阅读说明：本技术 一种富油煤原位热解的氮气电加热方法及系统 (Nitrogen electric heating method and system for in-situ pyrolysis of oil-rich coal ) 是由 肖国春 梁得亮 焦在滨 寇鹏 邱爱慈 于 2021-09-14 设计创作，主要内容包括：本发明公开了一种富油煤原位热解的氮气电加热方法及系统,第二输气管道一端连接高温高压储氮罐,另一端伸入注热井内,依次穿过发热电缆加热结构和电磁感应加热结构,电磁感应加热结构连接变频电源装置及冷却系统,发热电缆加热结构和变频电源装置及冷却系统分别与电源及控制系统连接；高温高压氮气经第二输气管道进入注热井内,使用加热结构对第二输气管道加热；注热井通过裂隙与开采井连通,高温高压氮气进入裂隙；富油煤层受热列解产生的混合气体进入开采井；经油气采集管道传输至油气综合分离装置获得富油煤层的列解产物。本发明提高加热系统的效率、增强了地下加热装置的环境适应性和富油煤层加热温度的可控性。(The invention discloses a nitrogen electric heating method and a nitrogen electric heating system for in-situ pyrolysis of oil-rich coal, wherein one end of a second gas transmission pipeline is connected with a high-temperature high-pressure nitrogen storage tank, the other end of the second gas transmission pipeline extends into a heat injection well and sequentially penetrates through a heating cable heating structure and an electromagnetic induction heating structure, the electromagnetic induction heating structure is connected with a variable-frequency power supply device and a cooling system, and the heating cable heating structure, the variable-frequency power supply device and the cooling system are respectively connected with a power supply and a control system; high-temperature high-pressure nitrogen enters the heat injection well through a second gas transmission pipeline, and the second gas transmission pipeline is heated by using a heating structure; the heat injection well is communicated with the production well through the crack, and high-temperature and high-pressure nitrogen enters the crack; mixed gas generated by heating and splitting the rich oil coal layer enters a production well; and (4) transmitting the oil-gas mixture to an oil-gas comprehensive separation device through an oil-gas acquisition pipeline to obtain a rank product of the oil-rich coal seam. The invention improves the efficiency of the heating system, and enhances the environmental adaptability of the underground heating device and the controllability of the heating temperature of the rich oil coal bed.)

1. A nitrogen electric heating system for in-situ pyrolysis of rich coal is characterized by comprising a high-temperature high-pressure nitrogen storage tank (10), wherein the output end of the high-temperature high-pressure nitrogen storage tank (10) is connected with one end of a second gas transmission pipeline (16), the other end of the second gas transmission pipeline (16) extends into a heat injection well (21), a first heating cable heating structure (23) arranged at the upper layer (17) of non-rich coal is penetrated, a second heating cable heating structure (24) and an electromagnetic induction heating structure (27) arranged at a rich coal layer (18) are penetrated in sequence, the electromagnetic induction heating structure (27) is connected with a corresponding variable frequency power supply device and a corresponding cooling system (26), the first heating cable heating structure (23), the second heating cable heating structure (24) and the variable frequency power supply device and cooling system (26) are respectively connected with the power supply and control system (13) through high temperature resistant cables (14);

high-temperature high-pressure nitrogen (15) in the high-temperature high-pressure nitrogen storage tank (10) enters the heat injection well (21) through a hot fluid injection port (25) arranged on the second gas transmission pipeline (16), and the second gas transmission pipeline (16) is heated through the first heating cable heating structure (23), the second heating cable heating structure (24), the variable frequency power supply device and cooling system (26) and the electromagnetic induction heating structure (27);

the heat injection well (21) is communicated with the production well (28) through a crack (19), and high-temperature and high-pressure nitrogen (15) enters the crack (19) in the rich oil coal seam (18); mixed gas generated by the heated row of the oil-rich coal seam (18) enters a production well (28); and the oil gas is transmitted to an oil gas comprehensive separation device (31) through an oil gas collecting pipeline (30) arranged in the production well (28) to obtain a rank product of the oil-rich coal seam (18).

2. The nitrogen electric heating system for in-situ pyrolysis of oil-rich coal according to claim 1, wherein the first heating cable heating structure (23) comprises a first heating cable (232), the first heating cable (232) is arranged outside the second gas transmission pipeline (16), and an insulation structure (231) is arranged outside the first heating cable (232).

3. The nitrogen electric heating system for in-situ pyrolysis of oil-rich coal according to claim 1, wherein the second heating cable heating structure (24) comprises a second heating cable (241), and the second heating cable (241) is arranged outside the second gas transmission pipeline (16).

4. The nitrogen electric heating system for in-situ pyrolysis of oil-rich coal according to claim 1, wherein the electromagnetic induction heating structure (27) comprises an electromagnetic induction coil (271), the electromagnetic induction coil (271) is arranged outside the second gas transmission pipeline (16), and a spiral flow guide plate (272) is arranged in the second gas transmission pipeline (16) corresponding to the electromagnetic induction coil (271).

5. The nitrogen electric heating system for in-situ pyrolysis of oil-rich coal according to claim 1, wherein the first heating cable heating structure (23) and the second heating cable heating structure (24) are connected with the power supply and control system (13) through high temperature resistant cables (14).

6. The nitrogen electric heating system for in-situ pyrolysis of rich coal according to claim 1, wherein a plurality of variable frequency power supply devices and cooling systems (26) are connected with the nitrogen storage tank (5) through a cold nitrogen gas pipeline (12) through a third supercharging device (11), and pressurized cold nitrogen gas enters the heat injection well (21) through the cold nitrogen gas pipeline (12) to cool the variable frequency power supply devices and the variable frequency power supply devices of the cooling systems (26).

