In-layer authigenic chemical thermal plug removal-production increasing system and application thereof

Abstract

The invention discloses an in-layer authigenic chemical thermal plug removal-production increasing system and application thereof, and belongs to the technical field of crude oil recovery. Dimethyl fumarate and chitosan are used as main agents and can generate CO2 and N2 at the temperature of 40 DEG C under the action of citric acid and hydrogen peroxide; meanwhile, heat is continuously generated in the process of conveying to the deeper part of the porous medium, and under the combined action of the formation temperature, the system is triggered by 2, 2 '-azodiisobutyronitrile at 60 DEG C to generate CO2 and N2 again and release a large amount of heat; in the continuous migration process, CO2 and N2 are generated again and a large amount of heat is released under the initiation of azodimethyl amide at 90 DEG C. The generated gas is foamed under the action of the foam stabilizing system, the stability and oil resistance of the foam are improved, the foam carries the foam stabilizer to a high part of an oil reservoir, crude oil at the high part is emulsified and viscosity-reduced, the crude oil on the wall surface can be stripped, and the oil washing efficiency is effectively improved.

Description

Technical Field

[0001] The invention belongs to the technical field of crude oil recovery, and in particular relates to an intra-layer autogenous chemical pyrolysis plugging-increasing recovery system and an application thereof. Background Art

[0002] Among many technologies for improving oil recovery, gas drive technology is highly favored and has become one of the most widely used technologies for improving unconventional oil recovery in the world. For example, in the development of shale and tight oil reservoirs, fracturing operations often cause fracturing fluid to remain in tiny pores or cracks in the formation, which cannot be normally returned to the ground, forming a "water-absorbing shield" that reduces the overall permeability of the reservoir, causing water lock damage, making it difficult for gases such as CO2 to effectively contact the crude oil in the matrix, and weakening the oil recovery effect. In addition, natural CO2 and other gas sources are scarce at the oil field site, the transportation cost is high, and the purchase and maintenance costs of ground equipment are also huge, which increases the difficulty of implementing gas drive technology. In the traditional CO2 oil recovery process, there are also risks of equipment corrosion and formation cold damage, especially the injected liquid CO2 may cause the precipitation of components such as paraffin and asphalt, which in turn causes blockage in the near-well area.

[0003] To overcome these limitations, the in-layer gas generation technology, which is not restricted by external gas source problems, is environmentally friendly and has low damage, has become an effective alternative. By injecting a gas agent solution into the formation, a chemical reaction occurs in the formation, releasing a large amount of gas. The commonly used in-layer gas in oil and gas field development technology are N2, CO2, ClO2, etc. The self-generation process of gas is an exothermic reaction. The heat generated can reduce the viscosity of crude oil and change the instantaneous pressure of the oil-water system, thereby enhancing the oil displacement effect. The in-layer self-generation gas technology is mainly divided into a single liquid method and a double liquid method. The single liquid method is simple to operate, but the reaction controllability is poor and the initial environment requirements are high. Since the reactants are already in a mixed state on the ground, there are certain safety hazards; the double liquid method has a controllable reaction, and separate injection improves safety. Different reactant combinations can be selected according to the conditions of the reservoir. The reservoir has strong adaptability, but the construction is complex. Both methods will generate different degrees of heat, and the heat generation is related to factors such as reactants, reaction concentration and reaction rate. However, its parameters such as reaction rate, reaction temperature and reaction time are difficult to accurately control in the complex environment of the reservoir. In addition, the autogenous heat system usually relies on the heat generated by chemical reactions inside the reservoir. The initial temperature requirement is usually high, and the heat distribution after the reaction is uneven. The heat may be concentrated in certain areas, and the heat utilization rate is not high. Inorganic reactions are also prone to produce additional toxic and harmful substances, leading to varying degrees of reservoir damage.

[0004] Therefore, there is an urgent need for a self-heating system that is non-toxic and harmless, has a controllable reaction, can effectively release heat, and has deep blockage removal and flooding effects to solve the above problems. Summary of the invention

[0005] In order to solve the above technical problems, the present invention proposes an intralayer autogenous chemical pyrolysis plugging-increasing production system and its application. The system reactants and products provided by the present invention are non-toxic, harmless, green and environmentally friendly. The reaction process is triggered in multiple stages by temperature. The reaction is controllable and can effectively release heat, effectively avoiding the problem of serious near-well thermal energy loss. At the same time, it has deep plugging removal, viscosity reduction and drive adjustment effects, and can achieve oil increase and water control in heterogeneous reservoirs, significantly increasing crude oil production.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] The present invention provides an intra-layer autogenous chemical thermal plugging removal-increasing production system, comprising an autogenous chemical thermal system and a foaming and stabilizing foam system;

[0008] The autogenous chemical heat system includes a main agent, an auxiliary agent and water;

[0009] The main agent includes dimethyl fumarate and chitosan; the auxiliary agent includes an initiator and a promoter;

[0010] The initiator is citric acid, hydrogen peroxide, 2,2'-azobisisobutyronitrile and azodicarbonamide;

[0011] The accelerator includes a heat stabilizer, a reaction regulator and a catalyst;

[0012] The foaming and stabilizing system comprises a foaming agent, a foam stabilizing agent and water.

[0013] Preferably, based on the mass of the intra-layer autogenous chemical pyrolysis plugging-increasing recovery system, the amount of dimethyl fumarate used is 10-20wt%, and the amount of chitosan used is 5-10wt%.

[0014] Preferably, based on the mass of the intra-layer autogenous chemical pyrolysis plugging-increased production system, the amount of citric acid is 1-2wt%; the amount of hydrogen peroxide is 0.8-1.2wt%; the amount of 2,2'-azobisisobutyronitrile is 1-1.5wt%; and the amount of azodicarbonamide is 0.6-0.8wt%.

