Same-well multi-layer oil extraction and gas injection pipe column mechanism and oil extraction and injection method

Abstract

The invention is suitable for the field of oil and gas exploitation, and discloses a same-well multi-layer oil extraction and gas injection tubular column mechanism and an oil extraction and gas injection method.The method comprises the steps that after a packing unit is lowered in a sleeve of an oil well to a designated position for setting and fixing, an oil extraction unit is lowered, the oil extraction unit penetrates through the packing unit, and a packing space is formed in the packing unit; the packing space penetrates through the casing pipe to be communicated with a stratum, carbon dioxide associated with oilfield development can be captured, separated and pressurized to be in a gas-liquid mixed supercritical state through the injection pipe, and the carbon dioxide is reinjected to a seabed salt water layer to be safely sealed and stored without being leaked into other spaces of the casing pipe. Petroleum liquid below can enter the platform through the punching pipe. The technology is simple and reliable, oil extraction and gas injection are mutually independent and do not influence each other, the problems that offshore oilfield well slot resources are precious and the cost is high due to the fact that one well is used for sealing carbon dioxide independently can be solved, and the purposes that an oilfield is green, low in carbon and normal in production can be achieved.

Description

Technical Field

[0001] The invention relates to the field of oil and gas production, and in particular to a same-well multi-layer oil production and gas injection pipe column mechanism and a production and injection method. Background Art

[0002] With the continuous exploration and development of offshore oil and gas, a lot of associated gas is produced during its production process. The current treatment method is mainly to burn or drain the associated gas, but this is not conducive to the realization of the "dual carbon" goal. At the same time, the well slot resources of offshore platforms are precious, and it is costly to use a single well to seal carbon dioxide. A new type of pipe string mechanism is urgently needed to inject carbon dioxide gas back into the seabed saline layer for geological sealing while producing oil. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a multi-layer oil production and gas injection pipe string mechanism and a production and injection method in the same well.

[0004] The technical solution adopted by the present invention to solve its technical problems includes: a casing arranged in an oil well, an oil production unit for sucking crude oil from the casing, a gas injection unit for reinjecting carbon dioxide into the bottom layer, and a sealing unit arranged at a specified position in the casing; wherein the sealing unit isolates the space above and below the sealing unit at the specified position of the casing, an isolated space is formed in the sealing unit, the gas injection unit is connected to the isolated space through a pipeline, the isolated space is connected to the formation through the casing, the oil production unit is penetrated by the sealing unit, and the oil production unit is connected to the space above and below the sealing unit.

[0005] In one embodiment, the isolation unit includes a bottom packer and a top packer, wherein the bottom packer and the top packer are arranged in the casing, and the top packer is arranged above the bottom packer, and the bottom packer and the top packer are expanded to abut against the casing through an outer circular contour to form a sealing belt.

[0006] In one embodiment, the isolation unit further comprises a filter barrier assembly, wherein the filter barrier assembly is disposed in the isolation space, and the filter barrier assembly is sealingly connected to the bottom packer and the top packer.

[0007] In one embodiment, the filter barrier assembly includes a blind pipe and a sand control screen pipe. The blind pipe is arranged at the upper and lower parts of the filter barrier assembly. The blind pipe is used to prevent mud impurities from entering the isolation space. The sand control screen pipe is arranged in the middle part of the filter barrier assembly. The sand control screen pipe is tubular and connects the internal and external spaces of the filter barrier assembly. A screen is provided at one end of the sand control screen pipe.

[0008] In one embodiment, the oil production unit includes a perforated pipe, an anchor seal and a positioning seal. The perforated pipe is inserted into the isolation unit, the anchor seal and the positioning seal are sleeved on the perforated pipe, the anchor seal is sealingly connected to the bottom isolation unit, and the positioning seal is sealingly connected to the top isolation unit.

[0009] In one embodiment, the oil production unit is also provided with a canned pump assembly, a production packer and a downhole safety valve. The canned pump assembly is arranged on the upper part of the perforated pipe and is used to draw liquid flowing out of the perforated pipe. The production packer is sleeved on the canned pump assembly and interference fits with the inner wall of the casing to form a sealing belt. The downhole safety valve is arranged in the canned pump assembly and controls the flow of the canned pump assembly.

