Oil displacement system and optimization method, injection method and application thereof

Abstract

The invention discloses an oil displacement system as well as an optimization method, an injection method and application thereof. The oil displacement system comprises a pH regulator, non-condensate gas, water vapor, a foaming agent, a nano foam stabilizer, a dispersing aid and a solvent, wherein the mass ratio of the water vapor to the non-condensate gas is 1: 1-1: 3 under the condition of preset underground temperature and pressure; based on the mass percentage of the water vapor, the mass fraction of the foaming agent is 0.3 to 3.0 percent, the mass fraction of the nano foam stabilizer is 0.1 to 5.0 percent, the mass fraction of the dispersing aid is 0.1 to 2.0 percent, and the mass fraction of the solvent is 1.0 to 5.0 percent; the nano foam stabilizer comprises a nano anionic polyelectrolyte and a nano cationic polyelectrolyte. In crude oil extraction, the oil displacement system can stabilize gas for a long time, meet energy supplementation of gas foam, improve flow resistance and inhibit rapid discharge of gas, so that the huff-puff development effect and huff-puff recovery rate of a composite medium are greatly improved.

Description

Technical Field

[0001] The invention relates to an oil displacement system and an optimization method, an injection method and an application thereof. Background Art

[0002] Steam stimulation technology is one of the main technologies for heavy oil production, accounting for more than 60% of heavy oil technical output for many years. Therefore, new technologies to improve the effect of steam stimulation are crucial to heavy oil reservoirs developed by steam stimulation.

[0003] Statistics show that the viscosity of heavy oil reservoirs currently developed by steam stimulation is usually 2000-20000mPa.s under degassing conditions of 50℃, of which 2000-10000mPa.s is ordinary heavy oil reservoirs, and 10000mPa.s or more is extra heavy oil reservoirs. Steam stimulation cycles are usually around 20 cycles, but for extra heavy oil with high crude oil viscosity, after the 10th stimulation cycle, it is in a low-yield and low-efficiency stimulation stage.

[0004] In order to significantly improve the development effect of huff and puff, the formation energy is usually supplemented in the later stage of huff and puff. This process requires the injection of a large amount of steam. During gas-assisted steam huff and puff, the gas in the production stage will be discharged and degassed first, which seriously affects the huff and puff effect. For gas foam that reduces gas mobility and inhibits the rapid discharge of gas to assist steam huff and puff, due to the influence of the stability of the foaming agent, the performance of the foaming agent fails during the 2-3 days of well soaking after injection, and it is difficult to play a long-term role in stabilizing the foam. It can be seen that the conventional gas foam has a short stability time and limited development effect. Summary of the invention

[0005] In order to at least partially solve the above-mentioned technical problems existing in the prior art, an embodiment of the present invention provides an oil recovery system and its preferred method, injection method and application, so as to form a long-term stable gas foam, thereby assisting steam throughput, exerting the energy replenishment effect of gas for a long time, and extending the effective production time and output of throughput.

[0006] As one aspect of the present invention, an oil displacement system is provided, wherein the system comprises: a pH regulator, a non-condensable gas, water vapor, a foaming agent, a nano foam stabilizer, a dispersing aid and a solvent; wherein:

[0007] Under preset underground temperature and pressure conditions, the mass ratio of the water vapor to the non-condensable gas is 1:1 to 1:3;

[0008] Calculated by mass percentage of the water vapor, the mass fraction of the foaming agent is 0.3-3.0%, the mass fraction of the nano foam stabilizer is 0.1-5.0%, the mass fraction of the dispersing aid is 0.1-2.0%, and the mass fraction of the solvent is 1.0-5.0%;

[0009] The nano foam stabilizer comprises nano anionic polyelectrolyte and nano cationic polyelectrolyte.

[0010] In one or some possible embodiments, the pH regulator is selected from oxalic acid, citric acid, HCL or H 2 SO 4 One or more of .

[0011] In one or some possible embodiments, the non-condensable gas is selected from CO 2 , CH 4 、N 2 Or one or more of oxygen-reduced air.

[0012] In one or some possible embodiments, the foaming agent is selected from anionic surfactants and / or nonionic surfactants.

[0013] In one or some possible embodiments, the anionic surfactant is selected from one or more of ammonium dodecyl sulfate, sodium dodecyl sulfate, sodium lauryl ether sulfate, sodium lauryl ether sulfate, dioctyl sodium sulfosuccinate, perfluorooctane sulfonic acid, perfluorobutane sulfonic acid, alkyl aryl ether phosphate or alkyl ether phosphate;

[0014] The nonionic surfactant is selected from one or a combination of fatty alcohols, polyoxyethylene glycol alkyl ethers, octyl glycol monododecyl ether, polyoxypropylene glycol alkyl ethers, glucoside alkyl ethers, decyl glucoside, polyoxyethylene glycol alkylphenol ethers, sorbic acid esters, sorbitol alkyl esters, dodecyl dimethylamine oxide, and block copolymers of polyethylene glycol and polypropylene glycol.

