Oil extraction method for light oil reservoir

Abstract

The invention discloses an oil extraction method for a light oil reservoir. The method comprises the steps that a catalytic mixing aid and air are injected through a gas injection well in the light oil reservoir; the injected air is subjected to thermal oxidation through the catalytic mixing aid, a thermal oxidation mode is formed, and mixed-phase gas is generated; wherein the mixed-phase gas is a mixed gas of CO2 and N2; and when the light oil reservoir is in the thermal oxidation mode, light components in the crude oil are gasified or light hydrocarbons are distilled and are mixed with mixed-phase gas generated by thermal oxidation to realize a thermal mixed phase, and the crude oil is driven to be extracted from a production well.

Description

Technical Field

[0001] The present invention relates to the field of air injection development technology, and in particular to an oil recovery method for a light oil reservoir. Background Art

[0002] Most oil fields rely on the exhaustion of natural energy in the formation in the early stage of development. When natural energy cannot sustain economic development, water or gas is injected into the reservoir to restore the reservoir energy. Over the years, gas injection technology has developed into a series of technologies including natural gas drive, carbon dioxide drive, nitrogen drive, and flue gas drive. Air injection development technology: refers to injecting air into the oil layer to cause combustion / oxidation of crude oil and air, transfer heat to the far end of the oil layer, drive energy, and achieve efficient development of the oil reservoir.

[0003] However, as the prices of natural gas and crude oil continue to rise, considering economic factors, carbon dioxide, nitrogen and flue gas are often used to replace natural gas as the main injection medium. In the process of gas injection development, miscible displacement is an efficient oil recovery method. By achieving miscible conditions, the driving medium and the driven medium dissolve each other and the interface disappears. The oil recovery efficiency after miscible displacement is as high as over 90%. Miscible displacement technology: By achieving miscible conditions, the driving medium and the driven medium dissolve each other and the interface disappears, which is manifested as the surface tension and capillary force are reduced to 0, and the oil recovery efficiency can reach 90%. Summary of the invention

[0004] The inventors of the present application discovered that:

[0005] From the perspective of miscibility, carbon dioxide can easily mix with crude oil, but the injection of carbon dioxide involves issues such as gas source, corrosion, and transportation costs, making it difficult to implement in most oil fields.

[0006] Compared with carbon dioxide flooding, nitrogen flooding and flue gas flooding technologies save complex purification processes and costs, and can also achieve the storage of carbon dioxide gas, which can effectively reduce greenhouse gas emissions and achieve rational use of resources. Although nitrogen and flue gas resources are relatively sufficient and the gas is safe and reliable, once the nitrogen content is too high (N2>50%), it is difficult to mix with crude oil, especially heavy crude oil. Therefore, the field application is mostly immiscible flooding and gravity flooding. Immiscible flooding greatly reduces the development effect, and gravity flooding has high requirements for the development environment, which increases the technical threshold of application. Therefore, it is urgent to find new miscible technologies and gas media to improve the effect of gas injection development.

[0007] The present application provides an oil production method for a light oil reservoir, which includes injecting a catalytic promoter and air through an injection well in the light oil reservoir; thermally oxidizing the injected air through the catalytic promoter to form a thermal oxidation mode and generate a mixed-phase gas; when the light oil reservoir is in the thermal oxidation mode, the light components in the crude oil are gasified or the light hydrocarbons are distilled, and mixed with the mixed-phase gas generated by thermal oxidation to achieve thermal miscibility, thereby driving the crude oil to be produced from the production well. This method can overcome the mechanism problems of capillary force, interfacial tension, etc. during the air injection development process, greatly improve the displacement efficiency, and the oil displacement efficiency can reach more than 90%.

[0008] In a first aspect, the present application provides a method for oil production from a light oil reservoir, the method comprising:

[0009] Injecting catalytic promoters and air through gas injection wells in light oil reservoirs;

[0010] The injected air is thermally oxidized by the catalytic promoter to form a thermal oxidation mode and generate a mixed-phase gas; wherein the mixed-phase gas is a mixed gas of CO2 and N2;

[0011] When the light oil reservoir is in the thermal oxidation mode, the light components in the crude oil are gasified or distilled into light hydrocarbons, which are mixed with the mixed-phase gas generated by thermal oxidation to achieve thermal miscibility, thereby driving the crude oil to be produced from the production well.

