Viscosity-reducing foaming agent for improving recovery efficiency of heavy oil reservoir as well as preparation method and application of viscosity-reducing foaming agent

Abstract

The invention discloses a viscosity-reducing foaming agent for improving the recovery efficiency of a heavy oil reservoir. The viscosity-reducing foaming agent is prepared from 1 to 20 parts of alkylbenzene polyether sulfonate, 5 to 30 parts of alpha-olefin sulfonate, 1 to 20 parts of lauryl alcohol polyoxyethylene ether sulfosuccinic acid monoester salt, 2 to 20 parts of cocamidopropyl betaine, 1 to 20 parts of fatty alcohol polyether carboxylate and 30 to 70 parts of water. The invention discloses a preparation method of a viscosity-reducing foaming agent for improving the recovery efficiency of a heavy oil reservoir, which comprises the following steps: (1) taking alkylbenzene polyether sulfonate with a formula amount into a reaction container, adding water with a formula amount of 20-60% into the reaction container, and continuously stirring to obtain a first mixed solution; (2) sequentially adding alpha-olefin sulfonate, laurinol polyoxyethylene ether sulfosuccinic acid monoester salt, fatty alcohol polyether carboxylate and cocamidopropyl betaine into the reaction container according to the formula ratio, and uniformly stirring to obtain a second mixed solution; and (3) adding the rest formula amount of water into the reaction container, and continuously stirring.

Description

Technical Field

[0001] The present invention belongs to the technical field of viscosity reduction and cold production for enhanced oil recovery of heavy oil, and relates to a viscosity reduction type foaming agent for improving the recovery rate of heavy oil reservoirs, a preparation method thereof, and an application thereof. Background Art

[0002] Heavy oil reservoir resources are very rich, but the conventional method of enhanced oil recovery by water injection has a low recovery rate, and heavy oil thermal recovery has high energy consumption, which is contrary to the general trend of energy conservation and emission reduction. For example, the article "Physical Simulation Experiment of High-Quality Steam Flooding in Deep Heavy Oil Reservoirs" published by Zhao Yan et al. in the second issue of "Fault-Block Oil & Gas Field" in 2018 pointed out that the heavy oil resources in Shengli Oilfield are rich, most of the heavy oil reservoirs are buried deep, the edge and bottom water are active, it is difficult to reduce the reservoir pressure to 5 MPa, and the bottom-hole steam injection dryness of the conventional steam flooding implemented in the field is about 30%, and the improvement of the recovery rate is not obvious.

[0003] Chinese Patent Application CN 103510932A discloses a chemical cold production method applicable to medium-deep and low-permeability heavy oil reservoirs. The method is carried out according to the following steps: a. Select a medium-deep and low-permeability heavy oil reservoir with an oil layer depth of 1500 - 2800 m, a permeability ≤ 50×10 -3 um 2 , an oil layer total thickness ≥ 3.0 m, a net-to-gross thickness ratio ≥ 0.3, an oil layer porosity ≥ 0.10, and a permeability variation coefficient ≤ 0.8; inject a microemulsion viscosity reduction system + liquid carbon dioxide into the selected oil layer, and the microemulsion viscosity reduction system and liquid carbon dioxide are alternately injected in the form of slugs. After shut-in soaking and open-hole flowback, a pump is lowered for continuous oil production. Another example is that Chinese Patent Application CN 108729893A discloses a foam composite cold production method for improving the recovery rate of heavy oil reservoirs. The method mainly includes: alternately injecting a heavy oil viscosity reduction and oil displacement agent, water, and a polymer composite foam oil displacement system into an injection well, and then performing water flooding. It can be seen from the above two patent technical documents that in order to improve the effect of viscosity reduction and cold production, viscosity reduction chemical flooding must be combined with a method for improving the reservoir sweep efficiency to significantly improve the recovery rate of heavy oil reservoirs.

