Mining method and system for oil shale stratum

Abstract

The invention provides a mining method for an oil shale stratum, which comprises the following steps of: 1, drilling a mining well from the earth surface to a target oil shale stratum, artificially forming fractures to form fracturing fractures in the target oil shale stratum, and forming a suction channel in the mining well; secondly, a hot well is drilled and injected in the area corresponding to the fracturing crack; thirdly, a ground auxiliary equipment device is installed at a well mouth of the heat injection well; fourthly, according to the stratum depth, a heating device is installed in the heat injection well; 5, the ground auxiliary equipment device is started, high-pressure water flow and alkali powder are injected into the heating device to generate chemical reaction, so that heat is released to heat the external target oil shale layer, fluid generated by the reaction enters the fracturing crack, and the fracturing crack is expanded into a corrosion crack; and 6, shale oil produced by the target oil shale layer enters the mining well through the corrosion cracks, and oil extraction production is conducted through the suction channel. The invention further provides a mining system used in the mining method for the oil shale stratum.

Description

Technical Field

[0001] The present invention belongs to the technical field of in-situ mining of oil shale formations, and specifically relates to a mining method and mining system for oil shale formations, especially an in-situ critical water-alkali corrosion catalytic reaction thermal composite mining method and mining system for oil shale. Background Art

[0002] The increase in energy demand and the low reserves of petroleum resources have made the exploitation and utilization of alternative energy sources extremely urgent. Oil shale is a fine-grained sedimentary rock rich in organic matter (kerogen). After heating, the organic matter inside can be converted into shale oil and gas. Due to its abundant reserves and wide distribution, it has attracted much attention as an unconventional alternative energy source. Compared with directly burning oil shale as a power generation fuel for power generation, the more promising approach at present is to produce shale oil and shale gas by ground distillation and underground in-situ pyrolysis. Among them, underground in-situ pyrolysis technology directly heats underground oil shale formations to extract liquid or gaseous hydrocarbons. It has the advantages of avoiding environmental pollution and greatly reducing costs, and is considered to be the most promising oil shale mining technology.

[0003] In recent years, more than ten oil shale in-situ conversion technologies have been proposed at home and abroad, such as Shell's ICP technology, ExxonMobil's ElectroFractTM technology, Chevron's Crush technology, etc. However, due to the influence of uncertainties and unfavorable factors such as complex underground equipment, high cost, and long heating time, all oil shale in-situ conversion technologies are still in the research and development stage and cannot meet the requirements of commercial mining. Existing oil shale in-situ mining methods have problems such as slow heat transfer rate, low heating efficiency, long mining cycle, and high cost. Summary of the invention

[0004] In response to the technical problems mentioned above, the present invention aims to propose a mining method and mining system for oil shale formations, which can effectively improve the heat transfer rate, improve the heating efficiency, reduce the mining cycle, and can significantly improve the output rate of oil shale formations, effectively reducing production costs.

[0005] To this end, according to a first aspect of the present invention, there is provided a method for mining oil shale formations, comprising the following steps:

[0006] Step 1: drilling a production well from the surface to the target oil shale layer, and artificially creating fractures through the production well to form a hydraulic fracture in the target oil shale layer, and forming a suction channel in the production well;

[0007] Step 2: drilling a hot well in the area corresponding to the hydraulic fracture;

[0008] Step 3: installing a ground auxiliary equipment device at the wellhead of the heat injection well;

[0009] Step 4: installing a heating device in the heat injection well according to the depth of the formation;

[0010] Step 5: starting the ground auxiliary equipment device, injecting high-pressure water flow and alkali powder into the heating device to generate a chemical reaction, thereby releasing heat to heat the target oil shale layer, and the fluid generated by the reaction enters the hydraulic fracture, so that the hydraulic fracture expands into a corrosion fracture;

[0011] Step six: the shale oil produced from the target oil shale layer enters the production well through the corrosion cracks, and oil production is carried out through the suction channel.

[0012] In one embodiment, in step one, hydraulic fracturing is used to artificially create fractures.

[0013] In one embodiment, when there are one or two extraction wells, the extraction well and the heat injection well are distributed in a straight line; when there are multiple extraction wells, the heat injection well is set at the center position of the multiple extraction wells so that the multiple extraction wells are evenly distributed around the heat injection well.

