A steam huff and puff and viscosity breaker flood combination oil recovery process

Abstract

The application discloses a kind of steam huff and puff and viscosity reducer drive combination oil production process, belong to the technical field of reservoir development.The steam huff and puff and viscosity reducer drive combination oil production process, characterized in that, including the following steps: in selected thick oil area drilling a group of injection wells and production wells, viscosity reducer is injected into injection well;Production well injection steam huff and puff effect, and establish effective displacement relationship between injection well;Change the mode of injecting viscosity reducer into injection well, production well continuous production.The method combines steam huff and puff with viscosity reducer drive, effectively improves the reservoir percolation capacity, expands the sweep area of viscosity reducer, improves oil recovery efficiency, realizes the development of deep heavy oil reservoir.

Description

Technical Field

[0001] This application relates to an oil recovery process that combines steam injection with viscosity reducer flooding, belonging to the field of reservoir development technology. Background Technology

[0002] Petroleum is a non-renewable and vital energy source and a high-quality chemical raw material, as well as a crucial strategic resource related to national economy and people's livelihood. The petroleum industry is a vital industry concerning national security, economic and social development, people's livelihood stability, and national industrial security. China's heavy oil resources are widely distributed, with onshore oilfields accounting for more than 20% of total petroleum resources. The abundance of heavy oil resources and the domestic energy sustainability situation jointly determine the importance and necessity of research on heavy oil extraction technology.

[0003] Heavy oil is an important component of the world's oil and gas resources. Its prominent characteristics include high density, high pour point, high viscosity, and difficulty in flow, making it inconvenient to extract. Therefore, to increase crude oil production, reducing the pour point and viscosity of high-pour-point, high-viscosity crude oil and improving its fluidity are key to solving the problems of heavy oil extraction and transportation.

[0004] In existing technologies, chemical viscosity reducers have achieved breakthroughs in oil reservoir development. For example, patent 201410449917.X, "A Composite Catalytic Emulsified Viscosity Reducer for Heavy Oil Steam Injection and Its Preparation Method," provides a composite viscosity reducer for steam injection development, comprising a catalyst and an emulsifier. It can catalytically react with heavy oil at 200°C, reducing the viscosity of heavy oil by more than 98.5%. However, because it is a chemical reaction, its interaction time and efficiency with heavy oil are far slower than physical reactions, making it unsuitable for heavy oil extraction. On the other hand, chemical viscosity reducers also need to meet the harsh oilfield environment of high temperature and high salinity. For example, patent 201610644842.X, "A Composite Viscosity Reducer for Heavy Oil Thermal Recovery and Its Preparation Method," provides a viscosity reducer for heavy oil thermal recovery. This viscosity reducer is composed of a terpolymer and a carboxylated polyether nonionic surfactant, exhibiting good viscosity reduction effect and low production cost. However, its temperature resistance and salt resistance are lower compared to other viscosity reducers. In addition, relying solely on viscosity reducers results in slow effectiveness, low fluid production, low oil recovery rate, and poor overall efficiency, making it difficult to meet the current needs of reservoir development. Summary of the Invention

[0005] To address the aforementioned issues, an oil recovery process combining steam injection and viscosity reducer flooding is proposed. This method combines steam injection with viscosity reducer flooding, effectively improving reservoir permeability, expanding the reach of viscosity reducers, increasing oil recovery efficiency, and enabling the development of deep heavy oil reservoirs.

[0006] According to one aspect of this application, this application provides an oil recovery process combining steam injection and viscosity reducer flooding, comprising the following steps:

[0007] (1) Drill a set of injection wells and production wells in the selected heavy oil area, and inject viscosity reducer into the injection wells;

[0008] (2) The steam injection and huffing effect of the production well establishes an effective displacement relationship with the injection well;

[0009] (3) Change the way the viscosity reducer is injected into the injection well so that the production well can produce continuously.

[0010] Optionally, the injection of viscosity reducer into the injection well in step (1) can be carried out in three ways: low-concentration high-pressure rapid injection, low-concentration medium-pressure medium-speed injection, and high-concentration high-pressure rapid injection; and / or

[0011] In step (3), the viscosity reducer is injected using a high-concentration, medium-pressure, low-speed injection method.

