CN113236210B - Oil shale composite heating in-situ mining system and method - Google Patents
Oil shale composite heating in-situ mining system and method Download PDFInfo
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
- E21B43/24—Enhanced recovery methods for obtaining hydrocarbons using heat, e.g. steam injection
- E21B43/2401—Enhanced recovery methods for obtaining hydrocarbons using heat, e.g. steam injection by means of electricity
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- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B33/00—Sealing or packing boreholes or wells
- E21B33/10—Sealing or packing boreholes or wells in the borehole
- E21B33/13—Methods or devices for cementing, for plugging holes, crevices, or the like
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/14—Obtaining from a multiple-zone well
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- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
- E21B43/166—Injecting a gaseous medium; Injecting a gaseous medium and a liquid medium
- E21B43/168—Injecting a gaseous medium
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- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
- E21B43/24—Enhanced recovery methods for obtaining hydrocarbons using heat, e.g. steam injection
- E21B43/2405—Enhanced recovery methods for obtaining hydrocarbons using heat, e.g. steam injection in association with fracturing or crevice forming processes
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- E—FIXED CONSTRUCTIONS
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- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/25—Methods for stimulating production
- E21B43/26—Methods for stimulating production by forming crevices or fractures
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- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/295—Gasification of minerals, e.g. for producing mixtures of combustible gases
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- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/30—Specific pattern of wells, e.g. optimizing the spacing of wells
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- E21—EARTH DRILLING; MINING
- E21C—MINING OR QUARRYING
- E21C41/00—Methods of underground or surface mining; Layouts therefor
- E21C41/16—Methods of underground mining; Layouts therefor
- E21C41/24—Methods of underground mining; Layouts therefor for oil-bearing deposits
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Abstract
The invention discloses an oil shale composite heating in-situ mining system and a method, belonging to the field of oil shale in-situ mining, wherein the mining system comprises an in-well heating system, a ground gas injection system, a well pattern system and a high-pressure breakdown system; a hot wall effect is formed in the heating process of the heating well, and the heating is stable and controllable; the breakdown electrode discharges electricity in a high-pressure atmosphere at the bottom of the well to generate air gap breakdown, the permeability of a target layer of the oil shale is further improved, the heater well is fixed and is constructed in a combined manner with underground gas injection, heat heats the stratum in a heat conduction and heat convection combined heating mode, the heat transfer effect is further improved, the energy consumption output ratio is remarkably reduced, and the in-situ mining period and the mining cost are further close to commercial mining.
Description
Technical Field
The invention relates to the field of oil shale in-situ mining, in particular to an oil shale composite heating in-situ mining system and method.
Background
Along with the increase of the exploration strength of resources such as oil shale, oil sand, rich coal, coal bed gas and shale gas of unconventional energy sources in recent years, the resource exploration reserves of the unconventional energy sources are increasing year by year, and the exploitation application prospect is wide.
The oil shale in-situ exploitation technology is also called underground in-situ conversion technology, and the exploitation of a target interval is realized by injecting a heat carrier medium into a target reservoir on the ground or underground. And the oil shale in the target interval is subjected to hydraulic fracturing and shock wave fracturing technology to realize reservoir transformation. The heat carrier medium exchanges heat with the oil shale of the target interval in the modes of conduction and convection, and when kerogen existing in the oil shale of the target interval reaches the cracking temperature, the hydrocarbon mixture generated by cracking is transported together with the heat carrier medium and extracted to the ground surface.
The processes for exploring unconventional reservoir underground in-situ exploitation at the present stage mainly comprise an ICP (inductively coupled plasma) in-situ conversion technology, a TSA (TSA) local chemical reaction technology, an MTI (methanol to olefins) steam injection technology, an HVF (high-pressure power frequency) technology, an LLNL (low-pressure nuclear magnetic resonance) radio frequency heating technology, an RF (radio frequency)/CF (compact flash) eddy current heating technology and the like. The ICP in-situ conversion technology for removing the shell by the process is used for carrying out relevant field tests in the United states and the jordan area to produce oil gas, and the TSA local chemical reaction technology of Jilin university is used for carrying out relevant field tests in China to produce oil shale oil gas, and other technologies are still in a laboratory stage.
In the underground in-situ mining process, oil shale is used as a compact rock stratum, the internal porosity and permeability of the oil shale are extremely low, the opening degree of an artificial crack formed in a rock body after reservoir transformation is very low, most heat in the early stage of heat injection is conducted in a heat conduction mode, convection heating is an important expression mode for realizing efficient heat exchange of the rock body, ground heat injection is extremely serious in heat loss along the way in the heat process, and the phenomenon causes that the temperature rise rate in the rock body is extremely slow and the energy utilization rate is low. In the practice process of the residual oil shale in-situ mining test field of Jilin university, the thermal expansion effect caused by the heterogeneity of the oil shale and the coking phenomenon of kerogen seriously obstruct the formation of heat injection, and the problem of sealing failure caused by overlarge gas injection pressure often occurs in the operation process of the conventional underground gas injection-heating integrated structure. Therefore, exploring a practicable compact underground oil shale heat conduction-convection combined heating construction system and process is an important means for realizing the commercial exploitation of unconventional compact reservoirs.
Disclosure of Invention
The purpose of the invention is: in order to solve the problems in the background art, the system and the method for oil shale composite heating in-situ exploitation are provided, and are used for solving the problems that the formation of heat injection is seriously hindered by the thermal expansion effect and the kerogen coking phenomenon caused by the heterogeneity of the oil shale in the in-situ exploitation process of the oil shale, and the sealing failure caused by overlarge gas injection pressure often occurs in the operation process of a conventional underground gas injection-heating integrated structure, so that the heat injection efficiency is improved, and the exploitation cost is reduced.