[0015] Preferably, based on the mass of the intralayer autogenous chemical pyrolysis plugging-increased production system, the amount of the thermal stabilizer is 0.3-0.5wt%; the amount of the reaction regulator is 0.4-0.6wt%; and the amount of the catalyst is 0.5-0.7wt%.

[0016] Preferably, the heat stabilizer comprises methyl ether; the reaction regulator comprises polycarboxylate; and the catalyst comprises polyamide.

[0017] Preferably, based on the mass of the intra-layer autogenous chemical pyrolysis plugging-increase recovery system, the concentration of the foaming agent is 0.2-0.4wt%; the concentration of the foam stabilizer is 25-100mg / L.

[0018] Preferably, the foaming agent includes one or more of sodium lauryl sulfate, alkyl alcohol amide, alkyl betaine, polyoxyethylene ether, fatty alcohol polyoxyethylene ether, and nonylphenol polyoxyethylene ether.

[0019] Preferably, the foam stabilizer is a sheet-like nano material.

[0020] The present invention provides a method for preparing the intra-layer autogenous chemical pyrolysis plugging-increasing production system described in the above technical solution, comprising the following steps:

[0021] (1) dissolving chitosan in water and adjusting the pH value of the solution to obtain a chitosan solution; adding citric acid to the chitosan solution to obtain a mixed solution A;

[0022] (2) dissolving dimethyl fumarate in water to obtain a dimethyl fumarate solution; mixing hydrogen peroxide with the dimethyl fumarate solution to obtain a mixed solution B;

[0023] (3) preparing a 2,2'-azobisisobutyronitrile solution and an azodicarbonamide solution respectively;

[0024] (4) adding a catalyst to the mixed solution B obtained in step (2), and then sequentially adding a heat stabilizer and a reaction regulator to obtain a mixed solution C; the mixed solution C, the mixed solution A prepared in step (1), the 2,2'-azobisisobutyronitrile solution prepared in step (3), and the azodicarbonamide solution form an autogenous chemical thermal system;

[0025] (5) preparing a foaming agent solution and a foam stabilizing agent solution respectively;

[0026] (6) adding the foam stabilizer solution in step (5) to the foaming agent solution to obtain a foaming and stabilizing foam system;

[0027] (7) The autogenous chemical thermal system obtained in step (4) and the foaming and stabilizing foam system obtained in step (6) constitute the autogenous chemical thermal deblocking and enhanced production system in the layer.

[0028] The present invention also provides the application of the intra-layer autogenous chemical pyrolysis plugging-increasing recovery system described in the above technical solution in crude oil recovery.

[0029] Compared with the prior art, the present invention has the following advantages and technical effects:

[0030] The dimethyl fumarate and chitosan in the present invention can generate CO2, N2 and other additional products at 40°C under the action of citric acid and hydrogen peroxide; at the same time, heat generation will continue to occur during the transportation of dimethyl fumarate and chitosan to the deeper part of the porous medium. Under the joint action of the formation temperature, the system is triggered by 2,2'-azobisisobutyronitrile at 60°C to generate CO2, N2 and other additional products again, and release a large amount of heat; during the continued migration, at 90°C, it is triggered by azodimethylamide to generate CO2, N2 and other additional products again, and release a large amount of heat. The generated CO2 and N2 foam under the action of the foaming and stabilizing foam system, while improving the stability and oil resistance of the foam. The foam carries the foam stabilizer to the high part of the reservoir, emulsifies and reduces the viscosity of the crude oil in the high part, and can also peel off the wall crude oil, effectively improving the oil washing efficiency. The contact between CO2 and crude oil and the deblocking effect of dissolving in water to form a weak acid can relieve the water lock and gas lock damage of the reservoir after fracturing and reduce the viscosity of crude oil. At the same time, it has the characteristics of "efficient oil increase - drive adjustment and deblocking - green and environmental protection".

[0031] The intra-layer autogenous chemical pyrolysis plugging-increasing production system provided by the present invention effectively avoids the problem of serious near-well thermal energy loss and has the effects of deep plugging removal, viscosity reduction and flooding.

[0032] The intralayer autogenous chemical pyrolysis plugging and production enhancement system provided by the present invention has an exothermic chemical reaction during use, does not cause cold damage to the reservoir, has no solid-phase reactants and products, does not plug the reservoir, and has the advantages of simple construction, no need for special equipment, short operation time, and repeatable construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0034] Figure 1 This is a physical picture of the foam stabilizing effect of the foaming and foam stabilizing system prepared in Example 6;

[0035] Figure 2 It is the comprehensive foam index of different types of foaming agents;

[0036] Figure 3 This is a diagram showing the effect of heavy oil viscosity reduction by "multi-stage initiation" of the intra-layer autogenous chemical heat-blocking removal system prepared in Example 8;

[0037] Figure 4 This is a diagram showing the oil displacement effect of the intra-layer autogenous chemical heat-blocking removal system prepared in Example 8. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0040] The embodiment of the present invention provides an intra-layer autogenous chemical thermal plugging removal-increase production system, including an autogenous chemical thermal system and a foaming and stabilizing foam system;

[0041] The autogenous chemical heat system includes a main agent, an auxiliary agent and water;

[0042] The main agent includes dimethyl fumarate and chitosan; the auxiliary agent includes an initiator and a promoter;

[0043] The initiator is citric acid, hydrogen peroxide, 2,2'-azobisisobutyronitrile (AIBN) and azodicarbonamide;

[0044] The accelerator includes a heat stabilizer, a reaction regulator and a catalyst;

[0045] The foaming and stabilizing system comprises a foaming agent, a foam stabilizing agent and water.