7. The nitrogen electric heating system for in-situ pyrolysis of oil-rich coal according to claim 1, wherein the variable frequency power supply device and the cooling system (26) comprise a closed heat insulation structure (231), a main circuit, a driving circuit and a control circuit are arranged inside the heat insulation structure (231), and a power supply input (261), a high-frequency power supply output (262) and a control cable (263) are respectively arranged on the heat insulation structure (231); the pressurized cold nitrogen gas transmission pipeline (12) enters the heat insulation structure (231) from the side of the main circuit of the variable frequency power supply device and the cooling system (26), exchanges heat with the main circuit, the driving circuit and the control circuit and then is output from a hot nitrogen gas output port (264) on the other side of the heat insulation structure (231).

8. The nitrogen electric heating system for in-situ pyrolysis of rich coal according to claim 1, wherein the high-temperature and high-pressure nitrogen storage tank (10) is connected with the nitrogen making machine (1) after passing through the second supercharging device (9), the high-temperature nitrogen storage tank (8), the nitrogen heating device (7), the nitrogen storage tank (5), the check valve (4), the first supercharging device (3) and the valve (2) in sequence.

9. The nitrogen electric heating system for in-situ pyrolysis of rich coal according to claim 8, wherein the nitrogen generator (1) comprises a plurality of nitrogen generators (1), the plurality of nitrogen generators (1) are respectively connected with the nitrogen storage tank (5) through gas transmission pipelines, a plurality of first gas transmission pipelines (6) are arranged between the nitrogen storage tank (5) and the high-temperature nitrogen storage tank (8) in parallel, and a plurality of nitrogen heating devices (7) are arranged on each first gas transmission pipeline (6) in series.

10. The method for electrically heating nitrogen by using the nitrogen electric heating system for in-situ pyrolysis of oil-rich coal as claimed in claim 1, which is characterized by comprising the following steps:

drilling at least one heat injection well (21) and a production well (28) in the oil-rich coal seam (18);

fracturing a gap in the oil-rich coal seam (18) by adopting a fracturing mode to obtain a fracture (19), wherein the heat injection well (21) is communicated with the exploitation well (28) through the fracture (19);

high-temperature high-pressure nitrogen (15) in the high-temperature high-pressure nitrogen storage tank (10) enters a heat injection well (21) through a hot fluid injection port (25) on a second gas transmission pipeline (16), then enters an oil-rich coal seam (18) through a non-oil-rich coal upper layer (17), and the flow rate of the high-temperature high-pressure nitrogen (15) entering the heat injection well (21) is controlled through the hot fluid injection port (25), so that the flow rate of the high-temperature high-pressure nitrogen (15) entering cracks (19) in the oil-rich coal seam (18) is controlled;

according to the temperature of the oil-rich coal seam (18), a power supply and control system (13) is used for controlling the output power of a first heating cable heating structure (23), the output power of a second heating cable heating structure (24), a variable frequency power supply device and cooling system (26) and an electromagnetic induction heating structure (27) and adjusting a hot fluid jet orifice (25) so as to control the pyrolysis temperature of the oil-rich coal seam (18), and a second gas transmission pipeline (16) is heated through the first heating cable heating structure (23), the second heating cable heating structure (24), the variable frequency power supply device and cooling system (26) and the electromagnetic induction heating structure (27), so that the heat preservation and temperature rise treatment of high-temperature and high-pressure nitrogen (15) are realized;

mixed gas generated after the oil-rich coal seam (18) is heated and arranged enters a production well (28) through the crack (19); and then the oil gas is transmitted into an oil gas comprehensive separation device (31) through an oil gas collecting pipeline (30) to obtain a rank product of the oil-rich coal seam (18), and the nitrogen is recycled.

Technical Field

The invention belongs to the technical field of oil-rich coal oil gas resource development, and particularly relates to a nitrogen electric heating method and a nitrogen electric heating system for in-situ pyrolysis of oil-rich coal.

Background

Coal with Tar yield (Tar, d) of 7-12% is called oil-rich coal according to the manual of mineral resources industry requirements (2014 revision); coals with Tar yield (Tar, d) less than 7% are called oil-bearing coals; coals with Tar yields (Tar, d) greater than 12% are called high oil coals. Coal with a Tar yield (Tar, d) of more than 7% is broadly referred to as oil-rich coal. The oil-rich coal is not only a grading of coal tar yield, but also a special coal resource at present, and the oil-rich coal accounts for up to 45% of the reserve of the coal resource in China. Fully utilizes rich oil coal resources in China, increases oil gas supply ways, and has great significance to energy strategic safety in China.

At present, ground pyrolysis technology is mainly adopted for the pyrolysis conversion of the oil-rich coal. The utilization efficiency of ground pyrolysis is poor, and a large amount of semicoke is accumulated; meanwhile, the environment is adversely affected along with the discharge of waste water and waste gas in the separation process of pyrolysis products.

Different from the ground pyrolysis method of the oil-rich coal, the in-situ pyrolysis of the oil-rich coal refers to a technology that the oil-rich coal is directly pyrolyzed under the formation pressure by transferring heat through a heat carrier without being exploited, and the obtained oil gas product is led out of the ground through a collecting well (exploitation well) to be separated and deeply processed. The method is an environment-friendly sustainable mining conversion technology, has the advantages of small occupied area, low mining cost, good product quality, environmental protection and the like compared with the existing ground pyrolysis technology, and has important practical significance for realizing the aim of 'double carbon' in the early stage.

At the present stage, the oil-rich coal in-situ pyrolysis utilization technology is mostly in the initial conceptual and implementation scheme demonstration stage, and sufficient experimental research is lacked. In-situ pyrolysis of oil-rich coal first requires heating an underground large-scale oil-rich coal seam (mine) to pyrolysis temperature. The existing research shows that the pyrolysis temperature probably needs to reach 450-600 ℃. The heat transfer capability of the rich oil coal layer is poor, and the rich oil coal layer is difficult to heat in a conduction mode. The shale oil in-situ heating method is also not suitable.