[0012] Compared with the related art, the present application provides a method for oil production in a light oil reservoir, the method comprising: injecting a catalytic promoter and air through an injection well in the light oil reservoir; thermally oxidizing the injected air through the catalytic promoter to form a thermal oxidation mode and generate a mixed-phase gas; wherein the mixed-phase gas is a mixed gas of CO2 and N2; when the light oil reservoir is in the thermal oxidation mode, the light components in the crude oil are gasified or the light hydrocarbons are distilled, and mixed with the mixed-phase gas generated by thermal oxidation to achieve thermal miscibility, and drive the crude oil to be produced from the production well. This method can overcome the mechanism problems of capillary force, interfacial tension, etc. in the process of air injection development, greatly improve the displacement efficiency, and the oil recovery efficiency can reach more than 90%.

[0013] Other features and advantages of the present application will be described in the following description, and partly become apparent from the description, or be understood by implementing the present application. Other advantages of the present application can be realized and obtained by the schemes described in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The accompanying drawings are used to provide an understanding of the technical solution of the present application and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the technical solution of the present application and do not constitute a limitation on the technical solution of the present application.

[0015] Figure 1This is a flow chart of the oil recovery method for a light oil reservoir according to an embodiment of the present application;

[0016] Figure 2 Schematic diagram of the prediction curve of production wells in the air injection thermal miscible test area of ​​Block M in some exemplary embodiments. DETAILED DESCRIPTION

[0017] The present application describes multiple embodiments, but the description is exemplary rather than restrictive, and it is obvious to those skilled in the art that there may be more embodiments and implementations within the scope of the embodiments described in the present application. Although many possible feature combinations are shown in the drawings and discussed in the specific embodiments, many other combinations of the disclosed features are also possible. Unless specifically limited, any feature or element of any embodiment may be used in combination with any other feature or element in any other embodiment, or may replace any other feature or element in any other embodiment.

[0018] The present application includes and contemplates combinations of features and elements known to those of ordinary skill in the art. The embodiments, features and elements disclosed in the present application may also be combined with any conventional features or elements to form a unique invention scheme defined by the claims. Any features or elements of any embodiment may also be combined with features or elements from other invention schemes to form another unique invention scheme defined by the claims. Therefore, it should be understood that any feature shown and / or discussed in the present application may be implemented individually or in any appropriate combination. Therefore, except for the limitations made according to the attached claims and their equivalents, the embodiments are not subject to other restrictions. In addition, various modifications and changes may be made within the scope of protection of the attached claims.

[0019] In addition, when describing representative embodiments, the specification may have presented the method and / or process as a specific sequence of steps. However, to the extent that the method or process does not rely on the specific order of the steps described herein, the method or process should not be limited to the steps of the specific order described. As will be understood by those of ordinary skill in the art, other sequences of steps are also possible. Therefore, the specific sequence of the steps set forth in the specification should not be interpreted as a limitation to the claims. In addition, the claims for the method and / or process should not be limited to the steps of performing them in the order written, and those skilled in the art can easily understand that these sequences can be changed and still remain within the spirit and scope of the embodiments of the present application.

[0020] The embodiment of the present invention provides a method for oil production from a light oil reservoir, such as Figure 1 As shown, the method includes steps S100-S120:

[0021] S100: Injection of catalyst additives and air through gas injection wells in light oil reservoirs;

[0022] S110: thermally oxidizing the injected air by the catalytic promoter to form a thermal oxidation mode and generate a mixed-phase gas; the mixed-phase gas is a mixed gas of CO2 and N2;

[0023] S120: When the light oil reservoir is in the thermal oxidation mode, the light components in the crude oil are gasified or the light hydrocarbons are distilled and mixed with the mixed-phase gas generated by the thermal oxidation to achieve thermal miscibility, thereby driving the crude oil to be produced from the production well.

[0024] In this embodiment, the oil recovery method is targeted at light oil reservoirs that can be developed by air injection. Light oil reservoirs are: reservoir pressure > 15MPa, oil layer thickness > 5m, and residual oil saturation at the bottom of the gas injection well > 50%; it is implemented for this type of oil reservoir.

[0025] In an exemplary embodiment, before executing the oil production method, one or more groups of one-injection-multiple-production annular vertical well patterns are first deployed, and the injection-production well spacing S is set to 150-800 m.

