A pipe string structure, system and method for in-situ heat injection production of oil shale

Abstract

The present invention provides a tubing structure, system, and method for in-situ, same-well heat injection production of oil shale. The tubing structure includes casing and oil tubing. The annulus between the casing and the oil tubing has a packer to separate the wellbore from top to bottom into a conveying section, a production section, and a heat injection section. The production section and the heat injection section correspond to target production areas and each has perforations. The oil tubing includes a gas-liquid separation nipple that extends from the conveying section into the production section. The gas-liquid separation nipple has a heat injection channel and an output channel. The pyrolysis gas injected from the oil tubing can enter the heat injection section through the heat injection channel. The output channel connects the annulus corresponding to the production section and the conveying section. Based on the technical solution of the present invention, the pyrolysis gas is recycled, heat loss is avoided, and heat utilization is improved. At the same time, it can solve the problems of low heat transfer efficiency in oil shale layers and difficult flow control of injected gas and gas channeling.

Description

Technical Field

[0001] The present invention relates to the technical field of oil shale oil and gas resource exploitation, and in particular to a pipe string structure, system and method for in-situ, same-well heat injection exploitation of oil shale. Background Art

[0002] Oil shale oil is an important alternative energy source to petroleum, with global shale oil resources estimated at 411 billion tons. my country is particularly rich in oil shale resources. According to the 2006 National Oil and Gas Resource Assessment, my country's oil shale resources at depths less than 1,000 meters total 719.937 billion tons, equivalent to 47.644 billion tons of shale oil, ranking second in the world. However, existing oil shale extraction methods, primarily surface retorting, are not only costly, but also inefficient in refining and power generation, and pose environmental risks.

[0003] Since the 1970s, numerous energy companies and research institutions at home and abroad have proposed over a dozen technologies and methods for in-situ oil shale extraction. However, most are currently in the laboratory development stage and have yet to achieve commercial application. Only the U.S. Bureau of Mines and Shell have successfully conducted field pilot trials. Existing in-situ heating and conversion technologies for oil shale include electrical heating, combustion heating, fluid heating, and radiation heating.

[0004] Shell, ExxonMobil, and IEP all use electric heating technology, utilizing electric heaters to heat underground oil shale formations. However, electric heating suffers from long heating cycles (typically 2-4 years), slow heating rates, frequent heater failures, high energy consumption, and the inability of the electrolyte to reach pyrolysis temperatures. The heating technologies developed by Chevron, AMSO, Mountain West Energy, and Petro Probe all utilize fluid heating methods, which can present challenges such as difficulty injecting the hot fluid initially and the tendency for cross-flow to occur later. Lawrence Livermore National Laboratory, Phoenix Wyoming, and Raytheon are currently conducting experimental research on radiative heating technology. However, due to the complexity and high cost of radiative heating, these technologies remain at the laboratory testing stage and have yet to be field tested. Furthermore, the US Burean of Mines and Occidental Petroleum are both researching combustion-based in-situ conbustion technology. Field trials have been conducted, but due to the complexity of the process and the difficulty in controlling combustion, this technology is not yet suitable for use in deeper oil shale reservoirs. Overall, Shell's improved ICP technology represents the world's leading level for in-situ oil shale mining, but it still cannot be economically developed. Currently, there are some precedents for research and improvement of in-situ heating conversion technology for oil shale in the existing technology, such as:

[0005] A method for developing deep-lying oil shale using a combination of staged horizontal well fracturing and superheated steam-assisted gravity flooding. This method also employs fluid heating technology, using directional or horizontal wells as heat injection wells. Hot steam is injected to heat the reservoir, allowing liquid hydrocarbons to flow into production wells under gravity. This system uses at least two wells for heat injection and production, making it difficult to control the flow of injected steam, which can easily lead to steam channeling and reduce heating efficiency.

[0006] A method and apparatus for in-situ oil shale extraction utilizes downhole combustion equipment to heat a fuel-water mixture and oxygen-containing gas to a supercritical state, then injects the combustion products into the well in a pulsed jet. The well is then closed and sealed to allow for full pyrolysis of the oil shale, before the oil-gas mixture is extracted to the surface for separation. This method utilizes downhole combustion reactions, which complicates the injection of combustion medium components and reaction control, potentially leading to safety issues. Furthermore, due to the low output volume, it is difficult to achieve effective surface extraction through a cyclical recovery.