The existing heating scheme is a comprehensive heating method which adopts controllable shock waves to form cracks (enough and wide cracks) on the rich oil coal seam, and performs forced convection and conduction on the rich oil coal seam by means of long-time scale slow heating and short-time scale intensive heating (underground distributed electric heating) of a high-temperature high-pressure heat carrier (hot fluid) so as to enable the rich oil coal seam to reach the sufficient pyrolysis temperature. The heat carrier is selected from many kinds, such as high-temperature high-pressure steam and carbon dioxide (CO)₂) And nitrogen (N)₂) And the like. In connection with the subsequent products of the pyrolysis of oil-rich coal, one of the heat carriers that is currently considered to be ideal is high-temperature, high-pressure nitrogen. Considering the loss of the rich-oil coal bed in the heat transfer process, the highest temperature of the underground heat carrier can reach 700-800 ℃ or higher to meet the requirement of in-situ pyrolysis of the rich-oil coal. How to reliably and efficiently heat, transmit and control an underground heat carrier so as to uniformly heat and effectively arrange an oil-rich coal seam in situ is a very challenging subject at present.

Aiming at the problems that the heating schemes and methods of the rich coal seam in the existing rich coal in-situ pyrolysis utilization technology are few, and the practical heating environment of the rich coal seam is not considered in some proposed methods, the practicability is lacked.

Disclosure of Invention

The technical problem to be solved by the present invention is to provide a nitrogen electrical heating method and system for in-situ pyrolysis of rich coal, aiming at the defects in the prior art, so as to improve the efficiency of a heating system, enhance the environmental adaptability of an underground heating device and the controllability of the heating temperature of a rich coal seam, and solve the problems of large-scale electrical heating of high temperature, the heating efficiency of high-pressure nitrogen, the environmental adaptability of an underground heating device, the controllability of the heating temperature of a rich coal seam, and the like during in-situ pyrolysis of rich coal.

The invention adopts the following technical scheme:

a nitrogen electric heating system for in-situ pyrolysis of oil-rich coal comprises a high-temperature high-pressure nitrogen storage tank, wherein the output end of the high-temperature high-pressure nitrogen storage tank is connected with one end of a second gas transmission pipeline, the other end of the second gas transmission pipeline extends into a heat injection well, the high-temperature high-pressure nitrogen storage tank firstly penetrates through a first heating cable heating structure arranged at the upper layer of non-oil-rich coal and then sequentially penetrates through a second heating cable heating structure and an electromagnetic induction heating structure arranged at an oil-rich coal layer, the electromagnetic induction heating structure is connected with a corresponding variable-frequency power supply device and a corresponding cooling system, and the first heating cable heating structure, the second heating cable heating structure, the variable-frequency power supply device and the cooling system are respectively connected with a power supply and a control system through high-temperature-resistant cables;

high-temperature high-pressure nitrogen in the high-temperature high-pressure nitrogen storage tank enters the heat injection well through a hot fluid injection port arranged on the second gas transmission pipeline, and the second gas transmission pipeline is heated through the first heating cable heating structure, the second heating cable heating structure, the variable-frequency power supply device, the cooling system and the electromagnetic induction heating structure;

the heat injection well is communicated with the production well through a crack, and high-temperature and high-pressure nitrogen enters the crack in the oil-rich coal bed; mixed gas generated by heating and splitting the rich oil coal layer enters a production well; and (4) transmitting the oil gas to an oil gas comprehensive separation device through an oil gas collecting pipeline arranged in the production well to obtain a rank product of the oil-rich coal bed.

Specifically, first heating cable heating structure includes first heating cable, and first heating cable sets up in the outside of second gas transmission pipeline, and the outside of first heating cable is provided with insulation system.

Specifically, the second heating cable heating structure comprises a second heating cable, and the second heating cable is arranged outside the second gas transmission pipeline.

Specifically, the electromagnetic induction heating structure includes electromagnetic induction coil, and electromagnetic induction coil sets up in the outside of second gas transmission pipeline, and the department that corresponds electromagnetic induction coil in the second gas transmission pipeline is provided with spiral guide plate.

Specifically, the first heating cable heating structure and the second heating cable heating structure are connected with a power supply and a control system through high-temperature-resistant cables.

Specifically, the plurality of variable frequency power supply devices and the cooling system are connected with the nitrogen storage tank through a cold nitrogen gas pipeline through a third pressurizing device, and pressurized cold nitrogen gas enters the heat injection well through the gas pipeline to cool the variable frequency power supply devices and the variable frequency power supply devices of the cooling system.

Specifically, the variable frequency power supply device and the cooling system comprise a closed heat insulation structure, a main circuit, a driving circuit and a control circuit are arranged in the heat insulation structure, and a power supply input, a high-frequency power supply output and a control cable are respectively arranged on the heat insulation structure; the pressurized cold nitrogen gas transmission pipeline enters the heat insulation structure from the side of the variable frequency power supply device and the main circuit of the cooling system, exchanges heat with the main circuit, the driving circuit and the control circuit and then is output from a hot nitrogen gas output port on the other side of the heat insulation structure.

Specifically, the high-temperature high-pressure nitrogen storage tank is connected with the nitrogen making machine after sequentially passing through the second supercharging device, the high-temperature nitrogen storage tank, the nitrogen heating device, the nitrogen storage tank, the one-way valve, the first supercharging device and the valve.

Further, the system nitrogen machine includes a plurality ofly, and a plurality of system nitrogen machines are connected with the nitrogen storage tank through gas transmission pipeline respectively, and it is provided with many first gas transmission pipelines to connect in parallel between nitrogen storage tank and the high temperature nitrogen storage tank, and it is provided with a plurality of nitrogen gas heating device to establish ties on every first gas transmission pipeline.