[0004] In order to reduce the viscosity of heavy oil and improve the recovery rate, a viscosity-reducing oil displacement agent is generally used. For example, Chinese Patent Application CN111440604A discloses a self-demulsifying anti-salt heavy oil cold production oil displacement agent, which, by mass percentage, includes: 40-50 wt% active components, 15-20 wt% additives, 5-8 wt% penetrants, and the balance is deionized water; the active components include: fatty alcohol polyoxyethylene ether carboxylate, polyoxyethylene castor oil and fatty acid-amine complex with a mass ratio of (8-10):(1-3):(4-6). Another example is Chinese Invention Patent CN 114853958B, which discloses a supramolecular nano oil displacement agent for heavy oil cold production and its preparation method. The preparation method is as follows: allyl(diisopropylamino)dimethylsilane, potassium styrene trifluoroborate, 2-acrylamide-2-methylpropanesulfonic acid, polyoxyethylene allyl ether, diallylamine, tween80, sodium dodecyl sulfate, buffer salt, and water are sequentially added to the reaction kettle to form an emulsion; 80-90% of the emulsion is transferred to the first high-level tank, and tween80, sodium dodecyl sulfate, buffer salt, and water are added to the reaction kettle; an initiator is added to the second high-level tank, and a reducing agent is added to the third high-level tank, and the two are simultaneously added dropwise for pre-polymerization; an initiator is added to the second high-level tank, a reducing agent is added to the third high-level tank, and the first high-level tank, the second high-level tank, and the third high-level tank are simultaneously added dropwise for polymerization; the temperature is lowered to obtain the product. Although heavy oil viscosity reduction and cold production can give full play to the characteristics of the heavy oil viscosity-reducing oil displacement agent to reduce the viscosity of crude oil and improve the fluidity of heavy oil, with the injection of the viscosity-reducing oil displacement agent, the crude oil on the main flow line is more easily displaced, resulting in stronger heterogeneity of the reservoir, and the heavy oil in the non-main flow line and low-permeability area is more difficult to be displaced. The injected chemical agent will flow out along the high-permeability channel with less residual oil, reducing the efficiency of the viscosity-reducing displacement fluid and weakening the effect of viscosity-reducing chemical flooding to improve the recovery rate of the reservoir. Summary of the Invention

[0005] Object of the Invention: Aiming at the deficiencies of the above-mentioned existing technologies, the present invention provides a viscosity-reducing foam agent for improving the recovery rate of heavy oil reservoirs, its preparation method and application. The viscosity-reducing foam agent has good performance in reducing the viscosity of heavy oil, and at the same time has good foaming ability with gases such as nitrogen, air, and carbon dioxide. Through the dual effects of viscosity reduction and foaming in heavy oil reservoirs, the fluidity of heavy oil and the swept area of the displacement fluid are improved, thereby further improving the recovery rate of heavy oil reservoirs.

[0006] Technical Solution: The viscosity-reducing foam agent for improving the recovery rate of heavy oil reservoirs is composed of the following components in parts by mass:

[0007] 1-20 parts of alkylbenzene polyether sulfonate, 5-30 parts of α-olefin sulfonate, 1-20 parts of lauryl alcohol polyoxyethylene ether sulfosuccinate monoester salt, 2-20 parts of coconut oil amide propyl betaine, 1-20 parts of fatty alcohol polyether carboxylate, and 30-70 parts of water.

[0008] Further, the alkylbenzene polyether sulfonate is one of sodium alkylbenzene polyether sulfonate, potassium alkylbenzene polyether sulfonate, and ammonium alkylbenzene polyether sulfonate.

[0009] More specifically, the alkylbenzene polyether sulfonate is sodium alkylbenzene polyether sulfonate.

[0010] Further, the alkylbenzene polyether sulfonate is an alkylbenzene polyether sulfonate with a carbon chain length of 12 to 18.

[0011] Further, the α-olefin sulfonate is an α-olefin sulfonate with an olefinic carbon chain length of 12 to 18.

[0012] Further, the monolauryl polyoxyethylene ether sulfosuccinate is one of monolauryl polyoxyethylene ether sulfosuccinate disodium salt, monolauryl polyoxyethylene ether sulfosuccinate dipotassium salt, and monolauryl polyoxyethylene ether sulfosuccinate diammonium salt.

