Profile control viscosity breaker, method for preparing the same, and method for enhanced oil recovery by combined displacement

Abstract

This invention discloses a profile control and viscosity reducing agent and its preparation method, as well as a method for improving oil recovery through composite displacement. The preparation method of the profile control and viscosity reducing agent includes the following steps: S1, under the presence of an acid-coating agent and water as a solvent, and in the atmosphere of nitrogen or an inert gas, sodium hydroquinone sulfonate and acryloyl chloride undergo a polymerization reaction to generate monomer C; S2, under the presence of a nitrogen or inert gas atmosphere, and in the presence of an initiator and water as a solvent, monomer C obtained in step S1, acrylic acid, and acrylamide undergo a polymerization reaction to generate the profile control and viscosity reducing agent. The method for improving oil recovery through composite displacement, using the above-mentioned profile control and viscosity reducing agent, includes the following steps: Step (1): Screening of water-driven heavy oil reservoir well groups; Step (2): Controlling the flow line of injection wells, implementing composite displacement methods for water wells according to different injection-production well distances; Step (3): Drainage line of production wells, using single-well adjustment technology according to different production wells with strong and weak flow lines.

Description

Technical Field

[0001] This invention relates to the field of heavy oil reservoir development technology, and in particular to a profile control and viscosity reducing agent and its preparation method, and a method for enhancing oil recovery through composite displacement. Background Technology

[0002] Heavy oil reservoirs, due to their high crude oil viscosity and high oil-water mobility ratio, will experience severe fingering during the water drive stage, exhibiting characteristics of "high water cut, low recovery rate, and low oil production rate".

[0003] Currently, the recovery rate of water-driven heavy oil reservoirs in Shengli Oilfield is generally below 20%, and in some reservoirs it is even below 10%. To address these issues, a viscosity-reducing system is injected into water-driven heavy oil reservoirs to reduce crude oil viscosity, improve the oil-water mobility ratio, and increase the recovery rate.

[0004] Field practice shows that the effectiveness of viscosity reduction and displacement in water-driven heavy oil reservoirs mainly exhibits the following two distinct characteristics: First, only some wells show effectiveness after viscosity reduction and displacement, and the effective period of these wells is short, lasting only 1 to 3 months, exhibiting the characteristic of "effectiveness followed by failure"; Second, for wells that do not show effectiveness, viscosity reduction and churn-and-purge are mainly used to promote the formation of new flow lines between oil and water wells, but the success rate of field implementation is low.

[0005] The main reasons for the above pattern are as follows: First, the viscosity-reducing system used for viscosity reduction and displacement has a weak profile control function, the injected water wave and volume change are not significant, the remaining oil is not displaced, resulting in a small increase in oil production in the well; Second, the implemented well huff and puff process is too simple and does not change the well group streamline distribution from the perspective of oil-water well linkage, so as to achieve the purpose of controlling strong streamlines and guiding weak streamlines.

[0006] To address the aforementioned technical problems, those skilled in the art have made tireless explorations. For example, Chinese invention patent application CN110129020A discloses a viscoelastic surfactant system and its application in water-driven heavy oil reservoir development. The viscoelastic surfactant system disclosed in this method has both regulating and viscosity-reducing effects, effectively reducing the viscosity of heavy oil and significantly reducing the viscosity of heavy oil in rock pores; at the same time, it can also increase the viscosity of the aqueous phase, reduce the mobility ratio, and increase the swept volume, which can effectively improve water-drive efficiency. However, the aforementioned patent application only proposes a displacement method that expands the swept volume by using a viscosity reducer with both regulating and viscosity-reducing effects from the injection end, without further proposing single-well huff and puff processes for different production wells, or specific methods for controlling strong streamlines, guiding weak streamlines, and adjusting the streamlines of well groups.

[0007] Chinese invention patent CN112983368B discloses a method for achieving balanced crude oil displacement through optimized injection-production synergistic chemical flooding. The method includes the following steps: determining the median particle size and elastic modulus of viscoelastic particles based on the average permeability of the reservoir; optimizing the concentration ratio of the total chemical agent concentration under certain conditions; statistically analyzing the physical properties of each layer, and combining the layers using entropy weight algorithm and centroid-based cluster analysis; calculating the optimal segmented plug volume ratio for single-well injection under the heterogeneous permeability characteristics of the layer system; establishing an objective function based on the coefficient of variation of remaining oil saturation, the oil enhancement effect of chemical flooding, and cost, and optimizing it using a numerical simulator; and obtaining the chemical agent concentration and dosage of each injection well segmented plug and the production rate of the production well based on the above results. This patent only proposes injecting viscoelastic particles with profile control function from the injection end to improve the waterflooding effect, without further proposing single-well huff-and-puff processes for different production wells, or specific methods for controlling strong streamlines, guiding weak streamlines, and adjusting well group streamlines.

[0008] In summary, there is currently no method for enhancing oil recovery by combining oil and water well linkage, which involves profile control, viscosity reduction, plugging, and enhanced flow lines in water wells, and multi-component fluid injection and drainage effects in oil wells. Summary of the Invention

[0009] Purpose of the invention: After injecting viscosity reducers into water-driven heavy oil reservoirs, the technical drawbacks include uneven effect on production wells, short effective time for oil wells, and small increase in oil production.

[0010] The main reasons for the above-mentioned technical shortcomings are as follows: First, the viscosity reduction system used for viscosity reduction and displacement has a weak profile control function, the injected water wave and volume change are not significant, the remaining oil is not displaced, resulting in a small increase in oil production in the well; Second, the implemented well huff and puff process is too simple and does not change the well group streamline distribution from the perspective of oil-water well linkage, so as to achieve the purpose of controlling strong streamlines and guiding weak streamlines.

[0011] To address the shortcomings of the prior art, this invention discloses a profile control and viscosity reducing agent and its preparation method, as well as a method for improving oil recovery through composite displacement.

[0012] The first objective of this invention is to provide a profile-adjusting and viscosity-reducing agent.

[0013] The second objective of this invention is to provide a method for preparing a profile-adjusting and viscosity-reducing agent.

[0014] The third objective of this invention is to provide a method for improving oil recovery through compound displacement.

[0015] Compared with traditional water-driven viscosity reduction processes for heavy oil reservoirs, this invention transforms the process from a single oil displacement method to a combined "washing, displacement, conditioning, and extraction" method, significantly improving the recovery rate of inefficient water-driven heavy oil reservoirs. Specifically:

[0016] The high-efficiency viscosity reducer of the present invention can achieve a viscosity increase ratio of ≥10.0 in the aqueous phase and a viscosity reduction rate of ≥60% in the oil phase, thus exerting a "washing and displacement" effect;

[0017] The oil-water well linkage method of the present invention can promote streamline development, achieve uniform diffusion of viscosity reducer, make full use of residual oil, and play a "regulating and guiding" effect.

[0018] The profile control and viscosity reducer disclosed in this invention is a highly efficient viscosity reducer with profile control properties (the profile control effect is mainly achieved by increasing the viscosity of the aqueous phase and improving the oil-water mobility ratio, specific data are shown in Table 1). It belongs to polymer-type water-soluble surfactants. The partially hydrolyzed amide and carboxyl groups adsorb and capture water molecules. Water molecules enter the profile control and viscosity reducer molecules and combine with the amide and carboxyl groups, increasing the degree of molecular chain expansion, resulting in increased flow resistance and forming a gel network flocculent. At the same time, upon contact with oil, sulfonate ions reduce the interfacial tension of oil molecules, and benzene rings attract asphaltenes molecules, destroying the asphaltenes molecular structure and reducing the flow resistance of heavy oil. Ultimately, it achieves the performance of profile control in the aqueous phase and viscosity reduction in the oil phase.

[0019] Technical solution: Profile control and viscosity reducing agent, wherein the profile control and viscosity reducing agent has structural unit A, structural unit B and structural unit C, wherein structural unit A has the structure shown in formula (1), structural unit B has the structure shown in formula (2) and structural unit C has the structure shown in formula (3), wherein the molar ratio of structural unit A, structural unit B and structural unit C is (10000~700000):(10000~600000):(5000~20000), and the molecular weight of the profile control and viscosity reducing agent is 2 million to 40 million, preferably 10 million to 15 million;

[0020]

[0021] Furthermore, the molar ratio of structural unit A, structural unit B, and structural unit C is (50000~80000):(30000~60000):(8000~10000).

[0022] The profile control and viscosity reducer has the following structural formula:

[0023]

[0024] Where: a = 10000~700000; preferably a = 50000~80000;

[0025] b = 10000~600000; preferably b = 30000~60000;

[0026] c = 5000~20000; preferably c = 8000~10000;

[0027] The molecular weight of the profile-adjusting and viscosity-reducing agent is 2 million to 40 million, preferably 10 million to 15 million.

[0028] The preparation method of the profile control and viscosity reducer described in any of the above-mentioned methods includes the following steps:

[0029] S1. Under the presence of an acid-coating agent and water as a solvent, sodium hydroquinone sulfonate and acryloyl chloride are polymerized in a nitrogen or inert gas atmosphere to generate monomer C, wherein: monomer C has the structure shown in formula (4).

