Viscosifier and method for its preparation, composite plug oil displacement agent, enhanced recovery method

Abstract

The application discloses a tackifier, a preparation method of the tackifier, a composite plug oil displacement agent and an enhanced oil recovery method. The tackifier contains structural unit A, structural unit B, structural unit C and structural unit D, and the mass ratio of the structural unit A, the structural unit B, the structural unit C and the structural unit D is (2000-20000):(2000-40000):(4000-60000):(6000-100000), n is 1-15, m is 1-20, and the viscosity average molecular weight of the tackifier is 45-50 million. The tackifier has the following advantages: under the condition of a temperature of 60-70 DEG C and a salinity of 10000 mg / L, the viscosity of a polymer solution is greater than 100 mPa s; when the concentration of the polymer solution is 1000 mg / L, the surface tension is less than 40 mN / m, the tackifier has the function of emulsifying and dispersing crude oil, and the oil displacement efficiency of a physical model is increased by more than 12%.

Description

Technical Field

[0001] This invention belongs to the field of heavy oil reservoir cold production chemical viscosity reduction and flooding technology, specifically involving a viscosity enhancer and its preparation method, a composite slug flooding agent, and a method for improving oil recovery. Background Technology

[0002] The Shengli Oilfield has approximately 340 million tons of heavy oil reserves. Due to geological conditions such as high crude oil viscosity, high sensitivity, and low permeability, the development efficiency of water-drive and thermal recovery high-cycle throughput stages is not ideal, and the operating cost is higher than $30 per barrel, which is considered an inefficient development unit.

[0003] The inefficient thermal recovery heavy oil reservoirs cover 79 units with a geological reserve of 198 million tons. Currently, the average daily fluid production per well in these reservoirs is 15.7 t / d, and the average daily oil production per well is 1.7 t / d. The inefficient water-driven heavy oil reservoirs cover 49 units with a geological reserve of 139 million tons. The average daily fluid production per well in these reservoirs is 24.5 t / d, and the average daily oil production per well is 1.9 t / d. Compared with the overall development of heavy oil in the Shengli Oilfield, the development of inefficient heavy oil reservoirs is characterized by high water cut, low oil production rate, low recovery degree, low recovery rate, and low oil-gas ratio.

[0004] The geological reserves of water-driven heavy oil in Shengli are 890 million tons, currently in a stage of "extremely high water cut (93.2%) and low oil recovery rate (0.4%)". Water-driven heavy oil is prone to viscous fingering and water channeling due to the influence of the oil-water mobility ratio. The remaining oil is mainly in clusters in unaffected areas, characterized by overall enrichment and partial dispersion, with 50-70% of the remaining oil untouched.

[0005] Both field waterflooding development results and laboratory physical model displacement experiments show that waterflooding recovery rate decreases linearly with increasing crude oil viscosity. Medium-deep waterflooding heavy oil reservoirs, affected by factors such as large burial depth (>1500m), low permeability (<500md), and high temperature and salinity (>20000mg / L), exhibit poor adaptability to thermal recovery and polymer flooding. Therefore, there is an urgent need to shift development strategies and research balanced displacement technology to improve development effectiveness.

[0006] Chinese invention patent CN109135711B relates to a composite oil displacement agent composed of a hydrophobically associating polymer with opposite monomer charges, a preferred surfactant or a combination thereof, and water, and a single-stage plug oil displacement method. The preferred surfactant or its combination exhibits strong hydrophobic association with the hydrophobically associating polymer. The viscosity of the composite oil displacement agent initially increases and then decreases with the addition of surfactant, ultimately maintaining a low viscosity. Furthermore, the preferred surfactant has stronger adsorption on rock surfaces than the associating polymer. However, the technical solution of the aforementioned patent is primarily applicable only to single-stage plug injection in low-to-medium permeability reservoirs and is not suitable for multi-stage plug injection in inefficient water-driven heavy oil reservoirs.

[0007] Chinese invention patent CN103321621B relates to a method for flooding heavy oil reservoirs using wedge-shaped viscosity slugs, comprising the following steps: Step 1: Dividing the heterogeneous oil layer into several layers according to its water absorption capacity and obtaining the permeability Ki of each layer; Step 2: Designing three-part slugs based on the permeability Ki; Step 3: Injecting the pre-slug into the heavy oil reservoir to emulsify the crude oil; Step 4: Injecting multiple rounds of main wedge-shaped slugs into the reservoir; Step 5: Generally injecting a low concentration of type BⅢ surfactant or water into the tail slug. However, this patent's technical solution has the following shortcomings: The above patent selects fluids of different concentrations and combines them with different viscosities to inject into the oil reservoir based on the heterogeneity of the oil layer. However, inefficient water-flooded heavy oil reservoirs are affected by the oil-water mobility ratio, making them prone to viscous fingering and water channeling, requiring a plugging agent with high apparent viscosity for overall plugging and regulation to seal large channels. The above patent cannot be applied to inefficient water-flooded, highly heterogeneous heavy oil reservoirs. Summary of the Invention

[0008] Objective of the Invention: The technical problem this invention aims to solve is that inefficient water-driven, highly heterogeneous heavy oil reservoirs are prone to viscous fingering and water channeling, resulting in low oil recovery. To address this, this invention discloses a viscosity enhancer and its preparation method, a composite slug displacement agent, and methods for improving oil recovery.

[0009] This invention utilizes a composite injection process of "plugging agent + nonionic small molecule viscosity reducer + anionic small molecule viscosity reducer + viscosity enhancer" to effectively seal large channels formed after multiple rounds of huff and puff, adjust formation heterogeneity, and improve the emulsification and viscosity-reducing ability, oil washing efficiency, and sweepability of the injected chemical agents, thereby significantly improving the recovery rate of inefficient water-driven heavy oil reservoirs. Specifically:

[0010] The thickener of the present invention has a polymer solution viscosity >100mPa·s under the conditions of temperature 60-70℃ and mineralization of 10000mg / L; when the polymer solution concentration is 1000mg / L, the surface tension is less than 40mN / m, and it has the effect of emulsifying and dispersing crude oil; the oil displacement efficiency of the physical model is improved by more than 12%.

[0011] Technical solution: a tackifier, wherein the tackifier is an active polymer, the tackifier contains structural unit A, structural unit B, structural unit C and structural unit D, structural unit A has the structure shown in formula (1), structural unit B has the structure shown in formula (2), structural unit C has the structure shown in formula (3), structural unit D has the structure shown in formula (4), the molar ratio of structural unit A, structural unit B, structural unit C and structural unit D is (2000~20000):(2000~40000):(4000~60000):(6000~100000), n is a positive integer from 1 to 15, m is a positive integer from 1 to 20, and the viscosity-average molecular weight of the tackifier is 45 million to 50 million;

[0012]

[0013] Tackifiers have the following general structural formula:

[0014]

[0015] in:

[0016] x is a positive integer from 2000 to 20000, preferably a positive integer from 10000 to 15000;

[0017] y is a positive integer between 2000 and 40000, preferably a positive integer between 20000 and 40000;

[0018] z is a positive integer from 4000 to 60000, preferably a positive integer from 10000 to 60000;

[0019] p is a positive integer from 6000 to 100000, preferably a positive integer from 10000 to 80000;

[0020] n is a positive integer from 1 to 15, preferably a positive integer from 8 to 12;

[0021] m is a positive integer from 1 to 20, preferably a positive integer from 6 to 18;

[0022] The viscosity-average molecular weight of the tackifier is 45 million to 50 million, preferably 46 million to 48 million.

[0023] The above-mentioned method for preparing the tackifier involves a polymerization reaction of acrylamide, sodium 5-isopropylnaphthalenesulfonate, alkyl acrylate, and monomer AMCS (sodium 2-acrylamido-2-methylpropanesulfonate, CAS No.: 15214-89-8) in the presence of an initiator and a solvent.

[0024] The molar ratio of acrylamide, sodium 5-isopropylnaphthalenesulfonate, alkyl acrylate and monomer AMCS is (0.01-70):(0.01-60):(0.01-30):(0.01-10);

[0025] The alkyl group in the alkyl acrylate is a C1-C15 chain alkyl group;

[0026] The alkyl group in the monomer AMCS is a C1-C20 chain alkyl group;

[0027] The viscosity-average molecular weight of the prepared tackifier is 45 million to 50 million.

[0028] A method for preparing a thickener, comprising the following steps:

[0029] (1) Add a certain amount of surfactant to the solvent and stir to form a uniform emulsion. Weigh acrylamide, sodium 5-isopropylnaphthalenesulfonate, alkyl acrylate and monomer AMCS according to the ingredient ratio and dissolve them into the emulsion.

[0030] (2) Turn on the mechanical stirrer and stir and heat the mixture uniformly at a speed of at least 300 r / min, preferably 300-500 r / min. Purge with nitrogen or inert gas for at least 0.5 h, preferably 0.5-1 h. Then add the initiator and react at at least 70 °C, preferably 70-90 °C, for at least 5 h, preferably 5-8 h to obtain a mixed solution containing a precipitate. After the reaction is complete, cool the mixed solution, wash the product with a large amount of organic solvent and precipitate it. Take the precipitate and put it into a vacuum drying oven. Dry it at a constant temperature of at least 50 °C for at least 24 h to obtain the thickener.

[0031] The steps to improve the recovery rate are as follows:

[0032] (1) Screening of target blocks for inefficient water-driven heavy oil reservoirs;

[0033] (2) Inject gel-based plugging agents into the injection wells to seal the block and perform plugging and regulation on the entire block;

[0034] (3) The above-mentioned composite slug oil displacement agent is injected monthly in the water well slug system;

[0035] (4) Production wells are started to pump out.