The other technical scheme of the invention is that the method for electrically heating the nitrogen by the nitrogen electric heating system for the in-situ pyrolysis of the oil-rich coal comprises the following steps:

drilling at least one heat injection well and a production well in the oil-rich coal seam;

cracking the crack in the rich oil coal seam by adopting a cracking mode to obtain a crack, and communicating the heat injection well with the exploitation well through the crack;

high-temperature high-pressure nitrogen in the high-temperature high-pressure nitrogen storage tank enters the heat injection well through a hot fluid injection port on the second gas transmission pipeline, then passes through the upper layer of the non-oil-rich coal to enter the oil-rich coal bed, and the flow of the high-temperature high-pressure nitrogen entering the heat injection well is controlled through the hot fluid injection port, so that the flow of the high-temperature high-pressure nitrogen entering cracks in the oil-rich coal bed is controlled;

according to the temperature of the oil-rich coal bed, the first heating cable heating structure, the second heating cable heating structure, the output power of the variable-frequency power supply device, the cooling system and the electromagnetic induction heating structure and the hot fluid injection port are adjusted to control the pyrolysis temperature of the oil-rich coal bed, and the second gas transmission pipeline is heated through the first heating cable heating structure, the second heating cable heating structure, the variable-frequency power supply device, the cooling system and the electromagnetic induction heating structure to realize heat preservation and temperature rise treatment of high-temperature and high-pressure nitrogen;

mixed gas generated after the rich oil coal seam is heated and arranged enters a production well through the cracks; and then the oil gas is transmitted into an oil gas comprehensive separation device through an oil gas acquisition pipeline to obtain a product of the oil-rich coal bed, and nitrogen is recycled.

Compared with the prior art, the invention has at least the following beneficial effects:

according to the nitrogen electric heating system for in-situ pyrolysis of the oil-rich coal, considering that the thickness of the upper layer of the non-oil-rich coal and the thickness of the oil-rich coal layer to be heated can reach dozens of m to hundreds of m, even thousands of m, the transmission distance of the corresponding second gas transmission pipeline in the heat injection well at the part can also reach dozens of m to hundreds of m, even thousands of m; the second gas transmission pipeline needs to transmit high-temperature and high-pressure nitrogen, so that the second gas transmission pipeline adopts a heat-resistant and pressure-resistant metal pipeline with a certain diameter and thickness; the heat transfer effect of the metal is very good, the metal also has certain resistivity, and the metal can generate heat when current flows in the metal; the transmission distance between the upper layer of the non-rich coal and the rich coal layer of the second gas transmission pipeline is utilized, the first heating cable heating structure is arranged on the upper layer of the non-rich coal, the second heating cable heating structure and the electromagnetic induction heating structure are arranged on the rich coal layer, the metal pipeline of the second gas transmission pipeline is indirectly heated through heating of the heating cable, and the metal pipeline of the second gas transmission pipeline is directly heated through the electromagnetic induction heating structure, so that high-temperature and high-pressure nitrogen is heated and kept warm, the heating efficiency is high, and the implementation in the underground limited space is easy; in order to improve the power of electromagnetic induction heating, a high-frequency power supply is needed, and a variable-frequency power supply device and a cooling system are arranged to obtain the high-frequency power supply; in order to adapt to the cooling requirements of underground high-temperature and high-pressure environment and the variable-frequency power supply device, a cooling system and a heat insulation structure of the variable-frequency power supply device are arranged.

Furthermore, considering that the thickness of the upper layer of the non-oil-rich coal can reach dozens of meters to hundreds of meters, the transmission distance of the corresponding second gas transmission pipeline in the part can also reach dozens of meters to hundreds of meters, a first heating cable heating structure is arranged outside the second gas transmission pipeline, heating can be carried out on the second gas transmission pipeline in the part by adopting a heating cable to heat the second gas transmission pipeline, and then high-temperature and high-pressure nitrogen is heated and insulated; the heating cable is directly adopted to heat the second gas transmission pipeline, so that the heating efficiency is high, and the heating device is easy to implement in the underground limited space; the purpose of arranging the heat preservation structure outside the first heating cable can reduce the heat dissipation of the non-heating area, namely the upper layer of the non-oil-rich coal, and improve the heating efficiency of the system.

Furthermore, considering that the thickness of the rich oil coal seam to be heated may reach tens of meters to hundreds of meters, even thousands of meters, the transmission distance of the corresponding second gas transmission pipeline in the part also reaches tens of meters to hundreds of meters, even thousands of meters, a second heating cable heating structure is arranged outside the second gas transmission pipeline, heating cables can be adopted to heat the second gas transmission pipeline in the part of the distance, and then the high-temperature and high-pressure nitrogen gas is heated and insulated; the heating cable is directly adopted to heat the second gas transmission pipeline, so that the heating efficiency is high, and the heating device is easy to implement in the underground limited space; the purpose that does not set up insulation construction in second heating cable's outside is that second heating cable can directly heat the rich oil coal seam, improves system heating efficiency.

Furthermore, considering that the thickness of the rich oil coal seam to be heated may reach tens of meters to hundreds of meters, even thousands of meters, the transmission distance of the corresponding second gas transmission pipeline in the part also reaches tens of meters to hundreds of meters, even thousands of meters, an electromagnetic induction heating structure is arranged outside the second gas transmission pipeline, an electromagnetic induction coil can be arranged at the distance, the electromagnetic induction heating principle is used for directly heating the second gas transmission pipeline, and then the high-temperature and high-pressure nitrogen is heated and insulated; the electromagnetic induction heating principle is adopted to directly heat the second gas transmission pipeline, the heating speed is high, the efficiency is high, the system temperature is flexibly controlled, and the response time is short; underground limited space is easy to implement; the purpose of not arranging a heat insulation structure outside the electromagnetic induction coil is to directly heat the rich oil coal bed by utilizing the heating of partial current of the electromagnetic induction coil, thereby improving the heating efficiency of the system; the spiral guide plate is arranged in the second gas transmission pipeline corresponding to the electromagnetic induction coil, so that the heat exchange effect between the high-temperature high-pressure nitrogen and the second gas transmission pipeline is enhanced, and the heating speed and the heating efficiency of the high-temperature high-pressure nitrogen are improved.

Furthermore, the purpose of adopting the high temperature resistant cable is to adapt to the underground high temperature environment, and the purpose of being connected with the power supply and the control system and setting up is that the heating power control to first heating cable heating structure and second heating cable heating structure can be passed through power supply and control system, and then to the control of second gas transmission pipeline, high temperature high pressure nitrogen gas heating temperature, finally realize the control to rich oil coal seam heating temperature.

