Targeted chemical oil displacement agent, targeted chemical oil displacement system and application

Abstract

The invention belongs to the field of oil and gas field development, and particularly relates to a targeted chemical oil displacement agent, a targeted chemical oil displacement system and application. The invention relates to a targeted chemical oil displacement agent, which is composed of a microcapsule targeted tackifying polymer reverse emulsion and a surfactant, and the mass ratio of the microcapsule targeted tackifying polymer reverse emulsion to the surfactant is (3-5): (2-4). The invention further discloses a targeted chemical oil displacement system which is formed by mixing a targeted chemical oil displacement agent and a proper amount of water, and based on the total mass of the targeted chemical oil displacement system, the microcapsule targeted tackifying polymer reverse emulsion accounts for 0.3%-0.5% by weight, and the surfactant accounts for 0.2%-0.4% by weight. The invention further discloses application of the targeted chemical oil displacement system as chemical displacement in tertiary oil recovery. The polymer injection agent has strong shear resistance, realizes multi-layer fine polymer injection, realizes balanced displacement of a system in a stratum, and greatly improves the crude oil recovery rate of an oil displacement system.

Description

Technical Field

[0001] The present invention belongs to the field of oil and gas field development, and particularly relates to a targeted chemical oil displacement agent, a targeted chemical oil displacement system and an application thereof. Background Technique

[0002] In the field of oil and gas field development, chemical flooding is an important means to improve the oil recovery of extra-high water cut old oilfields.

[0003] At present, chemical flooding technology has been applied on a large scale in oilfields such as Daqing, Shengli, Dagang, Liaohe, and Xinjiang. The effect of increasing oil production by reducing water cut in the field and the economic benefits are remarkable. For example, Chinese Patent Application CN 113214815A discloses a nano-microemulsion oil displacement agent, which is composed of water, oil, surfactant, isopropanol and sodium chloride; the volume ratio of oil to water is 0.8-0.9:1, and based on the total weight of oil and water, the concentration of the surfactant is 2.0-2.5 wt%, the concentration of isopropanol is 3.0-8.0 wt%, and the concentration of sodium chloride is 2.0-5.5 wt%; the surfactant is a combination of polyoxyethylene ether non-ionic surfactant (Triton X) and sulfonated saponin. The nano-microemulsion oil displacement agent of the present invention belongs to a middle-phase microemulsion, which has a small particle size, and the droplet size is about 20-50 nm. The interfacial tension with the oil and water phases can be reduced to below 1.0×10 -4 mN / m, and the oil recovery can be increased by at least 10 percentage points compared with water flooding. Chinese Patent Application CN1865392A discloses a high-efficiency compound oil displacement agent for tertiary oil recovery and its preparation method. The oil displacement agent is prepared by compounding petroleum sulfonate as the main surfactant with other non-ionic surfactants, anionic surfactants, organic solvents and sodium chloride. Compared with the prior art, the high-efficiency compound oil displacement agent of the present invention has the characteristics of effectively reducing the interfacial tension between oil and water, having good compatibility with high salinity water, and the ability to reduce the interfacial tension is not affected by salinity. The binary oil displacement system formed with polymer can increase the oil recovery by more than 20%.

[0004] One of the main mechanisms of chemical flooding is to inject a high-viscosity polymer or a composite system of polymer and surfactant into the formation to reduce the water-oil mobility ratio, expand the swept volume, improve the oil washing efficiency, and ultimately improve the oil recovery.

[0005] The two most commonly used technologies in chemical flooding on-site are polymer flooding technology and binary composite flooding technology. In both technologies, polymers are needed to expand the swept volume of the system in the formation. However, the polymers currently used on-site are mainly dry powder partial hydrolysis polyacrylamide. Although dry powder partial hydrolysis polyacrylamide has the advantages of high active ingredient, easy packaging and transportation, and long shelf life, dry powder partial hydrolysis polyacrylamide needs to completely dissolve the polymer in the ground injection process and then inject it into the formation. Therefore, the following problems exist in the on-site application process:

[0006] (1) The dissolution and aging time of conventional dry powder partially hydrolyzed polyacrylamide is long, and the surface injection process is complex. It takes more than 2 hours for conventional dry powder polymers to be completely dissolved, which requires three stages: water absorption and swelling, dispersion and dissolution, and aging. The whole process requires corresponding dispersion, dissolution, aging and other equipment. Therefore, the surface process is long, the equipment occupies a large area, and the surface investment is large.

[0007] (2) After the conventional dry powder polymer is dissolved, due to its large molecular weight and long molecular chain, it is not shear-resistant. If the polymer solution is directly injected into the formation through the water injection string, due to the extremely large flow rate of the water nozzle in the water injection string, the shear force on the polymer is large, which will cause an 80-90% loss of the polymer viscosity before entering the formation, and it is impossible to achieve good enhanced oil recovery effect. Therefore, before starting polymer injection in all current chemical flooding projects, it is necessary to replace the water injection string with a polymer injection string. Since most of the current polymer injection strings are two-stage stratified injection of inner and outer pipes and cannot achieve multi-stage stratified fine polymer injection like water injection, when the permeability difference between different formations is large, the polymer will still channel along the high-permeability layer, greatly affecting the chemical flooding effect.