[0015] In one or some possible embodiments, the mass ratio of the nano anionic polyelectrolyte to the nano cationic polyelectrolyte is 1:10 to 10:1;

[0016] The nano anionic polyelectrolyte is dextran sulfate;

[0017] The nano cationic polyelectrolyte is selected from one or more of polyethyleneimine, poly(allylamine) or chitosan.

[0018] In one or some possible embodiments, the dispersing aid is selected from one or more of ethanol, ethylene glycol or methanol.

[0019] In one or some possible embodiments, the solvent is selected from one or more of alkanes, aromatic hydrocarbons, natural gas condensate, liquefied petroleum gas, naphtha products, alcohols, ethers, aldehydes, ketones and crude oil refineries.

[0020] As another aspect of the present invention, it relates to a preferred method of the above system, the method comprising:

[0021] S101, determining the type of pH regulator selected and the amount to be added;

[0022] S102, determining the type of solvent to be selected and the amount to be added;

[0023] S103, determining the type of nano foam stabilizer to be selected.

[0024] In one or some possible embodiments, in S101, determining the selected pH regulator and its addition amount includes:

[0025] The specific types of the pH adjusters are mixed in any mass ratio to obtain multiple groups of different types of pH adjusters;

[0026] The formation water is divided into several groups, and the final pH value of each unit volume of formation water after adding various types of pH regulators is determined according to the initial pH value of the formation water;

[0027] The final pH value is adjusted to a set value to determine the optimal type of the selected pH adjuster and the amount of addition.

[0028] In one or some possible embodiments, in S102, determining the selected solvent type and the amount of solvent to be added includes:

[0029] The specific types of the solvents are mixed in any mass ratio to obtain multiple groups of different types of solvents;

[0030] Under a preset formation pressure condition, determining the saturation temperature of different solvents under the pressure condition according to the temperature of the water vapor;

[0031] According to the absolute value of the difference between the saturation temperature corresponding to each solvent and the temperature of the water vapor, a solvent whose absolute value is within a set range is selected;

[0032] According to the viscosity of the crude oil, determining the decrease in the viscosity of the crude oil when the solvent whose absolute value is selected is within a set range is added;

[0033] The optimum type of solvent to be selected and the amount of solvent to be added are determined according to the decrease in the viscosity of the crude oil.

[0034] In one or some possible embodiments, in S103, determining the type of the selected nano foam stabilizer includes:

[0035] The specific types of the nano cationic polyelectrolytes are mixed in any mass ratio to obtain multiple groups of different types of nano cationic polyelectrolytes;

[0036] Mixing the plurality of groups of different types of nano cationic polyelectrolytes with the plurality of groups of nano anionic polyelectrolytes in any mass ratio to obtain a plurality of groups of different types of nano foam stabilizers;

[0037] Determining a shear rate according to an injection flow rate of the oil displacement system;

[0038] According to the shear rate, the dispersibility of the nano foam stabilizer in the foam system under the action of the dispersing aid is determined;

[0039] Observe and verify the dispersibility of the nano foam stabilizer in the foam system according to an optical microscope, and evaluate different types of nano foam stabilizers;

[0040] According to the evaluation results of the different types of nano foam stabilizers, a nano foam stabilizer with a dispersion rate of more than 95% is selected.

[0041] As another aspect of the present invention, it relates to the application of the above oil displacement system in steam stimulation of heavy oil reservoirs.

[0042] As another aspect of the present invention, it relates to an injection method of the above-mentioned oil displacement system for steam stimulation of heavy oil reservoirs, wherein the method adopts a multi-stage plug injection method and comprises in sequence:

[0043] Injection of pre-placed steam slug;

[0044] injecting a pH adjuster slug;

[0045] Slugs of pre-solvent and dispersant injection;

[0046] Injection of steam and foam system slugs;

[0047] Injection of post-placed steam slug;

[0048] The foam system comprises non-condensable gas, a foaming agent, a nano foam stabilizer and a dispersing aid.

[0049] In one or some possible embodiments, the pore volume within the control range of a single well is calculated as the number of PVs of a single well:

[0050] The pre-placed steam slug is 0.02-0.1 PV;

[0051] The pH value regulator slug is 0.02 to 0.1 PV;

[0052] The pre-solvent and + dispersing agent segment plug is 0.02 to 0.1 PV;

[0053] The slug of the water vapor + foam system is 0.1 to 0.3 PV;

[0054] The post-placed water vapor segment plug is 0.01-0.1 PV.

[0055] As another aspect of the present invention, it relates to the application of the above-mentioned injection method in employment.

[0056] As another aspect of the present invention, a method for crude oil production is provided, the method comprising the injection method of the oil displacement system for steam stimulation of heavy oil reservoirs.

[0057] The oil displacement system of the present invention adopts anionic and cationic polyelectrolytes to form a foam stabilizer, which can polymerize into a steam foam stabilizer with super foam stabilizing effect under specific pH conditions, and can greatly increase the action time of gas foam added to steam and expand the action range of steam foam.