[0013] More specifically, the monolauryl polyoxyethylene ether sulfosuccinate is monolauryl polyoxyethylene ether sulfosuccinate disodium salt.

[0014] Further, the fatty alcohol polyether carboxylate is one of sodium fatty alcohol polyether carboxylate, potassium fatty alcohol polyether carboxylate, and ammonium fatty alcohol polyether carboxylate.

[0015] Further, the fatty alcohol group in the fatty alcohol polyether carboxylate contains an alkyl carbon chain with a length of 12 to 18.

[0016] The preparation method of the viscosity-reducing foam agent for improving the recovery rate of heavy oil reservoirs is as follows:

[0017] (1) Take the formulated amount of alkylbenzene polyether sulfonate in a reaction vessel, and while stirring, add 20% - 60% of the formulated amount of water to the reaction vessel, and continue stirring for a period of time to obtain a first mixture;

[0018] (2) Sequentially add the formulated amounts of α-olefin sulfonate, monolauryl polyoxyethylene ether sulfosuccinate, fatty alcohol polyether carboxylate, and cocamidopropyl betaine to the reaction vessel, and stir evenly to obtain a second mixture;

[0019] (3) Add the remaining formulated amount of water (i.e., 40% - 80% of the formulated amount of water) to the reaction vessel, and continue stirring for a period of time to obtain the viscosity-reducing foam agent for improving the recovery rate of heavy oil reservoirs.

[0020] Further, in step (1), the stirring speed is 60 - 100 revolutions per minute, and the stirring time is at least 20 minutes, preferably 20 - 30 minutes.

[0021] Further, in step (2), the stirring speed is 50 - 80 revolutions per minute, and the stirring time is at least 20 minutes, preferably 20 - 30 minutes.

[0022] Further, in step (3), the stirring speed is 50 - 80 revolutions per minute, and the stirring time is at least 30 minutes, preferably 30 - 60 minutes.

[0023] Application of the viscosity-reducing foam agent for improving the recovery rate of heavy oil reservoirs in oil exploitation.

[0024] Principle of the present invention: Utilizing the principle of the balanced distribution of surfactants at the oil-water interface and the gas-liquid interface, a variety of anionic surfactants and zwitterionic surfactants similar to the properties of crude oil are selected. Through the way of adduct synergism, a surfactant formulation is developed that has a wide range of applications for heavy oil, high viscosity reduction efficiency, and at the same time has good foaming ability and stability. And through a reasonable compounding method, an oil displacement agent product with good viscosity reduction and foam properties is formed, which can play a good role in the field of heavy oil viscosity reduction and cold production.

[0025] Advantages of the invention: The viscosity-reducing foam agent for improving the recovery rate of heavy oil reservoirs and its preparation method and application disclosed in the present invention have the following beneficial effects:

[0026] 1. Compared with other formulations for improving oilfield recovery, it has the characteristics of low cost and dual effects of one agent (foaming + viscosity reduction). It can not only play a role in significantly reducing the viscosity of heavy oil, but also has good foaming ability, foam stability, and good compatibility with formation water with a relatively high salinity. It can play the role of viscosity reducer and foam profile control according to the different oil and water contacts in the formation.

[0027] 2. All the chemical agent components used are surfactant raw materials with mature processes, large production volumes, relatively low prices, and environmental friendliness in the current market, and have good on-site application and promotion value. Description of the drawings

[0028] Figure 1 It is a flowchart of the preparation method of the viscosity-reducing foam agent for improving the recovery rate of heavy oil reservoirs disclosed in the present invention. Detailed description of the specific implementation manners:

[0029] The following is a detailed description of the specific implementation manners of the present invention. 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.

[0030] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to 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 "comprising" and / or "including" are used in this specification, they specify the presence of features, steps, operations, and / or combinations thereof.

[0031] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0032] For the instruments, reagents, materials, etc. involved in the following embodiments, unless otherwise specified, they are all conventional instruments, reagents, materials, etc. existing in the prior art and can be obtained through regular commercial channels. For the experimental methods, detection methods, etc. involved in the following embodiments, unless otherwise specified, they are all conventional experimental methods, detection methods, etc. existing in the prior art.