[0008] For the above reasons, the present invention provides a targeted chemical flooding agent and a targeted chemical flooding system for tertiary oil recovery, which can achieve on-site online injection and can use the existing water injection string to achieve multi-stage stratified fine polymer injection. Summary of the Invention

[0009] Object of the Invention: Aiming at the deficiencies in the current conventional chemical flooding system, such as the long dissolution and aging time of polymers, the complex surface injection process, and the fact that after the polymer is dissolved, due to its large molecular weight and long molecular chain, it is not shear-resistant and cannot use the existing water injection string for multi-stage stratified fine polymer injection, the present invention provides a targeted chemical flooding agent, a targeted chemical flooding system and their applications. The present invention can achieve on-site online injection and can use the existing water injection string to achieve multi-stage stratified fine polymer injection.

[0010] Technical Solution: A targeted chemical flooding agent is composed of a microcapsule targeted viscosity-increasing polymer reverse emulsion and a surfactant, wherein: the mass ratio of the microcapsule targeted viscosity-increasing polymer reverse emulsion to the surfactant is (3-5):(2-4).

[0011] Further, the microcapsule targeted viscosity-increasing polymer reverse emulsion is composed of a microcapsule shell and partially hydrolyzed polyacrylamide gel wrapped by the microcapsule shell.

[0012] Even further, the hydrolysis degree of the partially hydrolyzed polyacrylamide gel is 10-20%.

[0013] Even further, the viscosity-average molecular weight of the partially hydrolyzed polyacrylamide gel is 20 million - 30 million.

[0014] Furthermore, the microcapsule-targeted viscosity-increasing polymer is spherical, and its average particle size is 0.4 μm to 1.2 μm.

[0015] Furthermore, the material of the microcapsule shell is non-ionic polyurethane.

[0016] Furthermore, based on parts by mass, the preparation method of the microcapsule-targeted viscosity-increasing polymer reverse emulsion includes:

[0017] (1) Weigh 30 to 50 parts of water and add it to a reaction vessel. Under stirring conditions, add 50 to 70 parts of acrylamide, 15 to 25 parts of sodium acrylate, 1 to 3 parts of polymerizable polyurethane, 5 to 7 parts of non-ionic emulsifier. Add 70 to 80 parts of white oil, and vigorously stir to form a water-in-oil emulsion. Pass nitrogen for 40 to 60 minutes to remove oxygen, and then put it into a refrigeration device and refrigerate until the temperature reaches 5 to 10 °C;

[0018] (2) Add 0.001 to 0.0002 parts of sodium bisulfite, 0.002 to 0.0004 parts of ammonium persulfate, and 0.001 to 0.002 parts of azobisisobutyronitrile to the reaction vessel. After polymerization for at least 3 hours, raise the temperature to 65 to 75 °C and continue polymerization for 1 to 2 hours to obtain the microcapsule-targeted viscosity-increasing polymer reverse emulsion.

[0019] Furthermore, the non-ionic emulsifier is sorbitan monooleate or polysorbate.

[0020] Furthermore, the surfactant is composed of a combined non-ionic and anionic surfactant and a betaine surfactant, where:

[0021] The mass ratio of the combined non-ionic and anionic surfactant to the betaine surfactant is (2 to 3):1. The interfacial tension of the targeted chemical flooding system formed by the surfactant and the microcapsule-targeted viscosity-increasing polymer reaches 10 -3 mN / m.

[0022] Furthermore, the combined non-ionic and anionic surfactant is fatty alcohol polyoxyethylene ether carboxylate or fatty alcohol polyoxyethylene ether sulfonate.

[0023] Furthermore, the fatty alcohol polyoxyethylene ether carboxylate is one of sodium fatty alcohol polyoxyethylene ether carboxylate, potassium fatty alcohol polyoxyethylene ether carboxylate, and ammonium fatty alcohol polyoxyethylene ether carboxylate.

[0024] Furthermore, the fatty alcohol polyoxyethylene ether sulfonate is one of sodium fatty alcohol polyoxyethylene ether sulfonate, potassium fatty alcohol polyoxyethylene ether sulfonate, and ammonium fatty alcohol polyoxyethylene ether sulfonate.

[0025] Furthermore, the betaine surfactant is at least one of tetradecyl carboxy betaine, tetradecyl hydroxymethyl carboxy betaine, tetradecyl sulfo betaine, and hydroxymethyl sulfo pentadecyl betaine.

[0026] A targeted chemical flooding system is formed by mixing the targeted chemical flooding agent described in any one of the above with an appropriate amount of water. Among them: based on the total mass of the targeted chemical flooding system, the weight ratio of the microcapsule targeted viscosity-increasing polymer inverse emulsion is 0.3% - 0.5%, and the weight ratio of the surfactant is 0.2% - 0.4%.

[0027] Application of the above-mentioned targeted chemical flooding system in oil extraction.

[0028] Application of the above-mentioned targeted chemical flooding system as chemical flooding in tertiary oil recovery.