[0036] This invention employs a multi-stage plug injection method combining "plugging agent + composite oil displacement agent," which fully leverages the synergistic effects between chemical agents, achieving mutual functional complementarity. This increases the effectiveness of a single displacement agent on the formation, resulting in superior oil recovery compared to a single system. This achieves the goal of improving efficiency and reducing costs, thereby activating remaining oil and ultimately enhancing the recovery rate of inefficient water-driven heavy oil reservoirs. Specifically:

[0037] The thickener of the present invention has a polymer solution viscosity >100mPa·s under the conditions of temperature 60-70℃ and mineralization of 10000mg / L; when the polymer solution concentration is 1000mg / L, the surface tension is less than 40mN / m, and it has the effect of emulsifying and dispersing crude oil; the oil displacement efficiency of the physical model is improved by more than 12%.

[0038] The design concept of the technical solution of this invention is as follows:

[0039] First, a plugging agent gel is injected to seal the large water outlet channels, and the entire block is plugged and regulated to reduce the water content of the produced fluid;

[0040] Then, a composite slug displacement agent system consisting of "anionic small molecule viscosity reducer + nonionic small molecule viscosity reducer + viscosity modifier" is injected. The anionic small molecule viscosity reducer strongly disrupts the oil / water interface film and peels off the remaining oil adhering to the reservoir mineral surface, achieving efficient peeling and strong desorption of the remaining oil. The nonionic small molecule viscosity reducer utilizes its strong surface activity to emulsify and disperse larger oil droplets into smaller droplets, effectively utilizing the remaining oil in small pores and enhancing fluidity. The viscosity modifier is designed with active and thickening groups integrated (active groups such as sodium 5-isopropylnaphthalenesulfonate, alkyl acrylate, and monomer AMCS), possessing both efficient viscosity modulating function in the aqueous phase and viscosity reduction function in heavy oil emulsification. Under high-concentration slug conditions, its own apparent viscosity viscoelastic displacement effect dominates, effectively utilizing low-permeability layers by blocking high-permeability layers; under low-concentration conditions, it can emulsify and disperse heavy oil to form an emulsion, achieving emulsion displacement effect. The multi-stage plug flooding combination method utilizes plugging and regulating plugs to adjust the strong heterogeneity within and between formations, improving the dominant seepage channels in the formation. The subsequently injected composite oil displacement agent plugs can effectively seal the low permeability of the formation by utilizing the cumulative effect of small molecule viscosity reducers and viscosity enhancers, improving the water absorption profile, thereby increasing the oil washing efficiency of surfactants. The multi-stage plug injection method of "plugging and regulating agent + composite oil displacement agent" can give full play to the synergistic effect between chemical agents, achieve mutual functional complementarity, increase the degree of effect of a single displacement agent on the formation, and improve the recovery rate better than a single system, achieving the goal of improving efficiency and reducing costs, thereby activating the remaining oil and ultimately improving the recovery rate of inefficient water-driven heavy oil reservoirs.

[0041] Effects of the Invention: The viscosity improver and its preparation method, the composite slug displacement agent, and the method for improving oil recovery disclosed in this invention have the following beneficial effects:

[0042] (1) The thickener of the present invention is based on an acrylamide skeleton and incorporates sodium 5-isopropylnaphthalene sulfonate, alkyl acrylate, and AMCS hydrophobic monomer. Sodium 5-isopropylnaphthalene sulfonate and alkyl acrylate have strong surface activity, which can effectively reduce the interfacial tension between oil and water and emulsify and disperse heavy oil. AMCS monomer has strong salt resistance, which can ensure the stability of the surfactant component in highly salinized formation water.

[0043] (2) The viscosity of the polymer solution of the thickener of the present invention is >100mPa·s under the conditions of temperature 60~70℃ and mineralization 10000mg / L; when the polymer solution concentration is 1000mg / L, the surface tension is less than 40mN / m, which has the effect of emulsifying and dispersing crude oil, and the oil displacement efficiency of the physical model is increased by more than 12%.

[0044] (3) A multi-stage plug flooding combination method is adopted. The plugging and regulating plug can adjust the strong heterogeneity within and between layers of the inefficient water-driven, highly heterogeneous heavy oil reservoir, improve the formation's dominant seepage channels, and then inject a composite oil displacement agent plug. The cumulative effect of small molecule viscosity reducers and viscosity enhancers can effectively block the low permeability of the formation, improve the water absorption profile, and thus improve the oil washing efficiency of surfactants. The multi-stage plug injection method of "plugging and regulating agent + composite oil displacement agent" can give full play to the synergistic effect between chemical agents, achieve mutual functional complementarity, increase the degree of effect of a single displacement agent on the formation, and improve the recovery rate better than a single system, achieving the purpose of improving efficiency and reducing costs, thereby activating the remaining oil and ultimately improving the recovery rate of inefficient water-driven heavy oil reservoirs. Based on field test data, after adopting this plug flooding injection method, inefficient water-driven heavy oil reservoirs have achieved efficient development, with water cut reduced by more than 10%, an average daily oil increase of more than 4 tons per well, and an input-output ratio higher than 1:4. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of the process for improving the recovery rate disclosed in this invention.

[0046] Figure 2 This is a schematic diagram of the oil displacement efficiency of the physical simulation oil displacement experiment of DSFH-1 in Test Example 2.

[0047] Figure 3 This is a schematic diagram of the oil displacement efficiency of the physical simulation oil displacement experiment of JNQY in Test Example 2. Detailed Implementation

[0048] The specific embodiments of the present invention are described in detail below.

[0049] 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.

[0050] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0051] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0052] 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.

[0053] 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.

[0054] Unless otherwise specified, the reaction will proceed under normal temperature and pressure conditions.

[0055] Unless otherwise specified, all parts or percentages are by weight or by weight percentage.

[0056] In this invention, all the substances used are known substances that can be purchased or synthesized by known methods.

[0057] In this invention, all the devices or equipment used are conventional devices or equipment known in the art and are readily available.

[0058] The synthesis reaction equation for the thickener of the present invention is as follows:

[0059]

[0060] The tackifier is an active polymer containing structural unit A, structural unit B, structural unit C and structural unit D. Structural unit A has the structure shown in formula (1), structural unit B has the structure shown in formula (2), structural unit C has the structure shown in formula (3), and structural unit D has the structure shown in formula (4). The molar ratio of structural unit A, structural unit B, structural unit C and structural unit D is (2000~20000):(2000~40000):(4000~60000):(6000~100000), where n is a positive integer from 1 to 15 and m is a positive integer from 1 to 20. The viscosity-average molecular weight of the tackifier is 45 million to 50 million.

[0061]

[0062] Furthermore, the molar ratio of structural unit A, structural unit B, structural unit C and structural unit D is (10000~15000):(20000~40000):(10000~60000):(10000~80000), where n is a positive integer from 8 to 12; m is a positive integer from 6 to 18; and the viscosity-average molecular weight of the tackifier is 46 million to 48 million.

[0063] Tackifiers have the following general structural formula:

[0064]

[0065] in:

[0066] x is a positive integer from 2000 to 20000, preferably a positive integer from 10000 to 15000;

[0067] y is a positive integer between 2000 and 40000, preferably a positive integer between 20000 and 40000;

[0068] z is a positive integer from 4000 to 60000, preferably a positive integer from 10000 to 60000;

[0069] p is a positive integer from 6000 to 100000, preferably a positive integer from 10000 to 80000;

[0070] n is a positive integer from 1 to 15, preferably a positive integer from 8 to 12;

[0071] m is a positive integer from 1 to 20, preferably a positive integer from 6 to 18;

[0072] The viscosity-average molecular weight of the tackifier is 45 million to 50 million, preferably 46 million to 48 million.

[0073] The above-mentioned method for preparing the tackifier involves a polymerization reaction of acrylamide, sodium 5-isopropylnaphthalenesulfonate, alkyl acrylate, and monomer AMCS (sodium 2-acrylamido-2-methylpropanesulfonate, CAS No.: 15214-89-8) in the presence of an initiator and a solvent.

[0074] The molar ratio of acrylamide, sodium 5-isopropylnaphthalenesulfonate, alkyl acrylate and monomer AMCS is (0.01-70):(0.01-60):(0.01-30):(0.01-10);

[0075] The alkyl group in the alkyl acrylate is a C1-C15 chain alkyl group;

[0076] The alkyl group in the monomer AMCS is a C1-C20 chain alkyl group;

[0077] The viscosity-average molecular weight of the prepared tackifier is 45 million to 50 million.

[0078] Furthermore, the molar ratio of the acrylamide, sodium 5-isopropylnaphthalenesulfonate, alkyl acrylate and monomer AMCS is (6-7):(6-10):(3-7):(1-2);

[0079] The alkyl group in the alkyl acrylate is a C8-C12 chain alkyl group;

[0080] The alkyl group in the monomer AMCS is a C6-C18 chain alkyl group;

[0081] The viscosity-average molecular weight of the prepared tackifier is 46 million to 48 million.

[0082] Further, the initiator is one of benzoyl peroxide / sucrose, tert-butyl hydroperoxide / sodium thiosulfate, tert-butyl hydroperoxide / sodium metabisulfite, benzoyl peroxide / N,N-dimethylaniline, and ammonium persulfate / sodium bisulfite, and the amount of the initiator is 0.01 to 1% of the mass of acrylamide;

[0083] If the initiator is benzoyl peroxide / sucrose, the mass ratio of benzoyl peroxide to sucrose is 1:0.5 to 0.8;

[0084] If the initiator is tert-butyl hydroperoxide / sodium benzoate, the mass ratio of tert-butyl hydroperoxide to sodium benzoate is 1:2 to 5.

[0085] If the initiator is tert-butyl hydroperoxide / sodium metabisulfite, the mass ratio of tert-butyl hydroperoxide to sodium metabisulfite is 1:0.5 to 1.0;

[0086] If the initiator is benzoyl peroxide / N,N-dimethylaniline, the mass ratio of benzoyl peroxide to N,N-dimethylaniline is 1:1 to 4;

[0087] If the initiator is ammonium persulfate / sodium bisulfite, the mass ratio of ammonium persulfate to sodium bisulfite is 1:0.8–1.2. 。

[0088] Furthermore, the solvent is one of toluene, xylene, benzene, ethyl acetate, and butyl acetate, and the amount of solvent used is 1 to 5 times the total mass of all monomers.