[0010] In one embodiment, the gas injection unit includes a gas supply system and an injection pipe, and the gas supply system is connected to the injection pipe; the gas supply system includes a carbon dioxide injection pump, a corrosion inhibitor injection pump and a pressure gauge, and the carbon dioxide injection pump and the corrosion inhibitor injection pump are connected in parallel to the injection pipe, the pressure gauge is arranged at the parallel position of the injection pipe, and the injection pipe is connected to the enclosed space.

[0011] The present invention also provides a production and injection method of a multi-layer oil production and gas injection pipe string mechanism in the same well, comprising the following steps:

[0012] Step S1, lowering the isolation unit into the casing to a specified depth, and setting the isolation unit;

[0013] Step S2, lowering the oil production unit into the isolation unit and passing through the isolation unit, wherein the oil production unit is sealed with the isolation unit;

[0014] Step S3, the oil production unit sucks the crude oil below the packer unit to the space above the packer unit and supplies it to the oil production platform;

[0015] Step S4, starting the gas injection unit to inject carbon dioxide into the isolated space and into the formation through the casing.

[0016] In one embodiment, in step S1, after the isolation unit is sealed, it is necessary to verify the sealing, that is, use a maximum injection pressure greater than the injection pressure of the injection unit to verify the sealing of the isolation unit. If there is no obvious pressure drop in the isolation unit, the sealing is qualified and the step S2 can be continued.

[0017] In one embodiment, in the steps S1 to S4, when emergency shutdown is required, the gas injection unit needs to be shut down first, and then the oil production unit needs to be shut down.

[0018] The implementation of the multi-layer oil production and gas injection pipe column mechanism in the same well of the present invention has the following beneficial effects: after lowering the isolation unit to the designated position in the casing of the oil well for sealing and fixing, the oil production unit is lowered, and the oil production unit passes through the isolation unit, and an isolation space is formed in the isolation unit. The isolation space passes through the casing and communicates with the formation, and the carbon dioxide associated with the development of the oil field can be captured, separated, and pressurized to a supercritical state of gas-liquid mixture through the injection pipe, and then injected back into the seabed saline layer for safe storage without leaking into other spaces in the casing, while the petroleum liquid below can enter through the perforated pipe to reach the platform. The process is simple and reliable, and oil production and gas injection are independent of each other without affecting each other. It can not only solve the problem of precious well slot resources in offshore oil fields and the high cost of using a single well to store carbon dioxide, but also achieve the goal of green, low-carbon and normal production of oil fields.

[0019] The implementation of the production and injection method of the multi-layer oil production and gas injection pipe string mechanism in the same well of the present invention has the following beneficial effects: the installation of the isolation unit and the oil production unit is realized, and on this set of mechanisms, gas injection and oil production are performed synchronously without affecting each other, thereby greatly improving the production efficiency and the efficiency of reinjecting carbon dioxide. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solution of the present invention, the present invention will be further described below in conjunction with the accompanying drawings and embodiments. It should be understood that the following drawings only show certain embodiments of the present invention and should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work. In the drawings:

[0021] Figure 1 It is a structural diagram of a production and injection method of a multi-layer oil production and gas injection pipe string mechanism in a same well in one embodiment of the present invention;

[0022] Figure 2 It is a gas circuit diagram of a production and injection method of a multi-layer oil production and gas injection pipe string mechanism in the same well in one embodiment of the present invention;

[0023] Figure 3 It is an overall structural diagram of a production and injection method of a multi-layer oil production and gas injection pipe string mechanism in a same well in one embodiment of the present invention;

[0024] Figure 4 It is a flowchart of a method for installing a multi-layer oil production and gas injection pipe string mechanism in a same well in one embodiment of the present invention;

[0025] Figure 5 It is a flowchart of a production and injection method of a multi-layer oil production and gas injection pipe string mechanism in the same well in one embodiment of the present invention.