[0029] Furthermore, when the above-mentioned targeted chemical flooding system is used as chemical flooding in tertiary oil recovery, the specific steps are as follows:

[0030] (1) Prepare the targeted chemical flooding system online on the ground;

[0031] (2) Directly inject the targeted chemical flooding system obtained in step (1) into the layered fine injection pipe string, and use the layered fine injection pipe string to directly inject the targeted chemical flooding system into the formation.

[0032] Furthermore, the specific steps of step (1) are:

[0033] Put the formulated amount of microcapsule targeted viscosity-increasing polymer inverse emulsion and the formulated amount of surfactant into a solution tank respectively. After being pressurized by a booster pump and mixed with the formulated amount of water, the targeted chemical flooding system is obtained after passing through a static mixer.

[0034] Furthermore, the layered fine injection pipe string described in step (2) is divided into 4 - 11 stage multi-stage fine distribution injection, preferably 5 - 9 stage multi-stage fine distribution injection.

[0035] Furthermore, the injection volume of the targeted chemical flooding system injected into the formation is 50% - 90% of the formation pore volume.

[0036] Beneficial effects: A targeted chemical flooding agent, a targeted chemical flooding system and their applications disclosed by the present invention have the following beneficial effects:

[0037] 1. The present invention has the advantages of rapid dispersion and strong shear resistance, so it can realize online blending of the flooding system, effectively reduce the ground polymer blending system, and save ground investment;

[0038] 2. The present invention breaks through the current limitation that the polymer injection string can only achieve two - stage layered injection of the inner and outer pipes. It can use the existing water injection string to achieve multi - stage layered fine polymer injection, greatly delaying the risk of polymer channeling along the high - permeability layer in the case of a large formation permeability difference, realizing a more balanced displacement in chemical flooding, and greatly improving the effect of chemical flooding.

[0039] 3. The micro - capsule - targeted viscosity - increasing polymer inverse emulsion can release the inner - core polyacrylamide after a certain time under reservoir temperature conditions, and has the advantages of targeted viscosity - increasing and effectively expanding the swept volume. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1a SEM diagram of the targeted chemical flooding system prepared in Example 1.

[0041] Figure 1b SEM diagram of the conventional binary flooding system.

[0042] Figure 2 Schematic diagram of the comparison of the viscosities of the targeted chemical flooding system and the conventional binary flooding system in Example 1 with the thermal aging time.

[0043] Figure 3 Schematic diagram of the comparison of the shear resistance of the targeted chemical flooding system and the conventional binary flooding system in Example 1.

[0044] Figure 4a Schematic diagram of the oil displacement effect of the targeted chemical flooding system after strong shear.

[0045] Figure 4b Oil displacement effect of the conventional binary flooding system after strong shear. DETAILED DESCRIPTION OF THE EMBODIMENTS:

[0046] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0047] It should be noted that the terms used herein are only for describing the specific embodiments and are not intended to limit the exemplary embodiments of the present invention. As used herein, unless the context clearly indicates otherwise, the singular forms are also intended to include the plural forms. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, and / or combinations thereof.

[0048] In this application:

[0049] In parts by mass, the preparation method of the micro - capsule - targeted viscosity - increasing polymer inverse emulsion includes:

[0050] (1) Weigh 30 - 50 parts of water and add it to the reaction vessel. Under stirring conditions, add 50 - 70 parts of acrylamide, 15 - 25 parts of sodium acrylate, 1 - 3 parts of polymerizable polyurethane, 5 - 7 parts of non-ionic emulsifier. Then add 70 - 80 parts of white oil. After strong stirring, form a water-in-oil emulsion. Pass nitrogen for 40 - 60 minutes to remove oxygen, and then place it in a refrigeration device and refrigerate until the temperature reaches 5 - 10 °C;

[0051] (2) Add 0.001 - 0.0002 parts of sodium bisulfite, 0.002 - 0.0004 parts of ammonium persulfate, and 0.001 - 0.002 parts of azobisisobutyronitrile to the reaction vessel. After polymerization for at least 3 hours, raise the temperature to 65 - 75 °C and continue polymerization for 1 - 2 hours to obtain a microcapsule-targeted viscosity-increasing polymer inverse emulsion.

[0052] Furthermore, the non-ionic emulsifier is sorbitan monooleate or polysorbate.

[0053] That is: the microcapsule-targeted viscosity-increasing polymer inverse emulsion is prepared by an interfacial polymerization method from polymerizable monomers acrylamide, sodium acrylate, initiators azobisisobutyronitrile, sodium bisulfite, ammonium persulfate, polymerizable emulsifier non-ionic polyurethane prepolymer, emulsifier, and white oil.

[0054] Example 1

[0055] A targeted chemical oil displacement agent is composed of a microcapsule-targeted viscosity-increasing polymer inverse emulsion and a surfactant. Among them: the mass ratio of the microcapsule-targeted viscosity-increasing polymer inverse emulsion to the surfactant is 3:2.

[0056] Furthermore, the microcapsule-targeted viscosity-increasing polymer inverse emulsion is composed of a microcapsule shell and a partially hydrolyzed polyacrylamide gel encapsulated by the microcapsule shell.

[0057] Furthermore, the hydrolysis degree of the partially hydrolyzed polyacrylamide gel is 10%.