[0046] In a preferred embodiment, based on the mass of the intra-layer autogenous chemical pyrolysis plugging-increase production system, the amount of dimethyl fumarate is 10-20wt%, preferably 10-15wt%; the amount of chitosan is 5-10wt%, preferably 5-7wt%. The present invention selects environmentally friendly chemical materials chitosan and dimethyl fumarate as the main reaction agents, which reduces the impact of the system on the environment during application, while improving the reaction efficiency and economy. The dimethyl fumarate and chitosan in the present invention can start the catalytic decomposition reaction at a relatively low temperature, and the heat generated makes the formation reach a higher temperature under high pressure, providing independent thermal decomposition reaction conditions, releasing a large amount of heat and gas, and transforming the formation temperature distribution. Dimethyl fumarate aqueous solution is a high-concentration aqueous solution that does not respond to mechanical stimulation and can be safely injected into the formation through a mechanical pump. It is completely thermally decomposed under high temperature and high pressure. The heat and gas released by the decomposition reaction act on the heavy oil reservoir. The deeper into the reservoir, the higher the heat. The increase in temperature can improve the fluidity of the heavy oil, and the increase in gas provides additional driving force. The combined effect greatly increases the daily output and recovery rate.

[0047] In a preferred embodiment, the oxidative decomposition of the ester group in the dimethyl fumarate and the deamination reaction process of the chitosan amino group are as follows:

[0048] C4H4O4+C6H 11 NO4+H2O→CO2↑+N2↑+product+heat (under the action of catalyst).

[0049] The existing chemical thermogenic system integrates multiple production-increasing functions, mainly due to its unique reagent formula composition and products. From the existing underground thermogenic production technology of oil reservoirs, the reagent formula is mainly composed of a main agent and an auxiliary agent. Among them, the chemical thermogenic system using nitrite and ammonium salt as the main agent is more common. The reaction between nitrite and ammonium salt is a typical exothermic reaction, and the specific chemical equation is: Heat. The products of this reaction are N2 and water, both of which are non-toxic and harmless substances. They will not pollute the reservoir and the environment, and meet the requirements of green and environmentally friendly oil recovery technology. The reaction is violent and accompanied by the release of a large amount of heat, which can increase the temperature of the reservoir, reduce the viscosity of crude oil, and improve the fluidity of oil and water. The generated N2 is a non-corrosive, non-soluble gas, which can increase the reservoir pressure and enhance the oil recovery effect. Compared with CO2 gas, N2 has no problems such as corrosiveness and cold damage, and can form a good gas-driven environment in the formation, which helps to increase the formation pressure and drive the flow of crude oil. Although this system has significant advantages, if the water generated by this reaction is not discharged in time, it may cause "water lock" or reservoir damage in the near-well area, reduce the formation permeability or block the formation, hinder the flow of crude oil, and reduce the production capacity of the oil well. In addition, although the reaction rate can be achieved by adjusting the concentration of the two liquids, the exothermic reaction rate and time are difficult to accurately control, especially in a complex reservoir environment, which can easily lead to premature reaction, so that the gas and heat are concentrated in the near-well area, and cannot effectively cover the deep formation, affecting the oil recovery effect. In particular, the chemical exothermic system usually requires acidic conditions to trigger the reaction, and oxalic acid or acetic acid is generally used as a catalyst. The catalyst can easily lead to uncontrollable reactions and premature reactions, especially near the wellbore or bottom of the well. If the exothermic reaction is completed too early, it will limit the reaction from penetrating deep into the reservoir, making it difficult to achieve a comprehensive thermal effect and oil recovery efficiency enhancement.

[0050] The existing chemical heat generation system of urea and nitrite is also a dual-liquid technology that generates heat and gas inside the reservoir through chemical reactions to increase crude oil recovery. It has become a research hotspot due to its excellent oil recovery effect. - )The chemical equation for the reaction under certain conditions is: The products generated by this reaction are mainly N2, CO2 and H2O, all of which are non-toxic and harmless substances, but the additional product NO is toxic and will damage the reservoir, which does not meet the technical requirements of green environmental protection. At the same time, the gas is unevenly distributed in the porous medium, and the foaming ability is weak, making it difficult to achieve long-term and effective foam flooding in the formation. This reaction will also release a large amount of heat, significantly increase the reservoir temperature, reduce the viscosity of high-viscosity crude oil, thereby improving the fluidity of the reservoir and enhancing the oil recovery effect. However, due to the reaction rate being too fast or too slow and the high requirements for reaction conditions (such as acidic environment), the heat may be concentrated in the near-well area, and the crude oil viscosity reduction effect at the far-well position is not ideal. However, the reaction also needs to be carried out in an acidic environment. Usually, an acidic catalyst (such as sulfuric acid or hydrochloric acid) needs to be added to maintain acidic conditions. In addition, the agent is easily adsorbed in large quantities in the near-wellbore area during the injection process. The agent interaction time is short, and the concentrated heat released leads to heat energy loss. The reaction is not thorough and difficult to conduct to the deep layer. The effect of improving the fluidity of crude oil in the overall reservoir is limited. The acid and CO2 generated by the reaction may also react with precipitates or minerals, resulting in blockage in the near-wellbore area. At the same time, the addition of catalysts may cause equipment corrosion and increase operational complexity and cost. For water-based modified fracturing fluid, when mixed with the system in the presence of catalyst hydrochloric acid, heat and gas are generated. The generated gas is distributed in the liquid to form a performance similar to that of foam fracturing fluid, but the amount of residue contained cannot be effectively reduced, and its damage is high, which will affect the fracturing effect. Although the reaction rate can be controlled by adjusting the concentration of urea and nitrite, in actual applications, the temperature and acidic conditions of the formation vary greatly, which may lead to uneven reaction rate, thereby affecting the distribution of heat and gas and reducing the oil displacement effect. In addition, due to the violent reaction, the pressure in the local area may rise too quickly, affecting the stability of the overall injection pressure; the CO2 produced by some reactions is a soluble gas, and the adjustment and displacement effect is not as significant as that of insoluble gases (such as N2), especially in fractured reservoirs, where CO2 tends to flow rapidly in the fractures, resulting in poor adjustment and displacement effects.