[0012] Specifically, low-concentration, high-pressure, rapid injection, using higher pressure, allows the viscosity reducer to penetrate deeper into the formation more quickly, overcoming formation resistance and rapidly diffusing over a wider area. Choosing high-pressure, rapid injection at low concentrations serves two purposes: firstly, it allows for the initial creation of a viscosity-reducing atmosphere in the formation with a relatively small amount of reagent, lowering crude oil viscosity and paving the way for further displacement; secondly, it avoids the problem of excessive accumulation in the near-wellbore zone that might occur with high concentrations initially, ensuring the reagent can be pushed more evenly into the distance. Rapid injection allows the viscosity reducer to achieve a certain distribution scale in the formation within a short time, quickly exerting its viscosity-reducing effect. Combined with subsequent steam injection and other processes, this allows the crude oil to begin flowing more smoothly as early as possible.

[0013] Specifically, low-concentration, medium-pressure, medium-speed injection—meaning that medium pressure, compared to high pressure, focuses more on further and stably promoting the distribution of viscosity reducers in formation areas that have already undergone initial viscosity reducer injection and steam huff and puff, resulting in a more uniform and sustained viscosity-reducing effect. Medium-speed injection ensures the stable entry of the viscosity reducer into the formation, avoiding localized pressure anomalies caused by excessively rapid injection. Simultaneously, the lower injection rate combined with medium pressure allows for more sufficient contact time between the viscosity reducer and the crude oil, continuously reducing crude oil viscosity and optimizing the displacement effect.

[0014] Specifically, after the preceding treatment stages, using a high-concentration viscosity reducer can significantly enhance the viscosity-reducing effect, further modifying crude oils that still have high viscosity and are difficult to displace. High-pressure rapid injection is also intended to allow the high-concentration viscosity reducer to quickly reach deep formations and some difficult-to-reach areas, fully exerting its effect of reducing crude oil viscosity, strengthening the overall displacement system, and improving oil displacement efficiency.

[0015] Optionally, the heavy oil zone is an oil reservoir with a burial depth of 1500~2000m and a permeability of 150×10⁻⁶ m. -3μm 2 ~300×10 -3 μm 2 The viscosity of the formation crude oil is 3000~4000 mPa·s.

[0016] Optionally, the low-concentration high-pressure rapid injection refers to a concentration of 10-20% and a pressure of 20-30 MPa at a depth of 1500-2500 m³. 3 / day injection for 5-15 days; the low-concentration, medium-pressure, medium-speed injection is at a concentration of 10-20%, 12-15 MPa, and 500-800 ml / day. 3 / d injection for 5~8 days; the high-concentration, high-pressure rapid injection is at a concentration of 20~30%, at a pressure of 20~30MPa, and a flow rate of 1500~2500m. 3 / d injection for 8~12 days.

[0017] Optionally, the high-concentration, medium-pressure, low-speed injection is a 20-30% concentration, injected at 12-15 MPa at a pressure of 100-200... 3 / d injection.

[0018] Specifically, during this stage, the production wells are continuously producing, and high-concentration viscosity reducers are injected at a low speed and medium pressure. This is to maintain the low viscosity of the formation crude oil during the production process. Low-speed injection allows for more precise replenishment of viscosity reducers based on the production situation, ensuring that the crude oil can flow smoothly to the production wells continuously and avoiding a rebound in crude oil viscosity due to untimely replenishment of viscosity reducers, which would affect the recovery rate.

[0019] Optionally, in step (2), the steam injection effect is 1000~1500t of steam injected per round, with an injection rate of 200~300m / s. 3 / d, well shut-in for 5-15 days, production for 30-50 days, 3-5 cycles of throughput.

[0020] After high-temperature steam is injected into the formation, heat is transferred to the crude oil, raising its temperature. Based on the characteristic that crude oil viscosity decreases with increasing temperature, the viscosity drops significantly, improving its fluidity and making it easier to flow through formation pores and displace towards the production well. Steam injection also increases formation energy, raising formation pressure and creating a pressure differential, providing the driving force for crude oil to flow towards the production well, overcoming formation resistance. Well shut-in allows the injected steam to fully exchange heat with the crude oil in the reservoir, distributing heat more evenly. The crude oil absorbs heat more fully, further reducing its viscosity. Simultaneously, the condensed steam and other substances interact better with the crude oil, improving its rheological properties. After steam injection and well shut-in, the crude oil viscosity decreases and formation energy increases. During the production phase, relying on the pressure differential between the formation and the production well, crude oil continuously flows to the production well for extraction. Multiple injection-extraction cycles can repeat this process, gradually increasing the oil recovery rate.

[0021] Optionally, the viscosity reducer comprises, by weight, 60-80 parts of a composite surfactant, 10-15 parts of an organic solvent, 2-5 parts of an alkaline additive, and 0.5-1 parts of a thickener.

[0022] Specifically, this application also specifies the components of the viscosity reducer and the weight percentage of each component to meet the harsh reservoir environment such as heavy oil extraction and high temperature and high salinity.