The technical scheme adopted by the invention for realizing the purpose is as follows:
oil shale composite heating normal position exploitation system, its characterized in that includes: heating system, ground gas injection system, well pattern system and high-voltage breakdown system in the well, wherein:
the heating system in the well comprises a continuous oil pipe, an upper sealing interlayer in the well, a heater fixing layer, a lower sealing interlayer in the well and a heater, wherein the upper sealing interlayer in the well, the heater fixing layer and the lower sealing interlayer in the well are sequentially arranged from top to bottom; the heater is arranged in the heating well and positioned in the oil shale target stratum section, and the heater is tightly contacted with the heater fixing layer to form sealing; the continuous oil pipe is in threaded connection with the heater;
the ground gas injection system comprises a nitrogen making machine, a compressor, a pressure stabilizing tank, a supercharger, an electric valve, a flowmeter, a temperature sensor and a pressure sensor, wherein the nitrogen making machine and the compressor are respectively connected with the gas inlet end of the pressure stabilizing tank through pipelines, and manual valves are respectively arranged between the nitrogen making machine and the pressure stabilizing tank and between the compressor and the pressure stabilizing tank; the inlet end of the supercharger is connected with the outlet end of the surge tank through a pipeline, the outlet end of the supercharger is communicated with the wellhead of the injection and production well through a pipeline, and an electric valve, a flowmeter, a temperature sensor and a pressure sensor are sequentially arranged on the pipeline between the supercharger and the injection and production well;
the well pattern system comprises injection and production wells and heating wells, the injection and production wells comprise first injection and production wells and second injection and production wells, the number of the first injection and production wells is one, the number of the second injection and production wells is eight, the number of the heating wells is four, the first injection and production wells and the four heating wells form a central well pattern, the central well pattern is arranged in a square five-point well pattern structure, the four heating wells are respectively positioned at four vertex positions of the square, and the first injection and production wells are positioned at the central position of the square; the eight second injection and production wells are uniformly distributed in an annular shape to form a peripheral well pattern surrounding the outside of the central well pattern;
the high-voltage breakdown system comprises insulating ceramic, a breakdown electrode, a high-frequency high-voltage emitter and a transformer, wherein the upper part of the insulating ceramic is in threaded connection with the heater, and the lower part of the insulating ceramic is in threaded connection with the breakdown electrode; the transformer is positioned on the ground surface and connected with an external power supply, and the transformer is used for converting 380V three-phase voltage provided by the external power supply into 220V single-phase voltage; the input end of the high-frequency high-voltage transmitter is connected with the output end of the transformer, the high-frequency high-voltage transmitter is used for converting 220V voltage output by the transformer into power frequency high voltage of 50kV and 50Hz, and the high-frequency high-voltage transmitter is connected with the breakdown electrode through an insulated copper-clad cable.
Furthermore, the plane of the upper surface of the downhole lower sealing layer is higher than the plane of the bottom surface of the oil shale target layer, and the distance between the plane of the upper surface of the downhole lower sealing layer and the plane of the bottom surface of the oil shale target layer is 2 m; the plane of the top of the heater is 5m away from the plane of the bottom surface of the upper cladding layer; the plane of the upper surface of the heater fixing layer is lower than the plane of the bottom surface of the upper covering layer, the plane distance difference is 2m, the plane of the lower surface of the heater fixing layer is higher than the plane of the top surface of the lower covering layer, and the plane distance difference is 2 m; the thickness of the in-well upper packing layer is 10m in total, wherein the thickness of the in-well upper packing layer in the oil shale target layer is 2m, the thickness of the in-well upper packing layer in the upper packing layer is 8m, and the in-well upper packing layer is in close contact with the heater fixing layer.
Further, the flowmeter is a coriolis flowmeter.
Further, the side length of the square in the square five-point well pattern structure is 25 m; the distance between the second injection and production well and the first injection and production well is 100 m.
Further, the pressure in the eight second injection and production wells is maintained between 0.3MPa and 1.0 MPa.
Further, the heating well, the first injection and production well and the second injection and production well are drift diameter vertical wells, the well diameter of the heating well is 311mm, and the well diameters of the first injection and production well and the second injection and production well are 244 mm.
Further, the oil shale target layer is located 467 m-488 m underground.
The oil shale composite heating in-situ mining method is characterized by being based on the oil shale composite heating in-situ mining system for mining, and specifically comprises the following steps, wherein the following steps are sequentially carried out:
step one, selecting an oil shale in-situ mining block;
drilling nine injection-production wells in the selected oil shale in-situ production block, performing fracturing construction on oil shale in a target stratum section of the oil shale from the injection-production wells to complete reservoir transformation, performing connectivity test, and entering the next step after the test is qualified;
drilling four heating wells in the oil shale in-situ mining block;
injecting CA-50 aluminate high-strength cement into all the heating wells until the bottom surface of the oil shale target layer faces downwards by 2m from the normal direction, and forming an in-well lower sealing interlayer after curing;
fifthly, the heater is in threaded connection with the coiled tubing, the heater is conveyed to the target position of the heating well through the coiled tubing by ground cable car equipment, quartz sand is filled into the heating well and is vibrated and compacted to form a heater fixing layer;
injecting CA-50 aluminate high-strength cement into all the heating wells, pouring for 10m in total, wherein the oil shale target layer sections correspond to 2m, the overburden layer sections correspond to 8m, forming an upper sealing interlayer in the well after curing, installing well heads of the heating wells and completing pipeline connection;
step seven, starting all heaters in the heating well to heat the target layer of the oil shale, wherein the operation period is five days;
step eight, in a first mining period, starting a nitrogen making machine, wherein the first injection and production well is used as an injection well, high-purity nitrogen is injected into the first injection and production well through a supercharger, the purity of the high-purity nitrogen is greater than or equal to 99.7%, the high-purity nitrogen is heated through a heating area of a target layer of the oil shale, the heated nitrogen heats the target layer section of the oil shale to accelerate the oil shale cracking of the target layer section of the oil shale, eight second injection and production wells are used as mining wells, oil-gas mixed products are extracted from the mining wells to the ground, and the operation period is ten days;
step nine, turning off heaters in all heating wells, starting a high-frequency high-voltage transmitter, transmitting an electric signal to breakdown electrodes of all heating wells by the high-frequency high-voltage transmitter through insulated copper-clad cables, shielding the heaters from the breakdown electrodes by using insulated ceramics, generating an air gap breakdown effect in an oil shale target layer under the high-temperature high-voltage atmosphere, electrically breaking the oil shale target layer, generating the air gap breakdown effect along with high temperature in the generation process, wherein the construction period is twenty-four hours, and then turning off the high-frequency high-voltage transmitter;
step ten, in a second mining period, starting a compressor, supplying gas to the compressor, injecting normal-temperature and high-pressure air into a first injection and production well by the compressor to enable a target layer of the underground oil shale to generate local chemical reaction, enabling the target layer of the oil shale to be in a continuous heating state through self-heating chemical reaction, and intermittently injecting gas, wherein one gas injection period is twelve hours, the duration is ten days, and oil-gas mixed products are extracted to the ground through eight second injection and production wells;
step eleven, opening a wellhead annulus valve of the first injection and production well, adjusting the pressure of the first injection and production well to be consistent with the pressure of a peripheral well pattern, taking eight second injection and production wells as injection wells, injecting normal-temperature high-pressure air into the wells by a supercharger, injecting gas intermittently, wherein one gas injection period is twelve hours, the duration time is five days, and further pyrolyzing the oil-gas mixed product in the central well pattern by using the residual heat of the oil shale target layer as a heat source and extracting the oil-gas mixed product to the ground surface through the first injection and production well for separation;
and step twelve, stopping gas injection after construction is finished, completing the recovery work of the continuous oil pipe, the heater, the insulating ceramic and the breakdown electrode, and fixedly sealing all the injection and production wells and the heating well by cement.