[0007] A method for in-situ oil shale recovery utilizes three parallel wells: a central heating well, flanked by gas injection and production wells. This method can, to a certain extent, mitigate the effects of heat generation during oil shale heating. However, after fracturing the three wells, the flow direction of the injected fluid is difficult to control, making channeling more likely and reducing heating efficiency. Furthermore, this recovery system requires three vertical wells, which places higher demands on surface equipment and production costs than the conventional method.

[0008] A method for in-situ extraction of hydrocarbon compounds from oil shale using downhole heating is proposed. This method utilizes carbon dioxide and heating to extract hydrocarbon compounds from oil shale in situ. This method also requires drilling at least one heating well and at least one production well. After fracturing the oil shale layer, carbon dioxide is injected at a certain pressure. The heated carbon dioxide is then used to crack and extract organic matter from the formation. This method combines the extraction effect of carbon dioxide with fluid heating. However, this method still requires the coordinated operation of heating and production wells, and the carbon dioxide, when combined with formation water, becomes corrosive, which is detrimental to maintaining the condition of downhole equipment.

[0009] As can be seen from the above, although there are some precedents for research and improvement of oil shale in-situ heating conversion technology in the existing technology, they all have defects to varying degrees. Therefore, it is necessary to propose an oil shale in-situ conversion technology that can overcome these defects. Summary of the Invention

[0010] In response to the problems existing in the above-mentioned prior art in-situ conversion technology of oil shale, the present application proposes a pipe string structure, system and method for in-situ heat injection production of oil shale.

[0011] In a first aspect, the present invention provides a tubular structure for in-situ, same-well heat injection production of oil shale, comprising a casing and an oil pipe passing through the casing, wherein a packer is provided in the annular region between the casing and the oil pipe to separate the wellbore from top to bottom into a conveying section, a production section, and a heat injection section, wherein the production section and the heat injection section correspond to target production areas and each have perforations;

[0012] The oil pipe includes a gas-liquid separation short section that passes from the conveying section to the production section. The gas-liquid separation short section has a heat injection channel and a production channel. The pyrolysis gas injected by the oil pipe can enter the heat injection section through the heat injection channel. The production channel connects the annular space areas corresponding to the production section and the conveying section.

[0013] In one embodiment, a gas-liquid separation structure is provided in the output channel, and the gas-liquid separation structure has a reinjection channel connected to the heat injection channel;

[0014] The gas-liquid separation structure is used to perform gas-liquid separation on the mixed fluid of the pyrolysis gas and produced oil input into the production channel, and to reinject the separated pyrolysis gas into the heat injection channel through the reinjection channel.

[0015] In one embodiment, the gas-liquid separation structure comprises:

[0016] a spiral baffle, used for guiding the mixed fluid input into the output channel so that the mixed fluid forms a vortex along its flow direction;

[0017] The separation chamber is connected to the reinjection channel and is located at one end of the production channel away from the mixed fluid input. A gas separation port is extended from the separation chamber in the direction of flow of the mixed fluid. The gas separation port is located at the axis of the production channel.

[0018] In one embodiment, the heat injection channel includes a variable diameter section located at one end of the pyrolysis gas input, the inner diameter of the variable diameter section gradually decreases along the flow direction of the pyrolysis gas and the throat is the smallest inner diameter, the re-injection channel is connected at the throat and its channel extension direction is perpendicular to the heat injection channel.

[0019] In one embodiment, the oil pipe further comprises at least one heater disposed after the gas-liquid separation nipple, wherein the heater is configured to heat the pyrolysis gas to match the thermal conversion temperature of the oil shale in the target production area.

[0020] In one embodiment, the oil pipe includes two heaters, and the two heaters are respectively located in the production section and the heat injection section.

[0021] In one embodiment, the terminal end of the oil pipe in the heat injection section is a heat injection port, and a one-way valve is provided at the heat injection port.

[0022] In one embodiment, a plurality of gas lift valves are provided on the oil pipe. The gas lift valves are located in the conveying section and the valve ports at the ends thereof face the wellhead.

