxygen-containing functional groups, and the adsorption performance and temperature resistance performance can also be improved accordingly, and the foam stability is further enhanced.

[0046] More preferably, the average particle size of the rice husk ash is 20 - 25 μm.

[0047] According to the present invention, the sodium alginate contained in the gel foam, due to its sensitivity to calcium ions, can form a protective shell on the gel surface when encountering calcium ions in the formation, preventing the dehydration of the gel and enhancing its stability.

[0048] The second aspect of the present invention provides the application of the gel foam system described in the first aspect in water plugging and profile control during oil exploitation.

[0049] Preferably, during oil exploitation, the temperature of the oil reservoir is 40 - 220 °C, preferably 90 - 220 °C.

[0050] More preferably, the salinity of the oil reservoir is 20,000 - 300,000 mg / L, preferably 100,000 - 300,000 mg / L.

[0051] The present invention will be described in detail below through examples. Among them, the room temperature is 15 - 35 °C.

[0052] Organic chromium, purchased from the chemical plant of Hengtaili Industrial Group Co., Ltd., with the model number HTL - 1.

[0053] Phenolic resin, purchased from Fushun Longfeng Chemical Plant, with the model number LF - 1.

[0054] Preparation Example 1

[0055] (1) Add 10 g of water-soluble monomer acrylamide (AM), 5 g of acrylic acid (AA), 3.75 g of 2-acrylamido-2-methylpropanesulfonic acid (AMPS), 7.5 g of vinylsulfonic acid, and 3.75 g of allylsulfonic acid to 100 g of deionized water. Under the conditions of a temperature of 20 °C and a rotation speed of 300 rpm, magnetically stir for 20 min; slowly add a NaOH solution with a mass fraction of 20%, and control the pH value of the solution between 7 and 8 to obtain an aqueous solution of the reactants.

[0056] (2) Under stirring conditions, add 0.15 g of initiator sodium persulfate (NaPS), 0.15 g of accelerator tetramethylethylenediamine (TEMED), and 0.1 g of sodium dodecyl sulfate (SDS) to the aqueous solution of the reactants obtained in step (1). Under the condition of nitrogen protection, carry out a polymerization reaction at 60 °C for 8 h to obtain an aqueous solution of the gel copolymer.

[0057] (3) Cool the aqueous solution of the gel copolymer obtained in step (2) to room temperature and filter it. Soak it in a large amount of distilled water, wash it 5 times with anhydrous ethanol, and dry it at 60 °C; place it in a Soxhlet extractor and extract it with acetone for 12 h to obtain a purified product.

[0058] (4) Soak the purified product in deionized water, dry it at 80 °C, and then grind it to obtain copolymer-1.

[0059] Example 1

[0060] According to the composition and ratio shown in Table 1, compound an ionic surfactant and a non-ionic surfactant, and after fully dispersing in water, obtain foaming agent solutions with different concentrations.

[0061] Table 1

[0062]

[0063]

[0064] Note: * is the weight ratio of the anionic surfactant to the non-ionic surfactant.

[0065] Among them, in the anionic surfactant of formulation #4, the weight ratio of cocamidopropyl betaine to sodium dodecylbenzenesulfonate is 2:1.

[0066] After stirring 100 mL of the foaming agent solution at a rotation speed of 800 r / min for 3 min respectively, measure the foam volume, and the results are shown in Table 2.

[0067] Table 2

[0068]

[0069] As shown in Table 2, the foaming volume generally increases with the increase of surfactant concentration, and then remains stable. This is because the surfactant reaches the critical micelle concentration. Beyond this concentration, the foam improvement effect is not obvious. When the mass fraction of the foaming agent in the solution is in the range of 0.6-0.9%, it has better foaming performance.