[0023] Specifically, organic solvents can dissolve some heavy components in crude oil, such as asphaltenes and gums, which are often important factors leading to high crude oil viscosity. Alkaline additives can adjust the pH of the formation environment. On the one hand, they can react with acidic substances in crude oil, changing the chemical structure of the crude oil and making it easier to flow. On the other hand, a suitable alkaline environment helps surfactants to play a better role, stabilize the viscosity reducer system, improve the durability of the viscosity reduction effect, and ensure that the crude oil maintains a low viscosity throughout the displacement process.

[0024] Optionally, the composite surfactant includes a polyoxyethylene ether nonionic surfactant and a modified petroleum sulfonate anionic surfactant, wherein the mass ratio of the polyoxyethylene ether nonionic surfactant to the modified petroleum sulfonate anionic surfactant is (1~3):1.

[0025] Specifically, polyoxyethylene ether nonionic surfactants include nonylphenol polyoxyethylene ether.

[0026] Specifically, polyoxyethylene ether nonionic surfactants possess excellent emulsifying and dispersing properties, reducing the interaction forces between crude oils and between crude oil and formation pore walls, thereby lowering the flow resistance of crude oil and reducing viscosity. Modified petroleum sulfonate anionic surfactants can also reduce oil-water interfacial tension and have good salt and temperature resistance properties, enabling them to function stably in complex formation environments. When combined with nonionic surfactants, they produce a synergistic effect, further enhancing the emulsifying and viscosity-reducing effects on crude oil, making it easier to flow and be displaced.

[0027] Specifically, the preparation method of the modified petroleum sulfonate anionic surfactant includes the following steps:

[0028] S1 petroleum sulfonate anionic surfactant is placed in a reaction vessel containing tetrahydrofuran. The initiator is dissolved in tetrahydrofuran to obtain an initiator solution. The initiator solution is then slowly injected into the reaction vessel while stirring is started to ensure that the initiator is uniformly dispersed in the system, thus initiating the polymerization reaction.

[0029] S2. Add γ-(methacryloyloxy)propyltrimethoxysilane dropwise into the reaction vessel. During the dropwise addition, the reaction temperature should be maintained at 60~70℃ and the mixture should be stirred evenly.

[0030] After adding γ-(methacryloyloxy)propyltrimethoxysilane, S3 continued to stir the reaction system under constant temperature conditions to ensure that the polymerization reaction proceeded fully. The reaction time was 10-15 hours.

[0031] After the S4 reaction is completed, the mixture is cooled to room temperature, and then subjected to alcohol precipitation, filtration, washing, and drying to obtain a modified petroleum sulfonate anionic surfactant.

[0032] Specifically, the molar ratio of petroleum sulfonate anionic surfactant to γ-(methacryloyloxy)propyltrimethoxysilane is 1:(0.3~0.8); the mass ratio of petroleum sulfonate anionic surfactant to tetrahydrofuran is 1:(3~5); the initiator is azobisisobutyronitrile, and the amount of initiator added is 0.5%~1% of the total mass of the reactants.

[0033] Specifically, petroleum sulfonate anionic surfactants include sodium dodecylbenzene sulfonate.

[0034] Specifically, this application introduces silicon-containing segments into petroleum sulfonate anionic surfactant molecules, enabling them to exhibit better stability and viscosity reduction performance under high temperature and high salinity environments, making them more suitable for corresponding oil production process requirements.

[0035] Optionally, the organic solvent includes toluene or xylene; the alkaline auxiliaries include sodium bicarbonate, sodium metaborate, triethanolamine, or sodium carbonate.

[0036] Optionally, the thickener includes sodium carboxymethyl cellulose and hydrophobically modified polyacrylamide, wherein the mass ratio of sodium carboxymethyl cellulose to hydrophobically modified polyacrylamide is (1~2):1.

[0037] Specifically, when sodium carboxymethyl cellulose and hydrophobically modified polyacrylamide are combined in a certain proportion, their advantages complement each other. Sodium carboxymethyl cellulose provides basic thickening and stabilizing effects, while hydrophobically modified polyacrylamide further enhances the thickening effect through hydrophobic association and improves the overall system's ability to cope with complex formation environments. For example, in the process of combining steam injection with viscosity reducer flooding, the composite thickener can maintain suitable viscosity and rheological properties of the viscosity reducer under different injection stages (such as different pressures and injection rates) and factors such as temperature and salinity changes in the formation, allowing it to better interact with heavy oil, achieve efficient viscosity reduction, and adapt to the complex requirements of the entire oil production process.