[0089] A method for preparing a thickener, comprising the following steps:

[0090] (1) A certain amount of surfactant is added to the solvent and stirred to form a uniform emulsion. Acrylamide, sodium 5-isopropylnaphthalenesulfonate, alkyl acrylate and monomer AMCS are weighed according to the ingredient ratio and dissolved into the emulsion, wherein:

[0091] The surfactant mentioned in step (1) is one of fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, Tween-80, Tween-60, and Tween-90;

[0092] The amount of surfactant added is 5% to 10% of the sum of the masses of all monomers;

[0093] The solvent mentioned in step (1) is one of toluene, xylene, benzene, ethyl acetate, and butyl acetate; the amount of solvent used is 1 to 5 times the total mass of all monomers.

[0094] (2) Turn on the mechanical stirrer and stir and heat the mixture uniformly at a speed of at least 300 r / min, preferably 300-500 r / min. Purge with nitrogen or inert gas for at least 0.5 h, preferably 0.5-1 h. Then add the initiator and react at at least 70 °C, preferably 70-90 °C, for at least 5 h, preferably 5-8 h to obtain a mixed solution containing a precipitate. After the reaction is complete, cool the mixed solution, wash the product with a large amount of organic solvent and precipitate it. Take the precipitate and put it into a vacuum drying oven. Dry it at a constant temperature of at least 50 °C for at least 24 h to obtain the thickener.

[0095] Further, the organic solvent in step (2) is one or more of acetone, ethanol, benzene, toluene, xylene, pentane, hexane, octane, chlorobenzene, dichlorobenzene, dichloromethane, cyclohexane, cyclohexanone, toluenecyclohexanone, methanol, isopropanol, and acetonitrile.

[0096] The composite slug displacement agent consists of anionic small molecule viscosity reducers, nonionic small molecule viscosity reducers, and the aforementioned viscosity modifiers, wherein:

[0097] The molar ratio of the anionic small molecule viscosity reducer, the nonionic small molecule viscosity reducer, and the above-mentioned viscosity improver is (4-6):(4-6):0.2.

[0098] Furthermore, the anionic small molecule viscosity reducer is a fatty acid salt, sodium alkylbenzene sulfonate, sodium dodecyl sulfonate, sodium alkyl sulfate, sodium alkyl polyoxyethylene ether sulfate, sodium fatty acid, or sodium oleoylmethyl taurate. 、 One of carboxylates, sulfates, sulfonates, phosphates, and fatty acyl-peptide condensates, preferably sodium dodecyl sulfonate.

[0099] Furthermore, the nonionic small molecule viscosity reducer is OP-10 emulsifier and fatty alcohol polyoxyethylene sulfate. 、 One of the following: fatty alcohol polyoxyethylene ether, fatty acid polyoxyethylene ester, alkylphenol polyoxyethylene ether, polyoxyethylene alkylamine, polyoxyethylene alkylolamide, glycerol fatty acid ester, pentaerythritol fatty acid ester, sucrose fatty acid ester, sorbitol fatty acid ester, dehydrated sorbitol fatty acid ester, polyether, alkylolamide, alkyl polyglycoside, preferably fatty alcohol polyoxyethylene sulfate.

[0100] The steps to improve the recovery rate are as follows:

[0101] (1) Screening of target blocks for inefficient water-driven heavy oil reservoirs;

[0102] (2) Inject gel-based plugging agents into the injection wells to seal the block and perform plugging and regulation on the entire block;

[0103] (3) The above-mentioned composite slug oil displacement agent is injected monthly in the water well slug system;

[0104] (4) Production wells are started to pump out.

[0105] Furthermore, in step (1), the selection criteria for the target block are:

[0106] (a) Take five-point well pattern, reverse seven-point well pattern or reverse nine-point well pattern blocks with water-oil mobility ratio >70 and maximum permeability difference of 40-50;

[0107] (b) Reservoir permeability ≥ 300 × 10 -3 μm 2 Porosity 20%–35%, crude oil viscosity ≤20000 mPa·s under reservoir conditions;

[0108] (c) No influence of bottom water at the edge, oil layer dip angle ≤ 5°.

[0109] (d) The well spacing of the five-point well network is 150m to 180m; the well spacing of the reverse seven-point well network is 190m to 350m; and the well spacing of the reverse nine-point well network is 360m to 450m.

[0110] Further, the specific steps for injecting gel into the injection well in step (2) are as follows: Prepare a gel-based plugging agent aqueous solution with a mass concentration of 10-12% using oilfield water at 40-50℃, and inject it into the formation using a forward extrusion method with a displacement of 5-10m³. 3 / h, replacing 20-30m of oilfield water 3 30-40m of water was displaced from the oilfield. 3 , well shut-in to diffuse pressure.

[0111] Furthermore, the gel-based plugging agent is formulated from polyacrylamide polymer powder, inorganic crosslinking agent, and organic crosslinking agent, wherein:

[0112] The molar ratio of the polyacrylamide polymer dry powder, inorganic crosslinking agent, and organic crosslinking agent is (3-6):1:(5-9).

[0113] Furthermore, the inorganic crosslinking agent is one of the following: chromium-based crosslinking agents, aluminum-based crosslinking agents, zirconium-based crosslinking agents, silane coupling agents, titanate coupling agents, aluminate coupling agents, metal oxides and peroxides, borate-based phosphides, sulfur and sulfur homologues, and metal halides, preferably a chromium-based crosslinking agent.

[0114] Furthermore, the organic crosslinking agent is dicumyl peroxide or a polycarbodiimide crosslinking agent. 、 One of epoxy resin, polyamide, polyether, and siloxane, preferably a polycarbodiimide crosslinking agent.

[0115] Furthermore, the polyacrylamide polymer powder is anionic polyacrylamide with a degree of hydrolysis of 1-6% and a molecular weight of 10 million-12 million.

[0116] Furthermore, in step (2), the injection method for sealing the injection well by injecting a gel-based plugging agent is as follows: injection is carried out from the central well at a low flow rate, where the low flow rate refers to a velocity of less than 2 m / s. 3 / h. A slug injection method is used, with one slug injected per month, and the monthly viscosity reducer dosage is injected within one day.

[0117] Further, in step (3), based on the daily injection rate of the injection well, the injection rate of the composite slug displacement agent is 4-10% by weight.

[0118] Furthermore, the specific steps in step (4) are as follows: each section of plug-driven effective well is pumped in-well for continuous production.

[0119] Furthermore, in step (4), production enhancement measures are adjusted based on the production dynamics of the affected oil wells:

[0120] When the water content of the produced fluid from an oil well exceeds 85%, the high water content is controlled by intermittent operation of the well, with an intermittent operation frequency of 1 to 3 days.

[0121] Furthermore, in steps (2) and (3), all injection rates must simultaneously meet the following conditions:

[0122] Below the formation fracturing pressure;

[0123] Below the equipment's maximum injection capacity;

[0124] Below the maximum absorption capacity of the formation.

[0125] In one embodiment

[0126] The tackifier is an active polymer containing structural unit A, structural unit B, structural unit C and structural unit D. Structural unit A has the structure shown in formula (1), structural unit B has the structure shown in formula (2), structural unit C has the structure shown in formula (3), and structural unit D has the structure shown in formula (4). The molar ratio of structural unit A, structural unit B, structural unit C and structural unit D is 2000:2000:4000:6000, n is 1, m is 1, and the viscosity-average molecular weight of the tackifier is 45 million.

[0127]

[0128]

[0129] In another embodiment, the molar ratio of structural unit A, structural unit B, structural unit C and structural unit D is 10000:20000:10000:10000, n is 8, m is 6, and the viscosity-average molecular weight of the tackifier is 46 million.

[0130] Tackifiers have the following general structural formula:

[0131]

[0132] in:

[0133] x is 2000;

[0134] y is 2000;

[0135] z is 4000;

[0136] p is 6000;

[0137] n is 1;

[0138] m is 1;

[0139] The viscosity-average molecular weight of the tackifier is 45 million.

[0140] In another embodiment, the tackifier has the following general structural formula:

[0141]

[0142] in:

[0143] x is 10000;

[0144] y is 20000;

[0145] z is 10000;

[0146] p is 10000;

[0147] n is 8;

[0148] m is 6;

[0149] The viscosity-average molecular weight of the tackifier is 46 million.

[0150] The above-mentioned method for preparing the tackifier involves a polymerization reaction of acrylamide, sodium 5-isopropylnaphthalenesulfonate, alkyl acrylate, and monomer AMCS (sodium 2-acrylamido-2-methylpropanesulfonate, CAS No.: 15214-89-8) in the presence of an initiator and a solvent.

[0151] The molar ratio of acrylamide, sodium 5-isopropylnphthalenesulfonate, alkyl acrylate, and monomer AMCS is 0.01:0.01:0.01:0.01;

[0152] The alkyl group in the alkyl acrylate is methyl;

[0153] The alkyl group in the monomer AMCS is methyl;

[0154] The viscosity-average molecular weight of the prepared tackifier is 45 million.

[0155] Furthermore, the molar ratio of the acrylamide, sodium 5-isopropylnaphthalenesulfonate, alkyl acrylate, and monomer AMCS is 6:6:3:1.

[0156] The alkyl group in the alkyl acrylate is a C8 chain alkyl group;

[0157] The alkyl group in the monomer AMCS is a C6 chain alkyl group;

[0158] The viscosity-average molecular weight of the prepared tackifier is 46 million.

[0159] Further, the initiator is benzoyl peroxide / N,N-dimethylaniline, and the amount of initiator used is 0.01% of the mass of acrylamide, with a mass ratio of benzoyl peroxide to N,N-dimethylaniline of 1:1. In another embodiment, the initiator is benzoyl peroxide / N,N-dimethylaniline, and the amount of initiator used is 0.01% of the mass of acrylamide, with a mass ratio of benzoyl peroxide to N,N-dimethylaniline of 1:4. In yet another embodiment, the initiator is benzoyl peroxide / N,N-dimethylaniline, and the amount of initiator used is 0.01% of the mass of acrylamide, with a mass ratio of benzoyl peroxide to N,N-dimethylaniline of 1:3.

