Supercritical steam injection exploitation process for medium-deep layer thick oil

Abstract

The invention relates to the technical field of heavy oil recovery, in particular to a supercritical steam injection recovery process for medium-deep layer heavy oil, thermal oil recovery is a main process technical measure for heavy oil reservoir development, and the supercritical heavy oil recovery process provided by the invention can effectively solve the existing problems of heavy oil recovery and greatly improve the recovery efficiency; the method specifically comprises the steps that steam is heated and pressurized through a boiler to become supercritical steam, then the supercritical steam is injected into a well through a supercritical steam injection well opening and a supercritical high-temperature and high-pressure heat insulation pipe, and meanwhile the supercritical steam injection well opening and the supercritical high-temperature and high-pressure heat insulation pipe are improved to be matched with the supercritical steam. The heat of steam is used for exchanging heat with an oil layer, so that the viscosity of the thickened oil is finally reduced, and the recovery efficiency is improved; the process not only can greatly improve the recovery rate of the thickened oil, but also has the advantages of high yield increase speed, simple process, low cost, small recovery risk and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of heavy oil exploitation, and particularly to a supercritical steam injection exploitation process for medium-deep heavy oil. Background Art

[0002] Heavy oil accounts for a large proportion of the world's oil and gas resources. However, due to its poor fluidity, high viscosity, high freezing point and other characteristics, its recovery rate is relatively low. At present, the main methods for exploiting heavy oil reservoirs include thermal oil recovery, in-situ combustion, chemical oil recovery, etc. Among them, steam thermal recovery is the most commonly used method. However, due to many factors such as the low temperature of the injected steam itself and the poor heat insulation effect of the heat-insulating oil pipe, the actual temperature of the steam reaching the oil layer surface is relatively low, and the heat exchange with the oil layer is poor, which cannot achieve the purpose of heating and reducing the pour point, resulting in poor exploitation effect.

[0003] Therefore, in view of the deficiencies of the prior art, it is very necessary to provide a supercritical steam injection exploitation process for medium-deep heavy oil to solve the deficiencies of the prior art. Summary of the Invention

[0004] The purpose of the present invention is to avoid the deficiencies of the prior art and provide a supercritical steam injection exploitation process for medium-deep heavy oil. Thermal oil recovery is the main process technical measure for the development of heavy oil reservoirs. The supercritical heavy oil exploitation process proposed by the present invention can effectively solve the existing problems in heavy oil exploitation and greatly improve the recovery rate. Specifically, the steam is heated and pressurized by a boiler to become supercritical steam, and then injected into the well through a supercritical steam injection wellhead and a supercritical high-temperature and high-pressure heat-insulating pipe. At the same time, the supercritical steam injection wellhead and the supercritical high-temperature and high-pressure heat-insulating pipe are improved to adapt to supercritical steam. The heat of the steam is used for heat exchange with the oil layer to finally achieve the purpose of reducing the viscosity of heavy oil and improving the recovery rate. This process can not only greatly improve the heavy oil exploitation rate, but also has many advantages such as rapid production increase, simple process, low cost, and small exploitation risk.

[0005] The above object of the present invention is achieved by the following technical means.

[0006] Provide a supercritical steam injection exploitation process for medium-deep heavy oil, including a supercritical gas injection boiler, the supercritical gas injection boiler is connected with a water treatment device, a supercritical steam injection pipeline is connected to the supercritical gas injection boiler, the supercritical steam injection pipeline is connected to a supercritical steam injection wellhead, a downhole structure is arranged below the supercritical steam injection wellhead, the downhole structure includes a cement sheath, a casing is arranged inside the cement sheath, two groups of heat-insulating oil pipes are arranged inside the casing, a supercritical high-temperature and high-pressure heat-insulating pipe is arranged between the two groups of heat-insulating oil pipes, and the top of the supercritical high-temperature and high-pressure heat-insulating pipe is connected to the supercritical steam injection wellhead;

[0007] The supercritical steam injection boiler includes a boiler body, which can be divided into a radiation section, a convection section, a superheat section, and a transition section inside. There are 20 rows of 160 finned tubes arranged in the convection section of the boiler body to increase the heating area of steam in the convection section and raise the steam temperature to 440 - 600 °C with a steam pressure of 27 - 40 MPa.