[0014] In one embodiment, in step four, the heating device is extended to correspond to the fracture area of ​​the target oil shale layer.

[0015] In one embodiment, in step five, the fluid generated by the reaction between high-pressure water flow and alkali powder includes critical state water, alkaline solution and hydrogen, and a part of the heat released by the reaction is directly transferred outward to heat the target oil shale layer, and the other part is transferred with the fluid generated by the reaction and then to the hydraulic fracture to heat the target oil shale formation again.

[0016] In one embodiment, the heat released by the reaction between the high-pressure water flow and the alkali powder can heat the target oil shale layer to 300-500°C, the concentration of the generated alkaline solution is 0.1-1 mol / L, and the pressure of the high-pressure water flow is 3-20 MPa.

[0017] According to a second aspect of the present invention, there is provided a production system for use in the production method for an oil shale formation as described above, comprising:

[0018] The heating device comprises a water injection unit, an alkali thermal reaction unit and a heat injection unit which are sequentially connected from top to bottom, wherein the water injection unit comprises a high-pressure water flow channel and an alkali powder injection channel; wherein the high-pressure water flow and the alkali powder can be respectively injected into the alkali thermal reaction unit through the high-pressure water flow channel and the alkali powder injection channel, and contact and chemically react in the alkali thermal reaction unit to release heat, and the fluid generated by the reaction enters the fracture through the heat injection unit.

[0019] In one embodiment, the water injection unit includes a main body, a first axial through hole is provided at the center of the main body to form the alkali powder injection channel, and a first axial annular space penetration portion is provided on the radial outside of the alkali powder injection channel to form the high-pressure water flow channel, and a pressure valve is provided at the lower end of the high-pressure water flow channel.

[0020] In one embodiment, the alkali thermal reaction unit includes an alkali thermal reaction chamber outer tube, a baffle disposed inside the alkali thermal reaction chamber outer tube, and a bottom filter plate fixedly connected to the lower end of the baffle.

[0021] In one embodiment, the heat injection unit includes a heat injection chamber outer tube, a heat injection chamber is formed inside the heat injection chamber, and a plurality of through heat injection holes are evenly opened on the side wall of the heat injection chamber outer tube, and the fluid generated by the reaction enters the fracture through the heat injection holes.

[0022] In one embodiment, a ground auxiliary equipment device is further included for injecting high-pressure water flow and alkali powder into the heating device, which includes a water supply unit connected to the high-pressure water flow channel and an alkali powder supply unit connected to the alkali powder injection channel.

[0023] In one embodiment, the water supply unit includes a water source, a water pump and a booster pump.

[0024] Wherein, the water source, the water pump and the booster pump are connected through a water injection pipeline, and the tail end of the water injection pipeline is connected to the high-pressure water flow channel.

[0025] In one embodiment, the alkali powder supply unit includes a high-pressure conveyor and a high-pressure conveying pipeline, and the high-pressure conveyor is connected to the alkali powder injection channel through the high-pressure conveying pipeline.

[0026] In one embodiment, it also includes a production device, which includes an oil storage tank installed at the wellhead of the production well, an oil extraction pipeline arranged in the production well and extending to the bottom, and an oil extraction pump connected between the oil storage tank and the oil extraction pipeline.

[0027] Compared with the prior art, the advantages of this application are:

[0028] The mining method for oil shale formation according to the present invention realizes the in-situ critical water alkali corrosion catalytic reaction thermal composite mining of oil shale by combining critical water, alkali corrosion, chemical heating and catalysis, which are beneficial to the in-situ mining of oil shale. The mining method is mined by a mining system formed by a heating device, a ground auxiliary equipment device and a mining device, which makes the mining method have the advantages of simple process, short mining cycle, wide application and high recovery rate. Demineralization treatment of oil shale formation by alkali corrosion can effectively deal with the thermal expansion problem of oil shale during heating. At the same time, the reaction heat released by the reaction of alkali and water, as well as the generated alkaline solution and hydrogen and other products are fully utilized, and the alkaline solution and hydrogen and other products have a catalytic effect on the cracking of oil shale. The high-pressure critical water generated after heating has a good dissolving and carrying effect on oil and gas products, which can greatly improve the oil and gas recovery rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The present invention will be described below with reference to the accompanying drawings.