[0051] In a preferred embodiment, based on the mass of the intralayer autogenous chemical pyrolysis plugging-increase recovery system, the amount of citric acid is 1-2wt%; the amount of hydrogen peroxide is 0.8-1.2wt%; the amount of 2,2'-azobisisobutyronitrile is 1-1.5wt%; and the amount of azodicarbonamide is 0.6-0.8wt%. The present invention uses citric acid, hydrogen peroxide, 2,2'-azobisisobutyronitrile and azodicarbonamide as initiators, realizes multi-stage initiation of dimethyl fumarate and chitosan, continuously generates gas and heat, and finally achieves the effects of unblocking, viscosity reduction and flooding.

[0052] In a preferred embodiment, the hydrogen peroxide participates in the reaction to generate O2, and the reaction process is:

[0053] The control of the dosage of dimethyl fumarate, chitosan, citric acid, hydrogen peroxide, 2,2'-azobisisobutyronitrile and azodicarbonamide in the present invention is the key to achieving a stable and efficient self-heating effect. By adjusting the concentration of each component, it is ensured that the system generates an appropriate amount of heat and gas under formation conditions to avoid overly fast or overly slow reactions.

[0054] In a preferred embodiment, based on the mass of the intralayer autogenous chemical pyrolysis plugging-increase production system, the amount of the thermal stabilizer is 0.3-0.5wt%; the amount of the reaction regulator is 0.4-0.6wt%; and the amount of the catalyst is 0.5-0.7wt%.

[0055] In a preferred embodiment, the heat stabilizer includes methyl ether; the reaction regulator includes polycarboxylate; and the catalyst includes polyamide. The catalyst in the present invention is used to promote the reaction rate of the chemical reaction; the heat stabilizer is used to improve the thermal stability of the system in the range of 40 to 90°C to prevent premature reaction; and the reaction regulator is used to adjust the reaction speed to avoid excessive reaction.

[0056] In a preferred embodiment, based on the mass of the intralayer autogenous chemical pyrolysis plugging-increasing recovery system, the concentration of the foaming agent is 0.2-0.4wt%, preferably 0.3-0.4wt%. The concentration of the foaming agent in the present invention is within the above range, which has a good foaming effect.

[0057] In a preferred embodiment, the foaming agent includes one or more of sodium dodecyl sulfate (SDS), alkyl alcohol amide (S-1), alkyl betaine (S-2), polyoxyethylene ether (S-3), fatty alcohol polyoxyethylene ether (S-4), and nonylphenol polyoxyethylene ether (S-5), preferably fatty alcohol polyoxyethylene ether. Fatty alcohol polyoxyethylene ether has a relatively large foaming volume and liquid separation half-life, and has the strongest comprehensive foaming ability.

[0058] In a preferred embodiment, based on the mass of the intralayer autogenous chemical pyrolysis plugging-increase production system, the concentration of the foam stabilizer is 25-100 mg / L, preferably 50-100 mg / L. The present invention controls the concentration of the foam stabilizer within the above range, which is beneficial to improving the liquid separation half-life of the foam system. If the concentration of the foam stabilizer is too high or too low, the liquid separation half-life of the foam system will be reduced.

[0059] In a preferred embodiment, the foam stabilizer is a flaky nano material, preferably flaky nano MoS2. The present invention uses flaky nano materials as foam stabilizers, and the interfacial activity of the flaky nano materials can increase the liquid separation half-life of the foam system.

[0060] The present invention provides a method for preparing the intra-layer autogenous chemical pyrolysis plugging-increasing production system described in the above technical solution, comprising the following steps:

[0061] (1) dissolving chitosan in water and adjusting the pH value of the solution to obtain a chitosan solution; adding citric acid to the chitosan solution to obtain a mixed solution A;

[0062] (2) dissolving dimethyl fumarate in water to obtain a dimethyl fumarate solution; mixing hydrogen peroxide with the dimethyl fumarate solution to obtain a mixed solution B;

[0063] (3) preparing a 2,2'-azobisisobutyronitrile solution and an azodicarbonamide solution respectively;

[0064] (4) adding a catalyst to the mixed solution B obtained in step (2), and then sequentially adding a heat stabilizer and a reaction regulator to obtain a mixed solution C; the mixed solution C, the mixed solution A prepared in step (1), the 2,2'-azobisisobutyronitrile solution prepared in step (3), and the azodicarbonamide solution form an autogenous chemical thermal system;

[0065] (5) preparing a foaming agent solution and a foam stabilizing agent solution respectively;

[0066] (6) adding the foam stabilizer solution in step (5) to the foaming agent solution to obtain a foaming and stabilizing foam system;

[0067] (7) The autogenous chemical thermal system obtained in step (4) and the foaming and stabilizing foam system obtained in step (6) constitute the autogenous chemical thermal deblocking and enhanced production system in the layer.

[0068] In a preferred embodiment, in step (1), the pH value of the solution is adjusted by using acetic acid to adjust the pH value of the solution to 4.5-5.5.

[0069] In a preferred embodiment, in step (2), the hydrogen peroxide is added in the form of a hydrogen peroxide solution; the concentration of the hydrogen peroxide solution is 30 wt%.

[0070] In a preferred embodiment, in step (3), the solvents of the 2,2'-azobisisobutyronitrile solution and the azodicarbonamide solution are both water.

[0071] In a preferred embodiment, in step (5), the foam stabilizer solution is prepared by mixing the foam stabilizer and simulated formation water with a mineralization of 5000 mg / L, and ultrasonicating for 30 minutes to obtain the foam stabilizer solution.

[0072] The present invention also provides the application of the intra-layer autogenous chemical pyrolysis plugging-increasing recovery system described in the above technical solution in crude oil recovery.