[0008] The supercritical steam injection wellhead consists of a tubing head cross, a valve stem, a valve plate, a valve seat, and a metal seal. The metal seal is made of alloy steel forgings.

[0009] The supercritical high-temperature and high-pressure heat-insulating pipe adopts an external pipe connection structure form. The supercritical high-temperature and high-pressure heat-insulating pipe includes a coupling. An external pipe is hermetically connected inside the coupling. A heat-insulating layer is arranged inside the external pipe, and an internal pipe is arranged inside the heat-insulating layer. A liner pipe is installed between the coupling and the external pipe, a bushing is arranged between the liner pipe and the coupling, and a sealing ring is installed at the top end of the bushing.

[0010] Specifically, the supercritical steam injection pipeline is made of high-strength alloy material and connected by flanges, and the connection part uses flexible graphite seals.

[0011] Specifically, the parallel slide gate valve of the supercritical steam injection wellhead adopts an exposed stem structure with a small operating torque. The sealing surfaces of the valve plate and the valve seat are both sprayed with high-temperature resistant hard alloy. A metal seal is arranged between the valve plate and the valve seat. The seals between the valve seat and the valve body, and between the valve cover and the valve stem are made of high-purity flexible graphite packing meeting the PR2 performance level requirements.

[0012] Preferably, the heat-insulating layer between the external pipe and the internal pipe is in a vacuum state.

[0013] Specifically, the supercritical high-temperature and high-pressure heat-insulating pipe is equipped with a telescopic pipe and a high-temperature and high-pressure thermal sensitive divider.

[0014] Furthermore, a packer is installed between the heat-insulating oil pipe and the casing to prevent steam from returning to the ground along the gap between the heat-insulating oil pipe and the casing, resulting in heat loss.

[0015] The thermal oil recovery of the present invention is the main process technology measure for the development of heavy oil reservoirs. The supercritical heavy oil recovery process proposed by the present invention can effectively solve the existing problems in heavy oil recovery and greatly improve the recovery rate. Specifically, it uses a boiler to heat and pressurize steam to make it supercritical steam, and then injects it into the well through a supercritical steam injection wellhead and a supercritical high-temperature and high-pressure heat-insulating pipe. At the same time, the supercritical steam injection wellhead and the supercritical high-temperature and high-pressure heat-insulating pipe are improved to adapt to supercritical steam. It uses the heat of the steam to exchange heat with the oil layer, ultimately reducing the viscosity of heavy oil to improve the recovery rate. This process can not only greatly improve the heavy oil recovery rate, but also has many advantages such as rapid production increase, simple process, low cost, and small production risk. Description of the Drawings

[0016] The present invention will be further described with reference to the accompanying drawings, but the content in the drawings shall not constitute any limitation to the present invention.

[0017] Figure 1 It is a schematic structural diagram of a supercritical steam injection production system for medium-deep heavy oil of the present invention.

[0018] Figure 2 It is a schematic structural diagram of a supercritical gas injection boiler in a supercritical steam injection production system for medium-deep heavy oil of the present invention.

[0019] Figure 3 It is a system block diagram of a high-temperature and high-pressure heat-insulating oil pipe in a supercritical steam injection production system for medium-deep heavy oil of the present invention.

[0020] Figure 4 It is a front view of a supercritical steam injection wellhead in a supercritical steam injection production system for medium-deep heavy oil of the present invention.

[0021] Figure 5 It is a supercritical steam injection production system for medium-deep heavy oil of the present invention Figure 4 An enlarged view of the flexible graphite seal at position A.