[0033] In this application: α-olefin sulfonate, which is abbreviated as AOS.

[0034] Sodium lauryl polyoxyethylene ether sulfosuccinate monoester, which is abbreviated as MES-30.

[0035] Cocamidopropyl betaine, which is abbreviated as CAB.

[0036] Alcohol polyether carboxylate, which is abbreviated as AEC.

[0037] The present invention discloses a viscosity-reducing foam agent for improving the recovery rate of heavy oil reservoirs, its preparation method and application. The viscosity-reducing foam agent for improving the recovery rate of heavy oil reservoirs can not only greatly reduce the viscosity of heavy oil, but also form foam by mixing with the injected gas, improve the swept area of the displacement medium, enable the chemical agent to interact with more heavy oil, reduce the viscosity of heavy oil, and thus be easily displaced. The viscosity-reducing foam agent has the characteristics of reducing the viscosity of heavy oil and increasing the swept area by foam, and can greatly improve the recovery rate of heavy oil reservoirs.

[0038] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments. The following embodiments are used to help understand the present invention and should not be construed as limiting the invention in the claims listed in any way.

[0039] Example 1

[0040] The viscosity-reducing foam agent for improving the recovery rate of heavy oil reservoirs is composed of the following components in parts by mass:

[0041] 10 parts of alkyl benzene polyether sulfonate, 15 parts of α-olefin sulfonate, 10 parts of lauryl alcohol polyoxyethylene ether sulfosuccinic acid monoester salt, 10 parts of coconut oil amide propyl betaine, 10 parts of fatty alcohol polyether carboxylate and 50 parts of water.

[0042] Further, the alkyl benzene polyether sulfonate is sodium alkyl benzene polyether sulfonate.

[0043] Further, the alkyl benzene polyether sulfonate is cetyl benzene polyether sulfonate.

[0044] Further, the α-olefin sulfonate is α-olefin sulfonate with an olefinic carbon chain length of 14.

[0045] Further, the lauryl alcohol polyoxyethylene ether sulfosuccinic acid monoester salt is disodium lauryl alcohol polyoxyethylene ether sulfosuccinic acid monoester.

[0046] Further, the fatty alcohol polyether carboxylate is sodium fatty alcohol polyether carboxylate.

[0047] Further, the fatty alcohol group in the fatty alcohol polyether carboxylate contains an alkyl carbon chain with a length of 14.

[0048] The preparation method of the viscosity-reducing foam agent for enhancing the recovery rate of heavy oil reservoirs is as follows:

[0049] (1) Take the formulated amount of alkyl benzene polyether sulfonate in a reaction vessel, add 40% of the formulated amount of water to the reaction vessel while stirring, and continue stirring for a period of time to obtain a first mixed solution;

[0050] (2) Sequentially add the formulated amounts of α-olefin sulfonate, lauryl alcohol polyoxyethylene ether sulfosuccinic acid monoester salt, fatty alcohol polyether carboxylate, and coconut oil amide propyl betaine to the reaction vessel, and stir evenly to obtain a second mixed solution;

[0051] (3) Add 60% of the formulated amount of water to the reaction vessel, and continue stirring for a period of time to obtain the viscosity-reducing foam agent for enhancing the recovery rate of heavy oil reservoirs, abbreviated as 1# viscosity-reducing foam agent.

[0052] Further, in step (1), the stirring speed is 80 revolutions per minute, and the stirring time is 25 minutes.

[0053] Further, in step (2), the stirring speed is 60 revolutions per minute, and the stirring time is 25 minutes.

[0054] Further, in step (3), the stirring speed is 60 revolutions per minute, and the stirring time is 45 minutes.

[0055] The application of the above-mentioned viscosity-reducing foam agent for enhancing the recovery rate of heavy oil reservoirs in oil extraction.