[0073] In a preferred embodiment, the application of the intra-layer autogenous chemical thermal deblocking and enhanced recovery system in crude oil recovery includes the following steps: first injecting the mixed liquid C and the mixed liquid A in the autogenous chemical thermal system, then injecting the foaming and stabilizing foam system, and then injecting 2,2'-azobisisobutyronitrile solution when the crude oil temperature is 60-70°C, and injecting azodicarbonamide solution when the crude oil temperature rises to 90°C.

[0074] In a preferred embodiment, when the crude oil temperature is 60-70°C, 2,2'-azobisisobutyronitrile solution is injected to achieve secondary initiation of the autogenous chemical thermal system; when the crude oil temperature rises to 90°C, azodicarbonamide solution is injected to achieve tertiary initiation of the autogenous chemical thermal system.

[0075] After the autogenous chemical thermal system is injected, the system undergoes a chemical reaction in the formation, releasing heat and gas, raising the system temperature, reducing the viscosity of the heavy oil, and providing an initial gas source for foam formation. The foaming and stabilizing system is then injected into the reservoir and mixed with the gas generated by the autogenous chemical thermal system to form stable foam. By utilizing the fluidity and volume expansion effect of the heavy oil, the foam expands to the deep part of the reservoir as the temperature rises, carrying the foam stabilizer to the high part of the reservoir, coming into contact with the residual oil, stripping off the residual oil and changing the wettability.

[0076] The room temperature in the embodiments of the present invention refers to "25±2°C".

[0077] In the following examples, the polycarboxylate is sodium polyacrylate, CAS No.: 9003-04-7, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0078] Unless otherwise specified, the raw materials in the examples of the present invention were purchased from commercial sources.

[0079] Example 1

[0080] A method for preparing an autogenous chemical thermal system:

[0081] (1) Dissolve chitosan in deionized water, then use acetic acid to adjust the pH value of the solution to 5.0, stir the solution until the chitosan is completely dissolved, and obtain a 5wt% (the amount of chitosan used is based on the mass of the in-layer autogenous chemical thermal decomposition plugging-increased production system) chitosan solution; add 1.0wt% (the amount added is based on the mass of the in-layer autogenous chemical thermal decomposition plugging-increased production system) of citric acid to the chitosan solution to obtain a mixed solution A.

[0082] (2) Dissolve dimethyl fumarate in deionized water and stir evenly to obtain a 10 wt% (the amount of dimethyl fumarate is based on the mass of the in-layer autogenous chemical pyrolysis plugging-increased production system) dimethyl fumarate solution, prepare a 30 wt% hydrogen peroxide solution into a 0.8 wt% (the amount of hydrogen peroxide is based on the mass of the in-layer autogenous chemical pyrolysis plugging-increased production system) solution, and then mix it with the above dimethyl fumarate solution to obtain a mixed solution B.

[0083] (3) Using deionized water as solvent, prepare 1 wt% (the amount of AIBN, based on the mass of the in-layer autogenous chemical pyrolysis plugging-enhanced production system) AIBN solution and 0.6 wt% (the amount of azodicarbonamide, based on the mass of the in-layer autogenous chemical pyrolysis plugging-enhanced production system) azodicarbonamide solution, and set them aside.

[0084] (4) 0.5 wt % (the amount added is calculated based on the mass of the intra-layer autogenous chemical thermal decomposition and blockage enhancement system) of polyamide is added to the mixed solution B obtained in step (2), and then 0.3 wt % (the amount added is calculated based on the mass of the intra-layer autogenous chemical thermal decomposition and blockage enhancement system) of methyl ether and 0.4 wt % (the amount added is calculated based on the mass of the intra-layer autogenous chemical thermal decomposition and blockage enhancement system) of polycarboxylate are added in sequence to obtain a mixed solution C; the obtained mixed solution C, the mixed solution A prepared in step (1), the AIBN solution prepared in step (3) and the azodicarbonamide solution form an autogenous chemical thermal system.

[0085] Example 2

[0086] A method for preparing an autogenous chemical thermal system:

[0087] (1) Dissolve chitosan in deionized water, then use acetic acid to adjust the pH value of the solution to 5.0, stir the solution until the chitosan is completely dissolved, and obtain a 7wt% (the amount of chitosan used is based on the mass of the in-layer autogenous chemical thermal decomposition plugging-increased production system) chitosan solution; add 1.5wt% (the amount added is based on the mass of the in-layer autogenous chemical thermal decomposition plugging-increased production system) citric acid to the chitosan solution to obtain a mixed solution A.

[0088] (2) Dissolve dimethyl fumarate in deionized water and stir evenly to obtain a 15 wt% (the amount of dimethyl fumarate is based on the mass of the in-layer autogenous chemical pyrolysis plugging-increased production system) dimethyl fumarate solution, prepare a 30 wt% hydrogen peroxide solution into a 1.0 wt% hydrogen peroxide solution (based on the mass of the in-layer autogenous chemical pyrolysis plugging-increased production system), and then mix it with the above dimethyl fumarate solution to obtain a mixed solution B.

[0089] (3) Using deionized water as solvent, prepare 1.2 wt% (the amount of AIBN, based on the mass of the in-layer autogenous chemical pyrolysis plugging-enhanced production system) of AIBN solution and 0.7 wt% (the amount of azodicarbonamide, based on the mass of the in-layer autogenous chemical pyrolysis plugging-enhanced production system) of azodicarbonamide solution, and set them aside.

[0090] (4) 0.6 wt % (the amount added is calculated based on the mass of the intra-layer autogenous chemical thermal decomposition and blockage enhancement system) of polyamide is added to the mixed solution B obtained in step (2), and then 0.4 wt % (the amount added is calculated based on the mass of the intra-layer autogenous chemical thermal decomposition and blockage enhancement system) of methyl ether and 0.5 wt % (the amount added is calculated based on the mass of the intra-layer autogenous chemical thermal decomposition and blockage enhancement system) of polycarboxylate are added in sequence to obtain a mixed solution C; the obtained mixed solution C, the mixed solution A prepared in step (1), the AIBN solution prepared in step (3) and the azodicarbonamide solution form an autogenous chemical thermal system.