[0030] Figure 1 It is a schematic diagram of the mining method for oil shale formation according to the present invention.

[0031] Figure 2 The present invention discloses a structure of a heating device used in an oil shale formation mining system.

[0032] Figure 3 yes Figure 2 A cross-sectional view with A-A' as the cut plane is shown in the figure of the heating device for use in the oil shale formation production system according to the present invention.

[0033] Figure 4 yes Figure 2 A partially enlarged view of the water injection unit and related parts in the heating device in the production system for oil shale formations according to the present invention.

[0034] In the present application, all drawings are schematic drawings, which are only used to illustrate the principles of the present invention and are not drawn according to the actual scale. DETAILED DESCRIPTION

[0035] The present invention will be described below with reference to the accompanying drawings.

[0036] For ease of understanding, in this application, the end close to the wellhead is defined as the upper end, the upstream end or similar terms, and the end away from the wellhead is defined as the lower end, the downstream end or similar terms. At the same time, the length direction along the heating device in the mining system for oil shale formations is called the longitudinal direction, the axial direction or similar terms, and the direction perpendicular thereto is called the lateral direction, the radial direction or similar terms. It should also be noted that the directional terms or qualifiers "upper", "lower", etc. used in this application are all directed to the attached drawings to which they are referred. Figure 1 The above description is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention.

[0037] Figure 1 The schematic diagram of the method for exploiting oil shale formation according to the present invention is shown in FIG. The method for exploiting oil shale formation according to the present invention mainly includes a drilling and completion stage, an equipment installation stage and a production stage. Each stage is described in detail below.

[0038] In the drilling and completion stage, first, a production well 92 is drilled from the surface to the target oil shale layer 7, and artificial fractures are created through the production well 92 to form fractures in the target oil shale layer 7, thereby forming a fracturing area. Figure 1 As shown, the strata in the mining area are, from top to bottom, an overlying stratum 6, an oil shale layer 7, and an underlying stratum 8. A mining well 92 is drilled from the ground, passes through the oil shale layer 7, and extends downward into the region of the underlying stratum 8. A suction channel is formed in the mining well 92. In one embodiment, hydraulic fracturing is used to artificially create fractures in the mining well 92.

[0039] Then, a heat injection well 91 is drilled in the area corresponding to the fracture. Specifically, a heat injection well 91 is drilled from the surface to the fractured area in the target oil shale layer 7. The heat injection well 91 enters the oil shale layer 7, and the lower end of the heat injection well 91 extends to the bottom area near the oil shale layer 7.

[0040] According to the present invention, the specific number of the mining wells 92 and the heat injection wells 91 can be selected according to the actual working conditions. When there are one or two mining wells 92, the mining wells 92 and the heat injection wells 91 are distributed in a straight line. In particular, when there are two mining wells 92, the heat injection well 91 is located in the middle of the line connecting the two mining wells 92. When there are multiple mining wells 92, the heat injection well 91 is set at the center of the multiple mining wells 92, so that the multiple mining wells 92 are evenly distributed around the heat injection well 91. For example, the multiple mining wells 92 can be distributed in a triangle, quadrilateral, hexagonal, circular or other annular shape with the heat injection well 91 as the center.

[0041] After the drilling and completion phase is completed, the equipment installation phase begins. First, the ground auxiliary equipment device 4 is installed at the wellhead of the heat injection well 91. At the same time, the production device is installed at the wellhead of the production well 92. The production device will be described in detail below.

[0042] Then, according to the formation depth, a heating device 100 is installed in the heat injection well 91. The heating device 100 extends to correspond to the fracture area of ​​the target oil shale layer 7.

[0043] After that, the production phase begins. In the production phase, the ground auxiliary equipment device 4 is started, and high-pressure water and alkali powder 46 are injected into the heating device 100 to generate a chemical reaction, thereby releasing heat to heat the target oil shale layer 7 outside, and the fluid generated by the reaction enters the fracture, causing the fracture to expand into a corrosion fracture 71. The alkali powder is, for example, nano alkali powder.