[0030]

[0031] S2. Under a nitrogen or inert gas atmosphere, and in the presence of an initiator and water as a solvent, the monomer C, acrylic acid, and acrylamide obtained in step S1 undergo a polymerization reaction to generate a profile control and viscosity reducer.

[0032] The preparation method of the profile control and viscosity reducer described in any of the above-mentioned methods includes the following steps:

[0033] (1) Sodium hydroquinone sulfonate and solvent water are added to a reactor equipped with a stirrer and stirred thoroughly to dissolve it in water at a stirring speed of at least 300 rpm, preferably 300-400 rpm. Then, triethylamine and / or 4-dimethylaminopyridine are added as acid-absorbing agents and stirred thoroughly to bring the pH value to 7.5-8.5. After maintaining this pH value for at least 30 minutes, the reactor is placed in an ice-water bath and acryloyl chloride is added dropwise. Nitrogen or inert gas is introduced for at least 10 minutes, preferably 10-20 minutes. After the reaction has proceeded for at least 1 hour, preferably 1-2 hours, the solvent is removed by rotary evaporation under reduced pressure to obtain monomer C. Monomer C has the structure shown in formula (4), wherein:

[0034] The amount of acryloyl chloride is 2.1-2.5 times the amount of sodium hydroquinone sulfonate;

[0035] The amount of the acid-coating agent used, by molar amount, is 0.5-0.8 times that of sodium hydroquinone sulfonate;

[0036]

[0037] (2) Dissolve monomer C, acrylic acid, acrylamide and solvent water in a reactor and stir at a stirring speed of at least 500 rpm, preferably 500-600 rpm, to disperse it evenly in water. Adjust the pH value to 8-8.5 with an aqueous solution of an alkaline substance. Add the prepared solution to the reaction vessel and circulate the 0°C ice-water mixture to the outside of the reaction vessel for cooling for 30-45 minutes. At the same time, introduce nitrogen or inert gas to stabilize the pressure of the reaction vessel at 1-2 MPa. Add sodium peroxide / sodium bisulfite mixture as an initiator and stir with a magnetic levitation stirrer at a stirring speed of at least 400 rpm, preferably 400-500 rpm. After reacting for at least 2 hours, cut the glue block into pieces, dry and grind it to obtain white polymer powder. Wash the white polymer powder repeatedly with ethanol at least three times and dry it in an oven at at least 80°C, preferably 80-85°C, for at least 1 hour to obtain the profile adjuster and viscosity reducer.

[0038] The profile control and viscosity reducer is prepared by the above-described preparation method.

[0039] Application of profile control and viscosity reduction agents in composite displacement operations of oil extraction.

[0040] The method for enhancing oil recovery through combined displacement, using the aforementioned profile control and viscosity reducing agents, includes the following steps:

[0041] Step (1): Screening of water-driven heavy oil reservoir well groups;

[0042] Step (2): Injection well control flow line, and implement composite displacement method for water wells with different injection and production well distances;

[0043] Step (3): Production well diversion line, the single-well adjustment process is adopted according to the different production wells with strong and weak flow lines.

[0044] The main design concept of this invention is as follows:

[0045] (1) A profile control and viscosity reducing agent was developed. Unlike traditional viscosity reducing agents, this profile control and viscosity reducing agent is a water-soluble polymer surfactant. It not only has a single viscosity reducing property, but also has a profile control effect (as shown in Table 3, the viscosity increase ratio of different viscosity reducing agents in the aqueous phase. When this substance is mixed with the aqueous phase, it can increase the viscosity of the aqueous phase. When it is mixed with the oil phase, it can decrease the viscosity of the oil phase, thereby achieving the purpose of profile control and improving the fluidity of heavy oil). When this substance is mixed with the aqueous phase, it can increase the viscosity of the aqueous phase. When it is mixed with the oil phase, it can decrease the viscosity of the oil phase, thereby achieving the purpose of profile control, improving the fluidity of heavy oil, and realizing the "washing and displacement" effect of the well group.

[0046] (2) For different injection-production well spacing, water wells adopt different "profile adjustment + displacement" methods to achieve balanced sweep;

[0047] (3) Based on the streamline distribution of the well group, different composite fluid viscosity reduction and injection processes are adopted for oil wells with strong and weak streamlines to achieve uniform development of streamlines in the well group.

[0048] Effects of the Invention: The profile control and viscosity reducing agent and its preparation method disclosed in this invention, as well as the method for improving oil recovery through composite displacement, have the following beneficial effects:

[0049] (1) The profile control and viscosity reducer disclosed in this invention is a polymer-type water-soluble surfactant. The partially hydrolyzed amide and carboxyl groups adsorb and capture water molecules. Water molecules enter the profile control and viscosity reducer molecules and combine with amide and carboxyl groups, which increases the degree of molecular chain expansion, resulting in increased flow resistance and forming a gel network flocculent. At the same time, after encountering oil, sulfonate ions reduce the interfacial tension of oil molecules, and benzene rings attract asphaltene molecules, destroying the asphaltene molecular structure and reducing the flow resistance of heavy oil. Ultimately, it achieves the performance of profile control in the aqueous phase and viscosity reduction in the oil phase.

[0050] (2) The high-efficiency viscosity reducer with profile control properties described in this invention can achieve a viscosity increase ratio of ≥10.0 in the aqueous phase and a viscosity reduction rate of ≥60% in the oil phase (see Table 3 for specific data);

[0051] (3) The injection well control flow line described in this invention is that the water well injects different combinations of viscosity reducers, nitrogen and foaming agents into the sluice block according to different injection and production well distances; the water phase viscosity-enhancing function of the high-efficiency viscosity reducer is used to slow down the water phase fingering and control the strong flow line; at the same time, the volume of injected water is expanded to form a weak flow line to drive away the remaining oil between the oil and water wells.

[0052] (4) The production well diversion line described in this invention is that the oil well adopts different diversion processes according to the different degrees of streamline development; strong streamlines are controlled by nitrogen and foaming agent; and the oil phase viscosity reduction function of high efficiency viscosity reducer is used to start crude oil in the near-wellbore zone and guide the formation of weak streamlines.

[0053] (5) The composite displacement enhanced oil recovery process provided by this invention transforms the single oil displacement into a composite oil displacement involving "washing, displacement, adjustment, and introduction," significantly improving the recovery rate of water-driven heavy oil reservoirs. Based on field test data, after adopting this method, inefficient water-driven heavy oil reservoirs can achieve efficient development with an input-output ratio higher than 1:2. Attached Figure Description

[0054] Figure 1 The infrared spectrum of the profile-adjusting and viscosity-reducing agent prepared in Example 1.

[0055] Figure 2 This is a streamline distribution diagram of the well group in Example 2.

[0056] Figure 3 This is a daily curve diagram of the well group in Example 2. Detailed Implementation

[0057] The specific embodiments of the present invention are described in detail below.

[0058] The "range" disclosed in this invention is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 10–50 is listed for a specific parameter, it is also expected that ranges of 10–40 and 20–50 are also included. Furthermore, if the minimum range values ​​are 1 and 2, and the maximum range values ​​are 3, 4, and 5, then the following ranges are all expected: 1–3, 1–4, 1–5, 2–3, 2–4, and 2–5. In this application, unless otherwise stated, the numerical range "a–b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0–5" means that all real numbers between "0–5" have been listed herein; "0–5" is merely a shortened representation of these numerical combinations.

[0059] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0060] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0061] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0062] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0063] Unless otherwise specified, the reaction will proceed under normal temperature and pressure conditions.

[0064] Unless otherwise specified, all parts or percentages are by weight or by weight percentage.

[0065] In this invention, all the substances used are known substances that can be purchased or synthesized by known methods.

[0066] In this invention, all the devices or equipment used are conventional devices or equipment known in the art and are readily available.

[0067] The technical synthesis route of the profile control and viscosity reducer of the present invention is as follows:

[0068]

[0069] A profile control and viscosity reducing agent, wherein the profile control and viscosity reducing agent has structural unit A, structural unit B and structural unit C, wherein structural unit A has the structure shown in formula (1), structural unit B has the structure shown in formula (2) and structural unit C has the structure shown in formula (3), wherein the molar ratio of structural unit A, structural unit B and structural unit C is (10000~700000):(10000~600000):(5000~20000), and the molecular weight of the profile control and viscosity reducing agent is 2 million to 40 million, preferably 10 million to 15 million;

[0070]

[0071] Furthermore, the molar ratio of structural unit A, structural unit B, and structural unit C is (50000~80000):(30000~60000):(8000~10000).

[0072] The profile control and viscosity reducer has the following structural formula:

[0073]

[0074] Where: a = 10000~700000; preferably a = 50000~80000;

[0075] b = 10000~600000; preferably b = 30000~60000;

[0076] c = 5000~20000; preferably c = 8000~10000;

[0077] The molecular weight of the profile-adjusting and viscosity-reducing agent is 2 million to 40 million, preferably 10 million to 15 million.

[0078] The preparation method of the profile control and viscosity reducer described in any of the above-mentioned methods includes the following steps:

[0079] S1. Under the presence of an acid-coating agent and water as a solvent, sodium hydroquinone sulfonate and acryloyl chloride are polymerized in a nitrogen or inert gas atmosphere to generate monomer C, wherein: monomer C has the structure shown in formula (4).