[0023] In a second aspect, the present invention provides a system for in-situ heat injection production of oil shale, comprising the above-mentioned pipe string structure; and

[0024] An on-hole heat injection assembly includes a heat injection pump, wherein the heat injection pump is connected to a hot fluid source and an oil pipe in the pipe string structure through pipelines;

[0025] The uphole product collection assembly includes an uphole gas-liquid separator and an oil storage device connected through a pipeline. The uphole gas-liquid separator is connected to the annular area of ​​the pipe string structure conveying section through the pipeline.

[0026] In a third aspect, the present invention provides a method for in-situ heat injection recovery of oil shale, which is applied to the above-mentioned pipe string structure and includes the following steps:

[0027] S1: Drilling and casing cementing are performed according to the location of the target production area, and perforation completion is performed in the well section corresponding to the target production area;

[0028] S2: Run the production string structure to separate the conveying section, the production section corresponding to the target production area, and the heat injection section in the wellbore;

[0029] S3: injecting pyrolysis gas into the heat injection section downhole through the tubing structure and maintaining continuous injection of the pyrolysis gas;

[0030] S4: Collecting the produced oil outputted from the tubing structure on the ground.

[0031] The above technical features can be combined in various suitable ways or replaced by equivalent technical features, as long as the purpose of the present invention can be achieved.

[0032] The present invention provides a pipe string structure, system, and method for in-situ heat injection recovery of oil shale, which, compared with the prior art, has at least the following beneficial effects:

[0033] 1. After the produced liquid-gas-liquid two-phase flow flows to the oil casing annulus, it will enter the downhole gas-liquid separation and reinjection device. After the gas-liquid separation by centrifugal action, the liquid components such as oil shale oil will continue to be transported from the annulus to the ground, and most of the heating gas will continue to flow back to the downhole heater through the reflux injection port, and then be heated again and injected into the formation, forming a small downhole thermal fluid circulation, thereby reducing the injection amount of ground hot fluid, avoiding unnecessary energy loss caused by transporting hot fluid from the downhole to the ground, and can effectively reduce development energy consumption, thereby reducing development costs.

[0034] 2. The produced oil shale oil is produced after oil and gas separation in the well, realizing pre-separation, which can reduce the pressure of the gas-liquid separation components on the ground.

[0035] 3. Injection and production based on a single-well structure can avoid the problems of low heat transfer efficiency of the oil shale layer, gas channeling of the injected gas, and difficulty in controlling the flow direction of the injected gas in the traditional injection-production well separation mode. The well network is easy to deploy, which can improve the in-situ conversion efficiency and recovery rate of the oil shale reservoir in the region. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The present invention will be described in more detail below based on embodiments and with reference to the accompanying drawings, wherein:

[0037] Figure 1 Shows the overall structural schematic diagram of the pipe string structure of the present invention;

[0038] Figure 2 A schematic structural diagram of a gas-liquid separation short section of a tubular column structure according to the present invention is shown.

[0039] In the drawings, like reference numerals are used for like parts, but the drawings are not necessarily true to scale.

[0040] Reference numerals:

[0041] 10-casing, 101-perforation, 102-packer, 11-transmission section, 12-production section, 13-heat injection section, 20-oil tubing, 201-gas lift valve, 21-gas-liquid separation pup joint, 211-heat injection channel, 2111-reducing section, 2112-throat, 212-production channel, 2121-mixed fluid inlet, 2122-liquid outlet, 22-heater, 23-heat injection port, 30-pyrolysis high-permeability oil shale layer, 31-original low-permeability oil shale layer, 40-gas-liquid separation structure, 401-reinjection channel, 41-spiral baffle, 42-separation chamber, 421-gas separation port, 50-on-hole heat injection assembly, 51-heat injection pump, 60-on-hole product collection assembly, 61-on-hole gas-liquid separator, 62-oil storage device. DETAILED DESCRIPTION

[0042] The present invention will be further described below with reference to the accompanying drawings.

[0043] The effective utilization of oil shale relies on in-situ modification methods, and fluid injection to heat the oil shale reservoir for in-situ mining is one of the more efficient and feasible heating methods currently available. The permeability of unmodified original oil shale is extremely low, and its heat transfer is extremely poor. The usual fluid injection heating method requires at least one production well and one heat injection well, and the original shale oil reservoir needs to be fractured to improve permeability. However, existing technologies make it difficult to achieve precise control of the fracture morphology of oil shale reservoirs, and the heat injection fluid in the reservoir is prone to gas channeling after fracturing, thereby reducing the heating efficiency of the reservoir. In the currently proposed fluid heating methods, the injected fluid needs to undergo a surface-underground flow cycle, and the heat injection fluid will inevitably lose a large amount of heat during this flow process, increasing the energy and cost required for in-situ conversion.