The oil shale composite heating in-situ mining method has the advantages that in the intermittent gas injection process, within the twelve-hour interval of gas injection, when the formation flow conductivity between the first injection and production well and the second injection and production well at the periphery is reduced due to the thermal expansion effect and coking phenomenon of the target layer of the heterogeneous oil shale, selecting the injection and production well with the largest flow reduction in the second injection and production well as an operation target according to the gas flow change condition in the second injection and production well, the gas migration track can move along the direction of the injection and production well with the maximum pressure difference gradient by closing the injection and production well and the adjacent injection and production well, forming a self-heating closed zone in the area with the largest flow change, increasing the temperature in the self-heating closed zone formed by the closed zone, converting kerogen into coking asphaltene, then the oil gas is converted into cracked oil gas to escape from the stratum hole crack, the blockage removal is completed, and the closed and adjacent injection and production wells are opened to complete the extraction of oil gas products.
Through the design scheme, the invention can bring the following beneficial effects: the invention provides an oil shale composite heating in-situ mining system and a method, wherein nine injection and production wells and four heating wells are drilled in an oil shale mining block to form a well pattern system, a heater is put into the heating wells through a coiled tubing, and grouting and coagulation waiting are carried out on the upper side and the lower side of the heater to form sealing, and the injection and production wells can be switched into an injection and production mode at will; after the heater heats the stratum, a three-dimensional hot wall effect is formed, the heating effect is stable and reliable, the heater fixing layer is filled with porous medium quartz sand, gas is injected into the central injection and production well, the heat of the heater and the peripheral heating area is heated in a forced convection heat exchange mode through a hydraulic fracture, and a composite heating mode of heat conduction and heat convection is formed; the heater is not influenced by high-pressure gas injection pressure in the heating process, the downhole accidents of the heater are few, the heating period is long, the heat exchange is uniform, the heat transfer effect is good, and the energy utilization rate is high; the high-frequency high-voltage emitter is used for discharging the breakdown electrode in the heating well discontinuously, and an air gap breakdown effect is generated under the high-temperature high-voltage atmosphere, so that the phenomena of hydraulic fracture closure and coking caused by high-temperature expansion in a central well pattern are effectively solved, the permeability of a target layer of the oil shale is further increased, and oil gas displacement and heat transfer are facilitated; the stratum between the central well pattern and the peripheral well pattern is thermally expanded or coked, and the stratum can be dredged by adjusting the pressure of the peripheral injection and production well, so that the process can normally run.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the invention without limiting the invention to the right, and in which:
FIG. 1 is a general layout of an oil shale complex heating in situ mining system;
FIG. 2 is a schematic plan view of a well pattern of the oil shale complex heating in situ production system;
FIG. 3 is a schematic diagram of the mining principle of the oil shale complex heating in-situ mining method;
FIG. 4 is a plan view of the equipment area of the oil shale combined heating in-situ mining system.
The respective symbols in the figure are as follows: 1-injection and production well I; 2-injection and production well II; 3-injection and production well III; 4-injection and production well four; 5-injection and production well five; 6-injection and production well six; 7-injection and production well seven; 8-eighth injection-production well; 9-ninth injection and production well; 10-heating a well I; 11-a second heating well; 12-heating well three; 13-heating well four; 14-well head; 15-coiled tubing; 16-upper sealing layer in well; 17-a heater fixing layer; 18-downhole lower seal layer; 19-a heater; 20-insulating ceramic; 21-a breakdown electrode; 22-hot wall; 23-gas-stop closed block; 24-a nitrogen generator; 25-a compressor; 26-a first manual valve; 27-manual valve two; 28-tee pipe; 29-a surge tank; 30-a supercharger; 31-an electrically operated valve; 32-a flow meter; 33-a temperature sensor; 34-a pressure sensor; 35-a pipeline; 36-a high frequency high voltage transmitter; 37-a transformer; 38-an upper cladding layer; 39-oil shale target layer; 40-underlying layer.
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 only a part of the embodiments of the present invention, and not all of the embodiments. 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. Well-known methods, procedures, components and circuits have not been described in detail so as not to obscure the present invention.
As shown in fig. 1, 2, 3 and 4, the oil shale complex heating in-situ mining system comprises: the system comprises an in-well heating system, a ground gas injection system, a well pattern system and a high-voltage breakdown system.