Furthermore, the nitrogen storage tank and the third supercharging device are arranged to improve the pressure of cold nitrogen in the cold nitrogen gas transmission pipeline and the stability and reliability of cold nitrogen gas supply, and ensure the cooling effect of the variable frequency power supply device and the cooling system; the purpose that a plurality of variable frequency power supply devices and cooling systems are connected with a nitrogen storage tank through a third supercharging device through cold nitrogen and gas pipelines is to increase the heating power required by heating the rich oil coal seam and improve the redundancy design of the heating device.

Furthermore, the high-frequency electromagnetic induction heating has high efficiency and high power, and the variable-frequency power supply device and the cooling system are arranged to invert direct current of a power frequency power supply or new energy into a high-frequency alternating current power supply to be supplied to an electromagnetic induction coil to directly perform electromagnetic induction heating on the second gas transmission pipeline; in consideration of the underground high-temperature environment and the temperature limitation of a main circuit, a driving circuit and power electronic switching devices and electronic elements in a control circuit of the variable-frequency power supply device during working, the device needs to be cooled, and a cold nitrogen gas transmission pipeline and a closed heat preservation structure are arranged to cool, insulate heat and preserve heat of the main circuit, the control circuit and other components in the variable-frequency power supply device, so that the normal working of the variable-frequency power supply device is ensured.

Further, large-scale, high-efficiency electrical heating of nitrogen is currently a challenging technology. In order to improve the heating capacity of nitrogen and enlarge the heating scale of nitrogen, the nitrogen is gradually heated and pressurized in stages on the ground, a plurality of nitrogen heating devices, a first pressurizing device and a second pressurizing device are arranged and are connected with a high-temperature nitrogen storage tank, a nitrogen storage tank and a nitrogen making machine through a one-way valve and a valve, the requirement of in-situ mining of rich oil coal on large-scale high-temperature and high-pressure nitrogen is met, the difficulty and the manufacturing cost of realizing the ground nitrogen electric heating device can be reduced, and the reliability of the system is improved.

Further, large-scale, high-efficiency electrical heating of nitrogen is currently a challenging technology. In order to improve the heating capacity of nitrogen and enlarge the heating scale of nitrogen, the nitrogen is gradually heated and pressurized in stages on the ground, a plurality of nitrogen heating devices are arranged on each first gas transmission pipeline in series and in parallel, a plurality of heating and pressurizing systems in series and in parallel are adopted to gradually heat and gradually pressurize the nitrogen in stages, and then the nitrogen heating devices are connected with a high-temperature nitrogen storage tank of the nitrogen storage tank, so that the requirement of in-situ mining of rich oil coal on large-scale high-temperature and high-pressure nitrogen is met, the difficulty and the manufacturing cost of realizing the nitrogen heating devices can be reduced, and the reliability of the nitrogen heating system is improved.

The nitrogen electric heating method for in-situ pyrolysis of the oil-rich coal has poor heat conduction capability; considering that the thickness of the upper layer of the non-oil-rich coal and the thickness of the oil-rich coal layer to be heated can reach dozens of meters to thousands of meters, the drilling depths of a heat injection well and a production well which are drilled correspondingly and the distance between the heat injection well and the production well need to consider the depth and the horizontal distance of high-temperature and high-pressure nitrogen which are required by convective heat transfer and the capability of cracking gaps, and gradually advancing according to the exploitation progress, and carrying out sectional heating and sectional exploitation; for example, the staged mining is started from the lower part of the rich oil coal bed, in the heat injection well, according to the mining progress and the temperature of the rich oil coal bed measured by the rich oil coal bed temperature measuring device, on one hand, the opening and closing of a hot fluid injection port on the second gas transmission pipeline and the flow rate are controlled, on the other hand, the power of a power supply and control system, a variable frequency power supply device and a cooling system is used for adjusting a first heating cable heating structure, the power of the second heating cable heating structure and the power of an electromagnetic induction heating structure, the temperature of the second gas transmission pipeline is controlled, and further, the temperature of high-temperature high-pressure nitrogen is adjusted to realize the control of the heating temperature of the rich oil coal bed of a part needing in-situ pyrolysis (staged); the mined part of the rich oil coal seam can be sealed by grouting cracks, so that the heat dissipation of high-temperature and high-pressure nitrogen is reduced, and the utilization rate of the high-temperature and high-pressure nitrogen is improved; when necessary, the working states of the heat injection well and the production well can be exchanged, the heating device in the heat injection well is arranged in the production well, the original heat injection well is used as the production well, the original production well is used as the heat injection well for in-situ pyrolysis, and the oil yield is improved.

In conclusion, the invention improves the efficiency of the heating system, enhances the environmental adaptability of the underground heating device and the controllability of the heating temperature of the rich oil coal bed, and solves the problems of the heating efficiency of large-scale electric heating high temperature and high-pressure nitrogen gas, the environmental adaptability of the underground heating device, the controllability of the heating temperature of the rich oil coal bed and the like during the in-situ pyrolysis of the rich oil coal.

The technical solution of the present invention is further described in detail by the accompanying drawings and embodiments.

Drawings

FIG. 1 is a diagram of an integrated heating system for electrically heating nitrogen;

FIG. 2 is a view of a first heating cable heating configuration;

FIG. 3 is a view of a second heating cable heating structure;

FIG. 4 is a diagram of a variable frequency power supply apparatus and a cooling system;

FIG. 5 is a view showing the structure of an electromagnetic induction heating;

fig. 6 is a top view of an electromagnetic induction heating structure.