[0044] The pipe string structure and corresponding mining method proposed in the present invention can overcome the above-mentioned shortcomings of the existing technical means of in-situ mining of oil shale reservoirs by fluid injection heating, which are described in detail through the following embodiments.

[0045] Example 1

[0046] An embodiment of the present invention provides a tubular structure for in-situ, same-well heat injection production of oil shale, comprising a casing 10 and an oil pipe 20 passing through the casing 10. A packer 102 is provided in the annular region between the casing 10 and the oil pipe 20 to separate the wellbore from top to bottom into a conveying section 11, a production section 12, and a heat injection section 13. The production section 12 and the heat injection section 13 correspond to target production areas and each have a perforation 101.

[0047] The oil pipe 20 includes a gas-liquid separation short section 21 that penetrates from the conveying section 11 to the mining section 12. The gas-liquid separation short section 21 has a heat injection channel 211 and a production channel 212. The pyrolysis gas injected by the oil pipe 20 can enter the heat injection section 13 through the heat injection channel 211. The production channel 212 connects the annular areas corresponding to the mining section 12 and the conveying section 11.

[0048] Specifically, as shown in the accompanying drawings Figure 1As shown, the present invention, based on a single well, achieves in-situ conversion of oil shale and production of shale oil through single-well cyclic heat injection through the design of a corresponding process tubing string structure. The tubing string structure of the present invention primarily comprises a casing 10 and an oil pipe 20 disposed within the casing 10. A packer 102 is located in the annulus between the casing 10 and the oil pipe 20, separating the well sections into three relatively sealed sections: a transport section 11, a production section 12, and a heat injection section 13. The production section 12 and the heat injection section 13 are located corresponding to the target production area underground. The production section 12 and the heat injection section 13 are completed using perforations 101 during well completion, resulting in each section having a corresponding perforation 101. The gas-liquid separation sub 21 of the oil pipe 20 has independent heat injection channels 211 and output channels 212. The injection channel connects to the oil pipe 20 itself, while the output channel 212 connects to the annulus corresponding to the production section 12 and the transport section 11.

[0049] In actual production, after drilling and completion, the corresponding pipe string components are lowered to form the wellbore as shown in the attached figure. Figure 1 The tubing string structure shown in FIG. Pyrolysis gas (thermal fluid) at a certain temperature is injected into the tubing 20 through the nozzle at the top of the tubing 20. The pyrolysis gas is transported through the tubing 20 to the gas-liquid separation sub 21. After passing through the heat injection channel 211 inside the gas-liquid separation sub 21, it is transported by the tubing 20 to the area corresponding to the production section 12 and then injected into the heat injection section 13. Due to the continuous injection of pyrolysis gas, the pyrolysis gas enters the formation of the target production area through the perforations 101 corresponding to the heat injection section 13. Due to the extremely low permeability of the original oil shale reservoir and the higher temperature of the pyrolysis gas than the ambient temperature, the pyrolysis gas moves upward along the path and returns to the annulus area of ​​the production section 12 through the perforations 101 corresponding to the upper production section 12.

[0050] During this process, due to the extremely low initial permeability of the oil shale, the injected hot fluid flows out from the bottom of the oil pipe 20, enters the formation through the perforations 101 of the lower heat injection section 13, and then flows only in the near-wellbore perforation 101 zone to the perforations 101 of the upper production section 12, and then returns to the casing annulus, forming a small circulation of hot fluid formation flow. As the pyrolysis gas continuously heats the formation in the target production area, the oil shale is pyrolyzed and gradually produces oil shale oil. As the pyrolysis of the oil shale continues, a high-permeability pyrolysis oil shale layer 30 is formed in the pyrolysis area, and the permeability increases. The low permeability of the original oil shale ensures the directional flow of the fluid within the pyrolysis reservoir. The pyrolysis gas maintains a bottom-up flow in the high-permeability pyrolysis oil shale layer 30, preventing gas channeling. At this time, the pyrolysis gas carries the oil shale oil produced by pyrolysis and returns to the annular area of ​​the mining section 12 through the perforations 101 corresponding to the upper mining section 12. The heat-injected circulating fluid will carry the oil shale oil to form a gas-liquid two-phase flow, and enter the annular area of ​​the conveying section 11 through the production channel 212 of the gas-liquid separation short section 21, and finally output the oil shale oil from the wellhead to the ground for storage.