[0038] Specifically, the preparation method of the viscosity reducer is as follows: weigh each raw material according to the weight proportions, add the composite surfactant to the reaction vessel equipped with a stirring device, stir and mix evenly at a stirring speed of 300~500 r / min for 15~30 min; then slowly add the organic solvent, alkaline additive and thickener in sequence, and continue stirring for 30~60 min to obtain the initial solution of the viscosity reducer; place the initial solution of the viscosity reducer at room temperature for 24~48 h to mature, and the viscosity reducer is obtained.

[0039] The beneficial effects of this application include, but are not limited to:

[0040] 1. This application discloses an oil recovery process combining steam injection and viscosity reducer flooding. By combining steam injection and viscosity reducer flooding, the advantages of both are complemented. Steam injection mainly uses injected high-temperature steam to heat the oil reservoir, reduce crude oil viscosity, and improve crude oil flowability. At the same time, the expansion force of steam increases formation energy, making it easier for crude oil to flow to production wells for extraction. Viscosity reducer flooding, on the other hand, involves injecting viscosity reducers into the formation to change the internal structure and surface properties of the crude oil, reducing its viscosity and making it easier to flow in the reservoir pores. The combination of the two involves steam injection first to induce a better displacement condition for subsequent viscosity reducer flooding, establishing an effective displacement relationship, followed by continuous injection of viscosity reducers and continuous production, further improving the oil recovery rate.

[0041] 2. According to the present application, an oil recovery process combining steam injection and viscosity reducer flooding is proposed, in which the components of the viscosity reducer and the weight proportions of each component are limited to meet the harsh reservoir environment such as heavy oil extraction and high temperature and high salinity.

[0042] 3. According to the oil recovery process combining steam injection and viscosity reducer flooding of this application, polyoxyethylene ether nonionic surfactants have good emulsifying and dispersing properties, reducing the interaction forces between crude oils and between crude oil and formation pore walls, thereby reducing the flow resistance of crude oil and playing a viscosity-reducing role. Modified petroleum sulfonate anionic surfactants can also reduce the oil-water interfacial tension and have good salt and temperature resistance properties, and can play a stable role in complex formation environments. When combined with nonionic surfactants, they produce a synergistic effect, further enhancing the emulsification and viscosity-reducing effect on crude oil, making the crude oil easier to flow and displace. Detailed Implementation

[0043] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0044] Unless otherwise specified, the raw materials used in the embodiments and comparative examples of this application were all purchased commercially.

[0045] Unless otherwise specified, the methods used in the embodiments and comparative examples of this application are conventional methods in the prior art. The preparation method of hydrophobic modified polyacrylamide involved in the following embodiments and comparative examples is as follows: 100g of 43wt% acrylamide aqueous solution, 10g of emulsifier dehydrated sorbitan monolaurate, and 2.5g of octylphenol polyoxyethylene ether were added sequentially to a 500ml four-necked flask equipped with a stirrer, thermometer, condenser, and gas inlet and outlet. After stirring for 10min, 100ml of kerosene was added, and the mixture was stirred for 30min while maintaining the water bath temperature at 25℃, while simultaneously purging carbon dioxide to remove oxygen from the system. 0.1ml of 1% ammonium persulfate aqueous solution and 0.5ml of 5% sodium bisulfite aqueous solution were added to initiate the reaction. After reaching the maximum temperature, the reaction was maintained at 60℃ for 1h to obtain a nonionic polyacrylamide reverse emulsion. Then, 5g of n-hydroxymethylbenzamide was added to the nonionic polyacrylamide reverse emulsion, the temperature was controlled at about 40℃, 5ml of acetic acid was added dropwise, and the reaction was allowed to proceed for about 10 hours. Then, 6.6ml of 50% sodium hydroxide aqueous solution was slowly added to neutralize the emulsion, thus obtaining a hydrophobic modified nonionic polyacrylamide reverse emulsion. After precipitation with acetone and drying, hydrophobic modified polyacrylamide was obtained.

[0046] Example 1

[0047] An oil recovery process combining steam injection and viscosity reducer flooding

[0048] (1) Drill a set of injection and production wells in the selected heavy oil area, which is a reservoir with a depth of 1500m and a permeability of 150×10⁻⁶ m. -3 μm 2The formation crude oil viscosity is 3000 Pa·s. Viscosity reducers are injected into the injection well sequentially using the following methods: low-concentration high-pressure rapid injection, low-concentration medium-pressure medium-speed injection, and high-concentration high-pressure rapid injection. The high-concentration high-pressure rapid injection method involves a 10% concentration injected at 20 MPa pressure over a depth of 1500 m. 3 / d injection for 5 days; low concentration, medium pressure, medium speed injection at a concentration of 10%, 12MPa, 500 / d injection for 5 days; high concentration, high pressure, rapid injection at a concentration of 20%, 20MPa, 1500m 3 / d injection 8d;

[0049] (2) Steam injection huff and puff effect in production wells: 1000t of steam is injected per cycle at a steam injection rate of 200m / s. 3 / d, 5 days of shut-in, 30 days of production, 3 cycles of inrush and out; establish an effective displacement relationship with the injection well;

[0050] (3) Change the method of injecting viscosity reducer into the injection well. Inject high-concentration, medium-pressure, low-speed injection into the production well for continuous production. The high-concentration, medium-pressure, low-speed injection is at a concentration of 20%, 100 mg / L at 12 MPa. 3 / d injection.