Wherein: 1. a nitrogen making machine; 2. a valve; 3. a first pressure boosting device; 4. a one-way valve; 5. a nitrogen storage tank; 6. a first gas transmission pipeline; 7. a nitrogen heating device; 8. a high temperature nitrogen storage tank; 9. a second supercharging device; 10. a high temperature and high pressure nitrogen storage tank; 11. a third supercharging device; 12. a cold nitrogen gas transmission pipeline; 13. a power supply and control system; 14. a high temperature resistant cable; 15. high temperature and high pressure nitrogen; 16. a second gas transmission pipeline; 17. the upper layer of the non-oil-rich coal; 171. a lower layer of non-oil-rich coal; 18. a rich coal seam; 19. cracking; 20. sealing the heat injection well; 21. injecting heat into the well; 22. a temperature measuring device for the rich oil coal bed; 23. a first heating cable heating structure; 231. a heat preservation structure; 232. a first power generation cable; 24. a second heating cable heating structure; 241. a second heating cable; 25. a thermal fluid injection port; 26. a variable frequency power supply device and a cooling system; 261. inputting a power supply; 262. outputting a high-frequency power supply; 263. a control cable; 264. a hot nitrogen gas outlet; 27. an electromagnetic induction heating structure; 271. an electromagnetic induction coil; 272. a spiral deflector; 28. a production well is produced; 29. sealing the production well; 30. an oil and gas collection pipeline; 31. oil-gas comprehensive separation device.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "one side", "one end", "one side", and the like indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of description and simplicity of description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed in a particular orientation, and be operated, and thus, are not to be construed as limiting the present invention. Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless otherwise specified.

In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

It will be understood that the terms "comprises" and/or "comprising," when used in this specification and the appended claims, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

It is also to be understood that the terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the specification of the present invention and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

It should be further understood that the term "and/or" as used in this specification and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

Various structural schematics according to the disclosed embodiments of the invention are shown in the drawings. The figures are not drawn to scale, wherein certain details are exaggerated and possibly omitted for clarity of presentation. The shapes of various regions, layers and their relative sizes and positional relationships shown in the drawings are merely exemplary, and deviations may occur in practice due to manufacturing tolerances or technical limitations, and a person skilled in the art may additionally design regions/layers having different shapes, sizes, relative positions, according to actual needs.

Referring to fig. 1, the nitrogen electric heating system for in-situ pyrolysis of oil-rich coal of the present invention includes a nitrogen generator 1, the nitrogen generator 1 is connected to an input end of a first pressure device 3 through a first gas transmission pipeline 6 provided with a valve 2, an output end of the first pressure device 3 is connected to a nitrogen storage tank 5 through a one-way valve 4, the nitrogen storage tank 5 is connected to a high temperature nitrogen storage tank 8 through a plurality of nitrogen heating devices 7 connected in series, and the high temperature nitrogen storage tank 8 is connected to a high temperature high pressure nitrogen storage tank 10 through a second pressure device 9; the output end of the high-temperature and high-pressure nitrogen storage tank 10 is connected with one end of a second gas transmission pipeline 16, the other end of the second gas transmission pipeline 16 enters a heat injection well 21 through a heat injection well seal 20 and then passes through a first heating cable heating structure 23 and then sequentially passes through a plurality of groups of second heating cable heating structures 24 and electromagnetic induction heating structures 27, a hot fluid injection port 25 is arranged on the second gas transmission pipeline 16 between the second heating cable heating structure 24 and the electromagnetic induction heating structures 27, the first heating cable heating structure 23 and the second heating cable heating structure 24 are respectively connected with a power supply and control system 13 and a corresponding variable-frequency power supply device and cooling system 26 through a high-temperature-resistant cable 14, the electromagnetic induction heating structures 27 are connected with the corresponding variable-frequency power supply device and cooling system 26, and the plurality of variable-frequency power supply devices and cooling systems 26 are connected with the nitrogen storage tank 5 through a cold nitrogen gas transmission pipeline 12 through a third supercharging device 11; an oil gas collecting pipeline 30 is arranged in the exploitation well 28 on one side of the heat injection well 21, one end of the oil gas collecting pipeline 30 is arranged in the exploitation well 28, an exploitation well seal 29 is arranged at the port of the exploitation well 28, the other end of the oil gas collecting pipeline 30 is connected with an oil gas comprehensive separation device 31, and the heat injection well 21 is communicated with the exploitation well 28 through a crack 19.

The upper section of the heat injection well 21 penetrates through the non-rich-oil coal upper layer 17, the lower section of the heat injection well penetrates through the rich-oil coal layer 18, the bottom of the heat injection well is located at the top of the non-rich-oil coal lower layer 171, the first heating cable heating structure 23 is arranged in the region of the non-rich-oil coal upper layer 17, the second heating cable heating structure 24 and the electromagnetic induction heating structure 27 are arranged in the region of the rich-oil coal layer 18, a plurality of cracks 19 are contained in the rich-oil coal layer 18, and a rich-oil coal layer temperature measuring device 22 is arranged in the rich-oil coal layer 18.

The high-temperature high-pressure nitrogen 15 in the high-temperature high-pressure nitrogen storage tank 10 enters the cracks 19 in the rich oil coal seam 18 through the hot fluid injection ports 25 to heat the rich oil coal seam 18; heating the rich oil coal seam 18 for separation, and allowing mixed gas generated after pyrolysis reaction to enter a production well 28; the production well 28 is sealed by a production well seal 29, and mixed gas generated after pyrolysis reaction enters an oil gas collection pipeline 30 and then is transmitted into an oil gas comprehensive separation device 31 through the oil gas collection pipeline 30; the oil-gas comprehensive separation device 31 is used for obtaining the rank products of the oil-rich coal seam 18 such as oil, nitrogen and the like, and the nitrogen can be recycled.

The connecting pipeline between the nitrogen making machine 1 and the nitrogen storage tank 5 at least comprises two connecting pipelines; connecting lines between the nitrogen storage tank 5 and the high-temperature nitrogen storage tank 8 at least comprise two lines, and each line is at least provided with two nitrogen heating devices 7.