[0022] From Figures 1 to 5 Among them, it includes:

[0023] 1. Water treatment device;

[0024] 2. Supercritical gas injection boiler;

[0025] 3. Supercritical steam injection pipeline;

[0026] 4. Supercritical steam injection wellhead;

[0027] 5. Cementing;

[0028] 6. Casing;

[0029] 7. Heat-insulating oil pipe;

[0030] 8. Supercritical high-temperature and high-pressure heat-insulating pipe;

[0031] 9. Tubing head cross;

[0032] 10. Valve seat;

[0033] 11. Valve cover;

[0034] 12. Valve stem;

[0035] 13. Metal seal;

[0036] 14. Valve plate;

[0037] 15. Convection section;

[0038] 16. Radiation section;

[0039] 17. Superheat section;

[0040] 18. Coupling;

[0041] 19. Outer pipe;

[0042] 20. Heat insulation layer;

[0043] 21. Inner pipe;

[0044] 22. Bushing;

[0045] 23. Liner;

[0046] 24. Sealing ring;

[0047] 25. High-purity flexible graphite packing;

[0048] 26. Packer

[0049] 27. Boiler body. Detailed implementation mode

[0050] The present invention will be further described in conjunction with the following embodiments.

[0051] Embodiment 1:

[0052] As Figures 1-5 shown, a supercritical steam injection mining process for medium-deep heavy oil includes a supercritical gas injection boiler 2, the supercritical gas injection boiler 2 is connected to a water treatment device 1, a supercritical steam injection pipeline 3 is connected to the supercritical gas injection boiler 2, the supercritical steam injection pipeline 3 is made of high-strength alloy material and connected by a flange, the connection part is sealed with flexible graphite, the supercritical steam injection pipeline 3 is connected to a supercritical steam injection wellhead 4, and a downhole structure is arranged below the supercritical steam injection wellhead 4. The downhole structure includes a cement casing 5, a casing 6 is arranged inside the cement casing 5, the material of the casing 6 is at least selected as TP130TT material according to parameters, two groups of heat insulation oil pipes 7 are arranged inside the casing 6, a supercritical high-temperature and high-pressure heat insulation pipe 8 is arranged between the two groups of heat insulation oil pipes 7, a telescopic pipe and a high-temperature and high-pressure thermal sensitive separator are installed in the supercritical high-temperature and high-pressure heat insulation pipe 8, and the top of the supercritical high-temperature and high-pressure heat insulation pipe 8 is connected to the supercritical steam injection wellhead 4.

[0053] The supercritical gas injection boiler 2 includes a boiler body 27. The inside of the boiler body 27 can be divided into a radiation section 16, a convection section 15, and a superheat section 17. 20 rows of 160 finned tubes are arranged in the convection section 15 of the boiler body 27 to increase the heat absorption area of the steam in the convection section 15 and raise the steam temperature to 440 - 600 °C and the steam pressure to 27 - 40 MPa.

[0054] Supercritical steam refers to a state of water when the temperature exceeds 374.15 °C and the pressure exceeds 22.14 MPa. Based on this standard, the existing supercritical gas injection boiler 2 heats the steam to about 380 °C, and the highest does not exceed 400 °C. After the heated steam is injected into the well, as the injection depth increases, heat will be dissipated, so that the temperature of the steam reaching the well may be lower than the critical point and cannot achieve the purpose of supercritical oil production. To solve this problem, the present invention proposes to increase the steam temperature to 450 °C - 600 °C, and increase the steam heat by increasing the steam temperature to ensure that the steam temperature reaching the well can meet the use requirements.

[0055] Therefore, the structure of the boiler body 27 is transformed as follows: 6 rows and 48 finned tubes are added to the convection section 15 of the existing boiler body 27 as the new convection section 15 of the boiler body 27. The transformed convection section 15 of the boiler body 27 is composed of 20 rows and 160 finned tubes. The heating area of the convection section 15 is increased from 264 m 2 to 374 m 2 , an increase of 41.7%, so that the original steam temperature of 374.15 °C and pressure exceeding 22.14 MPa are increased to a steam temperature of 440 - 600 °C and a steam pressure of 27 - 40 MPa.