[0160] Furthermore, the solvent is ethyl acetate, and the amount of solvent used is 1 times the total mass of all monomers.

[0161] A method for preparing a thickener, comprising the following steps:

[0162] (1) A certain amount of surfactant is added to the solvent and stirred to form a uniform emulsion. Acrylamide, sodium 5-isopropylnaphthalenesulfonate, alkyl acrylate and monomer AMCS are weighed according to the ingredient ratio and dissolved into the emulsion, wherein:

[0163] The surfactant mentioned in step (1) is Tween-60;

[0164] The amount of surfactant added is 5% of the sum of the masses of all monomers;

[0165] The solvent used in step (1) is ethyl acetate; the amount of solvent used is 1 times the total mass of all monomers.

[0166] (2) Turn on the mechanical stirrer and stir and heat evenly at a speed of 300 r / min. Purge with nitrogen for 0.5 h, then add the initiator and react at 70 °C for 8 h to obtain a mixed solution containing precipitate. After the reaction is complete, cool the mixed solution, wash the product with a large amount of organic solvent and precipitate it out. Take the precipitate and put it into a vacuum drying oven. Dry it at 50 °C for 24 h to obtain the thickener.

[0167] Furthermore, the organic solvent in step (2) is acetone.

[0168] The composite slug displacement agent consists of anionic small molecule viscosity reducers, nonionic small molecule viscosity reducers, and the aforementioned viscosity modifiers, wherein:

[0169] The molar ratio of the anionic small molecule viscosity reducer, the nonionic small molecule viscosity reducer, and the above-mentioned viscosity improver is 4:4:0.2.

[0170] Furthermore, the anionic small molecule viscosity reducer is a fatty acid salt.

[0171] Furthermore, the nonionic small molecule viscosity reducer is OP-10 emulsifier.

[0172] The steps to improve the recovery rate are as follows:

[0173] (1) Screening of target blocks for inefficient water-driven heavy oil reservoirs;

[0174] (2) Inject gel-based plugging agents into the injection wells to seal the block and perform plugging and regulation on the entire block;

[0175] (3) The above-mentioned composite slug oil displacement agent is injected monthly in the water well slug system;

[0176] (4) Production wells are started to pump out.

[0177] Furthermore, in step (1), the selection criteria for the target block are:

[0178] (a) Take five-point well pattern, reverse seven-point well pattern or reverse nine-point well pattern blocks with water-oil mobility ratio >70 and maximum permeability difference of 40-50 (high water-oil mobility ratio leads to large differences in the effectiveness of water injection in the plane and between layers, and uneven utilization of blocks).

[0179] (b) Reservoir permeability ≥ 300 × 10 -3 μm 2 Porosity 20%–35%, crude oil viscosity ≤20000 mPa·s under reservoir conditions;

[0180] (c) No influence of bottom water at the edge, oil layer dip angle ≤ 5°.

[0181] (d) The well spacing of the five-point well network is 150m to 180m; the well spacing of the reverse seven-point well network is 190m to 350m; and the well spacing of the reverse nine-point well network is 360m to 450m.

[0182] Further, the specific steps for injecting gel into the injection well in step (2) are as follows: Prepare a 10% (w / w) gel-based plugging agent aqueous solution with 40℃ oilfield water, and inject it into the formation using a forward extrusion method with a displacement of 5m³. 3 / h, replacing 20m of oilfield water 3 30m of water was replaced by oilfield water. 3 , well shut-in to diffuse pressure.

[0183] Furthermore, the gel-based plugging agent is formulated from polyacrylamide polymer powder, inorganic crosslinking agent, and organic crosslinking agent, wherein:

[0184] The molar ratio of the polyacrylamide polymer powder, inorganic crosslinking agent, and organic crosslinking agent is 3:1:5.

[0185] Furthermore, the inorganic crosslinking agent is a chromium-based crosslinking agent.

[0186] Furthermore, the organic crosslinking agent is dicumyl peroxide.

[0187] Furthermore, the polyacrylamide polymer powder is anionic polyacrylamide with a degree of hydrolysis of 1% and a molecular weight of 10 million.

[0188] Furthermore, in step (2), the injection method for sealing the injection well by injecting a gel-based plugging agent is as follows: injection is carried out from the central well at a low flow rate, where the low flow rate refers to a velocity of less than 2 m / s. 3 / h. A slug injection method is used, with one slug injected per month, and the monthly viscosity reducer dosage is injected within one day.

[0189] Further, in step (3), based on the daily injection rate of the injection well, the injection rate of the composite slug displacement agent is 4% by weight.

[0190] Furthermore, the specific steps in step (4) are as follows: each section of plug-driven effective well is pumped in-well for continuous production.

[0191] Furthermore, in step (4), production enhancement measures are adjusted based on the production dynamics of the affected oil wells:

[0192] When the water content of the produced fluid from an oil well exceeds 85%, the high water content is controlled by intermittent operation of the well, with an intermittent operation frequency of 1 to 3 days.

[0193] Furthermore, in steps (2) and (3), all injection rates must simultaneously meet the following conditions:

[0194] Below the formation fracturing pressure;

[0195] Below the equipment's maximum injection capacity;

[0196] Below the maximum absorption capacity of the formation.

[0197] In another embodiment

[0198] The tackifier is an active polymer containing structural unit A, structural unit B, structural unit C and structural unit D. Structural unit A has the structure shown in formula (1), structural unit B has the structure shown in formula (2), structural unit C has the structure shown in formula (3), and structural unit D has the structure shown in formula (4). The molar ratio of structural unit A, structural unit B, structural unit C and structural unit D is 20000:40000:60000:100000, n is 15, m is 20, and the viscosity-average molecular weight of the tackifier is 50 million.

[0199]

[0200] Furthermore, the molar ratio of structural unit A, structural unit B, structural unit C and structural unit D is 15000:40000:60000:80000, n is 12; m is 18; and the viscosity-average molecular weight of the tackifier is 48 million.

[0201] Tackifiers have the following general structural formula:

[0202]

[0203] in:

[0204] x is 20000;

[0205] y is 40000;

[0206] z is 60000;

[0207] p is 100000;

[0208] n is 15;

[0209] m is 20;

[0210] The viscosity-average molecular weight of the tackifier is 50 million. The tackifier has the following general structural formula:

[0211]

[0212] in:

[0213] x is 15000;

[0214] y is 40000;

[0215] z is 60000;

[0216] p is 80000;

[0217] n is 12;

[0218] m is 18;

[0219] The viscosity-average molecular weight of the tackifier is 48 million.

[0220] The above-mentioned method for preparing the tackifier involves a polymerization reaction of acrylamide, sodium 5-isopropylnaphthalenesulfonate, alkyl acrylate, and monomer AMCS (sodium 2-acrylamido-2-methylpropanesulfonate, CAS No.: 15214-89-8) in the presence of an initiator and a solvent.

[0221] The molar ratio of acrylamide, sodium 5-isopropylnaphthalenesulfonate, alkyl acrylate and monomer AMCS is 70:60:30:10.

[0222] The alkyl group in the alkyl acrylate is a C15 chain alkyl group;

[0223] The alkyl group in the monomer AMCS is a C20 chain alkyl group;

[0224] The viscosity-average molecular weight of the prepared tackifier is 50 million.

[0225] In another embodiment, the molar ratio of the acrylamide, sodium 5-isopropylnaphthalenesulfonate, alkyl acrylate and monomer AMCS is 7:10:7:2.

[0226] The alkyl group in the alkyl acrylate is a C12 chain alkyl group;

[0227] The alkyl group in the monomer AMCS is a C18 chain alkyl group;

[0228] The viscosity-average molecular weight of the prepared tackifier is 48 million.

[0229] Further, the initiator is ammonium persulfate / sodium bisulfite, and the amount of initiator used is 1% of the mass of acrylamide; the mass ratio of ammonium persulfate to sodium bisulfite is 1:0.8. In another embodiment, the initiator is ammonium persulfate / sodium bisulfite, and the amount of initiator used is 1% of the mass of acrylamide; the mass ratio of ammonium persulfate to sodium bisulfite is 1:1.2. In yet another embodiment, the initiator is ammonium persulfate / sodium bisulfite, and the amount of initiator used is 1% of the mass of acrylamide; the mass ratio of ammonium persulfate to sodium bisulfite is 1:1.

[0230] Furthermore, the solvent is butyl acetate, and the amount of solvent used is 5 times the total mass of all monomers.

[0231] A method for preparing a thickener, comprising the following steps:

[0232] (1) A certain amount of surfactant is added to the solvent and stirred to form a uniform emulsion. Acrylamide, sodium 5-isopropylnaphthalenesulfonate, alkyl acrylate and monomer AMCS are weighed according to the ingredient ratio and dissolved into the emulsion, wherein:

[0233] The surfactant mentioned in step (1) is Tween-90;

[0234] The amount of surfactant added is 10% of the sum of the masses of all monomers;

[0235] The solvent used in step (1) is butyl acetate; the amount of solvent used is 5 times the total mass of all monomers.

[0236] (2) Turn on the mechanical stirrer and stir and heat evenly at a speed of 500 r / min. After passing helium gas for 1 h, add the initiator and react at 90℃ for 5 h to obtain a mixed solution containing precipitate. After the reaction is completed, cool the mixed solution, wash the product with a large amount of organic solvent and precipitate it out. Take the precipitate and put it into a vacuum drying oven. Dry it at 80℃ for 48 h to obtain the thickener.

[0237] Further, the organic solvent in step (2) is ethanol.