[0044] Afterwards, the shale oil 93 produced by the target oil shale layer 7 enters the production well 92 through the corrosion cracks 71, and then is produced through the suction channel.

[0045] According to the present invention, the fluid generated by the reaction between high-pressure water flow and alkali powder includes critical state water, alkaline solution and hydrogen. Part of the heat released by the reaction is directly transferred to the outside to heat the target oil shale layer 7, and the other part is transferred with the fluid generated by the reaction to heat the target oil shale formation 7 again by fracture.

[0046] Specifically, after the high-pressure water flow contacts the nano-alkali powder 46, a chemical reaction occurs, releasing a large amount of heat and generating a large amount of alkaline solution and hydrogen, and the high-pressure water flow is then transformed into a critical state. A large amount of heat generated by the reaction is carried by the critical state water, alkaline solution and hydrogen through the external connecting pipe 21 (see below) in the heating device 100 to the external formation to heat the target oil shale layer 7. At the same time, the critical state water, a large amount of alkaline solution and hydrogen enter the fracture through the heat injection hole 32 (see below) on the heating device 100, and heat the target oil shale formation 7 again. At the same time, the alkaline solution can corrode the quartz minerals in the formation, so that the fracture cracks are expanded into corrosion cracks 71, thereby overcoming the thermal expansion problem generated by the target oil shale layer 7 during the heating process, and the catalytic effect of the alkali and hydrogen jointly promotes the cracking of kerogen. At the same time, critical water has the effect of dissolving and extracting organic matter, which can better help the oil and gas products to migrate outward. Under the above-mentioned combined action, the shale oil 93 produced by the target oil shale layer 7 enters the production well 92 through the corrosion cracks 71. Then, it is sucked into the oil storage tank 52 through the oil pumping pipeline 53 by the oil pump 51 in the production device, thereby achieving the purpose of producing the oil shale formation.

[0047] According to the present invention, during the production stage, the heat released by the reaction between the high-pressure water flow and the alkali powder can heat the adjacent oil shale layer in the target oil shale layer 7 to 300-500° C. The concentration of the generated alkaline solution is 0.1-1 mol / L. The pressure of the high-pressure water flow is 3-20 MPa.

[0048] The present invention also provides a production system 200 for oil shale formations, and the production system 200 is applied in the production method for oil shale formations as described above. The production system 200 includes a heating device 100. Figure 2As shown, the heating device 100 includes a water injection unit 1, an alkali thermal reaction unit 2 and a heat injection unit 3 connected in sequence from top to bottom, and the water injection unit 1 includes a high-pressure water flow channel 15 and an alkali powder injection channel 25. High-pressure water and alkali powder can be injected into the alkali thermal reaction unit 2 through the high-pressure water flow channel 15 and the alkali powder injection channel 25 respectively, and contact in the alkali thermal reaction unit 2 to produce a chemical reaction to release heat, and the fluid generated by the reaction enters the fracture through the heat injection unit 3.

[0049] like Figure 2 As shown, the water injection unit 1 includes a main body, a first axial through hole is provided at the center of the main body to form an alkali powder injection channel 25, and a first axial annular through portion is provided on the radial outer side of the alkali powder injection channel 25 to form a high-pressure water flow channel 15, and a pressure valve 14 is provided at the lower end of the high-pressure water flow channel 15.

[0050] like Figures 2 to 4 As shown, in one embodiment, the water injection unit 1 includes an upper joint 11, a water injection connecting pipe 12, a lower joint 13 and a pressure valve 14. The water injection connecting pipe 12 is constructed as a double-layer tube structure including an inner tube 121 and an outer tube 122, and there is a certain interval between the inner tube 121 and the outer tube 122, and the inner tube 121 and the outer tube 122 are connected by a connecting shaft (not shown). In this way, an alkali powder injection channel 25 is formed in the inner tube 121 of the water injection connecting pipe 12, and a high-pressure water flow channel 15 is formed between the inner tube 121 and the outer tube 122 of the water injection connecting pipe 12. Threads are provided at the upper and lower sides of the water injection connecting pipe 12, so that the upper joint 11, the water injection connecting pipe 12 and the lower joint 13 can be threadedly connected, and the outer part of the upper joint 11 is threadedly connected to the upper inner side of the outer connecting pipe 21 (see below) in the alkali thermal reaction unit 2. The outer diameters of the water injection connecting pipe 12 and the lower joint 13 are the same as the inner diameter of the outer connecting pipe 21. The pressure valve 14 is installed at the bottom of the lower joint 13. The upper joint 11, the water injection connecting pipe 12 and the lower joint 13 together form a main pipe body.