[0051] The preparation method of the viscosity reducer is as follows: Weigh each raw material according to the weight parts, add 60 parts of the composite surfactant to a reaction vessel equipped with a stirring device. The composite surfactant includes nonylphenol polyoxyethylene ether, a nonionic surfactant of polyoxyethylene ether, and modified petroleum sulfonate anionic surfactant. The mass ratio of nonylphenol polyoxyethylene ether to modified petroleum sulfonate anionic surfactant is 1:1. Stir and mix evenly at a stirring speed of 300 r / min for 15 min. Then, slowly add 10 parts of toluene, an organic solvent, 2 parts of sodium bicarbonate, an alkaline additive, and 0.5 parts of thickener. The thickener includes sodium carboxymethyl cellulose and hydrophobic modified polyacrylamide. The mass ratio of sodium carboxymethyl cellulose to hydrophobic modified polyacrylamide is 1:1. Continue stirring for 30 min to obtain the initial solution of the viscosity reducer. Let the initial solution of the viscosity reducer stand at room temperature for 24 h to mature, and the viscosity reducer is obtained.

[0052] The preparation method of modified petroleum sulfonate anionic surfactants includes the following steps:

[0053] Sodium dodecylbenzenesulfonate, a petroleum sulfonate anionic surfactant, was placed in a reaction vessel containing tetrahydrofuran. Azobisisobutyronitrile (AIB) was dissolved in tetrahydrofuran to obtain an initiator solution. The amount of initiator added was 0.5% of the total mass of the reactants. The initiator solution was then slowly injected into the reaction vessel while stirring was started to ensure that the initiator was uniformly dispersed in the system, thus initiating the polymerization reaction. The mass ratio of sodium dodecylbenzenesulfonate to tetrahydrofuran was 1:3.

[0054] S2. γ-(methacryloyloxy)propyltrimethoxysilane is added dropwise to the reaction vessel. The molar ratio of sodium dodecylbenzenesulfonate, a petroleum sulfonate anionic surfactant, to γ-(methacryloyloxy)propyltrimethoxysilane is 1:0.3. During the dropwise addition, the reaction temperature should be maintained at 60℃ and the mixture should be stirred evenly.

[0055] After adding γ-(methacryloyloxy)propyltrimethoxysilane, S3 continued to stir the reaction system under constant temperature conditions to ensure that the polymerization reaction was fully carried out. The reaction time was 10 hours.

[0056] After the S4 reaction is completed, the mixture is cooled to room temperature, and then subjected to alcohol precipitation, filtration, washing, and drying to obtain a modified petroleum sulfonate anionic surfactant.

[0057] Example 2

[0058] An oil recovery process combining steam injection and viscosity reducer flooding

[0059] (1) Drill a set of injection and production wells in the selected heavy oil area, which is a reservoir with a depth of 2000m and a permeability of 300×10⁻⁶ m. -3 μm 2 The formation crude oil viscosity was 4000 mPa·s. Viscosity reducers were injected into the injection well sequentially using the following methods: low-concentration high-pressure rapid injection, low-concentration medium-pressure medium-speed injection, and high-concentration high-pressure rapid injection. The high-concentration high-pressure rapid injection method involved a 20% concentration injection at 30 MPa pressure for 2500 m³ / h. 3 / day injection for 15 days; low concentration, medium pressure, medium speed injection at 20% concentration, 15MPa, 800 3 / d injection 8d; high concentration, high pressure, rapid injection at 30% concentration, 30MPa pressure, 2500m 3 / d injection 12d;

[0060] (2) Steam injection huff and puff effect in production wells: 1500t of steam is injected per cycle at a steam injection rate of 300m / s. 3 / d, 15 days of shut-in, 50 days of production, 5 cycles of inrush and out, and an effective displacement relationship is established between the well and the injection well;

[0061] (3) Change the method of injecting viscosity reducer into the injection well. Inject high-concentration, medium-pressure, low-speed injection into the production well for continuous production. The high-concentration, medium-pressure, low-speed injection is at a concentration of 30%, 200 mg / L at 15 MPa. 3 / d injection.