[0051] The pyrolysis of the high-permeability oil shale naturally forms a layer of original low-permeability oil shale 31 around it, forming the boundary of the pyrolysis zone. This concentrates the heat from the pyrolysis gases within a certain range for small-scale circulation. As pyrolysis progresses, the pyrolysis gases heat the formations in the target mining area over an increasingly wider area, gradually expanding the area of ​​the formation undergoing in-situ conversion. This achieves a gradual expansion of the pyrolysis range, rather than an instantaneous, excessively large pyrolysis range, and improves heat utilization.

[0052] The tubing structure of this embodiment is based on single-well thermal injection production. It utilizes the low permeability of the original low-permeability oil shale layer 31 to limit heat transfer, allowing the pyrolysis air to achieve a small circulation within a certain range of the formation in the target production area, avoiding the heat loss caused by the large-scale circulation from the underground to the surface. This effectively increases heat utilization, reduces the energy consumption of in-situ conversion, and lowers the cost of in-situ conversion and production of oil shale. At the same time, the low permeability of the original oil shale ensures directional flow of fluid within the pyrolysis reservoir, avoiding gas channeling and difficulty in controlling the injected gas flow direction. Furthermore, the well pattern is easily deployed, which can improve the in-situ conversion efficiency and recovery rate of the oil shale reservoir in the region.

[0053] Furthermore, the oil pipe 20 further includes at least one heater 22 disposed after the gas-liquid separation nipple 21 . The heater 22 is used to heat the pyrolysis gas to match the thermal conversion temperature of the oil shale in the target mining area.

[0054] Preferably, the oil pipe 20 includes two heaters 22 , which are respectively located in the production section 12 and the heat injection section 13 .

[0055] Specifically, the accompanying drawings Figure 1 As shown, the heater 22 is used to further heat the pyrolysis gas input into the pipe structure to compensate for the heat loss during the transportation of the pyrolysis gas to the underground. At the same time, it can also further accurately match the temperature required for the pyrolysis of oil shale in the target mining area, which is beneficial to the pyrolysis of oil shale.

[0056] Furthermore, the end pipe opening of the oil pipe 20 in the heat injection section 13 is a heat injection opening 23 , and a one-way valve is provided at the heat injection opening 23 .

[0057] Specifically, the one-way valve realizes the one-way discharge of the pyrolysis gas from the heat injection port 23, thereby preventing the pyrolysis gas from flowing back from the heat injection port 23 and preventing the possible backflow of the pyrolysis gas from interfering with the normal flow direction of the pyrolysis gas at the heat injection port 23.

[0058] Furthermore, a plurality of gas lift valves 201 are provided on the oil pipe 20 . The gas lift valves 201 are located in the conveying section 11 and the valve ports at the ends thereof face the wellhead.

[0059] Specifically, the gas lift valve 201 can spray air toward the wellhead, further providing flow power for the produced shale oil, and driving the shale oil to be transported to the wellhead more quickly.

[0060] Example 2

[0061] An embodiment of the present invention provides a tubular structure for in-situ, same-well heat injection production of oil shale, comprising a casing 10 and an oil pipe 20 passing through the casing 10. A packer 102 is provided in the annular region between the casing 10 and the oil pipe 20 to separate the wellbore from top to bottom into a conveying section 11, a production section 12, and a heat injection section 13. The production section 12 and the heat injection section 13 correspond to target production areas and each have a perforation 101.

[0062] The oil pipe 20 includes a gas-liquid separation short section 21 that penetrates from the conveying section 11 to the mining section 12. The gas-liquid separation short section 21 has a heat injection channel 211 and a production channel 212. The pyrolysis gas injected by the oil pipe 20 can enter the heat injection section 13 through the heat injection channel 211. The production channel 212 connects the annular areas corresponding to the mining section 12 and the conveying section 11.