[0080]

[0081] S2. Under a nitrogen or inert gas atmosphere, and in the presence of an initiator and water as a solvent, the monomer C, acrylic acid, and acrylamide obtained in step S1 undergo a polymerization reaction to generate a profile control and viscosity reducer.

[0082] Further, the acid-coating agent in step S1 is triethylamine and / or 4-dimethylaminopyridine, wherein:

[0083] The amount of the acid-coating agent used, by molar amount, is 0.5-0.8 times that of sodium hydroquinone sulfonate.

[0084] Further, the initiator in step S2 is sodium peroxide / sodium bisulfite, wherein:

[0085] The molar ratio of sodium peroxide to sodium bisulfite is 1:3 to 4;

[0086] The amount of sodium peroxide used is 0.05 to 0.1 times the amount of sodium hydroquinone sulfonate used, by molar amount.

[0087] Furthermore, the polymerization reaction in step S1 is carried out at a reaction temperature of at least 0°C, preferably 0 to 5°C, and the reaction time is controlled at at least 30 minutes, preferably 30 to 60 minutes.

[0088] Further, the molar ratio of acryloyl chloride in step S1, sodium hydroquinone sulfonate in step S1, acrylic acid in step S2, and acrylamide in step S2 is (2.1-2.5):1:(8.2-8.5):(16.4-17).

[0089] Furthermore, in step S1, the amount of water used as the solvent is 10 to 18 times that of sodium hydroquinone sulfonate, by molar amount.

[0090] The preparation method of the profile control and viscosity reducer described in any of the above-mentioned methods includes the following steps:

[0091] (1) Sodium hydroquinone sulfonate and solvent water are added to a reactor equipped with a stirrer and stirred thoroughly to dissolve it in water at a stirring speed of at least 300 rpm, preferably 300-400 rpm. Then, triethylamine and / or 4-dimethylaminopyridine are added as acid-absorbing agents and stirred thoroughly to bring the pH value to 7.5-8.5. After maintaining this pH value for at least 30 minutes, the reactor is placed in an ice-water bath and acryloyl chloride is added dropwise. Nitrogen or inert gas is introduced for at least 10 minutes, preferably 10-20 minutes. After the reaction has proceeded for at least 1 hour, preferably 1-2 hours, the solvent is removed by rotary evaporation under reduced pressure to obtain monomer C. Monomer C has the structure shown in formula (4), wherein:

[0092] The amount of acryloyl chloride is 2.1-2.5 times the amount of sodium hydroquinone sulfonate;

[0093] The amount of the acid-coating agent used, by molar amount, is 0.5-0.8 times that of sodium hydroquinone sulfonate;

[0094]

[0095] (2) Dissolve monomer C, acrylic acid, acrylamide and solvent water in a reactor and stir at a stirring speed of at least 500 rpm, preferably 500-600 rpm, to disperse it evenly in water. Adjust the pH value to 8-8.5 with an aqueous solution of an alkaline substance. Add the prepared solution to the reaction vessel and circulate the 0°C ice-water mixture to the outside of the reaction vessel for cooling for 30-45 minutes. At the same time, introduce nitrogen or inert gas to stabilize the pressure of the reaction vessel at 1-2 MPa. Add sodium peroxide / sodium bisulfite mixture as an initiator and stir with a magnetic levitation stirrer at a stirring speed of at least 400 rpm, preferably 400-500 rpm. After reacting for at least 2 hours, cut the glue block into pieces, dry and grind it to obtain white polymer powder. Wash the white polymer powder repeatedly with ethanol at least three times and dry it in an oven at at least 80°C, preferably 80-85°C, for at least 1 hour to obtain the profile adjuster and viscosity reducer.

[0096] Furthermore, the alkaline substance mentioned in step (2) is one or more of sodium carbonate, sodium bicarbonate, sodium hydroxide, and ammonia water.

[0097] The profile control and viscosity reducer is prepared by the above-described preparation method.

[0098] Application of profile control and viscosity reduction agents in composite displacement operations of oil extraction.

[0099] The method for enhancing oil recovery through combined displacement, using the aforementioned profile control and viscosity reducing agents, includes the following steps:

[0100] Step (1): Screening of water-driven heavy oil reservoir well groups;

[0101] Step (2): Injection well control flow line, and implement composite displacement method for water wells with different injection and production well distances;

[0102] Step (3): Production well diversion line, the single-well adjustment process is adopted according to the different production wells with strong and weak flow lines.

[0103] Furthermore, the selection criteria for water-driven heavy oil reservoir well groups in step (1) are as follows:

[0104] Well group recovery rate <30%; permeability greater than 100×10 －3 μm 2 The water injection time exceeds 2 years, and the viscosity of the formation crude oil is less than 1000 mPa·s.

[0105] Furthermore, the specific steps of step (2) are as follows:

[0106] (21) When 50 meters < well spacing ≤ 100 meters, based on the original daily water injection volume of the injection well, first inject 8% to 10% of the above-mentioned profile control and viscosity reducing agent into the injection well for at least one month, preferably one to three months. Then inject a foaming agent and nitrogen. The amount of foaming agent injected is 1% to 3% of the original daily water injection volume of the injection well. The foaming agent injection time is at least one week, preferably one to two weeks, and the gas-liquid ratio is 1:1 to 3:1, wherein:

[0107] The foaming agent is one of the following: sulfonate foaming agents and polyether foaming agents;

[0108] (22) When 100 meters < well spacing ≤ 200 meters, based on the original daily water injection volume of the injection well, inject 5% to 7% of the above-mentioned profile control and viscosity reducing agent into the injection well for at least 3 months, at least 3 to 6 months. Then inject a foaming agent and nitrogen. The amount of foaming agent injected is 1 to 3% of the original daily water injection volume of the injection well, and the injection time is at least 0.5 months, preferably 0.5 to 1 month. The gas-liquid ratio is 1:1 to 3:1, wherein:

[0109] The foaming agent is one of the following: sulfonate foaming agents and polyether foaming agents;

[0110] (23) When 200 meters < well spacing ≤ 300 meters, based on the original daily water injection volume of the injection well, the injection well continuously injects 2% to 4% of the above-mentioned profile adjustment and viscosity reducing agent.

[0111] (24) When the well spacing is greater than 300 meters, the above-mentioned profile adjustment and viscosity reduction agent is injected at high pressure into the injection well based on the original daily water injection volume of the injection well.

[0112] Furthermore, the specific steps of step (3) are as follows:

[0113] (31) When the oil well is a mainstream production well: For production wells with a water cut greater than or equal to 85%, based on the daily injection rate of the mainstream production well, inject a combination of high-concentration profile control and viscosity reducer + foaming agent + nitrogen + oil-soluble viscosity reducer + carbon dioxide in sequence:

[0114] First, a high-concentration profile control and viscosity reducer, a foaming agent, and nitrogen are injected sequentially as a plug. The high-concentration profile control and viscosity reducer has a concentration of 5% to 10% and an injection volume of 500 to 1000 cubic meters. Nitrogen is injected at a volume of 20,000 to 40,000 cubic meters, with a gas-liquid ratio of 1:1 to 3:1. The foaming agent is either a sulfonate foaming agent or a polyether foaming agent.

[0115] Next, an oil-soluble viscosity reducer and carbon dioxide are injected as a drain line plug, wherein: the oil-soluble viscosity reducer is one of aromatic hydrocarbon solvents or heavy alkyl solvents, and the injection intensity of the oil-soluble viscosity reducer is 1-5 t / m; the injection intensity of carbon dioxide is 15-40 t / m;

[0116] (32) When the oil well is a weakly streamlined oil well: For production wells with a water cut of less than 85%, based on the daily injection rate of the weakly streamlined oil well, inject nitrogen + low-concentration profile control and viscosity reducer + oil-soluble viscosity reducer + carbon dioxide combination in sequence:

[0117] First, inject 20,000 to 40,000 standard cubic meters of nitrogen to pressurize water and replenish formation energy;

[0118] Subsequently, 1% to 5% of the above-mentioned profile control and viscosity reducing agent is injected;

[0119] Finally, an oil-soluble viscosity reducer and carbon dioxide are injected, wherein:

[0120] The oil-soluble viscosity reducer is one of the aromatic hydrocarbon solvents and heavy alkyl solvents, and the injection strength of the oil-soluble viscosity reducer is 3-5 t / m;

[0121] The carbon dioxide injection intensity is 15–40 t / m.

[0122] Furthermore, the aromatic hydrocarbon solvent is one of benzene, toluene, o-xylene, m-xylene, p-xylene, or petroleum hydrocarbon solvents.

[0123] Furthermore, the heavy alkyl solvent is one of xylene, tetramethylbenzene, or polycyclic aromatic hydrocarbons.

[0124] In one embodiment:

[0125] The profile control and viscosity reducing agent has structural unit A, structural unit B, and structural unit C. Structural unit A has the structure shown in formula (1), structural unit B has the structure shown in formula (2), and structural unit C has the structure shown in formula (3). The molar ratio of structural unit A, structural unit B, and structural unit C is 10000:10000:5000, and the molecular weight of the profile control and viscosity reducing agent is 2 million.