[0238] The composite slug displacement agent consists of anionic small molecule viscosity reducers, nonionic small molecule viscosity reducers, and the aforementioned viscosity modifiers, wherein:

[0239] The molar ratio of the anionic small molecule viscosity reducer, the nonionic small molecule viscosity reducer, and the above-mentioned viscosity improver is 6:6:0.2.

[0240] Furthermore, the anionic small molecule viscosity reducer is sodium alkylbenzene sulfonate (LAS).

[0241] Furthermore, the nonionic small molecule viscosity reducer is fatty alcohol polyoxyethylene sulfate (AES).

[0242] The steps to improve the recovery rate are as follows:

[0243] (1) Screening of target blocks for inefficient water-driven heavy oil reservoirs;

[0244] (2) Inject gel-based plugging agents into the injection wells to seal the block and perform plugging and regulation on the entire block;

[0245] (3) The above-mentioned composite slug oil displacement agent is injected monthly in the water well slug system;

[0246] (4) Production wells are started to pump out.

[0247] Furthermore, in step (1), the selection criteria for the target block are:

[0248] (a) Take five-point well pattern, reverse seven-point well pattern or reverse nine-point well pattern blocks with water-oil mobility ratio >70 and maximum permeability difference of 40-50 (high water-oil mobility ratio leads to large differences in the effectiveness of water injection in the plane and between layers, and uneven utilization of blocks).

[0249] (b) Reservoir permeability ≥ 300 × 10 -3 μm 2 Porosity 20%–35%, crude oil viscosity ≤20000 mPa·s under reservoir conditions;

[0250] (c) No influence of bottom water at the edge, oil layer dip angle ≤ 5°.

[0251] (d) The well spacing of the five-point well network is 150m to 180m; the well spacing of the reverse seven-point well network is 190m to 350m; and the well spacing of the reverse nine-point well network is 360m to 450m.

[0252] Further, the specific steps for injecting gel into the injection well in step (2) are as follows: Prepare a 12% (w / w) gel-based plugging agent aqueous solution with 50℃ oilfield water, and inject it into the formation using a forward extrusion method with a displacement of 10m³. 3 / h, replacing 30m of oilfield water 3 40m of water was replaced by oilfield water. 3 , well shut-in to diffuse pressure.

[0253] Furthermore, the gel-based plugging agent is formulated from polyacrylamide polymer powder, inorganic crosslinking agent, and organic crosslinking agent, wherein:

[0254] The molar ratio of the polyacrylamide polymer powder, inorganic crosslinking agent, and organic crosslinking agent is 6:1:9.

[0255] Furthermore, the inorganic crosslinking agent is an aluminum-based crosslinking agent;

[0256] Furthermore, the organic crosslinking agent is a polycarbodiimide crosslinking agent.

[0257] Furthermore, the polyacrylamide polymer powder is anionic polyacrylamide with a degree of hydrolysis of 6% and a molecular weight of 12 million.

[0258] Furthermore, in step (2), the injection method for sealing the injection well by injecting a gel-based plugging agent is as follows: injection is carried out from the central well at a low flow rate, where the low flow rate refers to a velocity of less than 2 m / s. 3 / h. A slug injection method is used, with one slug injected per month, and the monthly viscosity reducer dosage is injected within one day.

[0259] Further, in step (3), the injection rate of the composite slug displacement agent is 10% by weight, based on the daily injection rate of the injection well.

[0260] Furthermore, the specific steps in step (4) are as follows: each section of plug-driven effective well is pumped in-well for continuous production.

[0261] Furthermore, in step (4), production enhancement measures are adjusted based on the production dynamics of the affected oil wells:

[0262] When the water content of the produced fluid from the oil well exceeds 85%, the high water content of the oil well is controlled by intermittent operation, with an intermittent operation frequency of 3 days.

[0263] Furthermore, in steps (2) and (3), all injection rates must simultaneously meet the following conditions:

[0264] Below the formation fracturing pressure;

[0265] Below the equipment's maximum injection capacity;

[0266] Below the maximum absorption capacity of the formation.

[0267] In yet another embodiment

[0268] The tackifier is an active polymer containing structural unit A, structural unit B, structural unit C and structural unit D. Structural unit A has the structure shown in formula (1), structural unit B has the structure shown in formula (2), structural unit C has the structure shown in formula (3), and structural unit D has the structure shown in formula (4). The molar ratio of structural unit A, structural unit B, structural unit C and structural unit D is 12000:30000:30000:40000, n is 10, m is 10, and the viscosity-average molecular weight of the tackifier is 47 million.

[0269]

[0270] Tackifiers have the following general structural formula:

[0271]

[0272] in:

[0273] x is 12000;

[0274] y is a positive integer of 30000;

[0275] z is 30000;

[0276] p is 40000;

[0277] n is 10;

[0278] m is 10;

[0279] The viscosity-average molecular weight of the tackifier is 47 million.

[0280] The above-mentioned method for preparing the tackifier involves a polymerization reaction of acrylamide, sodium 5-isopropylnaphthalenesulfonate, alkyl acrylate, and monomer AMCS (sodium 2-acrylamido-2-methylpropanesulfonate, CAS No.: 15214-89-8) in the presence of an initiator and a solvent.

[0281] The molar ratio of acrylamide, sodium 5-isopropylnaphthalenesulfonate, alkyl acrylate, and monomer AMCS is 6.5:8:5:1.5.

[0282] The alkyl group in the alkyl acrylate is a C10 chain alkyl group;

[0283] The alkyl group in the monomer AMCS is a C12 chain alkyl group;

[0284] The viscosity-average molecular weight of the prepared tackifier is 47 million.

[0285] Further, the initiator is benzoyl peroxide / sucrose, and the amount of initiator is 0.5% of the mass of acrylamide; the mass ratio of benzoyl peroxide to sucrose is 1:0.5. In one embodiment, the initiator is benzoyl peroxide / sucrose, and the amount of initiator is 0.5% of the mass of acrylamide; the mass ratio of benzoyl peroxide to sucrose is 1:0.8. In another embodiment, the initiator is benzoyl peroxide / sucrose, and the amount of initiator is 0.5% of the mass of acrylamide; the mass ratio of benzoyl peroxide to sucrose is 1:0.6.

[0286] Furthermore, the solvent is toluene, and the amount of solvent used is three times the total mass of all monomers.

[0287] A method for preparing a thickener, comprising the following steps:

[0288] (1) A certain amount of surfactant is added to the solvent and stirred to form a uniform emulsion. Acrylamide, sodium 5-isopropylnaphthalenesulfonate, alkyl acrylate and monomer AMCS are weighed according to the ingredient ratio and dissolved into the emulsion, wherein:

[0289] The surfactant mentioned in step (1) is a fatty alcohol polyoxyethylene ether;

[0290] The amount of surfactant added is 8% of the sum of the masses of all monomers;

[0291] The solvent used in step (1) is benzene; the amount of solvent used is three times the total mass of all monomers.

[0292] (2) Turn on the mechanical stirrer and stir and heat evenly at a speed of 400 r / min. After passing argon gas for 0.75 h, add the initiator and react at 80 °C for 6 h to obtain a mixed solution containing precipitate. After the reaction is completed, cool the mixed solution, wash the product with a large amount of organic solvent and precipitate it out. Take the precipitate and put it into a vacuum drying oven. Dry it at 60 °C for 36 h to obtain the thickener.

[0293] Further, the organic solvent in step (2) is acetone. In another embodiment, the organic solvent in step (2) is ethanol. In another embodiment, the organic solvent in step (2) is benzene. In another embodiment, the organic solvent in step (2) is toluene. In another embodiment, the organic solvent in step (2) is xylene. In another embodiment, the organic solvent in step (2) is pentane. In another embodiment, the organic solvent in step (2) is hexane. In another embodiment, the organic solvent in step (2) is octane. In another embodiment, the organic solvent in step (2) is chlorobenzene. In another embodiment, the organic solvent in step (2) is dichlorobenzene. In another embodiment, the organic solvent in step (2) is dichloromethane. In another embodiment, the organic solvent in step (2) is cyclohexane. In another embodiment, the organic solvent in step (2) is cyclohexanone. In another embodiment, the organic solvent in step (2) is toluenecyclohexanone. In another embodiment, the organic solvent in step (2) is methanol. In another embodiment, the organic solvent in step (2) is isopropanol. In another embodiment, the organic solvent in step (2) is acetonitrile. In yet another embodiment, the organic solvent in step (2) is a mixture of acetone, ethanol, benzene, toluene, xylene, pentane, hexane, octane, chlorobenzene, dichlorobenzene, dichloromethane, cyclohexane, cyclohexanone, methylcyclohexanone, methanol, isopropanol, and acetonitrile in equal mass ratios.

[0294] The composite slug displacement agent consists of anionic small molecule viscosity reducers, nonionic small molecule viscosity reducers, and the aforementioned viscosity modifiers, wherein:

[0295] The molar ratio of the anionic small molecule viscosity reducer, the nonionic small molecule viscosity reducer, and the above-mentioned thickener is 5:5:0.2.

[0296] Further, the anionic small molecule viscosity reducer is sodium dodecyl sulfonate. In another embodiment, the anionic small molecule viscosity reducer is sodium alkyl sulfate. In another embodiment, the anionic small molecule viscosity reducer is sodium alkyl polyoxyethylene ether sulfate (AES). In another embodiment, the anionic small molecule viscosity reducer is sodium fatty acid. In another embodiment, the anionic small molecule viscosity reducer is sodium oleoylmethyl taurate. In another embodiment, the anionic small molecule viscosity reducer is a carboxylate. In another embodiment, the anionic small molecule viscosity reducer is a sulfate salt. In another embodiment, the anionic small molecule viscosity reducer is a sulfonate. In another embodiment, the anionic small molecule viscosity reducer is a phosphate salt. In another embodiment, the anionic small molecule viscosity reducer is a fatty acyl-peptide condensate.