[0058] The optimization method of the oil displacement system provided by the present invention is to select the solvent closest to the saturation temperature of water vapor under the formation pressure condition, and to optimize the solvent type by mixing the same amount of solvent into the crude oil to reduce the viscosity of the crude oil; by dissolving the macromolecules by the solvent, it can prevent the gas, especially CO, from being injected into the oil in the process of simple gas injection. 2 The extraction deasphalting and blocking of the oil layer. In addition, the embodiment of the present invention also proposes a method of further stabilizing the steam foam by adjusting the pH value of the formation water by acid. Using acid to adjust the pH value to a slightly acidic environment is conducive to dissolving the calcium interlayer inside the heterogeneous oil layer, improving the effective permeability of the oil layer, and thus further improving the injection capacity of the thermal fluid.

[0059] The present invention adopts a multi-segment injection method, which can achieve the special effect of changing the reservoir properties and increasing oil production and efficiency. Among them, the mixed injection of solvent and dispersing agent segment plugs is conducive to increasing the scope of action of the solvent and avoiding solvent aggregation and premature extraction. The gas + foaming agent + foam stabilizer + dispersing agent segment plug is conducive to dispersing the foam stabilizer and the foaming agent, increasing the scope of action of the foam system, and can promote the gas to be evenly dispersed in the foam system to maximize its effectiveness. The post-placed steam segment plug can push the aforementioned injection system into the deep oil layer, greatly increasing the radius of action and swept volume of the injected hot fluid, thereby improving the development effect of steam throughput.

[0060] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention are realized and obtained by the structures particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 The figure is a process flow chart of the crude oil production method of the present invention. DETAILED DESCRIPTION

[0062] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0063] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0064] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as commonly understood by those skilled in the art to which the invention belongs. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0065] In the description of the present invention, it should be noted that the terms "include", "including", "have", "contain" and the like are open terms, meaning including but not limited to.

[0066] Embodiment 1

[0067] The embodiment of the present invention provides an oil displacement system, wherein the system comprises: a pH regulator, a non-condensable gas, water vapor, a foaming agent, a nano foam stabilizer, a dispersing aid and a solvent; wherein:

[0068] In an embodiment of the present invention, under preset underground temperature and pressure conditions, the mass ratio of the water vapor to the non-condensable gas is 1:1 to 1:3;

[0069] In a specific embodiment, the preset underground temperature and pressure are the temperature and pressure of the oil layer, including but not limited to: the temperature of the oil layer is 45° C., and the pressure of the oil layer is 10 MPa.

[0070] In a specific embodiment, the mass ratio of the water vapor to the non-condensable gas may be 1:1, 1:2 or 1:3, etc.

[0071] In the embodiment of the present invention, based on the mass percentage of the water vapor, the mass fraction of the foaming agent is 0.3-3.0%, the mass fraction of the nano foam stabilizer is 0.1-5.0%, and the mass fraction of the dispersing aid is 0.1-2.0%;

[0072] In a specific embodiment, based on the mass percentage of the water vapor, the mass fraction of the foaming agent can be 0.3%, 1.0%, 2.5% or 3.0%; the mass fraction of the nano foam stabilizer can be 0.1%, 0.8%, 1.5%, 2.2%, 3.0%, 4.0% or 5.0%; the mass fraction of the dispersing aid can be 0.1%, 1.0% or 2.0%.

[0073] In order to provide a steam foam stabilizer with good foam stabilization effect, the effect time of adding gas foam to steam can be greatly increased and the effect range of steam foam can be expanded. Therefore, in an embodiment of the present invention, a nano foam stabilizer is involved, and the nano foam stabilizer comprises a nano anionic polyelectrolyte and a nano cationic polyelectrolyte.

[0074] In an embodiment of the present invention, the mass ratio of the nano anionic polyelectrolyte to the nano cationic polyelectrolyte is 1:10 to 10:1;

[0075] The nano anionic polyelectrolyte is selected from dextran sulfate;

[0076] The nano cationic polyelectrolyte is selected from one or more of polyethyleneimine, poly(allylamine) or chitosan.

[0077] In a specific embodiment, the mass ratio of the nano-anionic polyelectrolyte to the nano-cationic polyelectrolyte includes but is not limited to 1:10, 1:1 or 10:1.

[0078] In a specific embodiment, the nano foam stabilizer can be a mixture of dextran sulfate and polyethylene imine; can be a mixture of dextran sulfate and polyethylene imine, poly (allylamine) , can be a mixture of dextran sulfate and vinylimine, poly (allylamine) or deacetylated chitosan.

[0079] In order to maximize the sustainable effect of the nano foam stabilizer in stabilizing foam, in the embodiments of the present invention, the application environment of the nano foam stabilizer of the present invention is fully considered. Therefore, a pH regulator is provided; the pH regulator is selected from oxalic acid, citric acid, HCL or H 2 SO 4 One or more of .