[0126]

[0127] In another embodiment, the molar ratio of structural unit A, structural unit B, and structural unit C is 50000:30000:8000, and the molecular weight of the profile control and viscosity reducer is 10 million.

[0128] The profile control and viscosity reducer has the following structural formula:

[0129]

[0130] Where: a = 10000;

[0131] b = 10000;

[0132] c = 5000;

[0133] The molecular weight of the profile-adjusting and viscosity-reducing agent is 2 million.

[0134] In another embodiment, the profile-adjusting viscosity reducer has the following structural formula:

[0135]

[0136] a = 50000, b = 30000, c = 8000, and the molecular weight of the profile-adjusting and viscosity-reducing agent is 10 million.

[0137] The preparation method of the profile control and viscosity reducer described in any of the above-mentioned methods includes the following steps:

[0138] S1. Under the presence of an acid-coating agent and water as a solvent, sodium hydroquinone sulfonate and acryloyl chloride are polymerized in a nitrogen atmosphere to generate monomer C, wherein: monomer C has the structure shown in formula (4).

[0139]

[0140] S2. Under a nitrogen atmosphere, in the presence of an initiator and water as a solvent, the monomer C, acrylic acid, and acrylamide obtained in step S1 undergo a polymerization reaction to generate a profile control and viscosity reducer.

[0141] Further, the acid-applying agent in step S1 is triethylamine, wherein:

[0142] The amount of the acid-coating agent used is 0.5 times that of sodium hydroquinone sulfonate, by molar amount.

[0143] Further, the initiator in step S2 is sodium peroxide / sodium bisulfite, wherein:

[0144] The molar ratio of sodium peroxide to sodium bisulfite is 1:3;

[0145] The amount of sodium peroxide used is 0.05 times the amount of sodium hydroquinone sulfonate used, by molar amount.

[0146] Furthermore, the polymerization reaction in step S1 is carried out at a temperature of 0°C and the reaction time is controlled at 60 minutes.

[0147] Furthermore, the molar ratio of acryloyl chloride in step S1, sodium hydroquinone sulfonate in step S1, acrylic acid in step S2, and acrylamide in step S2 is 2.1:1:8.2:16.4.

[0148] Furthermore, in step S1, the amount of water used as the solvent is 10 times that of sodium hydroquinone sulfonate, by molar amount.

[0149] The preparation method of the profile control and viscosity reducer described in any of the above-mentioned methods includes the following steps:

[0150] (1) Sodium hydroquinone sulfonate and solvent water were added to a reactor equipped with a stirrer and stirred thoroughly to dissolve it in water at a stirring rate of 300 rpm. Then, triethylamine was added as an acidifying agent and stirred thoroughly until the pH reached 7.5. After maintaining this pH for 90 minutes, the reactor was placed in an ice-water bath and acryloyl chloride was added dropwise. Nitrogen gas was introduced and purged for 10 minutes. After the reaction had proceeded for 2 hours, the solvent was removed by rotary evaporation under reduced pressure to obtain monomer C. Monomer C has the structure shown in formula (4), wherein:

[0151] The amount of acryloyl chloride is 2.1 times the amount of sodium hydroquinone sulfonate;

[0152] The amount of the acid-coating agent used, by molar amount, is 0.5 times that of sodium hydroquinone sulfonate;

[0153]

[0154] (2) Dissolve monomer C, acrylic acid, acrylamide and solvent water in a reactor and stir at a stirring rate of 500 rpm to disperse it evenly in water. Adjust the pH value to 8 with an aqueous solution of alkaline substance. Add the prepared solution to the reactor. Circulate the 0°C ice-water mixture to the outside of the reactor for 30 min to cool it down. At the same time, introduce nitrogen gas to stabilize the pressure of the reactor at 1 MPa. Add sodium peroxide / sodium bisulfite mixture as an initiator and stir with a magnetic levitation stirrer at a stirring rate of 400 rpm. After 6 hours of reaction, cut the glue block into pieces, dry and grind it to obtain white polymer powder. Wash the white polymer powder repeatedly with ethanol 3 times and dry it in an oven at 80°C for 9 hours to obtain the profile adjuster and viscosity reducer.

[0155] Furthermore, the alkaline substance mentioned in step (2) is sodium carbonate.

[0156] The profile control and viscosity reducer is prepared by the above-described preparation method.

[0157] Application of profile control and viscosity reduction agents in composite displacement operations of oil extraction.

[0158] The method for enhancing oil recovery through combined displacement, using the aforementioned profile control and viscosity reducing agents, includes the following steps:

[0159] Step (1): Screening of water-driven heavy oil reservoir well groups;

[0160] Step (2): Injection well control flow line, and implement composite displacement method for water wells with different injection and production well distances;

[0161] Step (3): Production well diversion line, the single-well adjustment process is adopted according to the different production wells with strong and weak flow lines.

[0162] Furthermore, the selection criteria for water-driven heavy oil reservoir well groups in step (1) are as follows:

[0163] Well group recovery rate <30%; permeability greater than 100×10 －3 μm 2 The water injection time exceeds 2 years, and the viscosity of the formation crude oil is less than 1000 mPa·s.

[0164] Furthermore, the specific steps of step (2) are as follows:

[0165] (21) When 50 meters < well spacing ≤ 100 meters, based on the original daily water injection volume of the injection well, the injection well first injects 8% of the above-mentioned profile control and viscosity reducing agent for 3 months, followed by the injection of foaming agent and nitrogen. The injection volume of foaming agent is 1% of the original daily water injection volume of the injection well, and the injection time of foaming agent is 2 weeks. The gas-liquid ratio is 1:1, wherein:

[0166] The foaming agent is a sulfonate foaming agent;

[0167] (22) When 100 meters < well spacing ≤ 200 meters, based on the original daily water injection volume of the injection well, inject 5% of the above-mentioned profile control and viscosity reducing agent into the injection well for 6 months. Then, inject a foaming agent and nitrogen. The amount of foaming agent injected is 3% of the original daily water injection volume of the injection well, and the injection time is 1 month. The gas-liquid ratio is 1:1, wherein:

[0168] The foaming agent is a sulfonate foaming agent;

[0169] (23) When 200 meters < well spacing ≤ 300 meters, based on the original daily water injection volume of the injection well, 2% of the above-mentioned profile adjustment and viscosity reducing agent is continuously injected into the injection well.

[0170] (24) When the well spacing is greater than 300 meters, the injection well shall be injected with 0.5% of the above-mentioned profile adjustment and viscosity reducing agent under high pressure, based on the original daily injection volume of the injection well.

[0171] Furthermore, the specific steps of step (3) are as follows:

[0172] (31) When the oil well is a mainstream production well: For production wells with a water cut greater than or equal to 85%, based on the daily injection rate of the mainstream production well, inject a combination of high-concentration profile control and viscosity reducer + foaming agent + nitrogen + oil-soluble viscosity reducer + carbon dioxide in sequence:

[0173] First, a high-concentration profile control and viscosity reducer, a foaming agent, and nitrogen are injected sequentially as a plugging slug. The high-concentration profile control and viscosity reducer has a concentration of 5% and an injection volume of 500 cubic meters. 20,000 cubic meters of nitrogen are injected, with a gas-liquid ratio of 1:1. The foaming agent is a sulfonate foaming agent.

[0174] Next, an oil-soluble viscosity reducer and carbon dioxide are injected as a drain line plug, wherein: the oil-soluble viscosity reducer is an aromatic hydrocarbon solvent, the injection intensity of the oil-soluble viscosity reducer is 1t / m; and the injection intensity of carbon dioxide is 150t / m.

[0175] (32) When the oil well is a weakly streamlined oil well: For production wells with a water cut of less than 85%, based on the daily injection rate of the weakly streamlined oil well, inject nitrogen + low-concentration profile control and viscosity reducer + oil-soluble viscosity reducer + carbon dioxide combination in sequence:

[0176] First, inject 20,000 standard cubic meters of nitrogen to pressurize the water and replenish the formation energy;

[0177] Subsequently, 1% of the aforementioned profile control and viscosity reducer was injected;

[0178] Finally, an oil-soluble viscosity reducer and carbon dioxide are injected, wherein:

[0179] The oil-soluble viscosity reducer is an aromatic hydrocarbon solvent, and the injection strength of the oil-soluble viscosity reducer is 3-5 t / m;

[0180] The carbon dioxide injection intensity is 15–40 t / m.

[0181] Furthermore, the aromatic hydrocarbon solvent is benzene. In another embodiment, the aromatic hydrocarbon solvent is toluene. In another embodiment, the aromatic hydrocarbon solvent is o-xylene. In another embodiment, the aromatic hydrocarbon solvent is m-xylene. In another embodiment, the aromatic hydrocarbon solvent is p-xylene. In yet another embodiment, the aromatic hydrocarbon solvent is a petroleum hydrocarbon solvent.

[0182] In another embodiment

[0183] The profile control and viscosity reducing agent has structural unit A, structural unit B, and structural unit C. Structural unit A has the structure shown in formula (1), structural unit B has the structure shown in formula (2), and structural unit C has the structure shown in formula (3). The molar ratio of structural unit A, structural unit B, and structural unit C is 700,000:600,000:20,000, and the molecular weight of the profile control and viscosity reducing agent is 40 million.