[0062] The preparation method of the viscosity reducer is as follows: Weigh each raw material according to the weight parts, add 80 parts of the composite surfactant to a reaction vessel equipped with a stirring device. The composite surfactant includes nonylphenol polyoxyethylene ether, a nonionic surfactant of polyoxyethylene ether, and modified petroleum sulfonate anionic surfactant. The mass ratio of nonylphenol polyoxyethylene ether to modified petroleum sulfonate anionic surfactant is 3:1. Stir and mix evenly at a stirring speed of 500 r / min for 30 min. Then, slowly add 15 parts of xylene, an organic solvent, 5 parts of sodium carbonate, an alkaline additive, and 1 part of thickener. The thickener includes sodium carboxymethyl cellulose and hydrophobic modified polyacrylamide. The mass ratio of sodium carboxymethyl cellulose to hydrophobic modified polyacrylamide is 2:1. Continue stirring for 60 min to obtain the initial solution of the viscosity reducer. Let the initial solution of the viscosity reducer stand at room temperature for 48 h to mature, and the viscosity reducer is obtained.

[0063] The preparation method of modified petroleum sulfonate anionic surfactants includes the following steps:

[0064] Sodium dodecylbenzenesulfonate, a petroleum sulfonate anionic surfactant, was placed in a reaction vessel containing tetrahydrofuran. Azobisisobutyronitrile (AIBN) was dissolved in tetrahydrofuran to obtain an initiator solution. The amount of initiator added was 1% of the total mass of the reactants. The initiator solution was then slowly injected into the reaction vessel while stirring was started to ensure that the initiator was uniformly dispersed in the system, thus initiating the polymerization reaction. The mass ratio of sodium dodecylbenzenesulfonate to tetrahydrofuran was 1:5.

[0065] S2. γ-(methacryloyloxy)propyltrimethoxysilane is added dropwise to the reaction vessel. The molar ratio of sodium dodecylbenzenesulfonate, a petroleum sulfonate anionic surfactant, to γ-(methacryloyloxy)propyltrimethoxysilane is 1:0.8. During the dropwise addition, the reaction temperature should be maintained at 70℃ and the mixture should be stirred evenly.

[0066] After adding γ-(methacryloyloxy)propyltrimethoxysilane, S3 continued to stir the reaction system under constant temperature conditions to ensure that the polymerization reaction was fully carried out. The reaction time was 15 hours.

[0067] After the S4 reaction is completed, the mixture is cooled to room temperature, and then subjected to alcohol precipitation, filtration, washing, and drying to obtain a modified petroleum sulfonate anionic surfactant.

[0068] Example 3

[0069] An oil recovery process combining steam injection and viscosity reducer flooding

[0070] (1) Drill a set of injection and production wells in the selected heavy oil area, which is a reservoir with a depth of 2000m and a permeability of 200×10⁻⁶ m. -3 μm 2 The formation crude oil viscosity was 4000 mPa·s. Viscosity reducers were injected into the injection well sequentially using the following methods: low-concentration high-pressure rapid injection, low-concentration medium-pressure medium-speed injection, and high-concentration high-pressure rapid injection. The high-pressure rapid injection method involved a 15% concentration injected at 25 MPa pressure over 2000 m³. 3 / day injection for 10 days; low concentration, medium pressure, medium speed injection at a concentration of 15%, 700 at 15MPa. 3 / d injection for 7 days; high-concentration, high-pressure, rapid injection at a concentration of 25%, 25MPa pressure, 2000m 3 / d injection 10d;

[0071] (2) Steam injection huff and puff effect in production wells: 1200t of steam is injected per cycle at a steam injection rate of 250m / s. 3 / d, 10 days of shut-in, 40 days of production, 4 cycles of inrush and out; establish an effective displacement relationship with the injection well;

[0072] (3) Change the method of injecting viscosity reducer into the injection well. Inject high-concentration medium-pressure low-speed injection into the production well for continuous production. The high-concentration medium-pressure low-speed injection is 25% concentration, 150 at 15MPa. 3 / d injection.