[0297] Further, the nonionic small molecule viscosity reducer is a fatty alcohol polyethylene oxide ether. In another embodiment, the nonionic small molecule viscosity reducer is a fatty acid polyethylene oxide ester. In another embodiment, the nonionic small molecule viscosity reducer is an alkylphenol polyethylene oxide ether. In another embodiment, the nonionic small molecule viscosity reducer is a polyethylene oxide alkylamine. In another embodiment, the nonionic small molecule viscosity reducer is a polyethylene oxide alkylolamide. In another embodiment, the nonionic small molecule viscosity reducer is a glycerol fatty acid ester. In another embodiment, the nonionic small molecule viscosity reducer is a pentaerythritol fatty acid ester. In another embodiment, the nonionic small molecule viscosity reducer is a sucrose fatty acid ester. In another embodiment, the nonionic small molecule viscosity reducer is a sorbitan fatty acid ester. In another embodiment, the nonionic small molecule viscosity reducer is a dehydrated sorbitan fatty acid ester. In another embodiment, the nonionic small molecule viscosity reducer is a polyether. In another embodiment, the nonionic small molecule viscosity reducer is an alkylolamide. In another embodiment, the nonionic small molecule viscosity reducer is an alkyl polyglycoside.

[0298] The steps to improve the recovery rate are as follows:

[0299] (1) Screening of target blocks for inefficient water-driven heavy oil reservoirs;

[0300] (2) Inject gel-based plugging agents into the injection wells to seal the block and perform plugging and regulation on the entire block;

[0301] (3) The above-mentioned composite slug oil displacement agent is injected monthly in the water well slug system;

[0302] (4) Production wells are started to pump out.

[0303] Furthermore, in step (1), the selection criteria for the target block are:

[0304] (a) Take five-point well pattern, reverse seven-point well pattern or reverse nine-point well pattern blocks with water-oil mobility ratio >70 and maximum permeability difference of 40-50 (high water-oil mobility ratio leads to large differences in the effectiveness of water injection in the plane and between layers, and uneven utilization of blocks).

[0305] (b) Reservoir permeability ≥ 300 × 10 -3 μm 2 Porosity 20%–35%, crude oil viscosity ≤20000 mPa·s under reservoir conditions;

[0306] (c) No influence of bottom water at the edge, oil layer dip angle ≤ 5°.

[0307] (d) The well spacing of the five-point well network is 150m to 180m; the well spacing of the reverse seven-point well network is 190m to 350m; and the well spacing of the reverse nine-point well network is 360m to 450m.

[0308] Further, the specific steps for injecting gel into the injection well in step (2) are as follows: Prepare an 11% (w / w) gel-based plugging agent aqueous solution with 45℃ oilfield water, and inject it into the formation using a forward extrusion method with a displacement of 8m³. 3 / h, replacing 25m of water from the oilfield. 3 35m of water was replaced by oilfield water. 3 , well shut-in to diffuse pressure.

[0309] Furthermore, the gel-based plugging agent is formulated from polyacrylamide polymer powder, inorganic crosslinking agent, and organic crosslinking agent, wherein:

[0310] The molar ratio of the polyacrylamide polymer powder, inorganic crosslinking agent, and organic crosslinking agent is 4:1:7.

[0311] Furthermore, the inorganic crosslinking agent is a zirconium-based crosslinking agent. In another embodiment, the inorganic crosslinking agent is a silane coupling agent. In another embodiment, the inorganic crosslinking agent is a titanate coupling agent. In another embodiment, the inorganic crosslinking agent is an aluminate coupling agent. In another embodiment, the inorganic crosslinking agent is a metal oxide and a peroxide. In another embodiment, the inorganic crosslinking agent is a borate-based phosphide. In another embodiment, the inorganic crosslinking agent is sulfur and sulfur homologues. In another embodiment, the inorganic crosslinking agent is a metal halide.

[0312] Furthermore, the organic crosslinking agent is dicumyl peroxide. In another embodiment, the organic crosslinking agent is a polycarbodiimide crosslinking agent. In another embodiment, the organic crosslinking agent is an epoxy resin. In another embodiment, the organic crosslinking agent is a polyamide. In another embodiment, the organic crosslinking agent is a polyether. In another embodiment, the organic crosslinking agent is a siloxane.

[0313] Furthermore, the polyacrylamide polymer powder is anionic polyacrylamide with a degree of hydrolysis of 3% and a molecular weight of 11 million.

[0314] Furthermore, in step (2), the injection method for sealing the injection well by injecting a gel-based plugging agent is as follows: injection is carried out from the central well at a low flow rate, where the low flow rate refers to a velocity of less than 2 m / s. 3 / h. A slug injection method is used, with one slug injected per month, and the monthly viscosity reducer dosage is injected within one day.

[0315] Further, in step (3), based on the daily injection rate of the injection well, the injection rate of the composite slug displacement agent is 6% by weight.

[0316] Furthermore, the specific steps in step (4) are as follows: each section of plug-driven effective well is pumped in-well for continuous production.

[0317] Furthermore, in step (4), production enhancement measures are adjusted based on the production dynamics of the affected oil wells:

[0318] When the water content of the produced fluid from the oil well exceeds 85%, the high water content of the oil well is controlled by intermittent operation, with an intermittent operation frequency of 2 days.

[0319] Furthermore, in steps (2) and (3), all injection rates must simultaneously meet the following conditions:

[0320] Below the formation fracturing pressure;

[0321] Below the equipment's maximum injection capacity;

[0322] Below the maximum absorption capacity of the formation.

[0323] Example 1

[0324] A method for preparing a thickener, comprising the following steps:

[0325] (1) Add a certain amount of surfactant to a three-necked flask and stir to form a homogeneous emulsion. Weigh acrylamide, sodium 5-isopropylnaphthalenesulfonate, alkyl acrylate, and AMCS monomer according to the ingredient ratio and dissolve them in the emulsion, wherein:

[0326] The three-necked flask is equipped with a rubber ball, a mechanical stirrer, a condenser, and a nitrogen port;

[0327] The surfactant mentioned in step (1) is a fatty alcohol polyoxyethylene ether;

[0328] The amount of surfactant added is 5% of the sum of the masses of all monomers;

[0329] The solvent mentioned in step (1) is toluene; the amount of solvent used is 1 times the total mass of all monomers.

[0330] Acrylamide, sodium 5-isopropylnaphthalenesulfonate, alkyl acrylate and monomer AMCS were weighed out according to a molar ratio of 0.01:60:20:10 and dissolved in the emulsion.

[0331] (2) Turn on the mechanical stirrer and stir and heat evenly at 300 r / min. After purging with nitrogen for 0.5 h, add an initiator with a mass fraction of 0.01% and react at 70 °C for 5 h to obtain a mixed solution containing precipitate. After the reaction is complete, cool the solution, wash the product with a large amount of acetone and ethanol and precipitate it out. Put it in a vacuum drying oven and dry it at 50 °C for 24 h. Then crush it with a crusher to obtain the thickener.

[0332] Further, the initiator is benzoyl peroxide / sucrose, with a mass ratio of benzoyl peroxide to sucrose of 1:0.5. In another embodiment, the initiator is benzoyl peroxide / sucrose, with a mass ratio of benzoyl peroxide to sucrose of 1:0.8. In yet another embodiment, the initiator is benzoyl peroxide / sucrose, with a mass ratio of benzoyl peroxide to sucrose of 1:0.6.

[0333] Example 2

[0334] A method for preparing a thickener, comprising the following steps:

[0335] (1) Add a certain amount of surfactant to a three-necked flask and stir to form a homogeneous emulsion. Weigh acrylamide, sodium 5-isopropylnaphthalenesulfonate, alkyl acrylate, and AMCS monomer according to the mixing ratio and dissolve them in the emulsion, wherein:

[0336] The three-necked flask is equipped with a rubber ball, a mechanical stirrer, a condenser, and a nitrogen port;

[0337] The surfactant mentioned in step (1) is an alkylphenol polyoxyethylene ether;

[0338] The amount of surfactant added is 5% to 10% of the sum of the masses of all monomers;

[0339] The solvent mentioned in step (1) is xylene; the amount of solvent used is 5 times the total mass of all monomers.

[0340] Acrylamide, sodium 5-isopropylnaphthalenesulfonate, alkyl acrylate and monomer AMCS were weighed out according to a molar ratio of 30:40:20:1 and dissolved in the emulsion.

[0341] (2) Turn on the mechanical stirrer and stir and heat evenly at 400 r / min. After passing nitrogen gas for 1 h, add an initiator with a mass fraction of 0.5% and react at 80℃ for 7 h to obtain a mixed solution containing precipitate. After the reaction is completed, cool the solution, wash the product with a large amount of acetone and ethanol and precipitate it out. Put it in a vacuum drying oven and dry it at 50℃ for 24 h. Then crush it with a crusher to obtain the thickener.

[0342] The initiator is tert-butyl hydroperoxide / sodium benzoate; the mass ratio of tert-butyl hydroperoxide to sodium benzoate is 1:2. In another embodiment, the initiator is tert-butyl hydroperoxide / sodium benzoate; the mass ratio of tert-butyl hydroperoxide to sodium benzoate is 1:5. In yet another embodiment, the initiator is tert-butyl hydroperoxide / sodium benzoate; the mass ratio of tert-butyl hydroperoxide to sodium benzoate is 1:3.

[0343] Example 3

[0344] A method for preparing a thickener, comprising the following steps:

[0345] (1) A certain amount of surfactant was added to a three-necked flask and stirred to form a homogeneous emulsion. Acrylamide, sodium 5-isopropylnaphthalenesulfonate, alkyl acrylate and monomer AMCS were weighed according to the mixing ratio and dissolved into the emulsion, wherein:

[0346] The three-necked flask is equipped with a rubber ball, a mechanical stirrer, a condenser, and a nitrogen port;

[0347] The surfactant mentioned in step (1) is Tween-80;

[0348] The amount of surfactant added is 8% of the sum of the masses of all monomers;

[0349] The solvent used in step (1) is ethyl acetate; the amount of solvent used is three times the total mass of all monomers.