[0184]

[0185] In another embodiment, the molar ratio of structural unit A, structural unit B, and structural unit C is 80000:60000:10000, and the molecular weight of the profile control and viscosity reducer is 15 million. The profile control and viscosity reducer has the following structural formula:

[0186]

[0187] Where: a = 700000;

[0188] b = 600000;

[0189] c = 20000;

[0190] The molecular weight of the profile-adjusting and viscosity-reducing agent is 40 million.

[0191] In another embodiment, the profile-adjusting viscosity reducer has the following structural formula:

[0192]

[0193] Where: a = 80000;

[0194] b = 60000;

[0195] c = 10000;

[0196] The molecular weight of the profile-adjusting and viscosity-reducing agent is 15 million.

[0197] The preparation method of the profile control and viscosity reducer described in any of the above-mentioned methods includes the following steps:

[0198] S1. Under the presence of an acid-coating agent and water as a solvent, sodium hydroquinone sulfonate and acryloyl chloride are polymerized in a helium atmosphere to generate monomer C, wherein: monomer C has the structure shown in formula (4).

[0199]

[0200] S2. Under a helium atmosphere, in the presence of an initiator and water as a solvent, the monomer C, acrylic acid, and acrylamide obtained in step S1 undergo a polymerization reaction to generate a profile control and viscosity reducer.

[0201] Further, the acid-applying agent in step S1 is 4-dimethylaminopyridine, wherein:

[0202] The amount of the acid-coating agent used is 0.8 times that of sodium hydroquinone sulfonate, by molar amount.

[0203] Further, the initiator in step S2 is sodium peroxide / sodium bisulfite, wherein:

[0204] The molar ratio of sodium peroxide to sodium bisulfite is 1:4;

[0205] The amount of sodium peroxide used is 0.1 times the amount of sodium hydroquinone sulfonate used, by molar amount.

[0206] Furthermore, the polymerization reaction in step S1 is carried out at a temperature of 5°C and the reaction time is controlled at 30 minutes.

[0207] Furthermore, the molar ratio of acryloyl chloride in step S1, sodium hydroquinone sulfonate in step S1, acrylic acid in step S2, and acrylamide in step S2 is 2.5:1:8.5:17.

[0208] Furthermore, in step S1, the amount of water used as the solvent is 18 times that of sodium hydroquinone sulfonate, by molar amount.

[0209] The preparation method of the profile control and viscosity reducer described in any of the above-mentioned methods includes the following steps:

[0210] (1) Sodium hydroquinone sulfonate and solvent water were added to a reactor equipped with a stirrer and stirred thoroughly to dissolve it in water at a stirring speed of at least 400 rpm. Then, 4-dimethylaminopyridine was added as an acid-absorbing agent and stirred thoroughly until the pH reached 8.5. After maintaining this pH for 30 minutes, the reactor was placed in an ice-water bath and acryloyl chloride was added dropwise. Helium gas was introduced and the gas flow time was 20 min. After the reaction was completed, the solvent was removed by rotary evaporation under reduced pressure to obtain monomer C. Monomer C has the structure shown in formula (4), wherein:

[0211] The amount of acryloyl chloride is 2.5 times the amount of sodium hydroquinone sulfonate;

[0212] The amount of the acid-coating agent used, by molar amount, is 0.8 times that of sodium hydroquinone sulfonate;

[0213]

[0214] (2) Dissolve monomer C, acrylic acid, acrylamide and solvent water in a reactor and stir at a stirring rate of 600 rpm to disperse it evenly in water. Adjust the pH value to 8.5 with an aqueous solution of alkaline substance. Add the prepared solution to the reaction vessel and circulate the 0°C ice-water mixture to the outside of the reaction vessel for 45 min to cool it down. At the same time, helium gas is introduced to stabilize the pressure of the reaction vessel at 2 MPa. Add sodium peroxide / sodium bisulfite mixture initiator and stir with a magnetic levitation stirrer at a stirring rate of 500 rpm. After the reaction is completed for 5 hours, the glue block is cut into pieces, dried and ground to obtain white polymer dry powder. Wash the white polymer dry powder repeatedly with ethanol 6 times and dry it in an oven at 85°C for 1 hour to obtain the profile adjuster and viscosity reducer.

[0215] Further, the alkaline substance in step (2) is sodium bicarbonate. In another embodiment, the alkaline substance in step (2) is sodium hydroxide. In yet another embodiment, the alkaline substance in step (2) is ammonia.

[0216] The profile control and viscosity reducer is prepared by the above-described preparation method.

[0217] Application of profile control and viscosity reduction agents in composite displacement operations of oil extraction.

[0218] The method for enhancing oil recovery through combined displacement, using the aforementioned profile control and viscosity reducing agents, includes the following steps:

[0219] Step (1): Screening of water-driven heavy oil reservoir well groups;

[0220] Step (2): Injection well control flow line, and implement composite displacement method for water wells with different injection and production well distances;

[0221] Step (3): Production well diversion line, the single-well adjustment process is adopted according to the different production wells with strong and weak flow lines.

[0222] Furthermore, the selection criteria for water-driven heavy oil reservoir well groups in step (1) are as follows:

[0223] Well group recovery rate <30%; permeability greater than 100×10 －3 μm 2 The water injection time exceeds 2 years, and the viscosity of the formation crude oil is less than 1000 mPa·s.

[0224] Furthermore, the specific steps of step (2) are as follows:

[0225] (21) When 50 meters < well spacing ≤ 100 meters, based on the original daily water injection volume of the injection well, the injection well first injects 10% of the above-mentioned profile control and viscosity reducing agent for 3 months, followed by the injection of foaming agent and nitrogen. The injection volume of foaming agent is 3% of the original daily water injection volume of the injection well, and the injection time of foaming agent is 2 weeks. The gas-liquid ratio is 3:1, wherein:

[0226] The foaming agent is a polyether-based foaming agent;

[0227] (22) When 100 meters < well spacing ≤ 200 meters, based on the original daily water injection volume of the injection well, inject 7% of the above-mentioned profile control and viscosity reducing agent into the injection well for 6 months. Then, inject a foaming agent and nitrogen. The amount of foaming agent injected is 3% of the original daily water injection volume of the injection well, and the injection time is 1 month. The gas-liquid ratio is 3:1, wherein:

[0228] The foaming agent is a polyether-based foaming agent;

[0229] (23) When 200 meters < well spacing ≤ 300 meters, based on the original daily water injection volume of the injection well, 4% of the above-mentioned profile adjustment and viscosity reducing agent is continuously injected into the injection well.

[0230] (24) When the well spacing is greater than 300 meters, the injection well shall be injected with 2% of the above-mentioned profile adjustment and viscosity reducing agent under high pressure, based on the original daily injection volume of the injection well.

[0231] Furthermore, the specific steps of step (3) are as follows:

[0232] (31) When the oil well is a mainstream production well: For production wells with a water cut greater than or equal to 85%, based on the daily injection rate of the mainstream production well, inject a combination of high-concentration profile control and viscosity reducer + foaming agent + nitrogen + oil-soluble viscosity reducer + carbon dioxide in sequence:

[0233] First, a high-concentration profile control and viscosity reducer, a foaming agent, and nitrogen are injected sequentially as a plug. The high-concentration profile control and viscosity reducer has a concentration of 10% and an injection volume of 1000 cubic meters. Nitrogen is injected at a volume of 40,000 cubic meters with a gas-liquid ratio of 3:1. The foaming agent is a polyether-based foaming agent.

[0234] Next, an oil-soluble viscosity reducer and carbon dioxide are injected as a drain line plug, wherein: the oil-soluble viscosity reducer is a heavy alkyl solvent, the injection intensity of the oil-soluble viscosity reducer is 5t / m; and the injection intensity of carbon dioxide is 40t / m.

[0235] (32) When the oil well is a weakly streamlined oil well: For production wells with a water cut of less than 85%, based on the daily injection rate of the weakly streamlined oil well, inject nitrogen + low-concentration profile control and viscosity reducer + oil-soluble viscosity reducer + carbon dioxide combination in sequence:

[0236] First, 40,000 standard cubic meters of nitrogen were injected to pressurize the water and replenish the formation energy.

[0237] Subsequently, 5% of the aforementioned profile control and viscosity reducer was injected;

[0238] Finally, an oil-soluble viscosity reducer and carbon dioxide are injected, wherein:

[0239] The oil-soluble viscosity reducer is a heavy alkyl solvent, and the injection strength of the oil-soluble viscosity reducer is 5t / m;

[0240] The carbon dioxide injection intensity is 40 t / m.

[0241] Furthermore, the heavy alkyl solvent is xylene. In another embodiment, the heavy alkyl solvent is tetramethylbenzene. In yet another embodiment, the heavy alkyl solvent is a polycyclic aromatic hydrocarbon.

[0242] In yet another embodiment

[0243] The profile control viscosity reducer has structural unit A, structural unit B, and structural unit C. Structural unit A has the structure shown in formula (1), structural unit B has the structure shown in formula (2), and structural unit C has the structure shown in formula (3). The molar ratio of structural unit A, structural unit B, and structural unit C is 60000:50000:9000, and the molecular weight of the profile control viscosity reducer is 12 million.