The heating system in the well comprises a continuous oil pipe 15, an upper sealing layer 16 in the well, a heater fixing layer 17, a lower sealing layer 18 in the well and a heater 19, wherein the upper sealing layer 16 in the well, the heater fixing layer 17 and the lower sealing layer 18 in the well are sequentially arranged from top to bottom, the heater fixing layer 17 is tightly contacted with the upper sealing layer 16 in the well and the lower sealing layer 18 in the well at two sides of the heater fixing layer to form sealing, the upper sealing layer 16 in the well and the lower sealing layer 18 in the well are poured by CA-50 aluminate high-strength cement, the heater fixing layer 17 is filled by quartz sand, and preferably, the mesh number of the quartz sand is 20 meshes; the heater 19 is arranged in the heating well and positioned in the 39-layer section of the oil shale target layer, and the heater 19 is tightly contacted with the heater fixing layer 17 to form sealing; the continuous oil pipe 15 is in threaded connection with the heater 19; the construction process of the heating system in the well is as follows: injecting CA-50 aluminate high-strength cement into the well, waiting for setting for twenty-four hours to form an underground lower sealing interlayer 18, wherein the plane of the upper surface of the underground lower sealing interlayer 18 is higher than the plane of the bottom surface of the oil shale target layer 39, and the distance between the plane of the upper surface of the underground lower sealing interlayer 18 and the plane of the bottom surface of the oil shale target layer 39 is 2 m; the heater 19 is in threaded connection with the coiled tubing 15, the coiled tubing 15 penetrates through the wellhead 14 of the heating well to lower the heater 19 to the target layer 39 interval of the oil shale, and the plane of the top of the heater 19 is 5m away from the plane of the bottom surface of the overlying layer 38; placing quartz sand into the well to be densely filled to form a heater fixing layer 17, wherein the plane of the upper surface of the heater fixing layer 17 is lower than the plane of the bottom surface of the upper covering layer 38, the distance difference between the planes is 2m, the plane of the lower surface of the heater fixing layer 17 is higher than the plane of the top surface of the lower covering layer 40, and the distance difference between the planes is 2 m; and injecting CA-50 aluminate high-strength cement into the well, and waiting for setting for twenty-four hours to form an in-well upper sealing interlayer 16, wherein the thickness of the in-well upper sealing interlayer 16 is 10m in total, the thickness of the in-well upper sealing interlayer 16 in the oil shale target layer 39 is 2m, the thickness of the in-well upper sealing interlayer 16 in the upper covering layer 38 is 8m, and the in-well upper sealing interlayer 16 is in close contact with the heater fixing layer 17.
The ground gas injection system comprises a nitrogen making machine 24, a compressor 25, a first manual valve 26, a second manual valve 27, a three-way pipe 28, a pressure stabilizing tank 29, a supercharger 30, an electric valve 31, a flowmeter 32, a temperature sensor 33, a pressure sensor 34 and a pipeline 35, the ground gas injection system is positioned in a ground surface equipment area, and the three-way pipe 28 comprises two inlets and one outlet; the nitrogen making machine 24 and the compressor 25 are respectively connected with two inlets of the three-way pipe 28 through a pipeline 35, a first manual valve 26 is installed on the pipeline 35 between the nitrogen making machine 24 and the three-way pipe 28, and a second manual valve 27 is installed on the pipeline 35 between the compressor 25 and the three-way pipe 28; the inlet end of the surge tank 29 is connected with the outlet of the three-way pipe 28 through a pipeline 35; the inlet end of the supercharger 30 is connected with the outlet end of the surge tank 29, the outlet end of the supercharger 30 is communicated with the wellhead 14 of the injection and production well through a pipeline 35, and an electric valve 31, a flow meter 32, a temperature sensor 33 and a pressure sensor 34 are sequentially arranged on the pipeline 35 between the supercharger 30 and the injection and production well; the temperature sensor 33 is a thermocouple sensor; the supercharger 30 and the compressor 25 are combined to realize five-stage compression, the compressor 25 and the nitrogen making machine 24 are in one stage, and the supercharger 30 is compressed in four cylinders step by step. Injecting normal-temperature high-purity nitrogen into the first heat injection well positioned in the center in the early stage, wherein the purity of the nitrogen is not lower than 99.7%, and injecting normal-temperature air into the first heat injection well positioned in the center in the later stage. The pipeline 35 is made of 304 stainless steel, the outer diameter of the pipeline 35 is 50mm, the wall thickness of the pipeline 35 is 10mm, the first manual valve 26 and the second manual valve 27 are high-pressure ball valves, two sides of the two manual valves are connected with the pipeline 35 in a welding mode through flanges, the flanges are in static pressure contact with the first manual valve 26 and the second manual valve 27 through flanges, the three-way pipe 28 is connected with the pipeline 35 in a welding mode, the pipeline 35 is in threaded connection with the pressure stabilizing tank 29, the booster 30 is in static pressure connection with the pressure stabilizing tank 29 through flanges, the installation mode of the electric valve 31 is the same as the connection mode of the first manual valve 26 and the second manual valve 27 in the pipeline 35, the flowmeter 32 is a Coriolis flowmeter, the flowmeter 32 is in threaded connection with the pipeline 35, the temperature sensor 33 and the pressure sensor 34 are respectively externally connected with welding bases, and the temperature sensor 33 and the pressure sensor 34 are respectively welded with the pipeline 35.