[0070] Example 2

[0071] A certain amount of NaCl, CaCl2, and MgCl2·6H2O were dispersed in deionized water to prepare solutions with mineralizations of 100,000, 120,000, 140,000, 160,000, 180,000, 220,000, 240,000, 260,000, 280,000, and 300,000 mg / L, respectively, to simulate formation water; frothers #1, #2, #3, and #4 were added, respectively, so that the mass fraction of the frother in the solution was 0.7%, and 100 mL of the frother solution was stirred at 800 r / min for 3 min, the foam volume was measured, and the salt resistance was evaluated. The experimental results are shown in Table 3.

[0072] Table 3

[0073]

[0074] It can be seen from Table 3 that under the conditions of 100,000, 120,000, 140,000, 160,000, 180,000, 220,000, 240,000, 260,000, 280,000 and 300,000 mg / L mineralization, the foaming volume of the foaming agent solution is 300 mL and above, indicating that the foaming agents with formulas #1, #2, #3 and #4, respectively, can maintain high foaming performance when added to a high salt environment with a mass fraction of 0.7%.

[0075] Example 3

[0076] Based on the total weight of the gel foam system, the gel foam system contains: 0.25% of the copolymer-1 prepared in Example 1, 0.7% of the foaming agent of formula #4, 0.3% of sodium alginate, 0.04% of sorbitol ester 80, 0.06% of rice husk ash with a particle size of 20-25 μm, 0.05% of polyethylene glycol 400 and 0.05% of thiourea. According to the percentage of the above components in the gel foam system, the above components are mixed with an oil field mineralization degree of 24×10 4 The polymer solution was prepared by stirring at 300-500 rpm for 20 min.

[0077] Divide the prepared polymer solution into two equal parts, and add a certain amount of organic chromium crosslinking agent to each part so that the mass fractions of the organic chromium crosslinking agent in the two solutions are 0.4% and 0.6% respectively, obtaining gel foam system - 1 and gel foam system - 2. After continuing to stir for 20 minutes respectively, conduct a gelation experiment at 120 °C, and measure the viscosities of the formed gel foams after different days. From the measurement results, it can be seen that for gel foam system - 1 with an organic chromium crosslinking agent mass fraction of 0.4%, the viscosity reaches 43800 mPa·s at 11 days, and shows a gradually decreasing trend with time, dropping to 6430 mPa·s at 50 days; for gel foam system - 2 with an organic chromium crosslinking agent mass fraction of 0.6%, the viscosity is 24000 mPa·s at 11 days, and also shows a gradually decreasing trend with time, with a viscosity of 3240 mPa·s at 50 days.

[0078] Example 4

[0079] Gel foam system - 3 contains: 0.25% copolymer - 1 prepared in Example 1, 0.3% sodium alginate, 0.04% polysorbate 80, 0.06% rice husk ash with a particle size of 20 - 25 μm, 0.05% polyethylene glycol 400, 0.05% thiourea, and 0.4% organic chromium.

[0080] Conduct a gelation experiment on gel foam system - 1 and gel foam system - 3 at 120 °C, and measure the viscosities of the formed gel foams after different days. The measurement results are shown in Table 4.

[0081] Table 4

[0082]

[0083] It can be obtained from Table 4 that at 11 days, the foaming agent can increase the viscosity of gel foam system - 3 from 13900 mPa·s to 43800 mPa·s; at 18 days, the foaming agent keeps the viscosity of gel foam system - 1 at 12420 mPa·s; at 35 days, the viscosity of gel foam system - 1 reaches about 3 times that of gel foam system - 3 without the foaming agent; at 50 days, the gel foam system - 1 containing the foaming agent can still maintain high stability, and the viscosity can still reach > 6000 mPa·s.

[0084] It shows that the foaming agent can improve the elasticity and viscosity of the crosslinked gel system and has high stability. And the gel foam system has a relatively high viscosity retention rate compared to the gel system.

[0085] Example 5

[0086] Based on the total weight of the gel foam system, the gel foam system contains: 0.25% copolymer-1 prepared in Example 1, 0.7% foaming agent, 0.3% sodium alginate, 0.04% polysorbate 80, 0.06% rice husk ash with a particle size of 20-25 μm, 0.05% polyethylene glycol 400, 0.05% thiourea and 0.4% phenolic resin; wherein the formulas of the foaming agents are #1, #2, #3 and #4 respectively.