[0056] Example 2

[0057] The viscosity-reducing foam agent for improving the recovery rate of heavy oil reservoirs is composed of the following components in parts by mass:

[0058] 1 part of alkylbenzene polyether sulfonate, 5 parts of α-olefin sulfonate, 1 part of monolauryl polyoxyethylene sulfosuccinate, 2 parts of cocamidopropyl betaine, 1 part of fatty alcohol polyether carboxylate, and 30 parts of water.

[0059] Further, the alkylbenzene polyether sulfonate is potassium alkylbenzene polyether sulfonate.

[0060] Further, the alkylbenzene polyether sulfonate is dodecylbenzene polyether sulfonate.

[0061] Further, the α-olefin sulfonate is an α-olefin sulfonate with a carbon chain length of 12 for the olefin group.

[0062] Further, the monolauryl polyoxyethylene sulfosuccinate is monolauryl polyoxyethylene sulfosuccinate dipotassium salt.

[0063] Further, the fatty alcohol polyether carboxylate is potassium fatty alcohol polyether carboxylate.

[0064] Further, the fatty alcohol group in the fatty alcohol polyether carboxylate contains an alkyl carbon chain with a length of 12.

[0065] The preparation method of the above viscosity-reducing foam agent for improving the recovery rate of heavy oil reservoirs is as follows:

[0066] (1) Take the formulated amount of alkylbenzene polyether sulfonate in a reaction vessel, add 20% of the formulated amount of water to the reaction vessel while stirring, and continue stirring for a period of time to obtain a first mixture;

[0067] (2) Add the formulated amounts of α-olefin sulfonate, monolauryl polyoxyethylene sulfosuccinate, fatty alcohol polyether carboxylate, and cocamidopropyl betaine to the reaction vessel in sequence, and stir evenly to obtain a second mixture;

[0068] (3) Add 80% of the formulated amount of water to the reaction vessel, and continue stirring for a period of time to obtain the viscosity-reducing foam agent for improving the recovery rate of heavy oil reservoirs, abbreviated as 2# viscosity-reducing foam agent.

[0069] Further, the stirring speed in step (1) is 60 revolutions per minute, and the stirring time is 30 minutes.

[0070] Further, the stirring speed in step (2) is 50 revolutions per minute, and the stirring time is 30 minutes.

[0071] Furthermore, in step (3), the stirring speed is 50 revolutions per minute and the stirring time is 60 minutes.

[0072] Application of the viscosity-reducing foam agent for enhancing the recovery factor of heavy oil reservoirs in petroleum exploitation.

[0073] Example 3

[0074] The viscosity-reducing foam agent for enhancing the recovery factor of heavy oil reservoirs is composed of the following components in parts by mass:

[0075] 20 parts of alkylbenzene polyether sulfonate, 30 parts of α-olefin sulfonate, 20 parts of monolauryl polyoxyethylene sulfosuccinate, 20 parts of cocamidopropyl betaine, 20 parts of fatty alcohol polyether carboxylate, and 70 parts of water.

[0076] Furthermore, the alkylbenzene polyether sulfonate is ammonium alkylbenzene polyether sulfonate.

[0077] Furthermore, the alkylbenzene polyether sulfonate is octadecylbenzene polyether sulfonate.

[0078] Furthermore, the α-olefin sulfonate is an α-olefin sulfonate with an olefinic carbon chain length of 18.

[0079] Furthermore, the monolauryl polyoxyethylene sulfosuccinate is monolauryl polyoxyethylene sulfosuccinate diammonium salt.

[0080] Furthermore, the fatty alcohol polyether carboxylate is ammonium fatty alcohol polyether carboxylate.

[0081] Furthermore, the fatty alcohol group in the fatty alcohol polyether carboxylate contains an alkyl carbon chain with a length of 18.