[0058] Furthermore, the viscosity-average molecular weight of the partially hydrolyzed polyacrylamide gel is 20 million.

[0059] Furthermore, the microcapsule-targeted viscosity-increasing polymer is spherical, and its average particle size is 0.4 μm.

[0060] Furthermore, the material of the microcapsule shell is non-ionic polyurethane.

[0061] Furthermore, the surfactant is composed of a compound of an anionic-nonionic amphoteric surfactant and a betaine surfactant. Among them:

[0062] The mass ratio of the anionic-nonionic amphoteric surfactant to the betaine surfactant is 2:1.

[0063] Further, the anionic-nonionic surfactant is fatty alcohol polyoxyethylene ether carboxylate.

[0064] Even further, the fatty alcohol polyoxyethylene ether carboxylate is sodium fatty alcohol polyoxyethylene ether carboxylate.

[0065] In another embodiment, the fatty alcohol polyoxyethylene ether carboxylate is potassium fatty alcohol polyoxyethylene ether carboxylate.

[0066] In yet another embodiment, the fatty alcohol polyoxyethylene ether carboxylate is ammonium fatty alcohol polyoxyethylene ether carboxylate.

[0067] Further, the betaine surfactant is tetradecyl carboxy betaine.

[0068] A targeted chemical flooding system is formed by mixing the above-mentioned targeted chemical flooding agent with an appropriate amount of water, wherein: based on the total mass of the targeted chemical flooding system, the weight ratio of the microcapsule targeted viscosity-increasing polymer reverse emulsion is 0.3%, and the weight ratio of the surfactant is 0.2%.

[0069] Application of the above-mentioned targeted chemical flooding system in oil exploitation.

[0070] Application of the above-mentioned targeted chemical flooding system as chemical flooding in tertiary oil recovery.

[0071] Further, when the above-mentioned targeted chemical flooding system is used as chemical flooding in tertiary oil recovery, the specific steps are as follows:

[0072] (1) Prepare the targeted chemical flooding system online on the ground;

[0073] (2) Directly inject the targeted chemical flooding system obtained in step (1) into the stratified fine injection pipe string, and use the stratified fine injection pipe string to directly inject the targeted chemical flooding system into the formation.

[0074] Further, the specific steps of step (1) are:

[0075] Load the formulated amount of microcapsule targeted viscosity-increasing polymer reverse emulsion and the formulated amount of surfactant into a solution tank respectively. After being pressurized by a booster pump and mixed with the formulated amount of water, the targeted chemical flooding system is obtained after passing through a static mixer.

[0076] Further, the stratified fine injection pipe string in step (2) is divided into 4 layer segments for multi-stage fine distribution injection, preferably 5-stage layer segment multi-stage fine distribution injection.

[0077] Further, the injection amount of the targeted chemical flooding system injected into the formation is 50% of the formation pore volume.

[0078] Example 2

[0079] It is substantially the same as Example 1, except that: the microcapsule-targeted tackifying polymer inverse emulsion used is different:

[0080] In parts by mass, the preparation method of the microcapsule-targeted tackifying polymer inverse emulsion includes:

[0081] (1) Weigh 30 parts of water and add it to a reaction vessel. Under stirring conditions, add 50 parts of acrylamide, 15 parts of sodium acrylate, 1 part of polymerizable polyurethane, and 5 parts of non-ionic emulsifier. Then add 70 parts of white oil, and form a water-in-oil emulsion after strong stirring. Pass nitrogen for 40 minutes to remove oxygen, and place it in a refrigeration device to refrigerate until the temperature reaches 5°C;

[0082] (2) Add 0.001 part of sodium bisulfite, 0.002 part of ammonium persulfate, and 0.001 part of azobisisobutyronitrile to the reaction vessel. After polymerization for 3 hours, raise the temperature to 65°C and continue polymerization for 2 hours to obtain the microcapsule-targeted tackifying polymer inverse emulsion.

[0083] Furthermore, the non-ionic emulsifier is sorbitan monooleate.

[0084] Example 3

[0085] A targeted chemical flooding agent is composed of a microcapsule-targeted tackifying polymer inverse emulsion and a surfactant, wherein: the mass ratio of the microcapsule-targeted tackifying polymer inverse emulsion to the surfactant is 5:4.

[0086] Furthermore, the microcapsule-targeted tackifying polymer inverse emulsion is composed of a microcapsule shell and a partially hydrolyzed polyacrylamide gel encapsulated by the microcapsule shell.

[0087] Furthermore, the hydrolysis degree of the partially hydrolyzed polyacrylamide gel is 20%.

[0088] Furthermore, the viscosity-average molecular weight of the partially hydrolyzed polyacrylamide gel is 30 million.

[0089] Furthermore, the microcapsule-targeted tackifying polymer is spherical, and its average particle size is 1.2 μm.

[0090] Furthermore, the material of the microcapsule shell is non-ionic polyurethane.

[0091] Furthermore, the surfactant is composed of a compound of an anionic-nonionic amphoteric surfactant and a betaine surfactant, wherein:

[0092] The mass ratio of the anionic-nonionic amphoteric surfactant to the betaine surfactant is 3:1.