[0080] In a specific embodiment, the pH adjuster can be oxalic acid, can be HCL, can be citric acid and H 2 SO 4 A mixture of oxalic acid, citric acid and HCL, or a mixture of oxalic acid, citric acid, HCL and H 2 SO 4 mixtures, etc.

[0081] In the embodiment of the present invention, the non-condensable gas is selected from CO 2 , CH 4 , N 2 Or one or more of oxygen-reduced air.

[0082] In a specific embodiment, the non-condensable gas may be CO 2 , which can be CH 4 and N 2 mixture, or CO 2 , CH 4 , N 2 and a mixture of oxygen-reduced air, etc.

[0083] In an embodiment of the present invention, the foaming agent is selected from anionic surfactants and / or nonionic surfactants.

[0084] In a specific embodiment, the foaming agent may be an anionic surfactant, a nonionic surfactant, or a mixture of an anionic surfactant and a nonionic surfactant.

[0085] In an embodiment of the present invention, the anionic surfactant is selected from one or more of ammonium dodecyl sulfate, sodium dodecyl sulfate, sodium lauryl ether sulfate, sodium dodecyl ether sulfate, dioctyl sodium sulfosuccinate, perfluorooctane sulfonic acid, perfluorobutane sulfonic acid, alkyl aryl ether phosphate or alkyl ether phosphate;

[0086] The nonionic surfactant is selected from one or a combination of fatty alcohols, polyoxyethylene glycol alkyl ethers, octyl glycol monododecyl ether, polyoxypropylene glycol alkyl ethers, glucoside alkyl ethers, decyl glucoside, polyoxyethylene glycol alkylphenol ethers, sorbic acid esters, sorbitol alkyl esters, dodecyl dimethylamine oxide, and block copolymers of polyethylene glycol and polypropylene glycol.

[0087] In a specific embodiment, the foaming agent can be ammonium dodecyl sulfate, can be a fatty alcohol, can be a mixture of sodium lauryl ether sulfate and sodium lauryl ether sulfate, can also be a mixture of sodium lauryl ether sulfate and polyoxyethylene glycol alkyl ether, etc.

[0088] In order to inject the oil displacement system of the present invention into the formation and achieve better experimental results, in an embodiment of the present invention, a dispersing aid is provided for dispersing the solvent and the foam system. The dispersing aid is selected from one or more of ethanol, ethylene glycol or methanol.

[0089] In a specific embodiment, the dispersing aid may be ethanol, a mixture of ethanol and ethylene glycol, or a mixture of ethanol, ethylene glycol and methanol.

[0090] To further dissolve and reduce the viscosity of the formation oil layer, in an embodiment of the present invention, a solvent is provided, and the solvent is selected from one or more of alkanes, aromatics, natural gas condensate, liquefied petroleum gas, naphtha products, alcohols, ethers, aldehydes, ketones and crude oil refineries.

[0091] In a specific embodiment, the solvent may be an alkane, may be natural gas condensate, may be a mixture of aromatic hydrocarbons and liquefied petroleum gas, may be a mixture of alcohol, ether and crude oil refinery, etc.

[0092] Embodiment 2

[0093] Based on the same inventive concept, the embodiment of the present invention relates to a preferred method of the oil displacement system described in embodiment 1, comprising:

[0094] S101, determining the selected pH regulator and the amount thereof to be added;

[0095] S102, determining the selected solvent and the amount thereof to be added;

[0096] S103, determining the selected nano foam stabilizer and the amount to be added.

[0097] In an embodiment of the present invention, the step of determining the selected pH adjusting agent and the amount thereof to be added comprises:

[0098] The specific types of the pH adjusters are mixed in any mass ratio to obtain multiple groups of different types of pH adjusters;

[0099] The formation water is divided into several groups, and the final pH value of each unit volume of formation water after adding various types of pH regulators is determined according to the initial pH value of the formation water;

[0100] The final pH value is adjusted to a set value to determine the optimal type of the selected pH adjuster and the amount of addition.

[0101] In the embodiment of the present invention, the set pH value is 5-7.

[0102] In a specific embodiment, for further explanation, the set pH value is selected as 5. At the same time, the pH adjuster that first reaches the set value is the best selected type, and its dosage is the optimal dosage.

[0103] In an embodiment of the present invention, the step of determining the selected solvent type and the amount of solvent to be added includes:

[0104] The specific types of the solvents are mixed in any mass ratio to obtain multiple groups of different types of solvents;

[0105] Under a preset formation pressure condition, determining the saturation temperature of different solvents under the pressure condition according to the temperature of the water vapor;

[0106] According to the absolute value of the difference between the saturation temperature corresponding to each solvent and the temperature of the water vapor, a solvent whose absolute value is within a set range is selected;

[0107] According to the viscosity of the crude oil, determining the decrease in the viscosity of the crude oil when the solvent whose absolute value is selected is within a set range is added;

[0108] The optimum type of solvent to be selected and the amount of solvent to be added are determined according to the decrease in the viscosity of the crude oil.