[0244]

[0245]

[0246] Where a = 60000;

[0247] b = 50000;

[0248] c = 9000;

[0249] The molecular weight of the profile-adjusting and viscosity-reducing agent is 12 million.

[0250] The preparation method of the profile control and viscosity reducer described in any of the above-mentioned methods includes the following steps:

[0251] S1. Under the presence of an acid-coating agent and water as a solvent, sodium hydroquinone sulfonate and acryloyl chloride are polymerized in an argon atmosphere to generate monomer C, wherein: monomer C has the structure shown in formula (4).

[0252]

[0253] S2. Under an argon atmosphere, in the presence of an initiator and water as a solvent, the monomer C, acrylic acid, and acrylamide obtained in step S1 undergo a polymerization reaction to generate a profile control and viscosity reducer.

[0254] Further, the acid-coating agent in step S1 is a mixture of triethylamine and 4-dimethylaminopyridine in equal mass ratios, wherein:

[0255] The amount of the acid-coating agent used is 0.6 times that of sodium hydroquinone sulfonate, by molar amount.

[0256] Further, the initiator in step S2 is sodium peroxide / sodium bisulfite, wherein:

[0257] The molar ratio of sodium peroxide to sodium bisulfite is 1:3.5;

[0258] The amount of sodium peroxide used is 0.08 times the amount of sodium hydroquinone sulfonate used, by molar amount.

[0259] Furthermore, the polymerization reaction in step S1 is carried out at a reaction temperature of 2°C and the reaction time is controlled at 45 minutes.

[0260] Furthermore, the molar ratio of acryloyl chloride in step S1, sodium hydroquinone sulfonate in step S1, acrylic acid in step S2, and acrylamide in step S2 is 2.3:1:8.4:16.8.

[0261] Furthermore, in step S1, the amount of water used as the solvent is 12 times that of sodium hydroquinone sulfonate, by molar amount.

[0262] The preparation method of the profile control and viscosity reducer described in any of the above-mentioned methods includes the following steps:

[0263] (1) Sodium hydroquinone sulfonate and solvent water were added to a reactor equipped with a stirrer and stirred thoroughly to dissolve it in water at a stirring speed of at least 350 rpm. Then, triethylamine and 4-dimethylaminopyridine in equal mass ratio were added as acid-coating agents and stirred thoroughly until the pH value reached 8. After maintaining this pH value for 45 minutes, the reactor was placed in an ice-water bath and acryloyl chloride was added dropwise. Argon gas was introduced and the gas introduction time was 15 min. After the reaction was completed for 1.5 hours, the solvent was removed by rotary evaporation under reduced pressure to obtain monomer C. Monomer C has the structure shown in formula (4), wherein:

[0264] The amount of acryloyl chloride is 2.3 times the amount of sodium hydroquinone sulfonate;

[0265] The amount of the acid-coating agent used, by molar amount, is 0.6 times that of sodium hydroquinone sulfonate;

[0266]

[0267] (2) Dissolve monomer C, acrylic acid, acrylamide and solvent water in a reactor and stir at a stirring rate of 550 rpm to disperse it evenly in water. Adjust the pH value to 8.3 with an aqueous solution of alkaline substance. Add the prepared solution to the reactor. Circulate the 0°C ice-water mixture to the outside of the reactor for 35 min to cool it down. At the same time, introduce argon gas to stabilize the pressure of the reactor at 1.5 MPa. Add sodium peroxide / sodium bisulfite mixture as an initiator. Stir with a magnetic levitation stirrer at a stirring rate of 450 rpm. After the reaction has been going on for 3 hours, cut the glue block into pieces, dry and grind it to obtain white polymer powder. Wash the white polymer powder repeatedly with ethanol 4 times and dry it in an oven at 82°C for at least 1 hour to obtain the profile adjuster and viscosity reducer.

[0268] Furthermore, the alkaline substance mentioned in step (2) is ammonia.

[0269] The profile control and viscosity reducer is prepared by the above-described preparation method.

[0270] Application of profile control and viscosity reduction agents in composite displacement operations of oil extraction.

[0271] The method for enhancing oil recovery through combined displacement, using the aforementioned profile control and viscosity reducing agents, includes the following steps:

[0272] Step (1): Screening of water-driven heavy oil reservoir well groups;

[0273] Step (2): Injection well control flow line, and implement composite displacement method for water wells with different injection and production well distances;

[0274] Step (3): Production well diversion line, the single-well adjustment process is adopted according to the different production wells with strong and weak flow lines.

[0275] Furthermore, the selection criteria for water-driven heavy oil reservoir well groups in step (1) are as follows:

[0276] Well group recovery rate <30%; permeability greater than 100×10 －3 μm 2 The water injection time exceeds 2 years, and the viscosity of the formation crude oil is less than 1000 mPa·s.

[0277] Furthermore, the specific steps of step (2) are as follows:

[0278] (21) When 50 meters < well spacing ≤ 100 meters, based on the original daily water injection volume of the injection well, the injection well first injects 9% of the above-mentioned profile control and viscosity reducing agent for 2 months, followed by the injection of foaming agent and nitrogen. The injection volume of foaming agent is 2% of the original daily water injection volume of the injection well, and the injection time of foaming agent is 10 days. The gas-liquid ratio is 2:1, wherein:

[0279] The foaming agent is a sulfonate foaming agent;

[0280] (22) When 100 meters < well spacing ≤ 200 meters, based on the original daily water injection volume of the injection well, inject 6% of the above-mentioned profile control and viscosity reducing agent into the injection well for 5 months. Then inject a foaming agent and nitrogen. The amount of foaming agent injected is 2% of the original daily water injection volume of the injection well, and the injection time is 0.75 months. The gas-liquid ratio is 2:1, wherein:

[0281] The foaming agent is a sulfonate foaming agent;

[0282] (23) When 200 meters < well spacing ≤ 300 meters, based on the original daily water injection volume of the injection well, the injection well continuously injects 2% to 4% of the above-mentioned profile adjustment and viscosity reducing agent.

[0283] (24) When the well spacing is greater than 300 meters, the injection well shall be injected with 1% of the above-mentioned profile adjustment and viscosity reducing agent under high pressure, based on the original daily injection volume of the injection well.

[0284] Furthermore, the specific steps of step (3) are as follows:

[0285] (31) When the oil well is a mainstream production well: For production wells with a water cut greater than or equal to 85%, based on the daily injection rate of the mainstream production well, inject a combination of high-concentration profile control and viscosity reducer + foaming agent + nitrogen + oil-soluble viscosity reducer + carbon dioxide in sequence:

[0286] First, a high-concentration profile control and viscosity reducer, a foaming agent, and nitrogen are injected sequentially as a plugging slug. The high-concentration profile control and viscosity reducer has a concentration of 8% and an injection volume of 800 cubic meters. Nitrogen is injected at a volume of 30,000 cubic meters with a gas-liquid ratio of 2:1. The foaming agent is a sulfonate foaming agent.

[0287] Next, an oil-soluble viscosity reducer and carbon dioxide are injected as a drain plug, wherein: the oil-soluble viscosity reducer is an aromatic hydrocarbon solvent, the injection intensity of the oil-soluble viscosity reducer is 3t / m; and the injection intensity of carbon dioxide is 25t / m.

[0288] (32) When the oil well is a weakly streamlined oil well: For production wells with a water cut of less than 85%, based on the daily injection rate of the weakly streamlined oil well, inject nitrogen + low-concentration profile control and viscosity reducer + oil-soluble viscosity reducer + carbon dioxide combination in sequence:

[0289] First, 30,000 standard cubic meters of nitrogen are injected to pressurize the water and replenish the formation energy;

[0290] Subsequently, 3% of the aforementioned profile control and viscosity reducer was injected;

[0291] Finally, an oil-soluble viscosity reducer and carbon dioxide are injected, wherein:

[0292] The oil-soluble viscosity reducer is one of the aromatic hydrocarbon solvents, and the injection strength of the oil-soluble viscosity reducer is 4t / m;

[0293] The carbon dioxide injection intensity is 25 t / m.

[0294] Furthermore, the aromatic hydrocarbon solvent is toluene.

[0295] Example 1

[0296] The preparation method of the profile control and viscosity reducer includes the following steps:

[0297] 1. Add sodium hydroquinone sulfonate and solvent water to a flask equipped with a stirrer, and stir thoroughly to dissolve it in water at a stirring speed of 300 rpm. Then add triethylamine as an acidifying agent and stir thoroughly to bring the pH value to 8. After 30 minutes, add acryloyl chloride (2.1 times the amount of sodium hydroquinone sulfonate) dropwise under an ice-water bath. Purge with nitrogen gas for 10 minutes. After the reaction has been going on for 1 hour, remove the solvent by rotary evaporation under reduced pressure to obtain monomer C. Monomer C has the structure shown in formula (4), wherein:

[0298]

[0299] 2. Dissolve monomer C, acrylic acid, acrylamide, and solvent water in a beaker and stir at 500 rpm to ensure uniform dispersion of the monomer in the water. Adjust the pH to 8.2 with 56% NaCO3 solution. Add the prepared solution to the reaction vessel and circulate a 0°C ice-water mixture to the outside of the reaction vessel for 30 minutes to lower the temperature. Simultaneously, introduce nitrogen gas to stabilize the pressure of the reaction vessel at 1 MPa. Add sodium peroxide / sodium bisulfite mixture as an initiator and stir using a magnetic levitation stirrer at 400 rpm. After reacting for 2 hours, cut the polymer block into small pieces, dry, and grind to obtain a white polymer powder. Wash the white polymer powder three times with ethanol solution and dry it in an 80°C oven to obtain the purified profile adjuster and viscosity reducer.