[0093] Furthermore, the anionic non-zwitterionic surfactant is fatty alcohol polyoxyethylene ether sulfonate.

[0094] Even further, the fatty alcohol polyoxyethylene ether sulfonate is sodium fatty alcohol polyoxyethylene ether sulfonate.

[0095] In another embodiment, the fatty alcohol polyoxyethylene ether sulfonate is potassium fatty alcohol polyoxyethylene ether sulfonate.

[0096] In yet another embodiment, the fatty alcohol polyoxyethylene ether sulfonate is ammonium fatty alcohol polyoxyethylene ether sulfonate.

[0097] Furthermore, the betaine surfactant is tetradecyl hydroxymethyl carboxy betaine.

[0098] A targeted chemical enhanced oil recovery system is formed by mixing the above-mentioned targeted chemical enhanced oil recovery agent with an appropriate amount of water, wherein: based on the total mass of the targeted chemical enhanced oil recovery system, the weight percentage of the microcapsule targeted viscosity-increasing polymer inverse emulsion is 0.5%, and the weight percentage of the surfactant is 0.4%.

[0099] Application of the above-mentioned targeted chemical enhanced oil recovery system in oil extraction.

[0100] Application of the above-mentioned targeted chemical enhanced oil recovery system as a chemical flooding agent in tertiary oil recovery.

[0101] Further, when the above-mentioned targeted chemical enhanced oil recovery system is used as a chemical flooding agent in tertiary oil recovery, the specific steps are as follows:

[0102] (1) Prepare the targeted chemical enhanced oil recovery system online on the ground;

[0103] (2) Directly inject the targeted chemical enhanced oil recovery system obtained in step (1) into a layered fine injection string, and use the layered fine injection string to directly inject the targeted chemical enhanced oil recovery system into the formation.

[0104] Further, the specific steps of step (1) are:

[0105] Load the formulated amount of microcapsule targeted viscosity-increasing polymer inverse emulsion and the formulated amount of surfactant into a solution tank respectively. After being pressurized by a booster pump and mixed with the formulated amount of water, the targeted chemical enhanced oil recovery system is obtained after passing through a static mixer.

[0106] Further, the layered fine injection string in step (2) is divided into 11 stage multi-stage fine allocation injection, preferably 9 stage multi-stage fine allocation injection.

[0107] Further, the injection volume of the targeted chemical enhanced oil recovery system injected into the formation is 90% of the formation pore volume.

[0108] Example 4

[0109] It is substantially the same as Example 3, with the only difference being that the microcapsule-targeted viscosity-increasing polymer inverse emulsion is different. By mass, the preparation method of the microcapsule-targeted viscosity-increasing polymer inverse emulsion includes:

[0110] (1) Weigh 50 parts of water and add it to a reaction vessel. Under stirring conditions, add 70 parts of acrylamide, 25 parts of sodium acrylate, 3 parts of polymerizable polyurethane, and 7 parts of non-ionic emulsifier. Add 80 parts of white oil. After strong stirring, form a water-in-oil emulsion. Pass nitrogen for 60 minutes to remove oxygen, and then place it in a refrigeration device and refrigerate until the temperature reaches 10 °C;

[0111] (2) Add 0.0002 parts of sodium bisulfite, 0.0004 parts of ammonium persulfate, and 0.002 parts of azobisisobutyronitrile to the reaction vessel. After polymerization for 6 hours, raise the temperature to 75 °C and continue polymerization for 1 hour to obtain the microcapsule-targeted viscosity-increasing polymer inverse emulsion.

[0112] Furthermore, the non-ionic emulsifier is polysorbate.

[0113] Example 5

[0114] A targeted chemical flooding agent is composed of a microcapsule-targeted viscosity-increasing polymer inverse emulsion and a surfactant, where: the mass ratio of the microcapsule-targeted viscosity-increasing polymer inverse emulsion to the surfactant is 4:3.

[0115] Further, the microcapsule-targeted viscosity-increasing polymer inverse emulsion is composed of a microcapsule shell and a partially hydrolyzed polyacrylamide gel encapsulated by the microcapsule shell.

[0116] Furthermore, the hydrolysis degree of the partially hydrolyzed polyacrylamide gel is 15%.

[0117] Furthermore, the viscosity-average molecular weight of the partially hydrolyzed polyacrylamide gel is 14 million.

[0118] Further, the microcapsule-targeted viscosity-increasing polymer is spherical, and its average particle size is 0.8 μm.

[0119] Further, the material of the microcapsule shell is non-ionic polyurethane.

[0120] Further, the surfactant is composed of a compound of an anionic-nonionic amphoteric surfactant and a betaine surfactant, where:

[0121] The mass ratio of the anionic-nonionic amphoteric surfactant to the betaine surfactant is 2.5:1.

[0122] Furthermore, the anionic-nonionic amphoteric surfactant is fatty alcohol polyoxyethylene ether carboxylate.

[0123] Still further, the fatty alcohol polyoxyethylene ether carboxylate is potassium fatty alcohol polyoxyethylene ether carboxylate.

[0124] Still further, the betaine surfactant is tetradecyl sulfobetaine.