[0063] Specifically, as shown in the accompanying drawings Figure 1 As shown, the present invention, based on a single well, achieves in-situ conversion of oil shale and production of shale oil through single-well cyclic heat injection through the design of a corresponding process tubing string structure. The tubing string structure of the present invention primarily comprises a casing 10 and an oil pipe 20 disposed within the casing 10. A packer 102 is located in the annulus between the casing 10 and the oil pipe 20, separating the well sections into three relatively sealed sections: a transport section 11, a production section 12, and a heat injection section 13. The production section 12 and the heat injection section 13 are located corresponding to the target production area underground. The production section 12 and the heat injection section 13 are completed using perforations 101 during well completion, resulting in each section having a corresponding perforation 101. The gas-liquid separation sub 21 of the oil pipe 20 has independent heat injection channels 211 and output channels 212. The injection channel connects to the oil pipe 20 itself, while the output channel 212 connects to the annulus corresponding to the production section 12 and the transport section 11.

[0064] In actual production, after drilling and completion, the corresponding pipe string components are lowered to form the wellbore as shown in the attached figure. Figure 1The tubing string structure shown in FIG. Pyrolysis gas (thermal fluid) at a certain temperature is injected into the tubing 20 through the nozzle at the top of the tubing 20. The pyrolysis gas is transported through the tubing 20 to the gas-liquid separation sub 21. After passing through the heat injection channel 211 inside the gas-liquid separation sub 21, it is transported by the tubing 20 to the area corresponding to the production section 12 and then injected into the heat injection section 13. Due to the continuous injection of pyrolysis gas, the pyrolysis gas enters the formation of the target production area through the perforations 101 corresponding to the heat injection section 13. Due to the extremely low permeability of the original oil shale reservoir and the higher temperature of the pyrolysis gas than the ambient temperature, the pyrolysis gas moves upward along the path and returns to the annulus area of ​​the production section 12 through the perforations 101 corresponding to the upper production section 12.

[0065] Furthermore, a gas-liquid separation structure 40 is provided in the output channel 212, and the gas-liquid separation structure 40 has a reinjection channel 401 connected to the heat injection channel 211;

[0066] The gas-liquid separation structure 40 is used to perform gas-liquid separation on the mixed fluid of the pyrolysis gas and produced oil input into the production channel 212 , and to reinject the separated pyrolysis gas into the heat injection channel 211 through the reinjection channel 401 .

[0067] Specifically, as shown in the accompanying drawings Figure 2 As shown, the gas-liquid separation structure 40 here is used to separate the mixed fluid of pyrolysis gas and produced oil shale oil. After the pyrolysis gas enters the formation and carries the produced oil back to the annulus area of ​​the pipe string, the pyrolysis gas and the output form a mixed fluid. The mixed fluid can be directly transported to the wellhead through the output channel 212, and gas-liquid separation is performed at the wellhead, but this will lose the pyrolysis gas with a certain amount of heat in the mixed fluid, resulting in heat waste. Therefore, a gas-liquid separation structure 40 is designed in the output channel 212 to separate the pyrolysis gas in the mixed fluid and re-inject it into the heat injection channel 211 through the reinjection channel 401. In this way, the amount of pyrolysis gas injected into the oil pipe 20 from the ground can be reduced, avoiding unnecessary energy loss, effectively reducing development energy consumption, and thus reducing development costs.

[0068] Furthermore, the gas-liquid separation structure 40 includes:

[0069] The spiral baffle 41 is used to guide the mixed fluid input into the output channel 212 so that the mixed fluid forms a vortex along its flow direction;

[0070] The separation chamber 42 is connected to the reinjection channel 401 and is located at one end of the output channel 212 away from the mixed fluid input. A gas separation port 421 extends from the output channel 212 in the direction of the mixed fluid flow. The gas separation port 421 is located at the axis of the output channel 212 .