[0091] Example 3

[0092] A method for preparing an autogenous chemical thermal system:

[0093] (1) Dissolve chitosan in deionized water, then use acetic acid to adjust the pH value of the solution to 5.0, stir the solution until the chitosan is completely dissolved, and obtain a 10wt% (the amount of chitosan used is based on the mass of the in-layer autogenous chemical thermal decomposition plugging-increased production system) chitosan solution; add 2.0wt% (the amount added is based on the mass of the in-layer autogenous chemical thermal decomposition plugging-increased production system) of citric acid to the chitosan solution to obtain a mixed solution A.

[0094] (2) Dissolve dimethyl fumarate in deionized water and stir evenly to obtain a 20 wt% (the amount of dimethyl fumarate is based on the mass of the in-layer autogenous chemical pyrolysis plugging-increased production system) dimethyl fumarate solution, prepare a 30 wt% hydrogen peroxide solution into a 1.2 wt% (the amount of hydrogen peroxide is based on the mass of the in-layer autogenous chemical pyrolysis plugging-increased production system) solution, and then mix it with the above dimethyl fumarate solution to obtain a mixed solution B.

[0095] (3) Using deionized water as solvent, prepare 1.5 wt% (the amount of AIBN, based on the mass of the in-layer autogenous chemical pyrolysis plugging-increased production system) of AIBN solution and 0.8 wt% (the amount of azodicarbonamide, based on the mass of the in-layer autogenous chemical pyrolysis plugging-increased production system) of azodicarbonamide solution, and set them aside.

[0096] (4) 0.7 wt % (the amount added is calculated based on the mass of the intra-layer autogenous chemical thermal decomposition and blockage enhancement system) of polyamide is added to the mixed solution B obtained in step (2), and then 0.5 wt % (the amount added is calculated based on the mass of the intra-layer autogenous chemical thermal decomposition and blockage enhancement system) of methyl ether and 0.6 wt % (the amount added is calculated based on the mass of the intra-layer autogenous chemical thermal decomposition and blockage enhancement system) of polycarboxylate are added in sequence to obtain a mixed solution C; the obtained mixed solution C, the mixed solution A prepared in step (1), the AIBN solution prepared in step (3) and the azodicarbonamide solution form an autogenous chemical thermal system.

[0097] Heat generation and gas evaluation of the self-generated chemical heat system in Examples 1-3: Mix the mixed solution C, mixed solution A, AIBN solution and azodicarbonamide solution and heat them to 40°C for reaction. During the reaction, a temperature sensor is used to monitor the temperature change of the system in real time. The temperature is recorded every 1 minute until the reaction is completed, and the maximum temperature rise of the system is measured. Use a gas capture device or flowmeter to monitor the gas generation of the system in real time, record the gas volume (mL) every 1 minute, and record the total generation. The reaction rate (°C / min) is determined by recording the gas generation rate (mL / min). After the reaction starts, as the temperature rises, it can be observed that the number of bubbles gradually increases, accompanied by the generation of CO2 and N2. During the reaction, the temperature continues to rise, accompanied by heat release, and the temperature change can be felt by touch.

[0098] Table 1 Changes of various indicators during the reaction of the self-generated chemical heat system prepared in Examples 1-3

[0099]

[0100] It can be seen from Table 1 that Example 2 performs best in all evaluation indicators, with the highest self-generated heat, CO2 and N2 production, reaction rate, and gas generation rate.

[0101] Example 4

[0102] 200 mL of S-1 to S-5 solutions and SDS solution with concentrations of 0.1 wt%, 0.2 wt%, 0.3 wt% and 0.4 wt%, respectively, were prepared with distilled water to obtain a foaming agent solution.

[0103] Test of the foaming effect of the foaming agent solution: At room temperature, the foaming agent solution obtained in Example 4 was stirred and foamed using a stirrer. The speed was set to 4000 r / min and the stirring time was 2 min. The generated foam was quickly poured into a 2000 mL measuring cylinder. The timing was started when the foam was poured and the foam volume V0 was read.

[0104] The foaming ability of different concentrations and types of foaming agent solutions is shown in Table 2.

[0105] Table 2 Foam volume V0 of different concentrations and types of foaming agent solutions

[0106]

[0107]

[0108] It can be seen from Table 2 that when the concentration is 0.3wt% and 0.4wt%, S-4, S-5 and SDS all have good foaming effects. The desired effect can be achieved when the foaming agent concentration is 0.3wt%. Therefore, considering the economy, the concentration of the foaming agent is preferably 0.3wt%.

[0109] Based on the test results of the foaming effect of the foaming agent solution, the half-life of the liquid separation and the comprehensive foam index of different types of foaming agents were tested when the foaming agent concentration was 0.3wt%. After reading the foam volume V0, 200mL of simulated formation water was poured into the vector cylinder and the foam liquid separation half-life t was recorded. 1 / 2 , calculate the comprehensive foam index F q The calculation method of the comprehensive foam index is shown in formula (1); the test temperatures are set at 20°C, 40°C, 60°C, 80°C and 100°C.

[0110]

[0111] Among them, t0 is the time corresponding to the maximum foaming volume, min; t 1 / 2 is the foam separation half-life, min; f(t) is the function of foaming volume changing with time.

[0112] The half-life of different types of foaming agents is shown in Table 3, and the comprehensive foam index is shown in Figure 2 .

[0113] Table 3 Liquid separation half-life of different foaming agents

[0114] Surfactant Type SDS S-1 S-2 S-3 S-4 S-5 Dialysis half-life (min) 138 99 61 46 173 167

[0115] From Table 3 and Figure 2 It can be seen that when S-4 is used as the foaming agent, the foaming agent solution has a relatively large foaming volume and liquid separation half-life, and the comprehensive foaming ability is the strongest. Therefore, S-4 with a concentration of 0.3% is preferably used as the foaming agent of the system.