[0125] In another embodiment, the betaine surfactant is hydroxymethyl pentadecyl sulfobetaine.

[0126] In another embodiment, the betaine surfactant is a mixture of tetradecyl carboxybetaine, tetradecyl hydroxymethyl carboxybetaine, tetradecyl sulfobetaine, and hydroxymethyl pentadecyl sulfobetaine in an equal mass ratio.

[0127] A targeted chemical flooding system is formed by mixing the above-mentioned targeted chemical flooding agent with an appropriate amount of water. Among them: based on the total mass of the targeted chemical flooding system, the weight ratio of the microcapsule targeted viscosity-increasing polymer inverse emulsion is 0.4%, and the weight ratio of the surfactant is 0.3%.

[0128] Application of the above-mentioned targeted chemical flooding system in oil extraction.

[0129] Application of the above-mentioned targeted chemical flooding system as chemical flooding in tertiary oil recovery.

[0130] Still further, when the above-mentioned targeted chemical flooding system is used as chemical flooding in tertiary oil recovery, the specific steps are as follows:

[0131] (1) Prepare the targeted chemical flooding system online on the ground;

[0132] (2) Directly inject the targeted chemical flooding system obtained in step (1) into the stratified fine injection pipe string, and use the stratified fine injection pipe string to directly inject the targeted chemical flooding system into the formation.

[0133] Still further, the specific steps of step (1) are as follows:

[0134] Load the formulated amount of microcapsule targeted viscosity-increasing polymer inverse emulsion and the formulated amount of surfactant into a solution tank respectively. After being pressurized by a booster pump and mixed with the formulated amount of water, the targeted chemical flooding system is obtained after passing through a static mixer.

[0135] Still further, the stratified fine injection pipe string in step (2) is divided into 7 stage multi-level fine distribution injection, preferably 7-stage multi-level fine distribution injection.

[0136] Still further, the injection amount of the targeted chemical flooding system injected into the formation is 70% of the formation pore volume.

[0137] Example 6

[0138] It is substantially the same as Example 5, except that: the microcapsule-targeted tackifying polymer inverse emulsion is different. By mass, the preparation method of the microcapsule-targeted tackifying polymer inverse emulsion includes:

[0139] (1) Weigh 30-50 parts of water and add it to a reaction vessel. Under stirring conditions, add 50-70 parts of acrylamide, 15-25 parts of sodium acrylate, 1-3 parts of polymerizable polyurethane, 5-7 parts of non-ionic emulsifier. Add 70-80 parts of white oil, and form a water-in-oil emulsion after strong stirring. Pass nitrogen for 40-60 minutes to remove oxygen, and place it in a refrigeration device and refrigerate until the temperature reaches 5-10 °C;

[0140] (2) Add 0.001-0.0002 parts of sodium bisulfite, 0.002-0.0004 parts of ammonium persulfate, and 0.001-0.002 parts of azodiisobutyronitrile to the reaction vessel. After the polymerization reaction for at least 3 hours, raise the temperature to 65-75 °C and continue polymerization for 1-2 hours to obtain the microcapsule-targeted tackifying polymer inverse emulsion.

[0141] Furthermore, the non-ionic emulsifier is sorbitan monooleate or polysorbate.

[0142] Verification and Characterization

[0143] Example 7

[0144] This example is mainly used to analyze the microscopic morphology of the targeted chemical flooding system in Example 1 and compare it with the conventional binary flooding system.

[0145] Take 1 drop of the targeted chemical flooding system in Example 1, place it on a mica sheet, dry it with nitrogen, and then use a scanning electron microscope to characterize the morphology. At the same time, take a conventional binary flooding system with the same concentration as the targeted chemical flooding system in Example 1, treat it in the same way, and then use a scanning electron microscope to characterize the morphology. The characterization results are as Figure 1a shown.

[0146] It can be seen from the characterization results that since the microcapsules encapsulate the polymer, obvious spherical microcapsules can be seen in the targeted chemical flooding system, and the size of the microcapsules is 400-600 nm( Figure 1a shown), and since the polymer macromolecular chains in the aqueous solution of the conventional binary flooding system are completely dissolved in water, the structure formed presents an obvious network structure (as Figure 1b shown).

[0147] Example 8

[0148] This example is mainly used to compare the viscosities of the targeted chemical flooding system and the conventional binary flooding system in Example 1 with the thermal aging time.

[0149] Take 200 g of the targeted chemical enhanced oil recovery system in Example 1. After deoxygenating with nitrogen, it is dispensed into ampoules, sealed, and placed in an oven at 75 °C. Samples are taken at different times to test the change in the viscosity of the targeted chemical enhanced oil recovery system with aging time.

[0150] Another 200 g of the conventional binary enhanced oil recovery system is taken. The treatment method is the same as that of the targeted chemical enhanced oil recovery system. The change in the viscosity of the conventional binary enhanced oil recovery system with aging time is tested and compared with that of the targeted chemical enhanced oil recovery system. The test comparison results are as Figure 2 shown.