[0082] The preparation method of the viscosity-reducing foam agent for enhancing the recovery factor of heavy oil reservoirs is as follows:

[0083] (1) Take the formula amount of alkylbenzene polyether sulfonate in a reaction vessel, and while stirring, add 60% of the formula amount of water to the reaction vessel, and continue stirring for a period of time to obtain a first mixed solution;

[0084] (2) Sequentially add the formula amount of α-olefin sulfonate, the formula amount of monolauryl polyoxyethylene sulfosuccinate, the formula amount of fatty alcohol polyether carboxylate, and the formula amount of cocamidopropyl betaine to the reaction vessel, and stir evenly to obtain a second mixed solution;

[0085] (3) Add 40% of the formula amount of water to the reaction vessel, and continue stirring for a period of time to obtain the viscosity-reducing foam agent for enhancing the recovery factor of heavy oil reservoirs, abbreviated as the 3# viscosity-reducing foam agent.

[0086] Further, in step (1), the stirring speed is 100 revolutions per minute and the stirring time is 20 minutes.

[0087] Further, in step (2), the stirring speed is 80 revolutions per minute and the stirring time is 20 minutes.

[0088] Further, in step (3), the stirring speed is 80 revolutions per minute and the stirring time is 30 minutes.

[0089] Application of the viscosity-reducing foam agent for improving the recovery rate of heavy oil reservoirs in petroleum exploitation as described above.

[0090] Verification test:

[0091] 1. Performance of reducing the viscosity of heavy oil:

[0092] Viscosity-reducing foam agent No. 1:

[0093] The ground viscosity of the crude oil in Block A of Shengli Oilfield at 50 °C is 86 mPa·s. After using the viscosity-reducing foam agent No. 1 prepared in Example 1, the viscosity after viscosity reduction is 5.6 mPa·s, and the viscosity reduction rate is as high as 93.4%.

[0094] Viscosity-reducing foam agent No. 2:

[0095] The ground viscosity of the crude oil in Block B of Shengli Oilfield at 50 °C is 686 mPa·s. After viscosity reduction, the viscosity is 15.2 mPa·s, and the viscosity reduction rate is 97.8%.

[0096] Viscosity-reducing foam agent No. 3:

[0097] The ground viscosity of the crude oil in Block C of Shengli Oilfield at 50 °C is 587 mPa·s. After viscosity reduction, the viscosity is 21.6 mPa·s, and the viscosity reduction rate is 96.3%.

[0098] 2. Good foaming ability with gases such as nitrogen, air, and carbon dioxide - Foam performance test:

[0099] Testing instrument: Foam scanner;

[0100] Testing temperature is 50 °C and concentration is 0.5%,

[0101] Viscosity-reducing foam agent No. 1:

[0102] When nitrogen is used as the foaming gas, the foaming volume is 230 ml and the half-life is 185 min. When air is used as the foaming gas, the foaming volume is 225 ml and the half-life is 181 min. When CO 2 is used as the foaming gas, the foaming volume is 180 ml and the half-life is 35 min.

[0103] Viscosity-reducing foam agent No. 2:

[0104] When nitrogen is used as the foaming gas, the foaming volume is 185 ml and the half-life is 160 min. When air is used as the foaming gas, the foaming volume is 175 ml and the half-life is 150 min. CO 2 When used for foaming, the foaming volume is 170 ml and the half-life is 24 min.

[0105] 3# Viscosity-reducing foam agent:

[0106] When nitrogen is used as the foaming gas, the foaming volume is 220 ml and the half-life is 175 min. When air is used as the foaming gas, the foaming volume is 200 ml and the half-life is 165 min. CO 2 When used for foaming, the foaming volume is 160 ml and the half-life is 30 min.

[0107] 3. Improve the fluidity of heavy oil and the swept area of the displacement fluid - verified by the double-tube oil displacement test:

[0108] 1# Viscosity-reducing foam agent:

[0109] Model size: φ25mm × 600mm. Permeability of the high-permeability tube is 1567×10 -3 μm 2 and that of the low-permeability tube is 452×10 -3 μm 2 When water flooding reaches a comprehensive water cut of 98%, the recovery rate of the high-permeability tube is 61.6%, that of the low-permeability tube is 22.5%, the comprehensive water flooding recovery is 42.5%, and the stable pressure difference in the later stage of water flooding is 0.1 MPa.