[0073] The preparation method of the viscosity reducer is as follows: Weigh each raw material according to the weight parts, add 70 parts of the composite surfactant to a reactor equipped with a stirring device. The composite surfactant includes nonylphenol polyoxyethylene ether, a nonionic surfactant of polyoxyethylene ether, and modified petroleum sulfonate anionic surfactant. The mass ratio of nonylphenol polyoxyethylene ether to modified petroleum sulfonate anionic surfactant is 2:1. Stir and mix evenly at a stirring speed of 400 r / min for 20 min. Then, slowly add 12 parts of toluene, an organic solvent, 4 parts of sodium metaborate, an alkaline additive, and 0.5 parts of thickener. The thickener includes sodium carboxymethyl cellulose and hydrophobic modified polyacrylamide. The mass ratio of sodium carboxymethyl cellulose to hydrophobic modified polyacrylamide is 1.5:1. Continue stirring for 40 min to obtain the initial solution of the viscosity reducer. Let the initial solution of the viscosity reducer stand at room temperature for 36 h to mature, and the viscosity reducer is obtained.

[0074] The preparation method of modified petroleum sulfonate anionic surfactants includes the following steps:

[0075] Sodium dodecylbenzenesulfonate, a petroleum sulfonate anionic surfactant, was placed in a reaction vessel containing tetrahydrofuran. Azobisisobutyronitrile (AIB) was dissolved in tetrahydrofuran to obtain an initiator solution. The amount of initiator added was 0.8% of the total mass of the reactants. The initiator solution was then slowly injected into the reaction vessel while stirring was started to ensure that the initiator was uniformly dispersed in the system, thus initiating the polymerization reaction. The mass ratio of sodium dodecylbenzenesulfonate to tetrahydrofuran was 1:4.

[0076] S2. γ-(methacryloyloxy)propyltrimethoxysilane is added dropwise to the reaction vessel. The molar ratio of sodium dodecylbenzenesulfonate, a petroleum sulfonate anionic surfactant, to γ-(methacryloyloxy)propyltrimethoxysilane is 1:0.5. During the dropwise addition, the reaction temperature should be maintained at 65℃ and the mixture should be stirred evenly.

[0077] After adding γ-(methacryloyloxy)propyltrimethoxysilane, S3 continued to stir the reaction system under constant temperature conditions to ensure that the polymerization reaction was fully carried out. The reaction time was 12 hours.

[0078] After the S4 reaction is completed, the mixture is cooled to room temperature, and then subjected to alcohol precipitation, filtration, washing, and drying to obtain a modified petroleum sulfonate anionic surfactant.

[0079] Example 4

[0080] The difference between Example 4 and Example 3 is that the viscosity reducer used is a commercially available viscosity reducer, while the rest are the same.

[0081] Example 5

[0082] The difference between Example 5 and Example 3 is that in step (1), the viscosity reducer is injected into the injection well using a high-concentration, high-pressure, rapid injection method, i.e., a concentration of 25% at a pressure of 25 MPa for 2000 m. 3 / d injection 27d, the rest are the same.

[0083] Example 6

[0084] The difference between Example 6 and Example 3 is that the composite surfactant in the viscosity reducer does not include modified petroleum sulfonate anionic surfactants. That is, the 70 parts of the composite surfactant in Example 6 are nonylphenol polyoxyethylene ether, a nonionic surfactant of polyoxyethylene ether type.

[0085] Example 7

[0086] The difference between Example 7 and Example 3 is that unmodified petroleum sulfonate anionic surfactant sodium dodecylbenzenesulfonate is used.

[0087] Example 8

[0088] The difference between Example 8 and Example 3 is that the mass ratio of polyoxyethylene ether nonionic surfactant and modified petroleum sulfonate anionic surfactant is 0.5:1, while all other aspects are the same.

[0089] Comparative Example 1

[0090] The difference between Comparative Example 1 and Example 3 is that the step of injecting a viscosity reducer into the well is not included; otherwise, they are the same.

[0091] Comparative Example 2

[0092] The difference between Comparative Example 2 and Example 3 is that the step of injecting steam into the well is not included; otherwise, they are the same.

[0093] Experimental Example 1

[0094] The viscosity reducers prepared in Examples 1-4 and 6-8 were tested for temperature resistance and salt resistance in accordance with QSH10202193-2018 "General Standard for Viscosity Reducers for Heavy Oil". The test results are shown in Table 1.

[0095] Table 1 Indoor Performance Test Results of Viscosity Reducers

[0096]

[0097] Table 1 shows that the viscosity reducers prepared in Examples 1-3 of this application have good temperature and salinity resistance, and are suitable for harsh oilfield environments such as high temperature and high salinity, which is superior to commercially available viscosity reducers. The temperature and salinity resistance of Examples 6 and 7 decreased significantly. The reason for this is that the composite surfactant in Example 6 did not include modified petroleum sulfonate anionic surfactants, and there was no synergistic effect between polyoxyethylene ether nonionic surfactants and modified petroleum sulfonate anionic surfactants. In Example 7, modified petroleum sulfonate anionic surfactants were not used, leading to a decrease in temperature and salinity resistance.