[0071] Specifically, as shown in the accompanying drawings Figure 2As shown, the two ends of the production channel 212 are respectively provided with a mixed fluid inlet 2121 connected to the annular area of ​​the production section 12, and a liquid outlet 2122 connected to the annular area of ​​the conveying section 11. The spiral baffles 41 of the gas-liquid separation structure 40 are distributed along the extension direction of the production channel 212. They can guide the mixed fluid, causing the mixed fluid to generate vortexes, thereby separating the pyrolysis gas and produced oil in the mixed fluid due to the difference in centrifugal force exerted on the gas and liquid. The produced oil is concentrated in the area near the wall of the production channel 212, while the pyrolysis gas is concentrated in the area near the axis of the production channel 212. The separation chamber 42 is arranged at one end of the output channel 212 close to the liquid outlet 2122, and has a gas separation port 421 for the pyrolysis gas to enter. The gas separation port 421 corresponds to the area in the output channel 212 close to its axis. The separated pyrolysis gas enters the separation chamber 42 through the gas separation port 421, and enters the heat injection channel 211 through the reinjection channel 401 connected to the separation chamber 42. As the pyrolysis gas in the heat injection channel 211 is re-injected into the heat injection section 13, the recycling of the pyrolysis gas is realized.

[0072] It should be noted that since the gas-liquid separation structure 40 cannot completely separate the pyrolysis gas and the produced oil, the efficiency cannot reach 100%. Therefore, it is still necessary to inject some pyrolysis gas from the ground for supplementation. Compared with the method of not recycling the pyrolysis gas, this method greatly reduces the amount of pyrolysis gas injected from the ground.

[0073] Furthermore, the heat injection channel 211 includes a reducing section 2111 located at one end of the pyrolysis gas input, the inner diameter of the reducing section 2111 gradually decreases along the flow direction of the pyrolysis gas and the smallest inner diameter is the throat 2112, the re-injection channel 401 is connected to the throat 2112 and its channel extension direction is perpendicular to the heat injection channel 211.

[0074] Specifically, as shown in the attached figure Figure 2 As shown, the heat injection channel 211 is located at the pyrolysis gas input end as a reducing section 2111, and the inner diameter of the reducing section 2111 gradually decreases along the extension direction of the heat injection channel 211. In this way, the flow rate of the pyrolysis gas input by the oil pipe 20 at this location is increased by reducing the flow area. As a result, due to the increase in local flow rate, a local negative pressure is formed at the throat 2112 of the reducing section 2111. The reinjection channel 401 is connected to the throat 2112. In this way, the pressure difference at the local negative pressure can be utilized to accelerate the injection of the pyrolysis gas reinjected in the reinjection channel 401 into the heat injection channel 211, thereby improving the efficiency of the pyrolysis gas reinjection.

[0075] Example 3

[0076] An embodiment of the present invention provides a system for in-situ heat injection production of oil shale, comprising the above-mentioned pipe string structure; and

[0077] The wellbore heat injection assembly 50 includes a heat injection pump 51, which is connected to the hot fluid source and the oil pipe 20 in the pipe string structure through pipelines;

[0078] The uphole product collection assembly 60 includes an uphole gas-liquid separator 61 and an oil storage device 62 connected by a pipeline. The uphole gas-liquid separator 61 is connected to the annulus area of ​​the pipe string structure conveying section 11 through the pipeline.

[0079] Specifically, as shown in the accompanying drawings Figure 1 As shown, the uphole heat injection assembly 50 is used to inject pyrolysis gas into the oil pipe 20. During the initial injection, the demand for pyrolysis gas is high. Once the pyrolysis gas circulates normally in the tubing, the injection rate can be reduced. The uphole gas-liquid separator 61 in the uphole product collection assembly 60 first further separates the gas and liquid from the produced oil transported to the surface. After separating the residual pyrolysis gas, the produced oil is transported to the oil storage device 62 for storage. In addition, the separated residual pyrolysis gas can be piped into the heat injection pump 51 for re-injection into the ground, further improving the utilization rate of the pyrolysis gas.

[0080] Example 4

[0081] An embodiment of the present invention provides a method for in-situ heat injection recovery of oil shale, which is applied to the above-mentioned pipe string structure and includes the following steps:

[0082] S1: Drilling and casing 10 cementing is performed according to the location of the target production area, and the well section corresponding to the target production area is completed by perforating 101;

[0083] S2: Lowering the production string structure to separate the conveying section 11, the production section 12 corresponding to the target production area, and the heat injection section 13 in the wellbore;

[0084] S3: injecting pyrolysis gas into the heat injection section 13 downhole through the tubing structure and maintaining continuous injection of pyrolysis gas;

[0085] S4: Collect the produced oil output by the tubing structure on the ground.