[0116] Examples 5-7 and Comparative Example 1

[0117] A preparation method of a foaming and stabilizing foam system:

[0118] (1) preparing 200 mL of a 0.3 wt % S-4 solution with distilled water to obtain a foaming agent solution;

[0119] (2) Using simulated formation water with a mineralization of 5000 mg / L, 0 mg / L (Comparative Example 1), 25 mg / L (Example 5), 50 mg / L (Example 6) and 100 mg / L (Example 7) flake nano MoS2 solutions were prepared respectively, and ultrasonicated for 30 minutes to obtain flake nano foam stabilizer solutions;

[0120] (3) adding the foaming agent solution obtained in step (1) to the flake nano foam stabilizer solution obtained in step (2), stirring evenly, to obtain a foaming and foam stabilizing system.

[0121] Figure 1 This is a physical picture of the foam stabilizing effect of the foaming and stabilizing foam system prepared in Example 6. Figure 1 It can be seen that the flake nano-MoS2 is in the upper layer of the mixed solution and is evenly dispersed.

[0122] Foam stabilization performance test: The foaming and stabilizing foam systems prepared in Examples 5-7 and Comparative Example 1 were stirred with a stirrer, the rotation speed was set to 4000 r / min, the stirring time was 2-3 min, the generated foam was quickly poured into a 2000 mL measuring cylinder, the timing was started when pouring, the foam volume V0 was read, 200 mL of simulated formation water was poured into the measuring cylinder, and the foam liquid separation half-life t under different concentrations of flaky nano-MoS2 was recorded. 1 / 2 , the results are shown in Table 4.

[0123] Table 4 Liquid separation half-life of foaming and stabilizing system under different concentrations of foam stabilizer

[0124] Comparative Example 1 Example 5 Example 6 Example 7 <![CDATA[Concentration of flaky nano-MoS2 (mg / L)]]> 0 25 50 100 Dialysis half-life (min) 173 214 346 243

[0125] It can be seen from Table 4 that the interfacial activity of the flaky nanomaterials increases the liquid precipitation half-life of the foam system. When the dosage of the flaky nano foam stabilizer is 50 mg / L, the liquid precipitation half-life doubles to 346 min. Therefore, 50 mg / L is preferably used as the dosage of the foam stabilizer in the intralayer autogenous chemical pyrolysis plugging-increased production system.

[0126] Example 8

[0127] A method for preparing an intra-layer autogenous chemical pyrolysis plugging-increasing production system, the specific steps are as follows:

[0128] Steps (1) to (4) are the same as in Example 2;

[0129] (5) Prepare 200 mL of a 0.3 wt% (based on the mass of the in-layer autogenous chemical pyrolysis plugging-increased production system) fatty alcohol polyoxyethylene ether solution with distilled water to obtain a foaming agent solution; use simulated formation water with a mineralization of 5000 mg / L to prepare a 50 mg / L (based on the mass of the in-layer autogenous chemical pyrolysis plugging-increased production system) flake nano MoS2 solution, ultrasonicate for 30 minutes, and obtain a flake nano foam stabilizer solution; add the foaming agent solution to the flake nano foam stabilizer solution, stir evenly, and obtain a foaming and stabilizing foam system;

[0130] (6) The autogenous chemical thermal system obtained in step (4) and the foaming and stabilizing foam system obtained in step (5) constitute an in-layer autogenous chemical thermal decontamination and blockage-enhancing system.

[0131] Static heavy oil viscosity reduction test: At room temperature, the layer autogenous chemical pyrolysis plugging-enhanced recovery system prepared in Example 8 was contacted with heavy oil with a viscosity of 150 mPa·s to form a mixed system; 2 mL of the mixed system was added to the measuring container of the Brookfield viscometer and sealed; the water bath was turned on and heated from 20°C, and the viscosity of the mixed system at different temperatures was recorded. The results are shown in Table 1. Figure 3 .

[0132] Figure 3 This is a diagram showing the effect of heavy oil viscosity reduction by the “multi-stage initiation” of the self-generated chemical heat-blocking removal system prepared in Example 8. Figure 3 It can be seen that the viscosity of the mixed system does not change significantly at room temperature. As the water bath heating temperature increases, the viscosity of the mixed system decreases in a "three-stage step-by-step" manner, indicating that the intralayer autogenous chemical heat-deblocking system does not react quickly and completely after contacting the heavy oil, but instead undergoes a multi-stage chain reaction as the temperature increases, creating conditions for the system to migrate deep into the reservoir to enhance oil recovery.

[0133] Double-tube parallel core flooding experiment: A parallel core model (permeability of 500 / 2500mD, permeability gradient of 5) was used, and the crude oil viscosity was 160mPa·s. The specific experimental process was as follows: the core was evacuated, saturated simulated formation water was introduced at a flow rate of 0.3mL / min, the permeability was tested and the core porosity was calculated; saturated heavy oil was introduced at a flow rate of 0.05mL / min, and the original oil saturation under bound water was calculated; water flooding was carried out at a flow rate of 1mL / min until the water content at the outlet reached 98%; and the core was flooded at a flow rate of 1mL / min. The autogenous chemical heat-blocking system prepared in Example 8 was injected at a flow rate of 0.85 PV. The injection segment plug combination is shown in Table 5. The injection timing of the 2,2'-azobisisobutyronitrile solution in the autogenous chemical heat system is when the crude oil temperature rises to 60-70°C, and the injection timing of the azodicarbonamide solution is when the crude oil temperature rises to 90°C. The injection volumes of the 2,2'-azobisisobutyronitrile solution and the azodicarbonamide solution are both 0.17 PV. The subsequent water flooding was carried out at a flow rate of 1 mL / min. When the water content at the outlet reached 98%, the water flooding was stopped. The oil displacement effect is shown in Table 5. Figure 4 .