[0051] like Figure 2As shown, the alkali thermal reaction unit 2 includes an external connection pipe 21, an alkali thermal reaction chamber outer pipe 22, a baffle 23 and a bottom filter plate 24. The upper portion of the external connection pipe 21 is threadedly connected to the upper joint 11, and the lower portion is threadedly connected to the upper portion of the alkali thermal reaction chamber outer pipe 22. The lower portion of the alkali thermal reaction chamber outer pipe 22 is threadedly connected to the upper portion of the heat injection chamber outer pipe 31 (see below) in the heat injection unit 3. The baffle 23 is preferably a strip plate, a cross-arranged plate or a spiral plate, and is at least partially located inside the alkali thermal reaction chamber outer pipe 22, and the bottom is welded to the bottom filter plate 24. An alkali thermal reaction chamber 26 is formed between the inside of the alkali thermal reaction chamber outer pipe 22 and the bottom filter plate 24. By arranging the baffle 23 in the alkali thermal reaction chamber 26, the high-pressure water flow and the alkali powder 46 can be fully contacted in the alkali thermal reaction chamber 26, promoting chemical reaction and improving reaction efficiency.

[0052] Preferably, the alkali-thermal reaction chamber outer tube 22, baffle 23, bottom filter plate 24 and heat injection chamber outer tube 31 in the alkali-thermal reaction unit 2 are all made of high-temperature resistant and alkali-corrosion resistant materials, or anti-alkali-corrosion coatings are added to the outer surfaces to ensure that they have good high-temperature resistance and alkali-corrosion resistance.

[0053] In actual use, multiple water injection connecting pipes 12 and alkali-thermal reaction chamber outer pipes 22 can be installed according to the depth of the formation until the alkali-thermal reaction unit 2 and the heat injection unit 3 can be kept inside the oil shale layer 7.

[0054] like Figure 2 As shown, the heat injection unit 3 includes a heat injection bin outer tube 31, a heat injection bin 33 is formed inside the heat injection bin outer tube 31, and a plurality of through heat injection holes 32 are evenly opened on the side wall of the heat injection bin outer tube 31, and the fluid generated by the reaction enters the fracture through the heat injection holes 32. The upper portion of the heat injection bin outer tube 31 is threadedly connected to the lower portion of the alkali thermal reaction bin outer tube 22.

[0055] According to the present invention, the mining system 200 for oil shale formations also includes a ground auxiliary equipment device 4 for injecting high-pressure water flow and alkali powder into the heating device 100, and the ground auxiliary equipment device 4 includes a water supply unit connected to the high-pressure water flow channel 15, and an alkali powder supply unit connected to the alkali powder injection channel 25.

[0056] like Figure 1 As shown, the water supply unit includes a water source 45, a water pump 41 and a booster pump 42, the water source 45, the water pump 41 and the booster pump 42 are connected through a water injection pipe 44, and the tail end of the water injection pipe 44 is connected to the high-pressure water flow channel 15 in the heating device 100. The alkali powder supply unit includes a high-pressure conveyor 43 and a high-pressure conveying pipe 47, and the high-pressure conveyor 43 is connected to the alkali powder injection channel 25 through the high-pressure conveying pipe 47.

[0057] The production system 200 for oil shale formation according to the present invention further includes a production device, which includes an oil storage tank 52 installed at the wellhead of the production well 92, an oil extraction pipeline 53 arranged in the production well 92 and extending to the bottom, and an oil extraction pump 51 connected between the oil storage tank 52 and the oil extraction pipeline 53. Specifically, Figure 1 As shown, the upper part of the oil pumping pipeline 53 is connected to the front end of the oil pump 51, and the lower part of the oil pumping pipeline 53 penetrates into the shale oil 93. The rear end of the oil pump 51 is connected to the oil storage tank 52.