[0109] In the embodiment of the present invention, the setting range of the absolute value is 5-10°C.

[0110] In a specific embodiment, for further explanation, a solvent having an absolute value within the range of 5 to 10° C. is first determined, and then the determined solvent is added to crude oil, and the decrease in crude oil viscosity is measured, and a group with the largest decrease in crude oil viscosity is found, and the solvent used in this group is determined to be the best solvent, and its dosage is the best dosage.

[0111] In an embodiment of the present invention, the step of determining the type of nano foam stabilizer to be selected includes:

[0112] The specific types of the nano cationic polyelectrolytes are mixed in any mass ratio to obtain multiple groups of different types of nano cationic polyelectrolytes;

[0113] Mixing the plurality of groups of different types of nano cationic polyelectrolytes with the plurality of groups of nano anionic polyelectrolytes in any mass ratio to obtain a plurality of groups of different types of nano foam stabilizers;

[0114] Determining a shear rate according to an injection flow rate of the oil displacement system;

[0115] According to the shear rate, the dispersibility of the nano foam stabilizer in the foam system under the action of the dispersing aid is determined;

[0116] Observe and verify the dispersibility of the nano foam stabilizer in the foam system according to an optical microscope, and evaluate different types of nano foam stabilizers;

[0117] According to the evaluation results of the different types of nano foam stabilizers, a nano foam stabilizer with a dispersion rate of more than 95% is selected.

[0118] In a specific embodiment, for further explanation, the theoretical dispersibility of the nano foam stabilizer is determined according to the shear rate, and the result is then observed and verified through an optical microscope, and different types of nano foam stabilizers are comprehensively evaluated to determine the best type to be selected.

[0119] In the embodiments of the present invention, the dispersing aid is mainly used to disperse the solvent and can be selected arbitrarily. The influence of different dispersing aids on the dispersing effect of the solvent can be ignored.

[0120] In the embodiment of the present invention, after determining the best type of nano foam stabilizer, the foaming agent to be used can be selected based on the effects of different types of foaming agents on the foaming volume and / or foam half-life of the oil displacement system. The method for selecting such a foaming agent can be operated and implemented by a person skilled in the art.

[0121] Embodiment 3

[0122] Refer to the attached Figure 1 Based on the same inventive concept, the embodiment of the present invention relates to the injection method of the oil displacement system described in the first or second embodiment. In order to achieve the special effect of changing the reservoir properties and increasing oil production and efficiency, the embodiment of the present invention adopts a multi-segment injection method when injecting the oil displacement system of the present invention, which specifically includes:

[0123] Injection of pre-placed steam slug;

[0124] injecting a pH adjuster slug;

[0125] Slugs of pre-solvent and dispersant injection;

[0126] Injection of steam and foam system slugs;

[0127] Injection of post-placed steam slug;

[0128] The foam system comprises non-condensable gas, a foaming agent, a nano foam stabilizer and a dispersing aid.

[0129] In the embodiment of the present invention, the pore volume within the control range of a single well is calculated as the number of PVs of a single well:

[0130] The pre-placed steam slug is 0.02-0.1 PV;

[0131] The pH value regulator slug is 0.02 to 0.1 PV;

[0132] The pre-solvent and + dispersing agent segment plug is 0.02 to 0.1 PV;

[0133] The slug of the water vapor + foam system is 0.1 to 0.3 PV;

[0134] The post-placed water vapor segment plug is 0.01-0.1 PV.

[0135] In the embodiment of the present invention, the injection of the front steam slug is intended to reduce the viscosity of the oil layer and reduce the resistance of subsequent media entering the oil layer.

[0136] In the embodiment of the present invention, the purpose of injecting the pH regulator plug is to adjust the system environment to be acidic so that the nano foam stabilizer can exert its maximum effect.

[0137] In the embodiment of the present invention, the purpose of injecting the slug of pre-solvent and dispersing aid is to increase the action range of the solvent and avoid solvent aggregation.

[0138] In the embodiment of the present invention, the purpose of injecting water vapor and foam system plugs is to facilitate the dispersion of foam stabilizers and foaming agents, increase the scope of action of the foam system, and promote the uniform dispersion of gas in the foam system to maximize its effectiveness.

[0139] In the embodiment of the present invention, the purpose of injecting the post-water steam plug is to push the injection system into the deep oil layer, greatly increase the effective radius and swept volume of the injected hot fluid, and thus improve the development effect of steam throughput.