[0026] Reference numerals

[0027] 1. Bottom packer; 2. Blind pipe; 3. Sand screen; 4. Top packer; 5. Round plug; 6. Perforated pipe; 7. Anchor seal; 8. Positioning seal; 9. Canned pump assembly; 10. Production packer; 11. Circulating sleeve; 12. Downhole safety valve; 13. Tubing hanger; 14. Carbon dioxide injection pump; 15. First regulating valve; 16. Three-way mixer; 17. Second regulating valve; 18. Corrosion inhibitor injection pump; 19. Switch valve; 20. Pressure gauge; 21. Injection pipe; 22. Seal space; 23. Casing. DETAILED DESCRIPTION

[0028] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific embodiments of the present invention are now described in detail with reference to the accompanying drawings. In the following description, it should be understood that the directions or positional relationships indicated by "front", "back", "up", "down", "left", "right", "longitudinal", "horizontal", "vertical", "horizontal", "top", "bottom", "inside", "outside", "head", "tail", etc. are based on the directions or positional relationships shown in the accompanying drawings, are constructed and operated in a specific direction, and are only for the convenience of describing the present technical solution, rather than indicating that the device or element referred to must have a specific direction, and therefore cannot be understood as a limitation to the present invention.

[0029] It should also be noted that, unless otherwise clearly specified and limited, the terms such as "installed", "connected", "connected", "fixed", "set" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. When an element is referred to as being "on" or "under" another element, the element can be "directly" or "indirectly" located on the other element, or there may be one or more intermediate elements. The terms "first", "second", "third", etc. are only for the convenience of describing the present technical solution, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first", "second", "third", etc. can explicitly or implicitly include one or more of the features. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0030] Figures 1 to 3A same-well multi-layer oil production and gas injection pipe string mechanism in an embodiment of the present invention is shown. The same-well multi-layer oil production and gas injection pipe string mechanism can be used to inject carbon dioxide gas back into the seabed saline layer for geological storage during oil production. The mechanism may include a casing 23 arranged in the oil well, an oil production unit for sucking crude oil from the casing 23, a gas injection unit for injecting carbon dioxide back into the bottom layer, and a sealing unit arranged at a specified position in the casing 23; wherein the sealing unit isolates the space above and below the sealing unit at the specified position of the casing 23, and an isolation space 22 is formed in the isolation unit, the gas injection unit is connected to the isolation space 22 through a pipeline, and the isolation space 22 is connected to the formation through the casing 23, the oil production unit is penetrated by the isolation unit, and the oil production unit is connected to the space above and below the isolation unit.

[0031] The isolation unit is lowered into the casing 23 of the oil well to a designated position for sealing and fixing, and then the oil production unit is lowered. The oil production unit passes through the isolation unit, and an isolation space 22 is formed in the isolation unit. The isolation space 22 passes through the casing 23 and communicates with the formation. The carbon dioxide associated with the development of the oil field can be captured, separated, and pressurized to a supercritical state of gas-liquid mixture through the injection pipe 21, and then injected back into the seabed saline layer for safe storage without leaking into other spaces of the casing 23, while the petroleum liquid below can enter the platform through the perforated pipe 6. This process is simple and reliable, and realizes the independence of oil production and gas injection without affecting each other. It can not only solve the problem of precious well slot resources in offshore oil fields and the high cost of storing carbon dioxide in a single well, but also achieve the goal of green, low-carbon and normal production of oil fields.

[0032] It can be understood that the space between the casing 23 and the formation is in communication with each other, and the high-pressure carbon dioxide in the casing 23 can pass through the casing 23 into the formation to dissolve with the salt water and be sealed in the salt water.

[0033] In a specific embodiment, the supercritical pressure of carbon dioxide gas-liquid is determined according to the ambient temperature and other environmental parameters.

[0034] Furthermore, the pressure of the carbon dioxide output does not exceed 18 MPa.

[0035] Figure 2 It is shown that the isolation unit may include a bottom packer 1 and a top packer 4 in one embodiment. The bottom packer 1 and the top packer 4 are arranged in a casing 23, and the top packer 4 is arranged above the bottom packer 1. The bottom packer 1 and the top packer 4 are expanded to abut against the casing 23 through an outer circular profile to form a sealing belt.

[0036] Figure 2The isolation unit may include a filter barrier assembly in one embodiment. The filter barrier assembly is arranged in an annular shape in the isolation space 22. The filter barrier assembly is sealed and connected to the bottom packer 1 and the top packer 4. The filter assembly can prevent the salt water mixed with sediment in the bottom layer from backwashing into the isolation space 22.