[0098] Experimental Example 2

[0099] Field tests were conducted on Examples 1-8 and Comparative Examples 1-2, and the daily oil level, oil-gas ratio, and recovery rate were statistically analyzed. The results are shown in Table 2.

[0100] Table 2. Field Test Results

[0101]

[0102] Table 2 shows that the field test results of Examples 1-3 of this application are better than those of Example 4. The commercially available viscosity reducer in Example 4 has poor temperature resistance, resulting in a decrease in daily oil level and a significant decrease in recovery rate. In Example 5, high-concentration, high-pressure, and rapid injection was used, which resulted in a decrease in the oil-gas ratio. The reason for this is that rapid spreading can be achieved in the early stage, but high pressure in the later stage leads to steam channeling, resulting in a decrease in the oil-gas ratio and recovery rate. Comparative Examples 1 and 2 use a single process. In Comparative Example 1, only steam injection is used, resulting in high crude oil viscosity, high flow resistance, and low recovery rate. In Comparative Example 2, the viscosity reducer cannot be effectively dispersed, resulting in a significant decrease in recovery rate.

[0103] The above description is merely an embodiment of this application, and the scope of protection of this application is not limited to these specific embodiments, but is determined by the claims of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the technical concept and principles of this application should be included within the scope of protection of this application.

Claims

1. An oil recovery process combining steam injection and viscosity reducer flooding, characterized in that, Includes the following steps: (1) Drill a set of injection wells and production wells in the selected heavy oil area, and inject viscosity reducer into the injection wells; (2) The steam injection and huffing effect of the production well establishes an effective displacement relationship with the injection well; (3) Change the way the viscosity reducer is injected into the injection well so that the production well can produce continuously; The viscosity reducer, by weight, comprises 60-80 parts of a composite surfactant, 10-15 parts of an organic solvent, 2-5 parts of an alkaline additive, and 0.5-1 parts of a thickener; The composite surfactant includes a polyoxyethylene ether nonionic surfactant and a modified petroleum sulfonate anionic surfactant, wherein the mass ratio of the polyoxyethylene ether nonionic surfactant to the modified petroleum sulfonate anionic surfactant is (1 ~ 3):1; In step (1), the injection of viscosity reducer into the injection well is carried out in three ways: low concentration high pressure rapid injection, low concentration medium pressure medium speed injection, and high concentration high pressure rapid injection; and / or in step (3), the method of injecting viscosity reducer is high concentration medium pressure low speed injection.

2. The oil recovery process combining steam injection and viscosity reducer flooding according to claim 1, characterized in that, The heavy oil zone has a reservoir depth of 1500 ~ 2000m, a permeability of 150×10-3 μm 2 ~ 300×10-3 μm 2, and a formation crude oil viscosity of 3000 ~ 4000mPa·s.

3. The oil recovery process combining steam injection and viscosity reducer flooding according to claim 1, characterized in that, The low-concentration high-pressure rapid injection is a 10-20% concentration, injected at 1500-2500 m³ / d under 20-30 MPa pressure for 5-15 days; the low-concentration medium-pressure medium-speed injection is a 10-20% concentration, injected at 500-800 m³ / d under 12-15 MPa pressure for 5-8 days; the high-concentration high-pressure rapid injection is a 20-30% concentration, injected at 1500-2500 m³ / d under 20-30 MPa pressure for 8-12 days.

4. The oil recovery process combining steam injection and viscosity reducer flooding according to claim 1, characterized in that, The high-concentration, medium-pressure, low-speed injection refers to an injection of 100-2003 mg / d at a concentration of 20-30% and a pressure of 12-15 MPa.

5. The oil recovery process combining steam injection and viscosity reducer flooding according to claim 1, characterized in that, In step (2), the steam injection and spitting effect is as follows: each round of steam injection is 1000 ~ 1500t, the steam injection rate is 200 ~ 300m3 / d, the well is shut down for 5 ~ 15 days, production lasts for 30 ~ 50 days, and there are 3 ~ 5 rounds of spitting.

6. The oil recovery process combining steam injection and viscosity reducer flooding according to claim 1, characterized in that, The organic solvent includes toluene or xylene; the alkaline additive includes sodium bicarbonate, sodium metaborate, triethanolamine, or sodium carbonate.

7. The oil recovery process combining steam injection and viscosity reducer flooding according to claim 1, characterized in that, The thickener includes sodium carboxymethyl cellulose and hydrophobically modified polyacrylamide, wherein the mass ratio of sodium carboxymethyl cellulose to hydrophobically modified polyacrylamide is (1 ~ 2):1.

Images