[0140] Embodiment 4

[0141] See attached Figure 1 The embodiment of the present invention provides a specific application of an oil recovery system in a steam-throwing heavy oil reservoir, wherein vertical wells are deployed in the reservoir, the well spacing is 60m, the effective thickness of the oil layer is 10m, the porosity is 30%, and the original oil saturation is 62%. The oil recovery method comprises the following steps:

[0142] (1) Optimization of the oil displacement system includes:

[0143] a) The pH value of the formation water was determined to be 7.2, which is a weakly alkaline environment. On this basis, the pH value of the formation water per unit volume after adding different acids was measured. It was determined that after adding 0.1 tons of HCL to one ton of water, the pH value was adjusted to the range of 6-7. Since vertical wells were deployed in this well area, the PV of a single well was 60m*60m*10m*0.3=10800m 3 , and the formation water saturation is 0.38, the steam production radius is calculated as 50%, thus determining the amount of acid fluid to be injected into each cycle of a single well as 205.2m 3 ;

[0144] b) Determine the steam temperature Ts corresponding to the formation pressure, and measure the saturation temperature Tb of different solvents at this pressure. In this embodiment, the reservoir pressure is 3.5MPa, and under this pressure condition, the saturated steam temperature is 242.5°C; among different solvent types, the saturation temperature of cyclohexane under this pressure condition is 239.8°C, and the absolute value of the difference between Tb and Ts is within the range of 5-10°C, which is determined to be the best solvent type;

[0145] c) Determine the viscosity of crude oil and the reduction of the viscosity of crude oil by different solvent types, and determine that after adding 5% cyclohexane, the viscosity reduction rate of crude oil is 91%, which is higher than the viscosity reduction rate of other solvents with the same dosage, and determine the dosage of solvent to be 5%;

[0146] d) Determine the shear rate based on the injection flow rate, and measure the dispersibility of the foam stabilizer in the foam liquid under the action of the dispersing aid at the shear rate. Use an optical microscope to observe its dispersibility, comprehensively evaluate different types of foam stabilizers, and select the type with a dispersion rate of more than 95% as the best foam stabilizer.

[0147] According to the above principles, the dispersing agent is determined to be ethanol, the foam stabilizer is 50nm dextran sulfate and polyethyleneimine nanopowder (mass ratio 1:1), the foaming agent is a mixture of 70% sodium dodecyl ether sulfate + 30% sodium lauryl ether sulfate, and the solvent is n-heptane;

[0148] (2) Injection method of oil displacement system, including:

[0149] a) Pre-placed steam slug 0.02PV, i.e. 216m 3 ;

[0150] b) pH adjustment slug 205.2m 3 ;

[0151] c) Pre-solvent + dispersant slug 0.02PV, i.e. 216m 3 ;

[0152] d) Water vapor + foam system slug (non-condensable gas + foaming agent + foam stabilizer + dispersing agent) 0.1PV, i.e. underground volume 1080m 3 , of which water vapor 300m 3 , underground volume of foam system 780m 3 ; Non-condensable gas is CO 2 ;

[0153] e) Rear steam slug 0.02PV, i.e. 216m 3 .

[0154] The total underground injection volume of the above slugs is 1944m 3After the injection is completed, the well is shut down for 2-3 days and then opened for production. When the production drops to 1t / d, the second round of throughput begins.

[0155] The production effect of the embodiment of the present invention shows that compared with adjacent oil wells with the same geological conditions, the periodic production of the steam throughput production well is increased by 78%, and the throughput recovery factor is increased from 18% of conventional throughput to 29%, an increase of 11 percentage points.

[0156] Embodiment 5

[0157] Refer to the attached Figure 1 The embodiment of the present invention provides a specific application of an oil recovery system in a steam-throwing heavy oil reservoir, in which vertical wells are deployed in the reservoir, the well spacing is 70m, the effective thickness of the oil layer is 12m, the porosity is 30%, and the original oil saturation is 65%. A low-carbon green oil recovery system and oil production method for steam-throwing heavy oil reservoirs are provided, the method comprising the following steps:

[0158] (1) Optimization of the oil displacement system includes:

[0159] a) The pH value of formation water was determined to be 7.5, which is a weak alkaline environment. On this basis, the pH value of unit volume of formation water after adding different acids was measured, and it was determined that adding 0.12 tons of H 2 SO 4 After that, the pH value was adjusted to the range of 6-7. Since vertical wells were deployed in this well area, the PV of a single well was 70m*70m*12m*0.3=17640m 3 , and the formation water saturation is 0.35, the steam production radius is calculated as 50%, thus determining the amount of acid fluid to be injected into each cycle of a single well is 402m 3 ;

[0160] b) Determine the steam temperature Ts corresponding to the formation pressure, and measure the saturation temperature Tb of different solvents under the pressure. In this embodiment, the reservoir pressure is 4.5MPa, and under this pressure condition, the saturated steam temperature is 257.4°C; among different solvent types, the saturation temperature of 90% n-pentane + 10% dimethyl ether under this pressure condition is 254.8°C, and the absolute value of the difference between Tb and Ts is within the range of 5-10°C, which is determined to be the best solvent type;

[0161] c) Determine the viscosity of crude oil and the reduction of the viscosity of crude oil by different solvent types. It is determined that after adding 5% of a 90% n-pentane + 10% dimethyl ether mixed system, the viscosity reduction rate of crude oil is 92%, which is higher than the viscosity reduction rate of other solvents with the same dosage. The dosage of the solvent is determined to be 5%;

[0162] d) Determine the pore flow rate and shear rate based on the injection flow rate, measure the dispersibility of the foam stabilizer in the foam liquid under the action of the dispersing aid according to the shear rate, and use an optical microscope to observe its dispersibility, evaluate different types of foam stabilizers, and select the type with a dispersion rate of more than 95% as the best foam stabilizer.