[0037] Figure 2 It is shown that the filter barrier assembly may include a blind pipe 2 and a sand screen 3 in one embodiment. The blind pipe 2 is arranged at the upper and lower parts of the filter barrier assembly. The blind pipe 2 is used to prevent mud impurities from entering the isolation space 22. The sand screen 3 is arranged in the middle part of the filter barrier assembly. The sand screen 3 is tubular and connects the internal and external spaces of the filter barrier assembly. A screen is provided at one end of the sand screen 3. The blind pipe 2 can block impurities such as mud and sand from entering the interior at the upper and lower parts, while the screen can prevent mud and sand of a certain size from entering, and the liquid can smoothly pass through the screen into the interior.

[0038] Figure 2 It is shown that the oil production unit in one embodiment may include a perforated pipe 6, an anchor seal 7 and a positioning seal 8. The perforated pipe 6 is inserted into the isolation unit, and the anchor seal 7 and the positioning seal 8 are sleeved on the perforated pipe 6. The anchor seal 7 is sealed connected to the bottom packer 1, and the positioning seal 8 is sealed connected to the top packer 4. After the sealing connection, the casing 23 is completely isolated to form an isolation space 22.

[0039] In a specific embodiment, the center of the bottom packer 1 and the top packer 4 is a light hole, the anchor seal 7 and the positioning seal 8 are cylindrical, and the side walls of the cylindrical anchor seal 7 and the positioning seal 8 are provided with sealing rings, the anchor seal 7 and the positioning seal 8 are directly inserted into the light hole, and the sealing ring and the light hole cooperate with each other to form a sealing belt.

[0040] It can be understood that there are a number of fine holes on the perforated tube 6 , which are arranged below the bottom packer 11 , and are used to absorb the liquid below and supply it to the top of the top packer 4 .

[0041] In a specific embodiment, a round plug 5 is further provided at the lower part of the perforated tube 6. The round plug 5 is located at the lowermost end of the perforated tube 6 and plays a role in sealing and sand settling.

[0042] Figure 2 It is shown that the oil production unit in one embodiment may include a canned pump assembly 9, a production packer 10 and a downhole safety valve 12. The canned pump assembly 9 is arranged on the upper part of the perforated pipe 6 to absorb the liquid flowing out of the perforated pipe 6. The production packer 10 is sleeved on the canned pump assembly 9 and is interference fit with the inner wall of the casing 23 to form a sealing belt. The downhole safety valve 12 is arranged in the canned pump group and controls the flow of the canned pump assembly 9. After the liquid enters the oil pipe through the perforated pipe 6, it can be transported to the offshore platform through the canned pump assembly 9, thereby achieving the purpose of oil production.

[0043] Figure 3 It is shown that the gas injection unit may include a gas supply system and an injection pipe 21 in one embodiment, and the gas supply system is connected to the injection pipe 21; the gas supply system includes a carbon dioxide injection pump 14, a corrosion inhibitor injection pump 18 and a pressure gauge 20, the carbon dioxide injection pump 14 and the corrosion inhibitor injection pump 18 are connected in parallel to the injection pipe 21, the pressure gauge 20 is arranged at the parallel position of the injection pipe 21, and the injection pipe 21 is connected to the enclosed space 22.

[0044] It can be understood that the corrosion inhibitor is mainly used to slow down the corrosion of the casing 23 and other parts by the acidic substances formed by carbon dioxide and water.

[0045] In a specific embodiment, the outlet of the injection pipe 21 is arranged in a circular space surrounded by the filter barrier assembly, because the liquid after filtering first will not cause serious damage to the injection pipe 21 and backwashing.

[0046] In a specific embodiment, the first minimum flow valve may include a carbon dioxide injection assembly including a carbon dioxide injection pump 14 and a first regulating valve 15, the carbon dioxide injection pump 14 is connected to the first regulating valve 15 and the injection pipe 21 in sequence through a pipeline, and the corrosion inhibitor injection assembly includes a corrosion inhibitor injection pump 18 and a second regulating valve 17, the corrosion inhibitor injection pump 18 is connected to the second regulating valve 17 and the injection pipe 21 in sequence through a pipeline.

[0047] Furthermore, the second regulating valve 17 is a one-way valve for preventing the high-pressure carbon dioxide from backwashing into the corrosion inhibitor injection pump 18 .

[0048] Furthermore, a three-way mixer 16 is provided at the parallel connection of the carbon dioxide injection assembly and the corrosion inhibitor injection assembly, and the carbon dioxide injection assembly, the corrosion inhibitor injection assembly and the injection pipe 21 are connected to the three-way mixer 16 in parallel.