[0056] The supercritical steam injection wellhead 4 plays a connecting role in supercritical heavy oil production. The supercritical steam injection wellhead 4 includes a tubing head cross 9, a valve stem 12, a valve plate 14, a valve seat 10, and a metal seal 13. The metal seal 13 is made of alloy steel forgings.

[0057] The flat gate valve of the supercritical steam injection wellhead 4 adopts an exposed stem structure with a small operating torque. The sealing surfaces of the gate plate and the valve seat 10 are both sprayed with high-temperature resistant hard alloy. A metal seal 13 is arranged between the gate plate and the valve seat 10. The seals between the valve seat 10 and the valve body, and between the valve cover 11 and the valve stem 12 are selected as high-purity flexible graphite packing 25 with the performance level requirement of PR2 to improve the sealing stability and service life of long-term steam injection.

[0058] The supercritical high-temperature and high-pressure heat-insulating pipe 8 adopts an external pipe 19 connection structure form. The supercritical high-temperature and high-pressure heat-insulating pipe 8 includes a coupling 18. Inside the coupling 18, an external pipe 19 is hermetically connected. An insulating layer 20 is arranged inside the external pipe 19, and an inner pipe 21 is arranged inside the insulating layer 20. A liner pipe 23 is installed between the coupling 18 and the external pipe 19 for connection. A bushing 22 is arranged between the liner pipe 23 and the coupling 18. A sealing ring 24 is installed at the top end of the bushing 22. The high-temperature and high-pressure heat-insulating oil pipe 7 adopts a double-wall oil pipe combined with the inner pipe 21 and the external pipe 19. Through the insulating layer 20 arranged between the inner pipe 21 and the external pipe 19, the insulating layer 20 between the external pipe 19 and the inner pipe 21 is in a vacuum state, reducing the heat consumption during the steam transmission process. The bushing 22 and the sealing ring 24 arranged between the external pipe 19 and the coupling 18 cooperate to tightly connect the external pipe 19 and the coupling 18, while increasing the connection sealing performance, adapting to the transmission of supercritical steam, and improving the heavy oil recovery efficiency.

[0059] A packer 26 is installed between the heat-insulating oil pipe 7 and the casing 6 to prevent steam from returning to the ground along the gap between the heat-insulating oil pipe 7 and the casing 6, resulting in heat loss. To prevent steam from returning to the ground along the gap between the heat-insulating oil pipe 7 and the casing 6, a packer 26 needs to be added between the heat-insulating oil pipe 7 and the casing 6 to ensure that the supercritical steam injected into the well can fully exchange heat with the oil layer.

[0060] This process specifically includes: remanufacturing a new supercritical injection boiler 2, raising the steam temperature to 450°C - 600°C, and supporting corresponding supercritical steam injection pipelines 3, supercritical steam injection wellheads 4, supercritical high-temperature and high-pressure heat-insulating pipes 8, packers 26, and drilling and completion technologies. The specific steam injection process flow is to use the supercritical injection boiler 2 to heat up and pressurize the steam to make it supercritical steam, and then inject it into the well through the supercritical steam injection pipeline 3, supercritical steam injection wellhead 4, and supercritical high-temperature and high-pressure heat-insulating pipe 8. A packer 26 is added to prevent steam from flowing back and causing heat loss, and a supercritical steam range with a certain radius is formed in the oil layer. Supercritical steam has high solubility and can widely dissolve various organic substances. Under certain conditions, it can dissolve plastics and nitrile rubber and dissolve heavy oil in a large proportion. After cooling and depressurizing, it forms an oil-in-water emulsion, enhancing the fluidity of heavy oil. Supercritical steam has high diffusivity. Its density is much larger than that of ordinary gases, its viscosity is smaller than that of liquids, and its diffusion speed is faster than that of liquids. Therefore, it has high diffusivity and strong penetration ability, effectively reducing the interfacial tension and improving the fluidity, which is beneficial to heat diffusion and expanding the heating radius. Supercritical steam has high miscibility and can be miscible with various gases such as nitrogen, hydrogen, carbon dioxide, and methane in any proportion to produce a single phase, having a good viscosity reduction and drainage assistance effect.