Nitrogen generated by a plurality of nitrogen making machines 1 is controlled by a valve 2, enters a first supercharging device 3 through a first gas transmission pipeline 6, and is collected to a nitrogen storage tank 5 through a one-way valve 4, and a plurality of nitrogen storage tanks 5 can be adopted; nitrogen in the nitrogen storage tank 5 enters a plurality of nitrogen heating devices 7 to heat the nitrogen under the control of a first gas transmission pipeline 6 and a valve 2; the high-temperature nitrogen heated by the nitrogen heating device 7 is collected into a high-temperature nitrogen storage tank 8, and the high-temperature nitrogen passes through the first gas transmission pipeline 6 and is controlled by the valve 2 to enter the second pressurizing device 9 to pressurize the nitrogen for the second time; the pressurized high-temperature and high-pressure nitrogen enters a high-temperature and high-pressure nitrogen storage tank 10 through the check valve 4 and the valve 2;

preferably, in order to expand the heating power and heating speed of the nitrogen heating device and improve the reliability of the nitrogen heating device, a plurality of nitrogen heating devices 7 may be connected in series or in parallel; the high-temperature nitrogen storage tank 8 comprises a plurality of tanks; the high-temperature and high-pressure nitrogen storage tank 10 includes a plurality of tanks.

Nitrogen in the nitrogen storage tank 5 passes through the first gas transmission pipeline 6, the valve 2 controls the nitrogen to enter the third pressurizing device 11 to pressurize the nitrogen, and the pressurized cold nitrogen enters the heat injection well 21 through the gas transmission pipeline 12 to cool the variable frequency power supply device and the variable frequency power supply device of the cooling system 26.

The power supply and control system 13 supplies power to the downhole equipment (the first heating cable heating structure 23, the second heating cable heating structure 24, the hot fluid injection port 25, the variable frequency power supply device and cooling system 26, and the electromagnetic induction heating structure 27) of the heat injection well 21 through the high temperature resistant cable 14, and underground (downhole) environmental information (temperature, pressure, etc.) and the equipment running state are also transmitted to the power supply and control system 13 through the high temperature resistant cable 14 for controlling the whole heating system.

High-temperature high-pressure nitrogen 15 (hot fluid) output from the high-temperature high-pressure nitrogen storage tank 10 enters a heat injection well 21 through a second gas transmission pipeline 16 and a heat injection well seal 20, and then passes through a non-oil-rich coal upper layer 17 to enter an oil-rich coal layer 18; the high-temperature high-pressure nitrogen 15 can reach the lower layer 171 of the non-oil-rich coal and can also enter a horizontal heat injection well; the flow rate of the high-temperature and high-pressure nitrogen 15 entering the heat injection well 21 is controlled through the hot fluid injection port 25, namely the flow rate of the high-temperature and high-pressure nitrogen 15 entering the fractures 19 in the rich oil coal seam 18 is controlled.

The first heating cable heating structure 23, the second heating cable heating structure 24, the variable frequency power supply device and cooling system 26 and the electromagnetic induction heating structure 27 are arranged to heat the second gas transmission pipeline 16, so as to keep and heat the high-temperature and high-pressure nitrogen 15; the power supply and control system 13 controls the first heating cable heating structure 23, the second heating cable heating structure 24, the variable frequency power supply device and cooling system 26 and the output power of the electromagnetic induction heating structure 27 and adjusts the hot fluid injection port 25 according to the temperature of the rich coal seam 18 measured by the rich coal seam temperature measuring device(s) 22, so as to control the pyrolysis temperature of the rich coal seam 18, and thus the rich coal seam is pyrolyzed efficiently.

The number and the arrangement sequence of the first heating cable heating structure 23, the second heating cable heating structure 24, the hot fluid injection port 25, the variable frequency power supply device and cooling system 26 and the electromagnetic induction heating structure 27 in the heat injection well 21 are increased, decreased and changed according to the needs.

Referring to fig. 2, the first heating cable heating structure 23 includes a heat insulation structure 231 and a first heating cable 232, the first heating cable 232 is disposed outside the second gas transmission pipeline 16, and the heat insulation structure 231 is disposed outside the first heating cable 232 and insulates heat of the first heating cable 232.

Referring to fig. 3, the second heating cable heating structure 24 includes a second heating cable 241, and the second heating cable 241 is disposed outside the second gas transmission pipe 16.

Referring to fig. 5 and 6, the electromagnetic induction heating structure 27 includes an electromagnetic induction coil 271 and a spiral baffle 272, the electromagnetic induction coil 271 is disposed outside the second gas transmission pipeline 16, the electromagnetic induction coil 271 is made of a high temperature resistant cable, and the spiral baffle 272 is located at a corresponding section (portion) of the electromagnetic induction coil 271 in the second gas transmission pipeline 16.

The first heating cable 232, the second heating cable 241 and the electromagnetic induction coil 271 are wound outside the second gas transmission pipeline 16, and a proper gap is left between the first heating cable 232, the second heating cable 241 and the electromagnetic induction coil 271 due to the installation process and the like, and heat preservation, insulation, necessary protection materials and the like for the first heating cable 232, the second heating cable 241 and the electromagnetic induction coil 271 can be further arranged; the heat generated by the first heating cable 232 of the first heating cable heating structure 23 and the second heating cable 241 of the second heating cable heating structure 24 is conducted to the second gas transmission pipeline 16, so as to heat the high-temperature and high-pressure nitrogen 15; the first heating cable 232 and the second heating cable 241 can be directly powered by a power frequency alternating current and a direct current power supply generated by new energy, if the power frequency alternating current is used for supplying power, besides heat generated by the heating cables, the alternating electromagnetic field has an electromagnetic induction heating effect on the second gas transmission pipeline 16, and the heating efficiency can be improved; the electromagnetic induction coil 271 of the electromagnetic induction heating structure 27 is powered by the variable frequency power supply device and the cooling system 26, and performs electromagnetic induction heating on the second gas transmission pipeline 16, so as to heat the high-temperature and high-pressure nitrogen 15; the spiral guide plate 272 is arranged to strengthen the convection heat transfer effect of the high-temperature and high-pressure nitrogen 15 and the second gas transmission pipeline 16; in the second gas transmission pipeline 16, the spiral diversion plate 272 may be disposed in segments, not continuously, except for the corresponding segments (parts) of the specifically designated electromagnetic induction coil 271.