The well pattern system is deployed in the exploitation region, and the well pattern system includes central well pattern and peripheral well pattern, and central well pattern is square five-point well pattern, and square five-point well pattern includes: the system comprises four heating wells and a first injection and production well, wherein the four heating wells are respectively positioned at four top points of a square, and the first injection and production well is positioned at the center of the square; according to the invention, a first injection and production well is designed to be positioned in the center of a production area, four heating wells are arranged to surround the first injection and production well, a heat forming wall 22 is formed by heating, the heat convection of the production area of the target layer 39 of the oil shale on the periphery of a central well pattern is realized, and the horizontal and vertical distances between the heating wells are 25 m; the peripheral well pattern comprises eight second injection and production wells which are uniformly distributed in an annular shape, the distance between the second injection and production wells and the first injection and production well in the central well pattern is 100m, and the pressure in the eight second injection and production wells is maintained at 0.3 MPa-1.0 MPa, so that a gas stop closed block 23 of the whole mining area is formed. The well diameter of the heating well is 311mm, the well diameters of the first injection and production well and the second injection and production well are 244mm, and the heating well, the first injection and production well and the second injection and production well are drift diameter vertical wells, as shown in fig. 1, 2, 3 and 4, the first injection and production well is a first injection and production well 1, and the four heating wells are respectively a first heating well 10, a second heating well 11, a third heating well 12 and a fourth heating well 13; the eight second injection and production wells are respectively an injection and production well II 2, an injection and production well III 3, an injection and production well IV 4, an injection and production well V5, an injection and production well VI 6, an injection and production well VII 7, an injection and production well VIII 8 and an injection and production well VII 9.
The high voltage breakdown system comprises an insulating ceramic 20, a breakdown electrode 21, a high frequency and high voltage emitter 36 and a transformerA presser 37, the upper part of the insulating ceramic 20 is connected with the heater 19 by screw thread, and the lower part of the insulating ceramic 20 is connected with the breakdown electrode 21 by screw thread; the breakdown electrode 21 adopts common CuAl2O3The high-temperature-resistant material comprises a transformer 37, the transformer 37 is located on the ground surface, the transformer 37 is connected with an external power supply, the transformer 37 is used for converting 380V three-phase voltage provided by the external power supply into 220V single-phase voltage, the input end of a high-frequency high-voltage transmitter 36 is connected with the output end of the transformer 37, the high-frequency high-voltage transmitter 36 is used for converting the 220V single-phase voltage output by the transformer 37 into 50kV and 50Hz power frequency high voltage, the high-frequency high-voltage transmitter 36 is communicated with a breakdown electrode 21 through an insulated copper-clad cable, an air gap breakdown effect is generated under the action of a high-pressure air medium, an oil shale target layer 39 between a first injection and production well and a heating well is reconstructed, the air gap breakdown prevents hydraulic cracks from being closed due to thermal expansion and coking thermal expansion effects, and a diversion channel can be further expanded. The high-frequency high-voltage transmitter 36 in the invention adopts a Giardian self-developed dielectric breakdown device with the model number of USG-150-.
Fig. 3 is a schematic diagram of a local in-situ mining principle of the oil shale composite heating in-situ mining method, wherein the mining well spacing is symmetrically distributed, and only a schematic diagram of local well location distribution is selected for presentation in order to facilitate visual representation of graphs.
The working principle and the process of the invention are as follows:
the heater 19 in the first heater well 10, the second heater well 11, the third heater well 12 and the fourth heater well 13 starts to heat the stratum, a sand filling layer in a heater fixing layer 17 is used as a porous medium, heat heats an oil shale target layer 39 in a heat conduction mode, the heater wells are distributed around the first injection and production well 1 in a square ring shape to heat the stratum, a stable and reliable hot wall 22 is formed, after five days of heating, a nitrogen generator 24 is started to supply air for a supercharger 30, high-pressure gas is injected into the first injection and production well 1 to enter the oil shale target layer 39, normal-temperature gas pushes the heat generated by the heater 19 and the heat obtained at the periphery of the stratum forward in a heat convection mode through stratum fracturing cracks to form forced heat exchange, heat flow is stable and uniform, the period lasts for ten days, and the heater 19 and the nitrogen generator 24 are closed; and starting the high-frequency high-voltage transmitter 36, transmitting the electric signal to the breakdown electrode 21 through the insulated copper-clad cable, enabling the breakdown electrode 21 to generate an air gap breakdown effect on the oil shale target layer 39 in a high-temperature high-voltage atmosphere environment, and closing the high-frequency high-voltage transmitter 36 when the construction period is twenty-four hours. At the moment, kerogen in the target layer 39 of the oil shale is cracked continuously, the pore permeability characteristic is further improved, the compressor 25 is started, air is injected into the injection and production well I1 through the supercharger 30, the air and the high-temperature kerogen generate self-heating local chemical reaction, the heat generated by the reaction is used for heating the stratum, so that the macromolecular kerogen is further cracked to form hydrocarbon oil gas products, the hydrocarbon oil gas products are extracted to the ground surface through the second injection and production well (namely, the injection and production well II 2 to the injection and production well IX 9), the construction period is one cycle for twelve hours, and the duration period is ten days; switching the injection well from the injection well II 2 to the injection well nine 9 into an injection well, starting a compressor 25, injecting normal-temperature high-pressure air into the injection well II 2 to the injection well nine 9 by a supercharger 30, heating the oil shale in the central well network by utilizing the residual heat of the stratum, intermittently injecting gas, wherein one period lasts for twelve hours, the mining period is five days, and a composite heating process integrating heat conduction and heat convection is formed for in-situ mining of the oil shale.