[0058] According to the present invention, the heating device 100 is assembled by a water injection unit 1, an alkali thermal reaction unit 2 and a heat injection unit 3 to form a critical water alkali corrosion catalytic reaction thermal composite heater, and a ground auxiliary equipment device 4 and a mining device constitute supporting equipment for the critical water alkali corrosion catalytic reaction thermal composite heater.

[0059] The following describes in detail the mining method and mining system 200 for oil shale formations according to different embodiments of the present invention.

[0060] Embodiment 1:

[0061] In Example 1, two production wells 92 and one heat injection well 91 are drilled to form a three-well structure. The quartz content in the oil shale layer is relatively high, and the injected alkali powder is sodium hydroxide.

[0062] In the drilling and completion stage: First, two production wells 92 are drilled from the surface to the target oil shale layer 7, and hydraulic fracturing is used to artificially create fractures in the production wells 92 to form fractures. Shale oil suction channels are formed in the production wells 92. Then, a heat injection well 91 is drilled in the center of the two production wells 92, and a fluid injection channel is formed in the heat injection well 91.

[0063] After the well drilling and completion phase is completed, the equipment installation phase is entered: first, the ground auxiliary equipment device 4 is installed at the wellhead of the heat injection well 91, and the water pump 41, the booster pump 42, the high-pressure conveyor 43, and the water injection pipeline 44 are installed on the ground at the wellhead of the heat injection well 91. Specifically, the water source 45, the water pump 41 and the booster pump 42 are connected through the water injection pipeline 44, and the tail end of the water injection pipeline 44 is connected to the high-pressure water flow channel 15. The high-pressure conveyor 43 is connected to the nano alkali powder 46 through the high-pressure delivery pipeline 47, and the tail end of the high-pressure delivery pipeline 47 is connected to the alkali powder injection channel 25. Thus, the installation of the ground auxiliary equipment device 4 is completed.

[0064] At the same time, the mining device is installed at the wellhead of the mining well 92. The oil pump 51, the oil storage tank 52 and the oil extraction pipeline 53 are installed on the ground at the wellhead of the mining well 92. Specifically, the upper part of the oil extraction pipeline 53 is connected to the front end of the oil pump 51, and the lower part is deep into the shale oil 93. The rear end of the oil pump 51 is connected to the oil storage tank 52. Thus, the installation of the mining device is completed.

[0065] Then, the heating device 100 is installed in the heat injection well 91. Specifically, according to the formation depth, an appropriate number of water injection system connecting pipes 12 and alkali thermal reaction chamber outer pipes 22 are installed to ensure that the heating device 100 extends to the corresponding fracture area of ​​the target oil shale layer 7, and the alkali thermal reaction unit 2 and the heat injection unit 3 of the heating device 100 are kept inside the oil shale layer 7.

[0066] After that, the production stage is entered. In the production stage, the ground auxiliary equipment device 4 is started, and nano sodium hydroxide is injected into the alkali thermal reaction chamber 26 through the alkali powder injection channel 25. At the same time, high-pressure water is injected into the alkali thermal reaction chamber 26 through the high-pressure water flow channel 15. After the high-pressure water flow contacts the nano sodium hydroxide in the alkali thermal reaction chamber 26 of the heating device 100, a chemical reaction occurs, releasing a large amount of heat, and generating a large amount of alkaline sodium hydroxide solution and hydrogen, and the high-pressure water flow is also transformed into a critical state. The ratio of nano sodium hydroxide to water is adjusted so that the concentration of the generated alkaline sodium hydroxide solution is 0.5 mol / L. The heat released by the reaction can heat the target oil shale layer 7 outside, and the fluid generated by the reaction enters the pressure fracture, causing the pressure fracture to expand into a corrosion crack 71.