[0026] In an exemplary embodiment, a 1-5% mass percentage of the catalyst additive mixture is injected into the gas injection well, the injection temperature is 0-40°C, and the injection amount is (1-1.5)×hm 3 , where h is the reservoir thickness.

[0027] In an exemplary embodiment, the thermal oxidation mode is: the pressure is greater than 15 MPa, and the temperature range is 250-400°C.

[0028] By continuously injecting air, the injection intensity is (3~5)×S Nm 3 / m (N is the standard condition, normal temperature and pressure), air is injected into the oil layer, mixed with the injected catalytic promoter at a position more than 2m from the bottom of the well, and oxidation heat is released by using the formation temperature. This process consumes about 5% of the heavy components in the crude oil to release heat. When the temperature at the hot miscible front reaches 250-400℃, the light components in the crude oil are continuously gasified / distilled, and cracked to form new light hydrocarbons, which are mixed with the miscible gas (15% CO2, 85% N2) generated by thermal oxidation, and hot miscibility is achieved under medium temperature and high pressure (>15MPa) conditions.

[0029] In an exemplary embodiment, the produced gas is monitored, and after the formation of a stable thermal front and a hot mixed phase zone is determined, the injection rate is gradually increased until the injection intensity reaches (5-15)×S Nm 3 / m (N is the standard condition, normal temperature and pressure), the production intensity of the generating well is (3~12)×S / n Nm 3 / m, where n is the number of production wells, stable production.

[0030] The present invention provides an oil recovery method for light oil reservoirs by air injection hot miscible flooding, which has the following advantages:

[0031] (1) This method breaks through the technical blind spot of oxidation startup in deep / ultra-deep wells, gives full play to the natural advantages of temperature and pressure of light oil reservoirs, forms a stable thermal oxidation front by injecting air, creates high temperature and high pressure conditions, and utilizes the drastic changes and rapid extraction of various components of crude oil under high temperature conditions to mix with the produced miscible gas to achieve miscibility.

[0032] (2) This method consumes air to efficiently generate miscible gas inside the reservoir, and through miscible displacement, the displacement efficiency is increased from 40% of conventional gas drive / water drive to more than 90%.

[0033] (3) This method has low cost and simple operation, overcoming the problems of corrosion, complex transportation and injection processes, and high completion costs in conventional gas injection development. At the same time, by optimizing the startup process, a protection mode for old well strings is formed with high temperature inside the reservoir and normal temperature in the injection and production stages, which can efficiently utilize the existing old wells in the oil field and does not require additional workover costs for production wells.

[0034] Example 1

[0035] For the light oil reservoir in Block M, the specific process of oil recovery by air injection hot miscible flooding in light oil reservoir is as follows:

[0036] Step 1: Determine the relevant reservoir parameters of Block M

[0037] Targeted selection of reservoirs that can be developed by air injection. The average burial depth of the layer in Block M is 2800m, the effective oil layer thickness is 20m, the permeability is 5mD, the current gas injection pressure is about 17-20MPa, the formation temperature is 102℃, the oil saturation is 55%, and it is a monocline lithological reservoir from southwest to northeast, with a formation dip angle of 7°;

[0038] Step 2: Deploy a circular well pattern in Block M

[0039] An annular well network is deployed at the high structural position of the block, with one vertical gas injection well and five vertical production wells, with the injection and production wells spaced 150 to 250 meters apart.

[0040] Step 3: Inject 30m into the gas injection well 3 Catalyst (wt 1%) plug, injection temperature 40°C, injection speed 10m 3 / h, maximum injection pressure 30MPa;

[0041] Step 4: Continue to inject air at a speed of 12000Nm 3 / d, formation temperature 102°C, near-wellbore crude oil oxidation;

[0042] Step 5: Increase the injection speed step by step. After 3 days, the injection speed is increased to 27000Nm 3 / d, after 7d, the injection speed was increased to 54000Nm 3 / d, and after 30 days, the injection speed was increased to 81000Nm 3 / d, inject air for stable operation.

[0043] like Figure 2 As shown, the test area has been stably injected with air for 16 months, with daily liquid production reaching 31.2t / d and daily oil production reaching 20.5t / d. Compared with depletion development, the daily oil production has increased by 47.1%. It is predicted that the stable oil production can reach 25.6t / d, and the stage recovery degree can reach 20.2%.