[0087] The above components and oilfield mineralization are 24×10 4 The water samples of 100 mg / L were mixed and fully dispersed to obtain gel foam system-4 (A), gel foam system-5 (B), gel foam system-6 (C) and gel foam system-7 (D), respectively. The gelling experiments were carried out at 90℃, 100℃, 120℃, 140℃, 160℃, 180℃, 200℃ and 220℃. When the system is in a yellow jelly state and can be poured out of a wide-mouth bottle with good elasticity, it is recorded as the gelling time. The gelling time of the four gel foam systems at different temperatures is shown in Table 5.

[0088] Table 5

[0089]

[0090] It can be seen from Table 5 that with the increase of temperature, the gelation time of gel foam system-4, gel foam system-5, gel foam system-6 and gel foam system-7 gradually shortens, and the gelation time at 90°C is 68h, 76h, 74h and 72h respectively; the gelation time at 220°C is 34h, 26h, 28h and 36h respectively; with the increase of temperature, the gelation viscosity of gel foam system-4, gel foam system-5, gel foam system-6 and gel foam system-7 gradually decreases, and the gelation viscosity at 90°C is 3.7×10 4 mPa·s, 3.3×10 4 mPa·s, 3.7×10 4 mPa·s, 4.2×10 4 mPa·s; the gel viscosity at 220℃ is 3×10 4 mPa·s, 2.2×10 4 mPa·s, 2.5×10 4 mPa·s, 2.4×10 4 mPa·s. It can be seen that with the increase of temperature, the gelation time and gelation viscosity of the four gel-foam systems show a decreasing trend, but they still meet the deep plugging control requirements under high-temperature and high-salinity reservoir conditions.

[0091] Example 6

[0092] The gel foam system - 4 was injected in multiple slugs into a high - salinity block with a salinity of 22×10 4 mg / L. It was found that: A total of 7 well - times were implemented, and the total dosage of the injected agent was 2.72×10 4 m 3 . The valid period was 586 days, the cumulative oil increment was 6550 tons, and the water cut decreased by 9.7 wt%.

[0093] Example 7

[0094] The gel foam system - 4 was injected in multiple slugs into a heavy - oil block for steam injection thermal recovery at a temperature of 200 - 220°C. It was found that: A total of 5 well - times were implemented, and the total dosage of the injected agent was 4250 m 3 . The valid period was 375 days, the cumulative oil increment was 4200 tons, and the water cut decreased by 8.5 wt%.

[0095] From the above examples, it can be seen that the foaming agent in the gel foam system has the advantages of both non - ionic and anionic surfactants. It not only has good foaming performance, improves the elasticity and viscosity of the gel system after cross - linking, and enhances the stability during the application of the gel foam, but also has good dispersion performance and compatibility, enabling the gel foam system to have good temperature and salt tolerance properties, which is beneficial to the development of high - temperature and high - salinity oil reservoirs.

[0096] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including combining each technical feature in any other suitable way. To avoid unnecessary repetition, the present invention will not separately describe various possible combination methods. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A gel foam system, characterized in that, The gel foam system includes: a foaming agent, a copolymer, a crosslinking agent, sodium alginate, a solubilizer, rice husk ash, a deoxidizer, a stabilizer, and water. Among them, based on the total weight of the gel foam system, the gel foam system contains: 0.3-1 wt% of the foaming agent, 0.25-0.4 wt% of the copolymer, 0.4-1 wt% of the crosslinking agent, 0.2-0.6 wt% of sodium alginate, 0.01-0.05 wt% of the solubilizer, 0.01-0.06 wt% of rice husk ash, 0.02-0.05 wt% of the deoxidizer, 0.02-0.05 wt% of the stabilizer, and 97.79-98.79 wt% of water; Among them, the foaming agent is a mixture of an ionic foaming agent and a non-ionic foaming agent; the weight ratio of the ionic foaming agent to the non-ionic foaming agent is 3:1-1:

3.