[0163] According to the above principles, the dispersing agent was determined to be ethylene glycol, the foam stabilizer was 70 nm dextran sulfate and chitosan nanopowder (mass ratio 1:2), the foaming agent was sodium dodecyl sulfate, and the solvent was xylene;

[0164] (2) Injection method of oil displacement system, including:

[0165] a) Pre-placed steam slug 0.1PV, i.e. 1764m 3 ;

[0166] b) pH adjustment slug 402m 3 ;

[0167] c) Pre-solvent + dispersant plug 0.02PV, i.e. 352.8m 3 ;

[0168] d) Water vapor + foam system slug (non-condensable gas + foaming agent + foam stabilizer + dispersing agent) 0.1PV, i.e. underground volume 1764m 3 , of which water vapor 700m 3 , underground volume of foam system 1064m 3 ; Non-condensable gas is N 2 ;

[0169] e) Rear steam slug 0.02PV, i.e. 352.8m 3 .

[0170] The total underground injection volume of the above slugs is 4635.6m 3 , a total of 0.26 PV. After the injection is completed, the well is shut down for 5 days and then opened for production. When the production drops to 1.5t / d, the second round of throughput begins.

[0171] The production effect of the embodiment of the present invention shows that compared with adjacent oil wells with the same geological conditions, the periodic production of the steam-throwing production well is increased by 98%, and the throughput recovery rate is increased from 15% of conventional throughput to 24%, an increase of 9 percentage points.

[0172] It should be understood that the specific order or hierarchy of steps in the disclosed process is an example of an exemplary method. Based on design preferences, it should be understood that the specific order or hierarchy of steps in the process can be rearranged without departing from the scope of protection of the present disclosure. The attached method claims present the elements of the various steps in an exemplary order and are not intended to be limited to the specific order or hierarchy described.

[0173] In the above detailed description, various features are grouped together in a single embodiment to simplify the disclosure. This method of disclosure should not be interpreted as reflecting an intention that the embodiments of the claimed subject matter require more features than are clearly stated in each claim. On the contrary, as reflected in the appended claims, the invention is in a state of having less than all the features of the disclosed individual embodiments. Therefore, the appended claims are hereby expressly incorporated into the detailed description, with each claim standing on its own as a separate preferred embodiment of the invention.

[0174] The above description includes examples of one or more embodiments. Of course, it is impossible to describe all possible combinations of components or methods for the purpose of describing the above embodiments, but it should be recognized by those skilled in the art that the various embodiments may be further combined and arranged. Therefore, the embodiments described herein are intended to cover all such changes, modifications and variations that fall within the scope of protection of the appended claims. In addition, with respect to the term "comprising" used in the specification or claims, the word is covered in a manner similar to the term "including", just as "including," is explained as a transitional word in the claims. In addition, any term "or" used in the specification of the claims is intended to mean "non-exclusive or".

Claims

1. An oil displacement system, characterized in that: The system includes: a pH regulator, a non-condensable gas, water vapor, a foaming agent, a nano foam stabilizer, a dispersing aid and a solvent; wherein: Under preset underground temperature and pressure conditions, the mass ratio of the water vapor to the non-condensable gas is 1:1 to 1:3; Calculated by mass percentage of the water vapor, the mass fraction of the foaming agent is 0.3-3.0%, the mass fraction of the nano foam stabilizer is 0.1-5.0%, the mass fraction of the dispersing aid is 0.1-2.0%, and the mass fraction of the solvent is 1.0-5.0%; The nano foam stabilizer comprises nano anionic polyelectrolyte and nano cationic polyelectrolyte.

2. The oil displacement system according to claim 1, characterized in that: The pH regulator is selected from one or more of oxalic acid, citric acid, HCL or H2SO4.

3. The oil displacement system according to claim 1, characterized in that: The non-condensable gas is selected from one or more of CO2, CH4, N2 or oxygen-reduced air.

4. The oil displacement system according to claim 1, characterized in that: The foaming agent is selected from anionic surfactants and / or nonionic surfactants.

5. The oil displacement system according to claim 4, characterized in that: The anionic surfactant is selected from one or more of ammonium dodecyl sulfate, sodium dodecyl sulfate, sodium lauryl ether sulfate, sodium lauryl ether sulfate, dioctyl sodium sulfosuccinate, perfluorooctane sulfonic acid, perfluorobutane sulfonic acid, alkyl aryl ether phosphate or alkyl ether phosphate; The nonionic surfactant is selected from one or a combination of fatty alcohols, polyoxyethylene glycol alkyl ethers, octyl glycol monododecyl ether, polyoxypropylene glycol alkyl ethers, glucoside alkyl ethers, decyl glucoside, polyoxyethylene glycol alkylphenol ethers, sorbic acid esters, sorbitol alkyl esters, dodecyl dimethylamine oxide, and block copolymers of polyethylene glycol and polypropylene glycol.