[0151] From Figure 2 the test results, it can be seen that since the targeted chemical enhanced oil recovery system needs to be slowly released in the high-temperature reservoir environment, the initial viscosity of the system is relatively low, and the polymer is completely encapsulated in the microcapsules. Therefore, it has good shear resistance when the system passes through the perforations. As the aging time at the formation temperature extends, the viscosity is gradually released. Combined with the surfactant contained, it plays a role in expanding the swept area and improving the oil washing efficiency in the deep formation. Under the initial conditions, since the polymer in the conventional binary enhanced oil recovery system is completely dissolved, it has a relatively high initial viscosity. However, as the thermal aging time extends, the polymer slowly undergoes thermal degradation and the viscosity slowly decreases. Eventually, after 60 days of thermal aging, the targeted chemical enhanced oil recovery system has a higher viscosity than the conventional binary enhanced oil recovery system. Therefore, the targeted chemical enhanced oil recovery system has better long-term thermal stability and stronger deep reservoir oil displacement ability under reservoir conditions.

[0152] Example 9

[0153] This example is mainly used for comparing the strong shear resistance of the targeted chemical enhanced oil recovery system and the conventional binary enhanced oil recovery system in Example 1.

[0154] Take 200 g of the targeted chemical enhanced oil recovery system in Example 1 and add it to a Waring blender. Start the Waring blender and shear at a high speed of 15,000 r / min for 2 minutes. Take the solution after high-speed shearing and the unsheared targeted chemical enhanced oil recovery system. After deoxygenating with nitrogen, they are dispensed into ampoules, sealed, and placed in an oven at 75 °C. After 5 days of thermal aging to completely release the microcapsule polymer, measure the viscosity of the solution after complete release of the targeted chemical enhanced oil recovery system after high-speed shearing and compare it with the viscosity after complete release of the unsheared targeted chemical enhanced oil recovery system to obtain the viscosity retention rate of the targeted chemical enhanced oil recovery system after high-speed shearing.

[0155] Another 200 g of the conventional binary enhanced oil recovery system is taken and added to a Waring blender. Shear at a high speed of 15,000 r / min for 2 minutes. Test the viscosity of the solution after shearing and compare it with the viscosity of the unsheared binary system solution to obtain the viscosity retention rate of the conventional binary system after high-speed shearing. The test comparison results are as Figure 3 shown.

[0156] It can be seen from the test results that during the high-speed shearing process of the targeted chemical flooding system by the Waring blender, since the polymer is included in the microcapsules, the microcapsules have a strong protective effect on the polymer. After high-temperature release, compared with the non-sheared targeted chemical flooding system, the viscosity retention rate reaches 99.5%. For the conventional binary system, since the molecular chains are exposed after complete dissolution, its resistance to the strong shearing action of the Waring blender is poor, and the viscosity retention rate is only 6.9% after high-speed shearing. Therefore, the targeted chemical flooding system has the ability to resist strong shearing.

[0157] Example 10

[0158] This example is mainly used to analyze the comparison of the oil displacement effects of the targeted chemical flooding system and the conventional binary flooding system after the strong shearing of the flooding system by simulating the water nozzle of the injection string with the Waring blender in the present invention.

[0159] Take a sandstone core with a size of 2.5 cm × 30 cm and a permeability of 1500×10 -3 μm 2 After water flooding until the water cut reaches 95%, inject the solution after the complete release of the high-speed sheared targeted chemical flooding system in Example 9 and the solution after the high-speed shearing of the conventional binary flooding system respectively. The injection solution slug size is 0.5 PV, and then subsequent water flooding is carried out until the water cut is above 98% until the oil displacement experiment ends, to obtain the enhanced oil recovery ability of the two systems after high-speed shearing by simulating the water nozzle of the injection string. The test comparison results are as Figure 4a and Figure 4b shown.

[0160] It can be seen from the comparison of the enhanced oil recovery in Table 1 that after water flooding, the high-speed sheared targeted chemical flooding system and the conventional binary flooding system are injected respectively. Since the targeted chemical flooding system has strong shear resistance, the flooded system can still maintain a high viscosity after the complete shell-breaking release after shearing. Finally, the enhanced oil recovery rate of the injected high-speed sheared targeted chemical flooding system reaches 31.4%, while the conventional binary flooding system has poor shear resistance and large viscosity loss after high-speed shearing. Finally, the enhanced oil recovery rate of the injected conventional binary flooding system after water flooding is only 2.8%. Therefore, only the targeted chemical flooding system can resist the strong shearing of the injection string water nozzle, realize the multi-stage fine distribution injection of the chemical flooding injection string, and thus achieve a greater increase in the crude oil recovery rate.

[0161] Table 1 Comparison of the oil displacement effects of the targeted chemical flooding system and the conventional binary flooding system after high-speed shearing

[0162]

[0163] The specific embodiments described above further elaborate on the object, technical solution, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A targeted chemical oil displacement agent, characterized in that: The invention is composed of a microcapsule targeted viscosity-enhancing polymer reverse emulsion and a surfactant, wherein the mass ratio of the microcapsule targeted viscosity-enhancing polymer reverse emulsion to the surfactant is (3-5): (2-4).