[0067] Specifically, under the action of the baffle 23, a large amount of heat generated by the reaction is carried by the critical water, alkaline sodium hydroxide solution and hydrogen through the flow in the baffle 23 and transferred to the external formation through the external connecting pipe 21, heating the target oil shale layer 7 outside. At the same time, the critical water, a large amount of alkaline sodium hydroxide solution and hydrogen enter the interior of the heat injection bin 33 through the bottom filter plate 24, and then enter the pressure fracture through the heat injection hole 32 on the outer pipe 31 of the heat injection bin, heating the target oil shale formation 7 again. At the same time, the alkaline sodium hydroxide solution can corrode the quartz minerals in the formation, so that the pressure fracture expands into a corrosion fracture 71, thereby overcoming the thermal expansion problem generated by the target oil shale layer 7 during the heating process, and the catalytic effect of sodium hydroxide and hydrogen jointly promotes the cracking of kerogen. In addition, critical water has the effect of dissolving and extracting organic matter, which can better help the oil and gas products to migrate outward.

[0068] Under the above-mentioned combined action, the shale oil 93 produced by the target oil shale layer 7 enters the production well 92 through the corrosion cracks 71. Then, it is sucked into the oil storage tank 52 by the oil pump 51 through the oil pumping pipeline 53, thereby achieving the purpose of exploiting the oil shale formation and realizing oil production.

[0069] Implementation Case 2:

[0070] In Example 2, three production wells 92 and one heat injection well 91 are drilled to form a group of wells. The quartz content in the oil shale layer is relatively low, and the injected alkali powder is potassium hydroxide.

[0071] In the drilling and completion stage: First, three production wells 92 are drilled from the surface to the target oil shale layer 7, arranged in an equilateral triangle, and artificial fractures are created in the production wells 92 by hydraulic fracturing to form fractures. Shale oil suction channels are formed in the production wells 92. A heat injection well 91 is drilled in the center of the three production wells 92, and a fluid injection channel is formed in the heat injection well 91.

[0072] After the well drilling and completion phase is completed, the equipment installation phase is entered: first, the ground auxiliary equipment device 4 is installed at the wellhead of the heat injection well 91, and the water pump 41, the booster pump 42, the high-pressure conveyor 43, and the water injection pipeline 44 are installed on the ground at the wellhead of the heat injection well 91. Specifically, the water source 45, the water pump 41 and the booster pump 42 are connected through the water injection pipeline 44, and the tail end of the water injection pipeline 44 is connected to the high-pressure water flow channel 15. The high-pressure conveyor 43 is connected to the nano alkali powder 46 through the high-pressure delivery pipeline 47, and the tail end of the high-pressure delivery pipeline 47 is connected to the alkali powder injection channel 25. Thus, the installation of the ground auxiliary equipment device 4 is completed.

[0073] At the same time, the mining device is installed at the wellhead of the mining well 92. The oil pump 51, the oil storage tank 52 and the oil extraction pipeline 53 are installed on the ground at the wellhead of the mining well 92. Specifically, the upper part of the oil extraction pipeline 53 is connected to the front end of the oil pump 51, and the lower part is deep into the shale oil 93. The rear end of the oil pump 51 is connected to the oil storage tank 52. Thus, the installation of the mining device is completed.

[0074] Then, the heating device 100 is installed in the heat injection well 91. Specifically, according to the formation depth, an appropriate number of water injection connecting pipes 12 and alkali thermal reaction chamber outer pipes 22 are installed to ensure that the heating device 100 extends to the corresponding fracture area of ​​the target oil shale layer 7, and the alkali thermal reaction unit 2 and the heat injection unit 3 of the heating device 100 are kept inside the oil shale layer 7.

[0075] After that, the production stage is entered. In the production stage, the ground auxiliary equipment device 4 is started, and nano potassium hydroxide is injected into the alkali thermal reaction chamber 26 through the alkali powder injection channel 25. At the same time, a high-pressure water flow is injected into the alkali thermal reaction chamber 26 through the high-pressure water flow channel 15. After the high-pressure water flow contacts the nano potassium hydroxide in the alkali thermal reaction chamber 26 of the heating device 100, a chemical reaction occurs, releasing a large amount of heat, and generating a large amount of alkaline potassium hydroxide solution and hydrogen, and the high-pressure water flow is also transformed into a critical state. The ratio of nano potassium hydroxide to water is adjusted so that the concentration of the generated alkaline potassium hydroxide solution is 0.2 mol / L. The heat released by the reaction can heat the target oil shale layer 7 outside, and the fluid generated by the reaction enters the pressure fracture, causing the pressure fracture to expand into a corrosion crack 71.