[0086] In the description of the present invention, it should be understood that the terms "upper", "lower", "bottom", "top", "front", "back", "inside", "outside", "left", "right", etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention.

[0087] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely illustrative of the principles and applications of the invention. It should be understood that many modifications may be made to the illustrative embodiments, and that other arrangements may be devised, without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in ways other than those described in the original claims. It should also be understood that features described in conjunction with individual embodiments may be employed in conjunction with other described embodiments.

Claims

1. A pipe string structure for in-situ heat injection production of oil shale, characterized in that: The wellbore comprises a casing and an oil pipe passing through the casing, wherein a packer is provided in the annular space between the casing and the oil pipe to separate the wellbore from top to bottom into a conveying section, a production section, and a heat injection section, wherein the production section and the heat injection section correspond to target production areas and are respectively provided with perforations; The oil pipe includes a gas-liquid separation nipple that passes from the conveying section to the production section. The gas-liquid separation nipple has a heat injection channel and a production channel. The pyrolysis gas injected from the oil pipe can enter the heat injection section through the heat injection channel. The production channel connects the annular areas corresponding to the production section and the conveying section. A gas-liquid separation structure is provided in the production channel, and the gas-liquid separation structure has a reinjection channel connected to the heat injection channel. The gas-liquid separation structure is used to perform gas-liquid separation on the mixed fluid of pyrolysis gas and produced oil input into the production channel, and to reinject the separated pyrolysis gas into the heat injection channel through the reinjection channel; The heat injection channel includes a variable diameter section located at one end of the pyrolysis gas input, the inner diameter of the variable diameter section gradually decreases along the flow direction of the pyrolysis gas and the throat is where the inner diameter is the smallest. The re-injection channel is connected to the throat and its channel extension direction is perpendicular to the heat injection channel.

2. The pipe string structure for in-situ heat injection recovery of oil shale according to claim 1 is characterized in that: The gas-liquid separation structure comprises: a spiral baffle, used for guiding the mixed fluid input into the output channel so that the mixed fluid forms a vortex along its flow direction; The separation chamber is connected to the reinjection channel and is located at one end of the production channel away from the mixed fluid input. A gas separation port is extended from the separation chamber in the direction of flow of the mixed fluid. The gas separation port is located at the axis of the production channel.

3. The pipe string structure for in-situ heat injection recovery of oil shale according to claim 1 is characterized in that: The oil pipe further includes at least one heater disposed after the gas-liquid separation nipple, and the heater is used to heat the pyrolysis gas to match the thermal conversion temperature of the oil shale in the target production area.

4. The pipe string structure for in-situ heat injection recovery of oil shale according to claim 3 is characterized in that: The oil pipe includes two heaters, which are respectively located in the production section and the heat injection section.

5. The pipe string structure for in-situ heat injection recovery of oil shale according to claim 1, characterized in that: The end pipe opening of the oil pipe in the heat injection section is a heat injection port, and a one-way valve is provided at the heat injection port.

6. The pipe string structure for in-situ heat injection recovery of oil shale according to claim 1, characterized in that: The oil pipe is provided with a plurality of gas lift valves, which are located in the conveying section and have valve ports at their ends facing the wellhead.

7. A system for in-situ heat injection recovery of oil shale, characterized in that: comprising the pipe column structure according to any one of claims 1 to 6; as well as An on-hole heat injection assembly includes a heat injection pump, wherein the heat injection pump is connected to a hot fluid source and an oil pipe in the pipe string structure through pipelines; The uphole product collection assembly includes an uphole gas-liquid separator and an oil storage device connected through a pipeline. The uphole gas-liquid separator is connected to the annular area of ​​the pipe string structure conveying section through the pipeline.

8. A method for in-situ heat injection recovery of oil shale, applied to the pipe string structure according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1: Drilling and casing cementing are performed according to the location of the target production area, and perforation completion is performed in the well section corresponding to the target production area; S2: Run the production string structure to separate the conveying section, the production section corresponding to the target production area, and the heat injection section in the wellbore; S3: injecting pyrolysis gas into the heat injection section downhole through the tubing structure and maintaining continuous injection of the pyrolysis gas; S4: Collecting the produced oil outputted from the tubing structure on the ground.

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