Referring to fig. 4, the variable frequency power supply device and the cooling system 26 are a sealed box, and include a power input 261, a high frequency power output 262, a control cable 263, a heat-insulating structure 231, and a hot nitrogen output 264.

A main circuit, a driving circuit and a control circuit are arranged in the box body, the heat preservation structure 231 is arranged outside the box body and used for insulating heat of the variable-frequency power supply device and the cooling system 26, a power supply input 261, a high-frequency power supply output 262 and a control cable 263 are respectively arranged on the heat preservation structure 231, and the power supply input 261 adopts a power-frequency alternating current and a direct current power supply generated by new energy to directly supply power; the pressurized cold nitrogen gas transmission pipeline 12 enters the closed box of the variable frequency power supply device and the cooling system 26 from the main circuit side of the variable frequency power supply device and the cooling system 26, exchanges heat with the main circuit and the driving and controlling circuit and then outputs the hot nitrogen gas from a hot nitrogen gas output port 264; the hot nitrogen output by the hot nitrogen output port 264 is directly discharged into the rich-oil coal or is recycled to the ground for reheating and utilization through a pipeline.

Except for special indication, each nitrogen storage tank body, valve, gas transmission pipeline and the like can be provided with heat preservation and insulation protective materials according to needs, so that the pipeline is protected, and heat loss is reduced.

The invention provides a nitrogen electric heating method for in-situ pyrolysis of oil-rich coal, which has the following characteristics:

(1) oil-rich coal in-situ (pyrolysis) comprehensive heating scheme with main ground and auxiliary underground

The space on the ground is large, and a large-scale and high-power heating device is easy to arrange; the underground space is narrow and small, the environment is severe, and the electric heating device is not suitable for being arranged on a large scale and with high power.

(2) The ground heater directly heats the nitrogen by adopting modes of an electric heater (pipe) and the like

The heater has simple structure and high heating efficiency; in order to improve the heating capacity and enlarge the heating scale, the ground heater adopts the methods of series-connection step-by-step heating and pressurization and multi-path parallel redundant heating and pressurization.

(3) The underground heater heats the nitrogen gas transmission metal pipeline to realize the heat preservation and the temperature rise of the nitrogen gas

The combination of high temperature heating (heat generating) cable heating (long time scale) and electromagnetic induction heating (short time scale) is adopted.

(4) Heating cable heating

The heating cable is directly wound on the outer wall of the underground nitrogen conveying metal pipeline, and the high-temperature-resistant heating cable heats the gas conveying metal pipeline to heat nitrogen; the heating cable is externally provided with a heat insulation structure in an unnecessary heating ore bed (non-oil-rich coal mine) area, so that the heat loss is reduced; in the area of a required heating ore bed (oil-rich coal mine), a heat insulation structure is not arranged (or arranged) outside the heating cable. The direct current power supply generated by power frequency alternating current or new energy is adopted for direct power supply. If power frequency alternating current is adopted for power supply, besides the heat generated by the heating cable, the alternating electromagnetic field also has the effect of induction heating on the gas transmission metal pipe, so that the heating efficiency can be improved.

(5) Electromagnetic induction heating

The underground gas transmission metal pipeline is directionally and intensively heated through high-frequency electromagnetic induction, so that the heat preservation, the temperature rise and the nitrogen temperature regulation of nitrogen are realized. The high-frequency electromagnetic induction heating speed is high, and the temperature control is flexible; the direct current power supply generated by power frequency alternating current and new energy is adopted for direct power supply, and the direct current power supply is inverted into a high-frequency power supply through a power electronic frequency conversion device and is output to a high-frequency electromagnetic induction heating coil; meanwhile, spiral guide plates are arranged in the gas transmission metal pipeline in a segmented (discontinuous) mode, and the forced convection heat exchange effect of heating nitrogen is improved.

Because of the processing and installation technological requirements, there is a gap between the coil (cable) and the gas transmission metal pipe. The high temperature resistant cable (heating wire or conducting wire) is insulated, and insulation and necessary protective materials can be added between the coil and the metal pipe according to the requirement.

(6) Method for strengthening heat transfer between gas pipeline and heat carrier (various gases and water vapor)

Spiral guide plates are arranged in the gas transmission pipeline at the corresponding position of the underground heater in a subsection mode (the whole gas transmission pipeline is not required), and the heat convection between the heat carrier and the metal pipe wall is enhanced.

(7) Heat insulation protection and cooling system for underground variable frequency power supply device

The power electronic variable frequency power supply device (a main circuit, a driving circuit and a control circuit) is arranged in a closed box body, and heat-preservation and heat-insulation materials are paved outside the box body to reduce the transmission of external heat into the box body; and low-temperature nitrogen is introduced into one side in the closed box body to cool circuit components of the variable-frequency power supply, and the hot nitrogen after heat exchange is directly discharged into the oil-rich coal rock from the other side in the closed box body or is recycled to the ground through a pipeline for reheating and utilization.

The method is not only suitable for electrically heating nitrogen, but also suitable for heating various high-temperature and high-pressure heat carriers (hot fluids) such as water vapor, air and carbon dioxide (CO)₂) And inert gases, hydrocarbon gases, and the like.

In summary, the nitrogen electric heating method and system for in-situ pyrolysis of the oil-rich coal provided by the invention take the actual heating environment of the oil-rich coal seam into consideration, organically combine long-time scale slow heating, short-time scale intensive heating and forced convection conduction heating of high-temperature and high-pressure heat carriers (hot fluids) on the ground and underground, improve the efficiency of a heating system, and enhance the adaptability of a heating device to the underground environment and the controllability of the heating temperature of the oil-rich coal seam.

The above-mentioned contents are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modification made on the basis of the technical idea of the present invention falls within the protection scope of the claims of the present invention.