[0350] Acrylamide, sodium 5-isopropylnaphthalenesulfonate, alkyl acrylate and monomer AMCS were weighed out according to a molar ratio of 7:6:3:1 and dissolved in the emulsion.

[0351] (2) Turn on the mechanical stirrer and stir and heat evenly at 500 r / min. After passing nitrogen gas for 1 h, add an initiator with a mass fraction of 1% and react at 90℃ for 8 h to obtain a mixed solution containing precipitate. After the reaction is completed, cool the solution, wash the product with a large amount of acetone and ethanol and precipitate it out. Put it in a vacuum drying oven and dry it at 50℃ for 24 h. Then crush it with a crusher to obtain the thickener.

[0352] Further, the initiator is tert-butyl hydroperoxide / sodium metabisulfite, with a mass ratio of tert-butyl hydroperoxide to sodium metabisulfite of 1:0.5. In another embodiment, the initiator is tert-butyl hydroperoxide / sodium metabisulfite, with a mass ratio of tert-butyl hydroperoxide to sodium metabisulfite of 1:1.0. In yet another embodiment, the initiator is tert-butyl hydroperoxide / sodium metabisulfite, with a mass ratio of tert-butyl hydroperoxide to sodium metabisulfite of 1:0.8.

[0353] Example 4

[0354] The steps to improve the recovery rate are as follows:

[0355] (1) Screening of target blocks for inefficient water-driven heavy oil reservoirs;

[0356] A certain water-driven heavy oil reservoir has a burial depth of 1250m, a total effective reservoir thickness of 9m, a clay content of 10.4%, is weakly water-sensitive, has an average porosity of 28%, an average permeability of 320mD, strong reservoir heterogeneity with a permeability gradient of 5, a remaining oil saturation of 54%, and a subsurface crude oil viscosity of 580mPa·s. The average water cut of the wells in the block is 98%. The selected test well group is a one-injection-eight-production system. The wells in the block are arranged in a vertical and inclined layout with a row-shaped well pattern, which meets the screening criteria of this invention.

[0357] (1) Inject gel-based plugging agent into the injection well to seal it and perform plugging and regulation on the entire block;

[0358] The plugging agent was prepared into a 10% (w / w) solution using 50°C hot oilfield water and injected into the formation at a rate of 6 m³ / h. 3 / h, replacing 20m of oilfield water 3 30m of water was replaced by oilfield water. 3 The wellhead 3-day diffusion pressure. The plugging agent is a compound of anionic polyacrylamide polymer (1% hydrolysis, molecular weight 12 million), inorganic crosslinking agent (chromium-based), and organic crosslinking agent (polycarbodiimide-based), with a compounding ratio of polyacrylamide polymer: inorganic crosslinking agent: organic crosslinking agent = 3:1:6. The dosage of the plugging agent Q1 = 3.14 × (16 - 0.25) × 9 × 0.28 × 1.3 × 1.2 × 10% = 19.4 m³. 3 (R1=4m, r1=0.5m, α1=1.3, β1=1.2).

[0359] (3) Monthly injection of the composite slug oil displacement agent prepared in Example 1 using water well slug injection;

[0360] A viscosity reducer solution with a mass concentration of 5% was prepared using oilfield water at 50℃. The solution was then applied at a concentration of 1.5m... 3 The water flow rate is injected from the central well at a rate of / h. The viscosifier dosage Q2 = 3.14 × (25 - 0.25) × 9 × 0.28 × 1.3 × 8 × 5% = 101.8 m³. 3 (R2=5m, r2=0.5m, α2=1.3, β2=8).

[0361] (4) Production wells are started to pump out.

[0362] Eight effective wells were put into production. After field application, the water cut decreased by 11%, and the average daily oil increase per well was 4.4 tons, with an input-output ratio of 1:5.

[0363] Example 5

[0364] The steps to improve the recovery rate are as follows:

[0365] (1) Screening of target blocks for inefficient water-driven heavy oil reservoirs;

[0366] A certain water-driven heavy oil reservoir has a burial depth of 1388m, a total effective reservoir thickness of 11.4m, a clay content of 9.2%, is weakly water-sensitive, has an average porosity of 33%, an average permeability of 337mD, strong reservoir heterogeneity with a permeability gradient of 7, a remaining oil saturation of 44%, and a subsurface crude oil viscosity of 757mPa·s. The average water cut of the wells in the block is 96%. The selected test well group is a two-injection, ten-production system. The wells in the block are arranged in a vertical and inclined layout with a row-shaped well pattern, which meets the screening criteria of this invention.

[0367] (2) Inject gel-based plugging agents into the injection wells to seal the block and perform plugging and regulation on the entire block;

[0368] The plugging agent was prepared into a 10% (w / w) solution using 50°C hot oilfield water and injected into the formation at a rate of 6 m³ / h. 3 / h, replacing 20m of oilfield water 3 30m of water was replaced by oilfield water. 3 The wellhead diffusion pressure after 3 days is determined. The plugging agent is a compound of anionic polyacrylamide polymer (1% hydrolysis, molecular weight 12 million), inorganic crosslinking agent (chromium-based), and organic crosslinking agent (polycarbodiimide-based), with a compounding ratio of polyacrylamide polymer: inorganic crosslinking agent: organic crosslinking agent = 3:1:6. The dosage of the plugging agent Q1 = 3.14 × (36 - 0.25) × 11.4 × 0.33 × 1.5 × 1.6 × 10% = 101.4 m³. 3 (R1=6m, r1=0.5m, α1=1.5,

[0369] β1 = 1.6).

[0370] (3) Monthly injection of the composite slug oil displacement agent prepared in Example 2 using water well slug injection;

[0371] A viscosity reducer solution with a mass concentration of 4% was prepared using oilfield water at 50℃. The solution was then applied at a concentration of 1.5m... 3 The water flow rate is injected from the central well at a rate of / h. The viscosifier dosage Q2 = 3.14 × (36 - 0.25) × 11.4 × 0.33 × 1.5 × 10 × 4% = 253.4 m³. 3 (R2=6m, r2=0.5m, α2=1.5, β2=10).

[0372] (4) Production well begins pumping:

[0373] Ten effective wells were put into production. After field application, the water cut decreased by 10.6%, the average daily oil increase per well was 4.1 tons, and the input-output ratio was 1:6.

[0374] Performance testing and characterization

[0375] Test Example 1, Basic Physical Properties

[0376] Referring to the industry standards "SY / T 5862-2020 Technical Requirements for Polymers for Oil Displacement" and "Q / SH10202871-2021 General Technical Conditions for Heavy Oil Viscosity Reducing and Displacement Agents", the apparent viscosity and surface tension of the aqueous solution of the viscosity improver prepared in Example 1 and the existing heavy oil viscosity reducing and displacement agent JNQY (a commercially available viscosity reducing and displacement agent product, obtained by compounding sodium dodecylbenzenesulfonate and ethoxylated alkyl sulfate) were tested.

[0377] Experimental temperature: 70℃, mineralization of water used for solution preparation: 10000mg / L, concentration of solution preparation: 1000mg / L.

[0378] Pharmaceutical system Apparent viscosity of aqueous solution (mPa·s) Surface tension mN / m Tackifier prepared in Example 1 126 35 Heavy oil viscosity reducer and displacement agent JNQY 81 66

[0379] Test Example 2: Physical Simulation of Oil Displacement

[0380] The displacement efficiency was evaluated according to the industry standard "SY / T 6315-2017 Method for Determination of High-Temperature Relative Permeability and Oil Displacement Efficiency in Heavy Oil Reservoirs":

[0381] Test subject: ①: Tackifier prepared in Example 1

[0382] ②: DSFH-1, a composite oil displacement agent obtained by combining two small molecule viscosity reducers (sodium dodecylbenzene sulfonate (SDBS) as anionic surfactant and fatty alcohol polyoxyethylene sulfate (AES) as nonionic surfactant);

[0383] ③: Existing heavy oil viscosity reducer and displacement agent JNQY (commercially available viscosity reducer and displacement agent product, obtained by compounding sodium dodecylbenzenesulfonate and sodium ethoxylated alkyl sulfate).

[0384] Experimental conditions: Experimental temperature 50℃, high and low permeability dual-pipe simulation of reservoir heterogeneity, crude oil viscosity of a certain well at 50℃ is 259mPa·s.

[0385] DSFH-1 system and JNQY system: 2% concentration was prepared using oilfield water (mineralization 4857.90 mg / L).

[0386] Experimental steps:

[0387] a. Water drive 3PV + chemical agent 5PV + 3PV water drive.

[0388] b. After water flooding for 3 PV in both high- and low-permeability tubes, a two-tube experiment was conducted, followed by chemical flooding for 5 PV and water flooding for 3 PV. The injection pressure, injection volume, and product volume were recorded during the injection process.

[0389] Table 1. Core tubes used in the experiment and parameters

[0390]

[0391]

[0392] Table 2 Summary of Displacement Efficiency of DSFH-1 and JNQY

[0393]

[0394] The oil displacement efficiency of the composite slug flooding agent system was determined using core displacement experiments. For low-permeability pipes, the oil displacement efficiency of DSFH-1 was 12.4% higher than that of JNQY, and the total displacement efficiency was 13.2% higher than that of waterflooding. DSFH-1 can effectively utilize the remaining oil in low-permeability zones and significantly improve the recovery rate of inefficient waterflooded heavy oil reservoirs.

[0395] 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 thickener, characterized in that, The tackifier is an active polymer, and the tackifier contains structural units A, B, C and D. Structural unit A has the structure shown in formula (1), structural unit B has the structure shown in formula (2), structural unit C has the structure shown in formula (3), and structural unit D has the structure shown in formula (4). The molar ratio of structural units A, B, C and D is (2000~20000):(2000~40000):(4000~60000):(6000~100000), where n is a positive integer from 1 to 15 and m is a positive integer from 1 to 20. The viscosity-average molecular weight of the tackifier is 45 million to 50 million.