2. A targeted chemical oil displacement agent according to claim 1, characterized in that: The microcapsule targeted viscosity-enhancing polymer reverse emulsion consists of a microcapsule shell and a partially hydrolyzed polyacrylamide gel wrapped by the microcapsule shell.

3. A targeted chemical oil displacement agent as claimed in claim 2, characterized in that: The hydrolysis degree of the partially hydrolyzed polyacrylamide gel is 10-20%, and the viscosity average molecular weight of the partially hydrolyzed polyacrylamide gel is 20 million-30 million.

4. A targeted chemical oil displacement agent according to claim 1, characterized in that: The microcapsule targeted viscosity-enhancing polymer is spherical ， The average particle size is 0.4 μm to 1.2 μm.

5. A targeted chemical oil displacement agent according to claim 1, characterized in that: The material of the microcapsule shell is non-ionic polyurethane.

6. A targeted chemical oil displacement agent according to claim 1, characterized in that: In parts by mass, the preparation method of the microcapsule targeted viscosity-enhancing polymer reverse emulsion comprises: (1) Weigh 30 to 50 parts of water and add it into a reaction container, add 50 to 70 parts of acrylamide, 15 to 25 parts of sodium acrylate, 1 to 3 parts of polymerizable polyurethane, 5 to 7 parts of nonionic emulsifier, and 70 to 80 parts of white oil under stirring, and form an oil-in-water emulsion after strong stirring, introduce nitrogen for 40 to 60 minutes to deoxygenate, and place in a refrigerator to refrigerate to a temperature of 5 to 10° C.; (2) Add 0.001-0.0002 parts of sodium bisulfite, 0.002-0.0004 parts of ammonium persulfate, and 0.001-0.002 parts of azobisisobutyl cyanide into a reaction container, and after the polymerization reaction for at least 3 hours, raise the temperature to 65-75° C. and continue the polymerization for 1-2 hours to obtain a microcapsule targeted viscosity-enhancing polymer reverse emulsion.

7. A targeted chemical oil displacement agent according to claim 6, characterized in that: The nonionic emulsifier is sorbitan monooleate or polysorbate.

8. A targeted chemical oil displacement agent according to claim 1, characterized in that: The surfactant is compounded by an anionic non-amphoteric surfactant and a betaine surfactant, wherein: The mass ratio of the anionic non-amphoteric surfactant to the betaine surfactant is (2-3):

1.

9. A targeted chemical oil displacement agent according to claim 8, characterized in that: The anionic non-amphoteric surfactant is fatty alcohol polyoxyethylene ether carboxylate or fatty alcohol polyoxyethylene ether sulfonate.

10. A targeted chemical oil displacement agent according to claim 9, characterized in that: The fatty alcohol polyoxyethylene ether carboxylate is one of fatty alcohol polyoxyethylene ether carboxylate sodium, fatty alcohol polyoxyethylene ether carboxylate potassium and fatty alcohol polyoxyethylene ether carboxylate ammonium.

11. A targeted chemical oil displacement agent according to claim 9, characterized in that: The fatty alcohol polyoxyethylene ether sulfonate is one of sodium fatty alcohol polyoxyethylene ether sulfonate, potassium fatty alcohol polyoxyethylene ether sulfonate and ammonium fatty alcohol polyoxyethylene ether sulfonate.

12. A targeted chemical oil displacement agent according to claim 8, characterized in that: The betaine surfactant is at least one of tetradecyl carboxy betaine, tetradecyl hydroxymethyl carboxy betaine, tetradecyl sulfobetaine, and hydroxymethyl sulfonyl pentadecyl betaine.

13. A targeted chemical flooding system, characterized in that: The targeted chemical oil displacement agent according to any one of claims 1 to 12 is mixed with an appropriate amount of water, wherein: based on the total mass of the targeted chemical oil displacement system, the weight proportion of the microcapsule targeted viscosity-enhancing polymer reverse emulsion is 0.3% to 0.5%, and the weight proportion of the surfactant is 0.2% to 0.4%.

14. Use of the targeted chemical oil recovery system according to claim 13 in oil production.

15. Use of the targeted chemical flooding system according to claim 13 as chemical flooding in tertiary oil recovery.

16. The use according to claim 15, characterized in that When the above-mentioned targeted chemical flooding system is used as chemical flooding in tertiary oil recovery, the specific steps are as follows: (1) Surface online preparation of targeted chemical flooding system; (2) directly injecting the targeted chemical oil recovery system obtained in step (1) into the layered fine water injection string, and directly injecting the targeted chemical oil recovery system into the formation using the layered fine water injection string.

17. The use according to claim 16, characterized in that The specific steps of step (1) are: A formulated amount of microcapsule targeted viscosity-enhancing polymer inverse emulsion and a formulated amount of surfactant are respectively placed in a solution tank, pressurized by a booster pump, mixed with a formulated amount of water, and passed through a static mixer to obtain a targeted chemical flooding system.

18. The use according to claim 16, characterized in that The layered fine water injection string described in step (2) is divided into 4 to 11 layers for multi-level fine injection, preferably 5 to 9 layers for multi-level fine injection.

19. The use according to claim 16, characterized in that The injection amount of the targeted chemical flooding system injected into the formation is 50% to 90% of the pore volume of the formation.

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