[0300] Performance testing and characterization

[0301] 1. Infrared spectroscopy test

[0302] Infrared spectroscopy was performed on the profile control and viscosity reducing agent prepared in Example 1, and the results are as follows: Figure 1 As shown. From Figure 1 It can be seen from this that: at 3432cm -1 The stretching vibration peaks attributed to -NH2 and -OH are located at 2889 cm⁻¹. -1 An asymmetric -CH2 stretching peak appears nearby, at 1681 cm⁻¹. -1 A C=O stretching vibration peak appears nearby, at 1399 cm⁻¹. -1 -COO appeared nearby - The stretching vibration peak is at 1195 cm⁻¹. -1 and 1126cm -1 The antisymmetric stretching peak at 1815 cm⁻¹, attributed to the -S=O double bond, is located at 1815 cm⁻¹. -1 and 978cm -1 An extremely strong -OC=OR asymmetric stretching peak appears at 1597 cm⁻¹. -1 and 838cm -1 The presence of a stretching peak at the para-benzene ring structure, along with infrared spectroscopy characterization, indicates the presence of a para-benzene ring structure, an anhydride structure, an amide group, a carboxylic acid group, and a sulfonate group in the polymer molecule, suggesting successful polymer synthesis.

[0303] 2. Apparent viscosity properties and evaluation of the viscosity-reducing effect on the heavy oil.

[0304] The apparent viscosity properties and viscosity-reducing effects on the heavy oil were evaluated using the profile control and viscosity reducer Z1 prepared in Example 1 of the present invention and commercially available polymeric surfactant products C1 (purchased from Shandong Baomo Biochemical Co., Ltd.) and C2 (purchased from Shandong Fangyuan Chemical Co., Ltd.).

[0305] The evaluation methods for apparent viscosity, shear viscosity retention rate, and thermal stability of high-efficiency viscosity reducers with profile control properties refer to Q / SH10201572-2017 Polyacrylamide for Oil Displacement in Heavy Oil.

[0306] For the viscosity-increasing ratio and displacement efficiency of the aqueous phase, refer to Q / SH10202861—2021 General Technical Conditions for Variable Displacement and Viscosity Reducing Agents.

[0307] The determination methods for viscosity reduction rate and natural sedimentation dehydration rate refer to Q / SH10201519-2016 General Technical Conditions for Heavy Oil Viscosity Reducers.

[0308] An alkaline environment with a pH of 9 was provided, using sodium carbonate as the reagent, and the pH value was measured using pH test paper. An acidic environment with a pH of 6 was provided, using acetic acid as the reagent, and the pH value was measured using pH test paper. The test results are shown in Tables 1-3.

[0309] Table 1 Apparent viscosity of different viscosity reducers

[0310]

[0311]

[0312] Table 2 Viscosity-reducing effects of different viscosity reducers

[0313]

[0314]

[0315] Table 3. Viscosity increase ratio and displacement efficiency of different viscosity reducers in aqueous phase

[0316]

[0317] Test results show that the high-efficiency viscosity reducer with profile control performance Z1 prepared in this invention has better apparent viscosity, aqueous phase viscosity increase factor, shear viscosity retention rate, thermal stability, viscosity reduction effect, and natural sedimentation dehydration effect than commercially available polymer surfactants.

[0318] At a mineralization of 11220 mg / L, a temperature of 60℃, and a concentration of 10000 mg / L, the apparent viscosity of the aqueous phase reaches over 400 mPa·s.

[0319] It has excellent shear resistance. After thousands of shear cycles, the viscosity retention rate reaches over 95%, and the apparent viscosity retention rate after standing for 30 days under anaerobic conditions reaches over 98%.

[0320] It has excellent acid and alkali resistance, and its apparent viscosity remains almost unchanged in acidic or alkaline environments. At the same time, this profile control high-efficiency viscosity reducer has a good viscosity reduction effect on heavy oil. Even when diluted to a concentration of 5000 mg / L, the viscosity reduction rate reaches more than 90%, which is higher than that of similar surfactants in acidic or alkaline environments.

[0321] The results show that the profile-modifying high-efficiency viscosity reducer of this invention can play a role in inhibiting cross-flow and regulating the flow in the process of viscosity reduction composite flooding of heavy oil. It is suitable for the needs of complex reservoir environments with different acid and alkali conditions. Its water phase viscosity increase factor is much greater than 10, which meets the indoor evaluation indicators of pH value 6.0-9.0, water phase viscosity increase factor ≥10.0, oil phase viscosity reduction rate ≥60%, natural sedimentation dehydration rate ≥80%, and improves the displacement efficiency of tubular model by ≥12%, thus meeting the technical requirements of viscosity reduction composite flooding in ordinary heavy oil reservoirs.

[0322] Example 2

[0323] The method for enhancing oil recovery through compound displacement, using profile control and viscosity reducing agent Z1 from Example 1, includes the following steps:

[0324] 1. Screening of water-driven heavy oil reservoir well groups:

[0325] A well group in Shengli Oilfield currently has a recovery rate of 22.1%, a reservoir temperature of 60℃, a crude oil viscosity of 412 mPa·s, and a crude oil viscosity of 828.4 mPa·s at 50℃, classifying it as ordinary heavy oil. The water salinity is 11220 mg / L, and the calcium and magnesium ion concentration is 320 mg / L. The permeability is 428 × 10⁻⁶. －3 μm 2 Since February 2012, water flooding has been carried out. Due to the high viscosity of crude oil, the mainstream oil wells have high water cut after water flooding, while ineffective oil wells have low production and low fluid content.

[0326] It meets the screening criteria for water-driven heavy oil reservoir well groups.

[0327] The well group consists of one injection and five production wells, with well spacing ranging from 150 to 200 meters. Wells WELL 1 and WELL 2 have water cuts of 92% and 95% respectively, classifying them as strongly streamlined wells; the other wells have water cuts of less than 90%, classifying them as weakly streamlined wells. Streamline analysis diagrams are shown below. Figure 2 As shown.

[0328] 2. Injection well control flow line

[0329] The injection well is continuously injected with a medium concentration of 5% profile control and viscosity reducer Z1 at a daily injection volume of 60 cubic meters (i.e., 60 kg * 5% = 3 kg, that is, 3 kg of profile control and viscosity reducer Z1 is mixed evenly with 60 cubic meters of water and then injected into the injection well). The injection period is 6 months. Then, a combination of foaming agent and nitrogen is injected for 1 month. The foaming agent concentration is 1% (i.e., the amount of foaming agent used is 60 kg * 1% = 0.6 kg), and the gas-liquid ratio is 1:1.

[0330] 3. Production well diversion line

[0331] Mainstream oil wells: Wells WELL 1 and WELL 2 have water cuts of 92% and 95% respectively, belonging to the mainstream well line. Each well uses a strong flow line adjustment process for the diversion line. First, 600 cubic meters of high-concentration 10% profile control and viscosity reducer were injected, followed by 20,000 cubic meters of nitrogen and 700 cubic meters of 1% foaming agent. Then, 15 tons of oil-soluble viscosity reducer and 120 tons of carbon dioxide were injected as diversion line plugs.

[0332] Weakly streamlined wells: WELL 3, WELL 4, and WELL 5 have a water cut of less than 90% and are classified as weakly streamlined wells. The weakly streamlined well adjustment process is adopted to guide the flow line. First, 20,000 cubic meters of nitrogen are injected, followed by 800 cubic meters of profile control and viscosity reducer with a 5% concentration. Finally, 20 tons of oil-soluble viscosity reducer and 150 tons of carbon dioxide are injected.

[0333] 4. Implementation Results

[0334] The method of enhancing oil recovery by combining water-driven displacement in heavy oil reservoir well groups, such as... Figure 3 As shown, the well group increased oil production by 16.6 tons per day and 1920 tons per stage, with an input-output ratio of 2.5.

[0335] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments, and various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention.

Claims

1. A profile control and viscosity reducer, characterized in that, The profile control and viscosity reducer has structural unit A, structural unit B, and structural unit C. Structural unit A has the structure shown in formula (1), structural unit B has the structure shown in formula (2), and structural unit C has the structure shown in formula (3). The molar ratio of structural unit A, structural unit B, and structural unit C is (10000~700000):(10000~600000):(5000~20000). The molecular weight of the profile control and viscosity reducer is 2 million to 40 million, preferably 10 million to 15 million.

2. The profile control and viscosity reducer as described in claim 1, characterized in that, The molar ratio of structural unit A, structural unit B, and structural unit C is (50000~80000):(30000~60000):(8000~10000).

3. A profile control and viscosity reducer, characterized in that, Its structural formula is as follows: Where: a = 10000~700000; preferably a = 50000~80000; b = 10000~600000; preferably b = 30000~60000; c = 5000~20000; preferably c = 8000~10000; The molecular weight of the profile-adjusting and viscosity-reducing agent is 2 million to 40 million, preferably 10 million to 15 million.