[0049] Furthermore, the injection pipe 21 is provided with a switch valve 19 , and the switch valve 19 can control the flow of the injection pipe 21 .

[0050] Figure 4 A method for producing and injecting oil and gas in a multi-layered oil production and gas injection pipe string mechanism in the same well is shown, comprising the following steps:

[0051] Step S1, lowering the isolation unit into the casing 23 to a specified depth, and setting the isolation unit;

[0052] Step S2, lowering the oil production unit and inserting it into the isolation unit, and sealing the oil production unit and the isolation unit;

[0053] Step S3, the oil production unit sucks the crude oil below the packer unit to the space above the packer unit and supplies it to the oil production platform;

[0054] Step S4, start the gas injection unit to inject carbon dioxide into the isolation space 22 and into the formation through the casing 23.

[0055] Figure 5 In one embodiment shown, the following steps are included:

[0056] Step S11, the bottom packer 1 and the top packer 4 are connected in sequence and lowered into the casing 23 to a specified depth, and the bottom packer 1 and the top packer 4 are set;

[0057] Step S12, the perforated pipe 6, the anchor seal 7, the positioning seal 8, the canned pump assembly 9, the production packer 10 and the downhole safety valve 12 are sequentially lowered into the casing 23, and the perforated pipe 6 is inserted through the bottom packer 1 and the top packer 4;

[0058] Step S13, the anchor seal 7 is sealed and connected to the bottom packer 1, the positioning seal 8 is sealed and connected to the top packer 4, the production packer 10 is sealed with the casing 23, and the injection pipe 21 is sequentially inserted into the production packer 10 and the top packer 4;

[0059] Step S21, the liquid enters the pipe through the perforated pipe 6 of the central production string, and is lifted to the oil production platform by the canned pump assembly 9, and the downhole safety valve 12 is in a pressure-open state;

[0060] Step S22, respectively start the carbon dioxide injection pump 14 and the corrosion inhibitor injection pump 18, and perform a pressure test when the output pressures of the carbon dioxide injection pump 14 and the corrosion inhibitor injection pump 18 are stable;

[0061] Step S23, after the pressure test is completed, open and adjust the output pressure of the first regulating valve 15 and the second regulating valve 17, and the mixed liquid composed of the carbon dioxide gas-liquid supercritical body and the corrosion inhibitor enters the injection pipe 21, and the mixed liquid flows through the injection pipe 21 and the isolation space 22, and finally flows into the formation and the saline layer for sealing.

[0062] Figure 4 It is shown that step S1 in one embodiment may include that after the isolation unit is sealed, it is necessary to test the sealing, that is, use a maximum injection pressure greater than the injection unit's maximum injection pressure to test the sealing of the isolation unit. If there is no obvious pressure drop in the isolation unit, the sealing is qualified and step S2 can be continued.

[0063] Figure 4 It is shown that in one embodiment, steps S1 to S4 may include the need to slowly shut down the gas injection unit first and then shut down the oil production unit when an emergency shutdown is required.

[0064] In a specific embodiment, it is necessary to first shut down the carbon dioxide injection pump 1414 and the corrosion inhibitor injection pump 18, then shut down the first regulating valve 15 and the second regulating valve 17, and finally close the downhole safety valve 12.

[0065] It can be understood that the above embodiments only express the preferred implementation modes of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the patent scope of the present invention. It should be pointed out that, for ordinary technicians in this field, without departing from the concept of the present invention, the above technical features can be freely combined, and several deformations and improvements can be made, which all belong to the protection scope of the present invention. Therefore, all equivalent changes and modifications made to the scope of the claims of the present invention should belong to the scope covered by the claims of the present invention.

Claims

1. A multi-layer oil production and gas injection pipe string mechanism in the same well, characterized in that: include: A casing (23) arranged in an oil well, an oil extraction unit for extracting crude oil from the casing (23), a gas injection unit for reinjecting carbon dioxide into a bottom layer, and a sealing unit arranged at a designated position in the casing (23); The isolation unit isolates the space above and below the isolation unit at a designated position of the casing (23), forming an isolation space (22) in the isolation unit, the gas injection unit is connected to the isolation space (22) through a pipeline, the isolation space (22) is connected to the formation through the casing (23), and the oil production unit is penetrated by the isolation unit, and the oil production unit is connected to the space above and below the isolation unit.