[0134] Table 5 Slug combination for double-tube parallel displacement experiment

[0135] order Slug combination Volume (PV) 1 Mixture A 0.17 2 Isolation slug (formation water) 0.125 3 Mixture C 0.17 4 Isolation water (formation water) 0.125 5 Foaming and stabilizing system 0.17

[0136] Note: PV refers to the volume of solution injected into the ground as a multiple of the total pore volume underground.

[0137] Figure 4 The oil displacement effect diagram of the self-generated chemical heat-blocking removal system prepared in Example 8, wherein (a) is the parallel model oil displacement dynamic diagram, and (b) is the core diversion rate dynamic diagram. Figure 4 It can be seen from part (a) that after the autogenous chemical heat-deblocking system in the layer was injected into the core, the injection pressure began to drop significantly, and the corresponding water content could be reduced by 49.33%, and the recovery rate increased by 24.5%. The injection pressure difference and water content showed a negative correlation during the system injection stage. The pressure increased to a certain extent at the beginning of the injection of the agent, and then the injection pressure began to gradually decrease. When the injection rate remained constant, the decrease in injection pressure indicated that the viscosity of the crude oil decreased and the permeability of the core had a certain recovery, and the water lock damage in the core was alleviated to a certain extent. Figure 4 It can be seen from part (b) that after the injection system, the diversion rate of the dominant channel decreased (from 60% to about 40%), and the diversion rate of the secondary channel increased (from 40% to about 60%), indicating that the intra-layer autogenous chemical heat-deblocking system has a certain improvement on the inter-layer contradiction, and the magnitude is large, indicating that the system has a certain adjustment and flooding effect under a permeability difference of 5 times.

[0138] The above are only preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. An intralayer autogenous chemical pyrolysis plugging-increasing production system, characterized in that: Including autogenous chemical thermal system and foaming and stabilizing foam system; The autogenous chemical heat system includes a main agent, an auxiliary agent and water; The main agent includes dimethyl fumarate and chitosan; the auxiliary agent includes an initiator and a promoter; The initiator is citric acid, hydrogen peroxide, 2,2'-azobisisobutyronitrile and azodicarbonamide; The accelerator includes a heat stabilizer, a reaction regulator and a catalyst; The foaming and stabilizing system comprises a foaming agent, a foam stabilizing agent and water.

2. The intralayer autogenous chemical pyrolysis plugging-enhancing system according to claim 1, characterized in that: Based on the mass of the intra-layer autogenous chemical pyrolysis plugging-increasing production system, the amount of dimethyl fumarate is 10-20wt%, and the amount of chitosan is 5-10wt%.

3. The intralayer autogenous chemical pyrolysis plugging-enhancing system according to claim 1, characterized in that: Based on the mass of the intralayer autogenous chemical pyrolysis plugging-increase production system, the amount of citric acid is 1-2wt%; the amount of hydrogen peroxide is 0.8-1.2wt%; the amount of 2,2'-azobisisobutyronitrile is 1-1.5wt%; and the amount of azodicarbonamide is 0.6-0.8wt%.

4. The intralayer autogenous chemical pyrolysis plugging-enhancing system according to claim 1, characterized in that: Based on the mass of the intralayer autogenous chemical pyrolysis plugging-increasing production system, the amount of the thermal stabilizer is 0.3-0.5wt%; the amount of the reaction regulator is 0.4-0.6wt%; and the amount of the catalyst is 0.5-0.7wt%.

5. The intralayer autogenous chemical pyrolysis plugging-enhancing system according to claim 1 or 4, characterized in that: The heat stabilizer includes methyl ether; the reaction regulator includes polycarboxylate; and the catalyst includes polyamide.

6. The intralayer autogenous chemical pyrolysis plugging-enhancing system according to claim 1, characterized in that: Based on the mass of the intra-layer autogenous chemical pyrolysis plugging-increase production system, the concentration of the foaming agent is 0.2-0.4wt%; the concentration of the foam stabilizer is 25-100mg / L.

7. The intralayer autogenous chemical pyrolysis plugging-enhancing system according to claim 1 or 6, characterized in that: The foaming agent includes one or more of sodium lauryl sulfate, alkyl alcohol amide, alkyl betaine, polyoxyethylene ether, fatty alcohol polyoxyethylene ether, and nonylphenol polyoxyethylene ether.

8. The intralayer autogenous chemical pyrolysis plugging-enhancing system according to claim 1 or 6, characterized in that: The foam stabilizer is a sheet-like nano material.

9. The method for preparing the intralayer authigenic chemical pyrolysis plugging-enhancing production system according to any one of claims 1 to 8, characterized in that: The following steps are involved: (1) dissolving chitosan in water and adjusting the pH value of the solution to obtain a chitosan solution; adding citric acid to the chitosan solution to obtain a mixed solution A; (2) dissolving dimethyl fumarate in water to obtain a dimethyl fumarate solution; mixing hydrogen peroxide with the dimethyl fumarate solution to obtain a mixed solution B; (3) preparing a 2,2'-azobisisobutyronitrile solution and an azodicarbonamide solution respectively; (4) adding a catalyst to the mixed solution B obtained in step (2), and then sequentially adding a heat stabilizer and a reaction regulator to obtain a mixed solution C; the mixed solution C, the mixed solution A prepared in step (1), the 2,2'-azobisisobutyronitrile solution prepared in step (3), and the azodicarbonamide solution form an autogenous chemical thermal system; (5) preparing a foaming agent solution and a foam stabilizing agent solution respectively; (6) adding the foam stabilizer solution in step (5) to the foaming agent solution to obtain a foaming and stabilizing foam system; (7) The autogenous chemical thermal system obtained in step (4) and the foaming and stabilizing foam system obtained in step (6) constitute the autogenous chemical thermal deblocking and enhanced production system in the layer.

10. Use of the intralayer autogenous chemical pyrolysis plugging-increasing recovery system according to any one of claims 1 to 8 in crude oil recovery.

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