4. The method for preparing the profile control and viscosity reducer according to any one of claims 1-3, characterized in that, Includes the following steps: S1. Under the presence of an acid-coating agent and water as a solvent, sodium hydroquinone sulfonate and acryloyl chloride are polymerized in a nitrogen or inert gas atmosphere to generate monomer C, wherein: monomer C has the structure shown in formula (4). S2. Under a nitrogen or inert gas atmosphere, and in the presence of an initiator and water as a solvent, the monomer C, acrylic acid, and acrylamide obtained in step S1 undergo a polymerization reaction to generate a profile control and viscosity reducer.

5. The method for preparing the profile control and viscosity reducer as described in claim 4, characterized in that, The acid-coating agent in step S1 is triethylamine and / or 4-dimethylaminopyridine, wherein: The amount of the acid-coating agent used, by molar amount, is 0.5-0.8 times that of sodium hydroquinone sulfonate, and / or The initiator in step S2 is sodium peroxide / sodium bisulfite, wherein: The molar ratio of sodium peroxide to sodium bisulfite is 1:3 to 4; The amount of sodium peroxide used, by molar amount, is 0.05 to 0.1 times the amount of sodium hydroquinone sulfonate used, and / or The polymerization reaction in step S1 is carried out at a reaction temperature of at least 0°C, preferably 0–5°C, and the reaction time is controlled at at least 30 minutes, preferably 30–60 minutes, and / or The molar ratio of acryloyl chloride in step S1, sodium hydroquinone sulfonate in step S1, acrylic acid in step S2, and acrylamide in step S2 is (2.1–2.5):1:(8.2–8.5):(16.4–17), and / or In step S1, the amount of water used as solvent is 10 to 18 times that of sodium hydroquinone sulfonate.

6. The method for preparing the profile control and viscosity reducer according to any one of claims 1-3, characterized in that, Includes the following steps: (1) Sodium hydroquinone sulfonate and solvent water are added to a reactor equipped with a stirrer and stirred thoroughly to dissolve it in water at a stirring speed of at least 300 rpm, preferably 300-400 rpm. Then, triethylamine and / or 4-dimethylaminopyridine are added as acid-absorbing agents and stirred thoroughly to bring the pH value to 7.5-8.

5. After maintaining this pH value for at least 30 minutes, the reactor is placed in an ice-water bath and acryloyl chloride is added dropwise. Nitrogen or inert gas is introduced for at least 10 minutes, preferably 10-20 minutes. After the reaction has proceeded for at least 1 hour, preferably 1-2 hours, the solvent is removed by rotary evaporation under reduced pressure to obtain monomer C. Monomer C has the structure shown in formula (4), wherein: The amount of acryloyl chloride is 2.1-2.5 times the amount of sodium hydroquinone sulfonate; The amount of the acid-coating agent used, by molar amount, is 0.5-0.8 times that of sodium hydroquinone sulfonate; (2) Dissolve monomer C, acrylic acid, acrylamide and solvent water in a reactor and stir at a stirring speed of at least 500 rpm, preferably 500-600 rpm, to disperse it evenly in water. Adjust the pH value to 8-8.5 with an aqueous solution of an alkaline substance. Add the prepared solution to the reaction vessel and circulate the 0°C ice-water mixture to the outside of the reaction vessel for cooling for 30-45 minutes. At the same time, introduce nitrogen or inert gas to stabilize the pressure of the reaction vessel at 1-2 MPa. Add sodium peroxide / sodium bisulfite mixture as an initiator and stir with a magnetic levitation stirrer at a stirring speed of at least 400 rpm, preferably 400-500 rpm. After reacting for at least 2 hours, cut the glue block into pieces, dry and grind it to obtain white polymer powder. Wash the white polymer powder repeatedly with ethanol at least three times and dry it in an oven at at least 80°C, preferably 80-85°C, for at least 1 hour to obtain the profile adjuster and viscosity reducer.

7. The method for preparing the profile control and viscosity reducer as described in claim 6, characterized in that, The alkaline substance mentioned in step (2) is one or more of sodium carbonate, sodium bicarbonate, sodium hydroxide, and ammonia water.

8. A profile control and viscosity reducer, characterized in that, Prepared by the preparation method described in any one of claims 4-7.

9. The application of the profile control and viscosity reducer according to any one of claims 1-3 and 8 as a profile control and viscosity reducer in the combined displacement operation of oil extraction.

10. A method for enhancing oil recovery through compound displacement, using the profile control and viscosity reducing agent described in any one of claims 1-3 and 8, characterized in that, Includes the following steps: Step (1): Screening of water-driven heavy oil reservoir well groups; Step (2): Injection well control flow line, and implement composite displacement method for water wells with different injection-production well spacing; Step (3): Production well diversion line, the single-well adjustment process is adopted according to the different production wells with strong and weak flow lines.

11. The method for enhancing oil recovery through compound displacement as described in claim 10, characterized in that, The selection criteria for water-driven heavy oil reservoir well groups in step (1) are as follows: Well group recovery rate <30%; permeability greater than 100×10 －3 μm 2 The water injection time exceeds 2 years, and the viscosity of the formation crude oil is less than 1000 mPa·s.

12. The method for enhancing oil recovery through compound displacement as described in claim 10, characterized in that, The specific steps of step (2) are as follows: (21) When 50 meters < well spacing ≤ 100 meters, based on the original daily water injection volume of the injection well, first inject 8% to 10% of the above-mentioned profile control and viscosity reducing agent into the injection well for at least one month, preferably one to three months. Then inject a foaming agent and nitrogen. The amount of foaming agent injected is 1% to 3% of the original daily water injection volume of the injection well. The foaming agent injection time is at least one week, preferably one to two weeks, and the gas-liquid ratio is 1:1 to 3:1, wherein: The foaming agent is one of the following: sulfonate foaming agents and polyether foaming agents; (22) When 100 meters < well spacing ≤ 200 meters, based on the original daily water injection volume of the injection well, inject 5% to 7% of the above-mentioned profile control and viscosity reducing agent into the injection well for at least 3 months, at least 3 to 6 months. Then inject a foaming agent and nitrogen. The amount of foaming agent injected is 1 to 3% of the original daily water injection volume of the injection well, and the injection time is at least 0.5 months, preferably 0.5 to 1 month. The gas-liquid ratio is 1:1 to 3:1, wherein: The foaming agent is one of the following: sulfonate foaming agents and polyether foaming agents; (23) When 200 meters < well spacing ≤ 300 meters, based on the original daily water injection volume of the injection well, the injection well continuously injects 2% to 4% of the above-mentioned profile adjustment and viscosity reducing agent. (24) When the well spacing is greater than 300 meters, the above-mentioned profile adjustment and viscosity reduction agent is injected at high pressure into the injection well based on the original daily water injection volume of the injection well.

13. The method for enhancing oil recovery through compound displacement as described in claim 10, characterized in that, The specific steps of step (3) are as follows: (31) When the oil well is a mainstream production well: For production wells with a water cut greater than or equal to 85%, based on the daily injection rate of the mainstream production well, inject a combination of high-concentration profile control and viscosity reducer + foaming agent + nitrogen + oil-soluble viscosity reducer + carbon dioxide in sequence: First, a high-concentration profile control and viscosity reducer, a foaming agent, and nitrogen are injected sequentially as a plug. The high-concentration profile control and viscosity reducer has a concentration of 5% to 10% and an injection volume of 500 to 1000 cubic meters. Nitrogen is injected at a volume of 20,000 to 40,000 cubic meters, with a gas-liquid ratio of 1:1 to 3:

1. The foaming agent is either a sulfonate foaming agent or a polyether foaming agent. Next, an oil-soluble viscosity reducer and carbon dioxide are injected as a drain line plug, wherein: the oil-soluble viscosity reducer is one of aromatic hydrocarbon solvents or heavy alkyl solvents, and the injection intensity of the oil-soluble viscosity reducer is 1-5 t / m; the injection intensity of carbon dioxide is 15-40 t / m; (32) When the oil well is a weakly streamlined oil well: For production wells with a water cut of less than 85%, based on the daily injection rate of the weakly streamlined oil well, inject nitrogen + low-concentration profile control and viscosity reducer + oil-soluble viscosity reducer + carbon dioxide combination in sequence: First, inject 20,000 to 40,000 standard cubic meters of nitrogen to pressurize water and replenish formation energy; Subsequently, 1% to 5% of the above-mentioned profile control and viscosity reducing agent is injected; Finally, an oil-soluble viscosity reducer and carbon dioxide are injected, wherein: The oil-soluble viscosity reducer is one of the aromatic hydrocarbon solvents and heavy alkyl solvents, and the injection strength of the oil-soluble viscosity reducer is 3-5 t / m; The carbon dioxide injection intensity is 15–40 t / m.

14. The method for enhancing oil recovery through compound displacement as described in claim 13, characterized in that, The aromatic hydrocarbon solvent is one of benzene, toluene, o-xylene, m-xylene, and p-xylene, or a petroleum hydrocarbon solvent, and / or The heavy alkyl solvent is one of xylene, tetramethylbenzene, or polycyclic aromatic hydrocarbons.

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