2. The thickener as described in claim 1, characterized in that, The molar ratio of structural unit A, structural unit B, structural unit C and structural unit D is (10000~15000):(20000~40000):(10000~60000):(10000~80000), where n is a positive integer from 8 to 12; m is a positive integer from 6 to 18; and the viscosity-average molecular weight of the tackifier is 46 million to 48 million.

3. A thickener, characterized in that, Its general structural formula is shown below: in: x is a positive integer from 2000 to 20000, preferably a positive integer from 10000 to 15000; y is a positive integer between 2000 and 40000, preferably a positive integer between 20000 and 40000; z is a positive integer from 4000 to 60000, preferably a positive integer from 10000 to 60000; p is a positive integer from 6000 to 100000, preferably a positive integer from 10000 to 80000; n is a positive integer from 1 to 15, preferably a positive integer from 8 to 12; m is a positive integer from 1 to 20, preferably a positive integer from 6 to 18; The viscosity-average molecular weight of the tackifier is 45 million to 50 million, preferably 46 million to 48 million.

4. The method for preparing the thickener according to any one of claims 1-3, characterized in that, Acrylamide, sodium 5-isopropylnaphthalenesulfonate, alkyl acrylate and monomer AMCS are obtained by polymerization in the presence of an initiator and solvent.

5. The method for preparing the thickener as described in claim 4, characterized in that, The molar ratio of the acrylamide, sodium 5-isopropylnaphthalenesulfonate, alkyl acrylate, and monomer AMCS is (0.01–70):(0.01–60):(0.01–30):(0.01–10), and / or The alkyl group in the alkyl acrylate is a C1-C15 chain alkyl group, and / or The alkyl group in the monomer AMCS is a C1-C20 chain alkyl group, and / or The viscosity-average molecular weight of the prepared tackifier is 45 million to 50 million.

6. The method for preparing the thickener as described in claim 5, characterized in that, The molar ratio of the acrylamide, sodium 5-isopropylnaphthalenesulfonate, alkyl acrylate, and monomer AMCS is (6-7):(6-10):(3-7):(1-2), and / or The alkyl group in the alkyl acrylate is a C8-C12 chain alkyl group, and / or The alkyl group in the monomer AMCS is a C6-C18 chain alkyl group, and / or The viscosity-average molecular weight of the prepared tackifier is 46 million to 48 million.

7. The method for preparing the thickener as described in claim 4, characterized in that, The initiator is one of the following: benzoyl peroxide / sucrose, tert-butyl hydroperoxide / sodium thiosulfate, tert-butyl hydroperoxide / sodium metabisulfite, benzoyl peroxide / N,N-dimethylaniline, ammonium persulfate / sodium bisulfite, and / or The amount of initiator used is 0.01-1% of the mass of acrylamide, and / or If the initiator is benzoyl peroxide / sucrose, the mass ratio of benzoyl peroxide to sucrose is 1:0.5 to 0.8; If the initiator is tert-butyl hydroperoxide / sodium benzoate, the mass ratio of tert-butyl hydroperoxide to sodium benzoate is 1:2 to 5. If the initiator is tert-butyl hydroperoxide / sodium metabisulfite, the mass ratio of tert-butyl hydroperoxide to sodium metabisulfite is 1:0.5 to 1.0; If the initiator is benzoyl peroxide / N,N-dimethylaniline, the mass ratio of benzoyl peroxide to N,N-dimethylaniline is 1:1 to 4; If the initiator is ammonium persulfate / sodium bisulfite, the mass ratio of ammonium persulfate to sodium bisulfite is 1:0.8–1.2, and / or The solvent is one of toluene, xylene, benzene, ethyl acetate, and butyl acetate, and the amount of solvent used is 1 to 5 times the total mass of all monomers.

8. A method for preparing the thickener according to any one of claims 1-3, characterized in that, The steps are as follows: (1) Add a certain amount of surfactant to the solvent and stir to form a uniform emulsion. Weigh acrylamide, sodium 5-isopropylnaphthalenesulfonate, alkyl acrylate and monomer AMCS according to the ingredient ratio and dissolve them into the emulsion. (2) Turn on the mechanical stirrer and stir and heat the mixture uniformly at a speed of at least 300 r / min, preferably 300-500 r / min. Purge with nitrogen or inert gas for at least 0.5 h, preferably 0.5-1 h. Then add the initiator and react at at least 70 °C, preferably 70-90 °C, for at least 5 h, preferably 5-8 h to obtain a mixed solution containing a precipitate. After the reaction is complete, cool the mixed solution, wash the product with a large amount of organic solvent and precipitate it. Take the precipitate and put it into a vacuum drying oven. Dry it at a constant temperature of at least 50 °C for at least 24 h to obtain the thickener.

9. The method for preparing the thickener as described in claim 8, characterized in that, The surfactant mentioned in step (1) is one of fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, Tween-80, Tween-60, and Tween-90, and / or The amount of surfactant added is 5% to 10% of the sum of the masses of all monomers, and / or The solvent mentioned in step (1) is one of toluene, xylene, benzene, ethyl acetate, and butyl acetate; the amount of solvent used is 1 to 5 times the total mass of all monomers, and / or The organic solvent in step (2) is one or more of the following: acetone, ethanol, benzene, toluene, xylene, pentane, hexane, octane, chlorobenzene, dichlorobenzene, dichloromethane, cyclohexane, cyclohexanone, toluenecyclohexanone, methanol, isopropanol, and acetonitrile.

10. A composite slug displacement agent, characterized in that, The composite slug displacement agent is composed of anionic small molecule viscosity reducers, nonionic small molecule viscosity reducers, and the aforementioned viscosity improvers, wherein: The molar ratio of the anionic small molecule viscosity reducer, the nonionic small molecule viscosity reducer, and the viscosity improver according to any one of claims 1-3 is (4-6):(4-6):0.2, and / or The anionic small molecule viscosity reducer is a fatty acid salt, sodium alkylbenzene sulfonate, sodium dodecyl sulfonate, sodium alkyl sulfate, sodium alkyl polyoxyethylene ether sulfate, sodium fatty acid, or sodium oleoylmethyl taurate. 、 One of the following: carboxylates, sulfates, sulfonates, phosphates, fatty acyl-peptide condensates, preferably sodium dodecyl sulfonate, and / or The nonionic small molecule viscosity reducer is OP-10 emulsifier and fatty alcohol polyoxyethylene sulfate. 、 One of the following: fatty alcohol polyoxyethylene ether, fatty acid polyoxyethylene ester, alkylphenol polyoxyethylene ether, polyoxyethylene alkylamine, polyoxyethylene alkylolamide, glycerol fatty acid ester, pentaerythritol fatty acid ester, sucrose fatty acid ester, sorbitol fatty acid ester, dehydrated sorbitol fatty acid ester, polyether, alkylolamide, alkyl polyglycoside, preferably fatty alcohol polyoxyethylene sulfate.

11. A method for improving oil recovery rate, characterized in that, The steps are as follows: (1) Screening of target blocks for inefficient water-driven heavy oil reservoirs; (2) Inject gel-based plugging agents into the injection wells to seal the block and perform plugging and regulation on the entire block; (3) Monthly injection of the composite slug displacement agent according to any one of claims 1-3 into a water well slug system; (4) Production wells are started to pump out.

12. The method for improving oil recovery as described in claim 11, characterized in that, In step (1), the selection criteria for the target block are: (a) Take five-point well pattern, reverse seven-point well pattern or reverse nine-point well pattern blocks with water-oil mobility ratio >70 and maximum permeability difference of 40-50; (b) Reservoir permeability ≥ 300 × 10 -3 μm 2 Porosity 20%–35%, crude oil viscosity ≤20000 mPa·s under reservoir conditions; (c) No influence from bottom water at the edge, oil layer dip angle ≤ 5°; (d) The well spacing of the five-point well network is 150m to 180m; the well spacing of the reverse seven-point well network is 190m to 350m; the well spacing of the reverse nine-point well network is 360m to 450m, and / or The specific steps for injecting gel into the injection well in step (2) are as follows: Prepare a gel-based plugging agent aqueous solution with a mass concentration of 10-12% using oilfield water at 40-50℃, and inject it into the formation using a forward extrusion method with a displacement of 5-10m³. 3 / h, replacing 20-30m of oilfield water 3 30-40m of water was displaced from the oilfield. 3 Well shut-in diffusion pressure, and / or The gel-type plugging agent is composed of polyacrylamide polymer dry powder, inorganic crosslinking agent, and organic crosslinking agent, wherein: The molar ratio of the polyacrylamide polymer dry powder, inorganic crosslinking agent, and organic crosslinking agent is (3-6):1:(5-9).

13. The method for improving oil recovery as described in claim 11, characterized in that, The inorganic crosslinking agent is one of the following: chromium-based crosslinking agents, aluminum-based crosslinking agents, zirconium-based crosslinking agents, silane coupling agents, titanate coupling agents, aluminate coupling agents, metal oxides and peroxides, borate-based phosphides, sulfur and sulfur homologues, and metal halides, preferably a chromium-based crosslinking agent, and / or The organic crosslinking agent is dicumyl peroxide or polycarbodiimide crosslinking agent. 、 One of epoxy resin, polyamide, polyether, and siloxane, preferably a polycarbodiimide crosslinking agent. The polyacrylamide polymer powder is anionic polyacrylamide with a degree of hydrolysis of 1-6% and a molecular weight of 10 million-12 million.

14. The method for improving oil recovery as described in claim 11, characterized in that, In step (3), based on the daily injection rate of the injection well, the injection rate of the composite slug displacement agent is 4-10% by weight, and / or In step (4), production enhancement measures are adjusted according to the production dynamics of the affected oil wells: When the water content of the produced fluid in an oil well exceeds 85%, the high water content is controlled by intermittent operation of the well, with an intermittent operation frequency of 1–3 days, and / or In steps (2) and (3), all injection rates must simultaneously meet the following conditions: Below the formation fracturing pressure; Below the equipment's maximum injection capacity; Below the maximum absorption capacity of the formation.

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