The oil shale composite heating in-situ mining method is based on the oil shale composite heating in-situ mining system, and the mining method is divided into four stages, wherein the first stage is a heater 19 underground heating stage and is heat conduction heating, so that the temperature of a stratum reaches a set value of 350 ℃; the second stage is a normal-temperature nitrogen injection and underground heating stage, which is heat conduction and heat convection combined heating; the third stage is an air gap breakdown stage, and the oil shale target layer 39 is modified; the fourth stage is a downhole normal-temperature air injection self-heating reaction stage, which is heat conduction and heat convection combined heating, and the method specifically comprises the following steps:
firstly, preferably selecting an oil shale in-situ mining landform and landform better block, wherein the landform and landform better block is a water system body with the surface fluctuation not more than 5m and no large surface;
drilling nine injection-production wells in the oil shale in-situ mining block, performing fracturing construction on the oil shale of the 39-layer section of the oil shale target layer from the injection-production wells to complete reservoir transformation, and performing connectivity test;
drilling four heating wells in the oil shale in-situ mining block;
injecting CA-50 aluminate high-strength cement into all the heating wells until the bottom surface of the oil shale target layer 39 faces downwards by 2m from the normal direction, and forming an in-well lower sealing interlayer 18 after curing;
fifthly, the heater 19 is in threaded connection with the coiled tubing 15, the heater 19 is conveyed to a target layer of the heating well through the coiled tubing 15 through ground cable car equipment, quartz sand is filled into the heating well, and the heating well is tightly vibrated to form a heater fixing layer 17;
step six, injecting CA-50 aluminate high-strength cement into all the heating wells, pouring for 10m in total, wherein the 39 layer sections of the oil shale target layer correspond to 2m, the 38 layer sections of the upper cladding layer correspond to 8m, forming an inner upper sealing interlayer 16 after curing, installing the well heads 14 of the heating wells and completing the connection of the pipelines 35;
seventhly, starting heaters 19 in the first heating well 10, the second heating well 11, the third heating well 12 and the fourth heating well 13 to heat the oil shale target layer 39, and forming a stable and reliable hot wall 22 in heating, wherein the operation period is five days;
step eight, in a first mining period, starting a nitrogen making machine 24, using the injection-production well 1 as an injection well, injecting high-purity nitrogen into the injection-production well 1 through a supercharger 30, heating the gas through an oil shale target layer 39 heating area, heating the ground normal-temperature nitrogen, heating the oil shale target layer 39 layer in a forced convection heat exchange mode, accelerating the oil shale cracking of the oil shale target layer 39 layer, injecting the high-purity nitrogen through the injection-production well 1, using the injection-production well 2, the injection-production well three 3, the injection-production well four 4, the injection-production well five 5, the injection-production well six 6, the injection-production well seven 7, the injection-production well eight 8 and the injection-production well nine 9 as mining wells through the heating area, extracting oil-gas mixed products from the mining wells to the ground, collecting the products by passing a mixture carrying the oil-gas products through the second injection-production well, and having an operation period of ten days;
the specific process of forced convection heat transfer is as follows: after the four heating wells heat the oil shale target layer 39, injecting normal-temperature high-pressure nitrogen from the first injection and production well, injecting heat into the gas through the heater fixing layer 17 and the peripheral heating stratum through hydraulic cracks, and realizing forced convection heat exchange with the oil shale target layer 39;
step nine, the heaters 19 in all the heating wells are closed, the high-frequency high-voltage transmitters 36 are started, the high-frequency high-voltage transmitters 36 transmit electric signals to the breakdown electrodes 21 of all the heating wells through insulated copper-clad cables, the insulated ceramics 20 shield the heaters 19 from contacting the breakdown electrodes 21, air gap breakdown effect occurs inside the oil shale target layer 39 under the high-temperature high-voltage atmosphere, the oil shale target layer 39 is broken through electric breakdown, hydraulic crack closing caused by shale high-temperature expansion and hydraulic crack blocking caused by coking of shale oil and gas products are improved, meanwhile, high temperature is generated in the air gap breakdown effect generation process, further cracking of the oil shale target layer 39 in the central well network is facilitated, the permeability is further improved, the construction period is twenty-four hours, and then the high-frequency high-voltage transmitters 36 are closed;
step ten, starting a compressor 25 to supply air to a supercharger 30, injecting normal-temperature high-pressure air into an injection-production well I1 by the supercharger 30 to enable a target layer 39 of the oil shale to generate a local chemical reaction, enabling the target layer 39 of the oil shale to be in a continuous heating state through a self-heating chemical reaction, injecting gas discontinuously, wherein one period is twelve hours, the duration is ten days, and mixed products are extracted to the ground through an injection-production well II 2, an injection-production well III 3, an injection-production well IV 4, an injection-production well V5, an injection-production well VI 6, an injection-production well VII 7, an injection-production well VIII 8 and an injection-production well VII 9;
step eleven, opening a well head 14 annulus valve of the injection-production well I1, adjusting the pressure of the injection-production well I1 to be consistent with the pressure of a peripheral well pattern, taking the injection-production well II 2, the injection-production well III 3, the injection-production well IV 4, the injection-production well V5, the injection-production well VI 6, the injection-production well VII 7, the injection-production well VIII 8 and the injection-production well VII 9 as injection wells, injecting normal-temperature high-pressure air into the wells by a supercharger 30, injecting gas intermittently, wherein the gas injection period is twelve hours and the duration is five days, and further pyrolyzing the oil and gas products in the central well pattern by taking the residual heat of the oil shale target layer 39 as a heat source and extracting the oil and gas products to the ground surface through the injection-production well I1 for separation;
and step twelve, stopping gas injection after construction is finished, completing the recovery work of the continuous oil pipe 15, the heater 19, the insulating ceramic 20 and the breakdown electrode 21, and sealing all injection and production wells and the heating wells with cement.
Wherein, in the intermittent gas injection process of the step ten, when the thermal expansion effect and coking phenomenon of the target layer 39 of the heterogeneous oil shale are avoided within the twelve-hour interval of the gas injection, so that the formation flow conductivity between the first injection and production well and the peripheral second injection and production well is reduced, selecting the injection and production well with the largest flow reduction in the second injection and production well as an operation target according to the gas flow change condition in the second injection and production well, the gas migration track can move along the direction of the injection and production well with the maximum pressure difference gradient by closing the injection and production well and the adjacent injection and production well, forming a self-heating closed zone in the area with the largest flow change, further increasing the temperature in the self-heating closed zone formed by the closed zone, converting kerogen into coking asphaltene, then the oil gas is converted into cracked oil gas to escape from the stratum hole crack, the blockage removal is completed, and the closed and adjacent injection and production wells are opened to complete the extraction of oil gas products.
In conclusion, the four heating wells and the central injection and production well form a five-point well network, and heating and injection and production are respectively carried out, so that the problem of sealing failure caused by overlarge gas injection pressure in injection and production-heating integrated heating can be effectively solved, the invasion and corrosion of gases such as hydrogen sulfide and the like can be effectively prevented, the service life of the heater 19 is prolonged, and the probability of underground accidents is reduced. The heater 19 forms a stable hot wall 22 during operation, and the heat output of the hot wall 22 is stable and reliable.