2. The gel foam system according to claim 1, wherein, Based on the total weight of the gel foam system, the content of the foaming agent is 0.6-0.9 wt%.

3. The gel foam system according to claim 1 or 2, wherein, The weight ratio of the ionic foaming agent to the non-ionic foaming agent is 1.5:1-1:

2.

4. The gel foam system according to any one of claims 1-3, wherein, The ionic foaming agent is selected from one or more of sodium α-olefin sulfonate, sodium dodecyl sulfate, sodium dodecyl benzene sulfonate, coconut diethanolamide, sodium fatty alcohol polyoxyethylene ether sulfate, fatty acid methyl ester sulfonate, cetyl trimethyl ammonium chloride, and coconut amide propyl betaine.

5. The gel foam system according to any one of claims 1-4, wherein, The ionic foaming agent is selected from one or more of sodium α-olefin sulfonate, sodium dodecyl sulfate, sodium dodecyl benzene sulfonate, and coconut amide propyl betaine.

6. The gel foam system according to any one of claims 1-5, wherein, The non-ionic foaming agent is selected from one or more of monoethanolamine, polyglycerol ether, and polypropylene glycol.

7. The gel foam system according to any one of claims 1-6, wherein, The copolymer contains structural unit A derived from a water-soluble monomer and structural unit B derived from a functional monomer.

8. The gel foam system according to any one of claims 1-7, wherein, The weight-average molecular weight of the copolymer is 2 million - 10 million g / mol.

9. The gel foam system according to any one of claims 1-8, wherein, The weight-average molecular weight of the copolymer is 3 million - 9 million g / mol.

10. The gel foam system according to any one of claims 7-9, wherein, The water-soluble monomer is selected from one or more of acrylamide, acrylic acid, and acrylonitrile.

11. The gel foam system according to any one of claims 7-10, wherein, The water-soluble monomer is selected from acrylamide and / or acrylic acid.

12. The gel foam system according to any one of claims 7-11, wherein, The functional monomer is selected from one or more of 2-acrylamide-2-methylpropanesulfonic acid, vinylsulfonic acid, allylsulfonic acid, N-vinylpyrrolidone, and N,N-dimethylacrylamide.

13. The gel foam system according to any one of claims 7-12, wherein, The functional monomer is selected from one or more of 2-acrylamide-2-methylpropanesulfonic acid, vinylsulfonic acid, allylsulfonic acid, and N,N-dimethylacrylamide.

14. The gel foam system according to any one of claims 7-13, wherein, The weight ratio of structural unit A to structural unit B is 5:1-1:

5.

15. The gel foam system according to any one of claims 7-14, wherein, The weight ratio of structural unit A to structural unit B is 1:1-1:1.

5.

16. The gel foam system according to any one of claims 1-15, wherein, The crosslinking agent is selected from one or more of phenolic resin crosslinking agents, polyethyleneimine, and organic chromium crosslinking agents.

17. The gel foam system according to any one of claims 1-16, wherein, The crosslinking agent is selected from phenolic resin crosslinking agents and / or organic chromium crosslinking agents.

18. The gel foam system according to any one of claims 1-17, wherein, The solubilizer is selected from one or more of benzyl alcohol, ethanol, propylene glycol, polysorbate 80, and cyclodextrin.

19. The gel foam system according to any one of claims 1-18, wherein, The deoxidizer is selected from one or more of thiourea, sodium sulfite, and sodium thiosulfate; and / or, the stabilizer is selected from one or more of ethanol, ethylene glycol, glycerol, sorbitol, sucrose, and polyethylene glycol; And / or, the average particle size of the rice husk ash is 10 - 40 μm.

20. Application of the gel foam system according to any one of claims 1 - 19 in water plugging and profile control during oil production.

21. The application according to claim 20, wherein, During oil production, the temperature of the reservoir is 40 - 220 °C, preferably 90 - 220 °C.

22. The application according to claim 21, wherein, The salinity of the reservoir is 20,000 - 300,000 mg / L, preferably 100,000 - 300,000 mg / L.

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