[0044] In this embodiment, air is preferentially injected into the formation through the injection well, and after catalysis, a stable thermal oxidation mode of high pressure (>15MPa) and medium temperature (250-400°C) is formed in the light oil reservoir. The light components in the crude oil are continuously gasified / distilled, and at the same time, they are cracked to form new light hydrocarbons, which are mixed with the mixed phase gas (15% CO2, 85% N2) generated by thermal oxidation to achieve thermal miscibility under medium temperature and high pressure (>15MPa) conditions. The gasification / distillation hot miscibility in the air injection development process can overcome the mechanism problems such as capillary force and interfacial tension, greatly improve the displacement efficiency, and the oil displacement efficiency can reach more than 90%.

[0045] It will be appreciated by those skilled in the art that all or some of the steps, systems, and functional modules / units in the methods disclosed above may be implemented as software, firmware, hardware, and appropriate combinations thereof. In hardware implementations, the division between the functional modules / units mentioned in the above description does not necessarily correspond to the division of physical components; for example, a physical component may have multiple functions, or a function or step may be performed by several physical components in cooperation. Some or all components may be implemented as software executed by a processor, such as a digital signal processor or a microprocessor, or implemented as hardware, or implemented as an integrated circuit, such as an application-specific integrated circuit. Such software may be distributed on a computer-readable medium, which may include a computer storage medium (or non-transitory medium) and a communication medium (or temporary medium). As known to those skilled in the art, the term computer storage medium includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storing information (such as computer-readable instructions, data structures, program modules, or other data). Computer storage media include, but are not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tapes, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store the desired information and can be accessed by a computer. In addition, it is well known to those of ordinary skill in the art that communication media typically contain computer-readable instructions, data structures, program modules, or other data in a modulated data signal such as a carrier wave or other transport mechanism, and may include any information delivery media.

Claims

1. A method for oil production from a light oil reservoir, characterized in that: The method comprises: Injecting catalytic promoters and air through gas injection wells in light oil reservoirs; The injected air is thermally oxidized by the catalytic promoter to form a thermal oxidation mode and generate a mixed-phase gas; wherein the mixed-phase gas is a mixed gas of CO2 and N2; When the light oil reservoir is in the thermal oxidation mode, the light components in the crude oil are gasified or distilled into light hydrocarbons, which are mixed with the mixed-phase gas generated by thermal oxidation to achieve thermal miscibility, thereby driving the crude oil to be produced from the production well.

2. The oil recovery method for light oil reservoirs according to claim 1, characterized in that: The mass percentage of the catalytic additive is in the range of 1% to 5%.

3. The oil recovery method for light oil reservoirs according to claim 1, characterized in that: The light oil reservoir has a reservoir pressure greater than 15 MPa, an oil layer thickness greater than 5 meters, and a residual oil saturation greater than 50% in the near-wellbore area at the bottom of the gas injection well.

4. The oil recovery method for light oil reservoirs according to claim 1, characterized in that: The injection temperature range of the catalytic oxygen consuming agent is 0-40°C.

5. The oil recovery method for light oil reservoirs according to claim 1, characterized in that: The optimal injection temperature range of the catalytic oxygen consuming agent is 20-35°C.

6. The oil recovery method for light oil reservoirs according to claim 1, characterized in that: The injection intensity range of air injected into the gas injection well is: 2500~5000Nm 3 / m; The injection speed range of the catalytic oxygen consuming agent is: 10~25m 3 / h.

7. The method for producing oil from a light oil reservoir according to claim 1, characterized in that: The thermal oxidation mode is: the pressure is greater than 15 MPa and the temperature range is 250-400°C.

8. The oil recovery method for light oil reservoirs according to claim 1, characterized in that: The mixed gas contains 15% CO2 and 85% N2.

9. The oil recovery method for light oil reservoirs according to claim 1, characterized in that: The method of driving crude oil to flow out of the production well comprises: When the production well is monitored to produce gas, the air injection intensity is adjusted to the oil production range to meet the production well to reach the predetermined production intensity range; Wherein, the oil production range is (2500-5000)Nm 3 / m; N is normal temperature and pressure.

10. The oil recovery method for light oil reservoirs according to claim 9, characterized in that: The predetermined extraction intensity range is (2250~4600) / n Nm 3 / m, n is the number of production wells.

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