The eight injection and production wells of the peripheral well pattern can change the oil and gas migration track through pressure regulation, specifically, the well head 14 is divided into two parts, namely a center part and an annular part, the center part is injected with gas, annular gas is exhausted, pressure regulation is realized by opening an annular valve, high-efficiency exploitation is realized, and meanwhile, the pressure is maintained at 0.3-1.0 Mpa, so that an effective gas stop sealed block 23 is formed, and oil and gas are prevented from escaping.
After the high-pressure breakdown system injects nitrogen and heats, an air gap breakdown effect is generated under the action of a high-pressure air medium, an oil shale target layer 39 between central well patterns is modified, hydraulic fracture closure and stratum blockage caused by oil shale thermal expansion of the oil shale target layer 39 are prevented, and a diversion channel is further expanded.
According to the invention, the breakdown electrode 21 is arranged at the bottom of the heater 19, the high-frequency high-voltage transmitter 36 is arranged on the ground, the oil shale target layer 39 is electrically broken down underground under a high-pressure air medium, the problem of closure of formation hydraulic cracks caused by thermal expansion of the oil shale target layer 39 and the problem of blockage of a flow guide channel caused by coking of organic matters are solved, the flow guide channel comprises collected hydraulic cracks and hole cracks generated by cracking of kerogen, the permeability of the oil shale target layer 39 is further increased, and the heat injection efficiency and the recovery ratio are obviously improved.
Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art will understand that various changes, modifications and substitutions can be made without departing from the spirit and scope of the invention as defined by the appended claims. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (9)
1. Oil shale composite heating normal position exploitation system, its characterized in that includes: heating system, ground gas injection system, well pattern system and high-voltage breakdown system in the well, wherein:
the heating system in the well comprises a continuous oil pipe (15), an upper sealing interlayer (16) in the well, a heater fixing layer (17), a lower sealing interlayer (18) in the well and a heater (19), wherein the upper sealing interlayer (16) in the well, the heater fixing layer (17) and the lower sealing interlayer (18) in the well are sequentially arranged from top to bottom, the heater fixing layer (17) is tightly contacted with the upper sealing interlayer (16) in the well and the lower sealing interlayer (18) in the well on two sides of the heater fixing layer to form sealing, the upper sealing interlayer (16) in the well and the lower sealing interlayer (18) in the well are both formed by pouring CA-50 aluminate high-strength cement, and the heater fixing layer (17) is formed by densely filling quartz sand; the heater (19) is arranged in the heating well and is positioned in the oil shale target layer (39) layer section, and the heater (19) is tightly contacted with the heater fixing layer (17) to form sealing; the continuous oil pipe (15) is in threaded connection with the heater (19);
the ground gas injection system comprises a nitrogen making machine (24), a compressor (25), a pressure stabilizing tank (29), a supercharger (30), an electric valve (31), a flow meter (32), a temperature sensor (33) and a pressure sensor (34), wherein the nitrogen making machine (24) and the compressor (25) are respectively connected with the gas inlet end of the pressure stabilizing tank (29) through a pipeline (35), and manual valves are respectively arranged between the nitrogen making machine (24) and the pressure stabilizing tank (29) and between the compressor (25) and the pressure stabilizing tank (29); the inlet end of a supercharger (30) is connected with the outlet end of a pressure stabilizing tank (29) through a pipeline (35), the outlet end of the supercharger (30) is communicated with a wellhead (14) of an injection and production well through the pipeline (35), and an electric valve (31), a flow meter (32), a temperature sensor (33) and a pressure sensor (34) are sequentially arranged on the pipeline (35) between the supercharger (30) and the injection and production well;
the well pattern system comprises injection and production wells and heating wells, the injection and production wells comprise first injection and production wells and second injection and production wells, the number of the first injection and production wells is one, the number of the second injection and production wells is eight, the number of the heating wells is four, the first injection and production wells and the four heating wells form a central well pattern, the central well pattern is arranged in a square five-point well pattern structure, the four heating wells are respectively positioned at four vertex positions of the square, and the first injection and production wells are positioned at the central position of the square; the eight second injection and production wells are uniformly distributed in an annular shape to form a peripheral well pattern surrounding the outside of the central well pattern;
the high-voltage breakdown system comprises insulating ceramics (20), a breakdown electrode (21), a high-frequency high-voltage emitter (36) and a transformer (37), wherein the upper part of the insulating ceramics (20) is in threaded connection with the heater (19), and the lower part of the insulating ceramics (20) is in threaded connection with the breakdown electrode (21); the transformer (37) is positioned on the earth surface, the transformer (37) is connected with an external power supply, and the transformer (37) is used for converting 380V three-phase voltage provided by the external power supply into 220V single-phase voltage; the input end of the high-frequency high-voltage transmitter (36) is connected with the output end of the transformer (37), the high-frequency high-voltage transmitter (36) is used for converting 220V voltage output by the transformer (37) into power frequency high voltage of 50kV and 50Hz, and the high-frequency high-voltage transmitter (36) is connected with the breakdown electrode (21) through an insulated copper-clad cable.
2. The oil shale combined heating in-situ mining system of claim 1, wherein: the plane of the upper surface of the downhole lower sealing layer (18) is higher than the plane of the bottom surface of the oil shale target layer (39), and the distance between the plane of the upper surface of the downhole lower sealing layer (18) and the plane of the bottom surface of the oil shale target layer (39) is 2 m; the plane of the top of the heater (19) is 5m away from the plane of the bottom surface of the upper cladding layer (38); the plane of the upper surface of the heater fixing layer (17) is lower than the plane of the bottom surface of the upper covering layer (38), the plane distance is different by 2m, the plane of the lower surface of the heater fixing layer (17) is higher than the plane of the top surface of the lower covering layer (40), and the plane distance is different by 2 m; the thickness of the downhole upper packing layer (16) is 10m in total, wherein the thickness of the downhole upper packing layer (16) in the oil shale target layer (39) is 2m, the thickness of the downhole upper packing layer (16) in the upper packing layer (38) is 8m, and the downhole upper packing layer (16) is in close contact with the heater fixing layer (17).