2. A multi-layer oil production and gas injection pipe string mechanism in the same well according to claim 1, characterized in that: The sealing unit comprises a bottom packer (1) and a top packer (4). The bottom packer (1) and the top packer (4) are arranged in the casing (23), and the top packer (4) is arranged above the bottom packer (1). The bottom packer (1) and the top packer (4) are abutted against the casing (23) through the expansion of the outer circular profile to form a sealing belt.

3. A multi-layer oil production and gas injection pipe string mechanism in the same well according to claim 2, characterized in that: The isolation unit further comprises a filtering barrier assembly, which is disposed in the isolation space (22) and is sealingly connected to the bottom packer (1) and the top packer (4).

4. A multi-layer oil production and gas injection pipe string mechanism in the same well according to claim 3, characterized in that: The filter barrier assembly comprises a blind pipe (2) and a sand screen (3), wherein the blind pipe (2) is arranged at the upper and lower parts of the filter barrier assembly, and the blind pipe (2) is used to prevent muddy impurities from entering the isolation space (22). The sand screen (3) is arranged in the middle part of the filter barrier assembly, and the sand screen (3) is tubular and connects the internal and external spaces of the filter barrier assembly, and a screen is provided at one end of the sand screen (3).

5. The same well multi-layer oil production and gas injection pipe string mechanism according to claim 2, characterized in that: The oil production unit comprises a perforated pipe (6), an anchor seal (7) and a positioning seal (8); the perforated pipe (6) is inserted into the isolation unit; the anchor seal (7) and the positioning seal (8) are sleeved on the perforated pipe (6); the anchor seal (7) is sealingly connected to the bottom isolation packer (1); and the positioning seal (8) is sealingly connected to the top isolation packer (4).

6. A multi-layer oil production and gas injection pipe string mechanism in the same well according to claim 5, characterized in that: The oil production unit is also provided with a canned pump assembly (9), a production packer (10) and a downhole safety valve (12); the canned pump assembly (9) is arranged on the upper part of the perforated pipe (6) and is used to draw liquid flowing out of the perforated pipe (6); the production packer (10) is sleeved on the canned pump assembly (9) and is interference-fitted with the inner wall of the casing (23) to form a sealing belt; the downhole safety valve (12) is arranged in the canned pump assembly (9) and controls the flow of the canned pump assembly (9).

7. The same well multi-layer oil production and gas injection pipe string mechanism according to claim 1, characterized in that: The gas injection unit comprises a gas supply system and an injection pipe (21), wherein the gas supply system is connected to the injection pipe (21); the gas supply system comprises a carbon dioxide injection pump (14), a corrosion inhibitor injection pump (18) and a pressure gauge (20), wherein the carbon dioxide injection pump (14) and the corrosion inhibitor injection pump (18) are connected in parallel to the injection pipe (21), the pressure gauge (20) is arranged at the parallel position of the injection pipe (21), and the injection pipe (21) is connected to the sealed space (22).

8. A production and injection method of a multi-layer oil production and gas injection pipe string mechanism in the same well, applied to a multi-layer oil production and gas injection pipe string mechanism in the same well as claimed in any one of claims 1 to 7, characterized in that: The following steps are involved: Step S1, lowering the isolation unit into the casing (23) to a specified depth, and setting the isolation unit; Step S2, lowering the oil production unit into the isolation unit and inserting the oil production unit into the isolation unit, wherein the oil production unit is sealed with the isolation unit; Step S3, the oil production unit sucks the crude oil below the packer unit to the space above the packer unit and supplies it to the oil production platform; Step S4, starting the gas injection unit to inject carbon dioxide into the isolated space (22) and into the formation through the casing (23).

9. The method for producing and injecting oil and gas using a multi-layered oil production and gas injection pipe string mechanism in the same well according to claim 8, characterized in that: In the step S1, after the isolation unit is sealed, it is necessary to verify the sealing, that is, use a maximum injection pressure greater than the injection pressure of the injection unit to verify the sealing of the isolation unit. If there is no obvious pressure drop in the isolation unit, the sealing is qualified and the step S2 can be continued.

10. The method for producing and injecting oil and gas using a multi-layered oil production and gas injection pipe string mechanism in the same well according to claim 8, characterized in that: In the steps S1 to S4, when emergency shutdown is required, the gas injection unit needs to be shut down first, and then the oil production unit is shut down.

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