[0110] After water flooding, viscosity reducer flooding is carried out (i.e., adding 1# viscosity-reducing foam agent). The concentration of 1# viscosity-reducing foam agent is 0.3%, the injection slug is 0.3 PV. After viscosity reducer flooding, the recovery rate of the high-permeability tube is 68.6%, with a 7 percentage point increase in recovery rate; the recovery rate of the low-permeability tube is 25.7%, with a 6.2 percentage point increase in recovery rate. After viscosity reducer flooding, water flooding is resumed, and the water flooding pressure difference is 0.07 MPa. The swept area is improved and the recovery rate is greatly increased.

[0111] 2# Viscosity-reducing foam agent:

[0112] Model size: φ25mm × 600mm. Permeability of the high-permeability tube is 1862×10 -3 μm 2 and that of the low-permeability tube is 396×10 -3 μm 2 When water flooding reaches a comprehensive water cut of 98%, the recovery rate of the high-permeability tube is 58.3%, the recovery rate of the low-permeability tube is 17.6%, the comprehensive water flooding recovery is 36.2%, and the stable pressure difference in the later stage of water flooding is 0.15 MPa.

[0113] After water flooding, viscosity reducer flooding is carried out (i.e., adding No. 2 viscosity-reducing foam agent). The concentration of the No. 2 viscosity-reducing foam agent is 0.3%, the injection slug is 0.3PV. After viscosity reducer flooding, the oil recovery rate of the high-permeability pipe is 64.5%, and the oil recovery rate is increased by 6.2 percentage points; the oil recovery rate of the low-permeability pipe is 23.4%, and the oil recovery rate is increased by 5.8 percentage points. After viscosity reducer flooding, water flooding is resumed, and the water flooding pressure difference is 0.11MPa. The swept area is improved, and the oil recovery rate is greatly increased.

[0114] No. 3 viscosity-reducing foam agent:

[0115] The model size is φ25mm×600mm. The permeability of the high-permeability pipe is 1579×10 -3 μm 2 , and the permeability of the low-permeability pipe is 386×10 -3 μm 2 , when water flooding is carried out until the comprehensive water cut reaches 98%, the oil recovery rate of the high-permeability pipe is 61.2%, and that of the low-permeability pipe is 20.5%. The comprehensive oil recovery rate by water flooding is 39.4%, and the stable pressure difference in the later stage of water flooding is 0.12MPa.

[0116] After water flooding, viscosity-reducing foam flooding is carried out (i.e., adding No. 3 viscosity-reducing foam agent). The concentration of the No. 3 viscosity-reducing foam agent is 0.3%, the gas-liquid ratio is 1:1, the injected gas is nitrogen, and the injection slug is 0.3PV. After viscosity-reducing foam flooding, the oil recovery rate of the high-permeability pipe is 85.2%, and the oil recovery rate is increased by 24 percentage points; the oil recovery rate of the low-permeability pipe is 53.9%, and the oil recovery rate is increased by 31.4 percentage points. The comprehensive oil recovery rate is increased by 27.5%. The injection-production pressure difference in foam flooding rises to 1.2MPa, and the pressure difference is 0.32MPa after water flooding for 1PV. The swept area is improved, and the oil recovery rate is greatly increased.

[0117] The above has made a detailed description of the embodiments of the present invention. However, the present invention is not limited to the above embodiments, and various changes can be made without departing from the gist of the present invention within the knowledge scope of those of ordinary skill in the art.

Claims

1. A viscosity-reducing foaming agent for improving the recovery rate of heavy oil reservoirs, characterized in that: In parts by mass, it is composed of the following components: 1-20 parts of alkylbenzene polyether sulfonate, 5-30 parts of α-olefin sulfonate, 1-20 parts of lauryl alcohol polyoxyethylene ether sulfosuccinic acid monoester salt, 2-20 parts of cocoamidopropyl betaine, 1-20 parts of fatty alcohol polyether carboxylate and 30-70 parts of water.

2. The viscosity-reducing foaming agent for improving the recovery rate of heavy oil reservoirs according to claim 1, characterized in that: The alkylbenzene polyether sulfonate is one of sodium alkylbenzene polyether sulfonate, potassium alkylbenzene polyether sulfonate and ammonium alkylbenzene polyether sulfonate.