3. The oil shale combined heating in-situ mining system of claim 1, wherein: the flow meter (32) is a coriolis flow meter.
4. The oil shale combined heating in-situ mining system of claim 1, wherein: the side length of the square in the square five-point well pattern structure is 25 m; the distance between the second injection and production well and the first injection and production well is 100 m.
5. The oil shale combined heating in-situ mining system of claim 1, wherein: and the pressure in the eight second injection and production wells is maintained between 0.3MPa and 1.0 MPa.
6. The oil shale combined heating in-situ mining system of claim 1, wherein: the heating well, the first injection and production well and the second injection and production well are drift diameter vertical wells, the well diameter of the heating well is 311mm, and the well diameter of the first injection and production well and the well diameter of the second injection and production well are 244 mm.
7. The oil shale combined heating in-situ mining system of claim 1, wherein: the oil shale target layer (39) is located 467 m-488 m underground.
8. The oil shale composite heating in-situ mining method is characterized in that the method is based on the oil shale composite heating in-situ mining system of any one of claims 1 to 7, and specifically comprises the following steps, and the following steps are carried out in sequence:
step one, selecting an oil shale in-situ mining block;
drilling nine injection-production wells in the selected oil shale in-situ production block, performing fracturing construction on oil shale in a layer (39) of an oil shale target layer from the injection-production wells to complete reservoir transformation, performing connectivity test, and entering the next step after the test is qualified;
drilling four heating wells in the oil shale in-situ mining block;
injecting CA-50 aluminate high-strength cement into all the heating wells until the bottom surface of the oil shale target layer (39) faces downwards by 2m from the normal direction, and forming an in-well lower sealing interlayer (18) after curing;
fifthly, the heater (19) is in threaded connection with the coiled tubing (15), the heater (19) is conveyed to the target position of the heating well through the coiled tubing (15) through ground cable car equipment, quartz sand is filled into the heating well and is vibrated and compacted to form a heater fixing layer (17);
injecting CA-50 aluminate high-strength cement into all the heating wells, pouring 10m in total, wherein the layer section of a target layer (39) of the oil shale corresponds to 2m, the layer section of an upper covering layer (38) corresponds to 8m, forming an inner upper sealing interlayer (16) after curing, installing well heads (14) of the heating wells and completing the connection of pipelines (35);
seventhly, starting heaters (19) in all the heating wells to heat the oil shale target layer (39), wherein the operation period is five days;
step eight, in a first mining period, starting a nitrogen making machine (24), wherein the first injection and production well is used as an injection well, high-purity nitrogen is injected into the first injection and production well through a supercharger (30), the purity of the high-purity nitrogen is more than or equal to 99.7%, the high-purity nitrogen is heated through a heating area of an oil shale target layer (39), the heated nitrogen heats an oil shale target layer (39) layer section, oil shale cracking of the oil shale target layer (39) layer section is accelerated, eight second injection and production wells are used as extraction wells, oil-gas mixed products are extracted to the ground from the extraction wells, and the operation period is ten days;
step nine, turning off heaters (19) in all the heating wells, starting a high-frequency high-voltage transmitter (36), transmitting an electric signal to breakdown electrodes (21) of all the heating wells through insulated copper sheet cables by the high-frequency high-voltage transmitter (36), shielding the contact between the heaters (19) and the breakdown electrodes (21) by insulating ceramics (20), generating an air gap breakdown effect inside an oil shale target layer (39) under a high-temperature high-voltage atmosphere, breaking the oil shale target layer (39) by electric breakdown, generating the air gap breakdown effect along with high temperature in the generation process, wherein the construction period is twenty-four hours, and then turning off the high-frequency high-voltage transmitter (36);
step ten, in a second mining period, starting a compressor (25), supplying gas to a supercharger (30) by the compressor (25), injecting normal-temperature and high-pressure air into a first injection and production well by the supercharger (30) to enable a target layer (39) of the underground oil shale to generate local chemical reaction, enabling the target layer (39) of the oil shale to be in a continuous heating state through self-heating chemical reaction, and intermittently injecting gas, wherein one gas injection period is twelve hours, the duration is ten days, and oil-gas mixed products are extracted to the ground through eight second injection and production wells;
step eleven, opening a wellhead (14) annulus valve of the first injection and production well, adjusting the pressure of the first injection and production well to be consistent with the pressure of a peripheral well pattern, taking eight second injection and production wells as injection wells, injecting normal-temperature high-pressure air into the wells by a supercharger (30), injecting gas discontinuously, wherein one gas injection period is twelve hours and the duration is five days, and further pyrolyzing the oil-gas mixed product in the central well pattern by using the residual heat of an oil shale target layer (39) as a heat source and extracting the oil-gas mixed product to the ground surface through the first injection and production well for separation;
and step twelve, stopping gas injection after construction is finished, completing the recovery work of the coiled tubing (15), the heater (19), the insulating ceramic (20) and the breakdown electrode (21), and sealing all the injection and production wells and the heating well by cement.
9. The oil shale composite heating in-situ mining method according to claim 8, characterized in that: in the intermittent gas injection process, when the formation flow conductivity between a first injection and production well and a peripheral second injection and production well is reduced due to the thermal expansion effect and coking phenomenon of a target layer (39) of heterogeneous oil shale within a twelve-hour interval of gas injection, the injection and production well with the largest flow reduction in the second injection and production well is selected as an operation target according to the gas flow change condition in the second injection and production well, the injection and production well and the adjacent injection and production well are closed, so that the gas migration track moves along the direction of the maximum pressure difference gradient injection and production well, a self-heating closed area is formed in the area with the largest flow change, the temperature in the self-closed area generated heat is increased, kerogen is converted into coking asphaltene and then converted into cracked oil gas to escape from stratum pore cracks, the blockage is removed, and the closed and adjacent injection and production wells are opened, and the extraction of oil gas products is completed.
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