[0061] In the production process, thermal oil recovery is the main technological measure for the development of heavy oil reservoirs. The supercritical heavy oil recovery process proposed by the present invention can effectively solve the existing problems in heavy oil recovery and greatly improve the recovery rate. Specifically, the supercritical injection boiler 2 is used to heat up and pressurize the steam to make it supercritical steam, and then it is injected into the well through the supercritical injection wellhead 4 and the supercritical high-temperature and high-pressure heat-insulating pipe 8. At the same time, the supercritical injection wellhead 4 and the supercritical high-temperature and high-pressure heat-insulating pipe 8 are improved to adapt to the supercritical steam. A process that uses the heat of the steam to exchange heat with the oil layer to ultimately reduce the viscosity of the heavy oil and improve the recovery rate. This process can not only greatly improve the heavy oil recovery rate, but also has many advantages such as rapid production increase, simple process, low cost, and small mining risk.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A supercritical steam injection production process for medium-deep viscous oil, characterized by: It comprises a supercritical gas injection boiler, the supercritical gas injection boiler is connected to a water treatment device, the supercritical gas injection boiler is connected to a supercritical steam injection pipeline, the supercritical steam injection pipeline is connected to a supercritical steam injection wellhead, a downhole structure is arranged below the supercritical steam injection wellhead, the downhole structure comprises cement cementing, a casing is arranged inside the cement cementing, two groups of heat-insulating oil pipes are arranged inside the casing, a supercritical high-temperature and high-pressure heat-insulating pipe is arranged between the two groups of the heat-insulating oil pipes, and the top of the supercritical high-temperature and high-pressure heat-insulating pipe is connected to the supercritical steam injection wellhead; The supercritical gas injection boiler comprises a boiler body, the interior of which can be divided into a radiation section, a convection section, a superheating section, and a transition section. The convection section of the boiler body is provided with 20 rows of 160 fin tubes to increase the heating area of ​​the steam in the convection section, thereby raising the steam temperature to 440-600°C and the steam pressure to 27-40MPa. The supercritical steam injection wellhead comprises a tubing head spool, a valve stem, a valve plate, a valve seat, and a metal seal, wherein the metal seal is made of alloy steel forgings; The supercritical high-temperature and high-pressure insulated pipe adopts an outer pipe connection structure, and the supercritical high-temperature and high-pressure insulated pipe includes a coupling, the inner part of the coupling is sealed and connected with the outer pipe, the outer pipe is provided with an insulation layer, the insulation layer is provided with an inner pipe, a liner pipe is installed between the coupling and the outer pipe, a sleeve is provided between the liner pipe and the coupling, and a sealing ring is installed at the top end of the sleeve.

2. A supercritical steam injection production process for medium-deep heavy oil according to claim 1, characterized in that: The supercritical steam injection pipeline is made of high-strength alloy material and connected by flanges, and the connecting part is sealed with flexible graphite.

3. A supercritical steam injection production process for medium-deep heavy oil according to claim 2, characterized in that: The flat gate valve of the supercritical steam injection wellhead adopts a rising stem structure with a small operating torque. The sealing surfaces of the gate plate and the valve seat are sprayed with high-temperature resistant hard alloy. The metal seal is arranged between the gate plate and the valve seat. The seals between the valve seat and the valve body and between the valve cover and the valve stem are made of high-purity flexible graphite fillers that meet the PR2 performance level requirements.

4. A supercritical steam injection production process for medium-deep heavy oil according to claim 3, characterized in that: The heat insulation layer between the outer tube and the inner tube is in a vacuum state.

5. The supercritical steam injection recovery process for medium-deep heavy oil according to claim 4, characterized in that: The supercritical high-temperature and high-pressure insulation pipe is equipped with a telescopic pipe and a high-temperature and high-pressure thermal divider.

6. The supercritical steam injection recovery process for medium-deep heavy oil according to claim 5, characterized in that: A packer is installed between the heat-insulating oil pipe and the casing to prevent steam from returning to the ground along the gap between the heat-insulating oil pipe and the casing to cause heat loss.

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