3. The viscosity-reducing foaming agent for improving the recovery rate of heavy oil reservoirs as claimed in claim 2, characterized in that: The alkylbenzene polyether sulfonate is sodium alkylbenzene polyether sulfonate.

4. The viscosity-reducing foaming agent for improving the recovery rate of heavy oil reservoirs according to claim 1, characterized in that: The alkylbenzene polyether sulfonate is an alkylbenzene polyether sulfonate with a carbon chain length of 12 to 18.

5. The viscosity-reducing foaming agent for improving the recovery rate of heavy oil reservoirs according to claim 1, characterized in that: The α-olefin sulfonate is an α-olefin sulfonate in which the carbon chain length of the olefin group is 12 to 18.

6. The viscosity-reducing foaming agent for improving the recovery rate of heavy oil reservoirs according to claim 1, characterized in that: The lauryl alcohol polyoxyethylene ether sulfosuccinic acid monofat salt is one of lauryl alcohol polyoxyethylene ether sulfosuccinic acid monofat disodium salt, lauryl alcohol polyoxyethylene ether sulfosuccinic acid monofat dipotassium salt and lauryl alcohol polyoxyethylene ether sulfosuccinic acid monofat diammonium salt.

7. The viscosity-reducing foaming agent for improving the recovery rate of heavy oil reservoirs according to claim 6, characterized in that: The lauryl alcohol polyoxyethylene ether sulfosuccinic acid monoester salt is lauryl alcohol polyoxyethylene ether sulfosuccinic acid monoester disodium salt.

8. The viscosity-reducing foaming agent for improving the recovery rate of heavy oil reservoirs according to claim 1, characterized in that: The fatty alcohol polyether carboxylate is one of sodium fatty alcohol polyether carboxylate, potassium fatty alcohol polyether carboxylate and ammonium fatty alcohol polyether carboxylate.

9. The viscosity-reducing foaming agent for improving the recovery rate of heavy oil reservoirs according to claim 1, characterized in that: The fatty alcohol group in the fatty alcohol polyether carboxylate contains an alkyl carbon chain with a length of 12 to 18.

10. The method for preparing the viscosity-reducing foaming agent for improving the recovery rate of heavy oil reservoirs according to any one of claims 1 to 9, characterized in that: Here are the steps: (1) taking a formulated amount of alkylbenzene polyether sulfonate in a reaction container, adding 20% ​​to 60% of the formulated amount of water into the reaction container while stirring, and continuing to stir for a period of time to obtain a first mixed solution; (2) Adding a formula amount of α-olefin sulfonate, a formula amount of lauryl alcohol polyoxyethylene ether sulfosuccinate monoester salt, a formula amount of fatty alcohol polyether carboxylate, and a formula amount of cocoamidopropyl betaine to the reaction container in sequence, stirring evenly to obtain a second mixed solution; (3) Add the remaining amount of water into the reaction container and continue stirring for a period of time to obtain a viscosity-reducing foaming agent for improving the recovery rate of heavy oil reservoirs.

11. The method for preparing the viscosity-reducing foaming agent for improving the recovery rate of heavy oil reservoirs according to claim 10, characterized in that: In step (1), the stirring speed is 60 to 100 rpm, and the stirring time is at least 20 minutes, preferably 20 to 30 minutes.

12. The method for preparing the viscosity-reducing foaming agent for improving the recovery rate of heavy oil reservoirs according to claim 10, characterized in that: In step (2), the stirring speed is 50 to 80 rpm, and the stirring time is at least 20 minutes, preferably 20 to 30 minutes.

13. The method for preparing the viscosity-reducing foaming agent for improving the recovery rate of heavy oil reservoirs according to claim 10, characterized in that: In step (3), the stirring speed is 50 to 80 rpm, and the stirring time is at least 30 minutes, preferably 30 to 60 minutes.

14. Use of the viscosity-reducing foaming agent for improving the recovery rate of heavy oil reservoirs according to any one of claims 1 to 9 in oil production.

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