6. The oil displacement system according to claim 1, characterized in that: The mass ratio of the nano anionic polyelectrolyte to the nano cationic polyelectrolyte is 1:10 to 10:1; The nano anionic polyelectrolyte is dextran sulfate; The nano cationic polyelectrolyte is selected from one or more of polyethyleneimine, poly(allylamine) or chitosan.

7. The oil displacement system according to claim 1, characterized in that: The dispersing aid is selected from one or more of ethanol, ethylene glycol or methanol.

8. The oil displacement system according to claim 1, characterized in that: The solvent is selected from one or more of alkanes, aromatic hydrocarbons, natural gas condensate, liquefied petroleum gas, naphtha products, alcohols, ethers, aldehydes, ketones and crude oil refineries.

9. A method for optimizing the oil displacement system according to any one of claims 1 to 8, characterized in that: The method comprises: S101, determining the type of pH regulator selected and the amount to be added; S102, determining the type of solvent to be selected and the amount to be added; S103, determining the type of nano foam stabilizer to be selected.

10. The optimization method of the oil displacement system according to claim 9, characterized in that: In S101, the step of determining the selected pH adjusting agent and the amount thereof to be added includes: The specific types of the pH adjusters are mixed in any mass ratio to obtain multiple groups of different types of pH adjusters; The formation water is divided into several groups, and the final pH value of each unit volume of formation water after adding various types of pH regulators is determined according to the initial pH value of the formation water; The final pH value is adjusted to a set value to determine the optimal type of the selected pH adjuster and the amount of addition.

11. The optimization method of the oil displacement system according to claim 9, characterized in that: In S102, the step of determining the selected solvent type and the amount of solvent to be added includes: The specific types of the solvents are mixed in any mass ratio to obtain multiple groups of different types of solvents; Under a preset formation pressure condition, determining the saturation temperature of different solvents under the pressure condition according to the temperature of the water vapor; According to the absolute value of the difference between the saturation temperature corresponding to each solvent and the temperature of the water vapor, a solvent whose absolute value is within a set range is selected; According to the viscosity of the crude oil, determining the decrease in the viscosity of the crude oil when the solvent whose absolute value is selected is within a set range is added; The optimum type of solvent to be selected and the amount of solvent to be added are determined according to the decrease in the viscosity of the crude oil.

12. The optimization method of the oil displacement system according to claim 9, characterized in that: In S103, the step of determining the type of nano foam stabilizer to be selected includes: The specific types of the nano cationic polyelectrolytes are mixed in any mass ratio to obtain multiple groups of different types of nano cationic polyelectrolytes; Mixing the plurality of groups of different types of nano cationic polyelectrolytes with the plurality of groups of nano anionic polyelectrolytes in any mass ratio to obtain a plurality of groups of different types of nano foam stabilizers; Determining the shear rate of the oil displacement system according to the injection flow rate of the oil displacement system; According to the shear rate, the dispersibility of the nano foam stabilizer in the foam system under the action of the dispersing aid is determined; Observe and verify the dispersibility of the nano foam stabilizer in the foam system according to an optical microscope, and evaluate different types of nano foam stabilizers; According to the evaluation results of the different types of nano foam stabilizers, a nano foam stabilizer with a dispersion rate of more than 95% is selected.

13. Use of the oil displacement system according to any one of claims 1 to 8 in steam stimulation of heavy oil reservoirs.

14. An injection method for an oil displacement system for a steam-throwing heavy oil reservoir as claimed in claim 13, characterized in that: The method adopts a multi-segment injection method, which includes: Injection of pre-placed steam slug; injecting a pH adjuster slug; Slugs of pre-solvent and dispersant injection; Injection of steam and foam system slugs; Injection of post-placed steam slug; The foam system comprises non-condensable gas, a foaming agent, a nano foam stabilizer and a dispersing aid.

15. The injection method for the oil displacement system of steam stimulation heavy oil reservoir according to claim 14, characterized in that: According to the pore volume within the control range of a single well, the PV number of a single well is calculated as: The pre-placed steam slug is 0.02-0.1 PV; The pH value regulator slug is 0.02 to 0.1 PV; The pre-solvent and + dispersing agent segment plug is 0.02 to 0.1 PV; The slug of the water vapor + foam system is 0.1 to 0.3 PV; The post-placed water vapor segment plug is 0.01-0.1 PV.

16. Use of the injection method of the oil displacement system for steam stimulation of heavy oil reservoirs as claimed in claim 14 or 15 in oil production.

17. A method for producing crude oil, characterized in that: The method includes the injection method of 14 or 15 for the oil displacement system used for steam stimulation of heavy oil reservoirs.

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