[0076] Specifically, under the action of the baffle 23, a large amount of heat generated by the reaction is carried by the critical water, alkaline potassium hydroxide solution and hydrogen through the flow in the baffle 23 and transferred to the external formation through the external connecting pipe 21, heating the target oil shale layer 7 outside. At the same time, the critical water, a large amount of alkaline potassium hydroxide solution and hydrogen enter the interior of the heat injection bin 33 through the bottom filter plate 24, and then enter the pressure fracture through the heat injection hole 32 on the outer pipe 31 of the heat injection bin, heating the target oil shale formation 7 again. At the same time, the alkaline potassium hydroxide solution can corrode the quartz minerals in the formation, so that the pressure fracture expands into a corrosion fracture 71, thereby overcoming the thermal expansion problem generated by the target oil shale layer 7 during the heating process, and the catalytic effect of potassium hydroxide and hydrogen jointly promotes the cracking of kerogen. In addition, critical water has the effect of dissolving and extracting organic matter, which can better help the oil and gas products to migrate outward.

[0077] Under the above-mentioned combined action, the shale oil 93 produced by the target oil shale layer 7 enters the production well 92 through the corrosion cracks 71. Then, it is sucked into the oil storage tank 52 by the oil pump 51 through the oil pumping pipeline 53, thereby achieving the purpose of exploiting the oil shale formation and realizing oil production.

[0078] The mining method for oil shale formation according to the present invention realizes the in-situ critical water alkali corrosion catalytic reaction thermal composite mining of oil shale by combining critical water, alkali corrosion, chemical heating and catalysis, which are beneficial to the in-situ mining of oil shale. The mining method is mined by a mining system formed by a heating device 100, a ground auxiliary equipment device 4 and a mining device, which makes the mining method have the advantages of simple process, short mining cycle, wide application and high recovery rate. Demineralization treatment of oil shale formation by alkali corrosion can effectively deal with the thermal expansion problem of oil shale during heating. At the same time, the reaction heat released by the reaction of alkali and water, as well as the generated alkaline solution and hydrogen and other products, are fully utilized, and the alkaline solution and hydrogen and other products have a catalytic effect on the cracking of oil shale. The high-pressure critical water generated after heating has a good dissolving and carrying effect on oil and gas products, which can greatly improve the oil and gas recovery rate.

[0079] In the description, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0080] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0081] In addition, in the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0082] Finally, it should be noted that the above is only a preferred embodiment of the present invention and does not constitute any limitation to the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for a person skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for mining oil shale formations, comprising the following steps: Step 1: drilling a production well (92) from the surface to the target oil shale layer (7), and artificially creating fractures through the production well (92) to form pressure fractures in the target oil shale layer (7), and forming a suction channel in the production well (92); Step 2: drilling a hot well (91) in the area corresponding to the hydraulic fracture; Step 3: installing a surface auxiliary equipment device (4) at the wellhead of the heat injection well (91); Step 4: installing a heating device (100) in the heat injection well (91) according to the depth of the formation; Step 5: Start the ground auxiliary equipment device (4), inject high-pressure water flow and alkali powder into the heating device (100) to generate a chemical reaction, thereby releasing heat to heat the target oil shale layer (7), and the fluid generated by the reaction enters the pressure fracture, causing the pressure fracture to expand into a corrosion fracture (71); Step six: the shale oil (93) produced by the target oil shale layer (7) enters the production well (92) through the corrosion cracks (71), and oil production is carried out through the suction channel.

2. The method for mining oil shale formation according to claim 1, characterized in that: In the step 1, artificial fractures are created by hydraulic fracturing.

3. The method for mining oil shale formation according to claim 1 or 2, characterized in that: When there are one or two extraction wells (92), the extraction wells (92) and the heat injection wells (91) are distributed in a straight line; when there are multiple extraction wells (92), the heat injection well (91) is arranged at the center of the multiple extraction wells (92) so that the multiple extraction wells (92) are evenly distributed around the heat injection well (91).

4. The method for mining oil shale formation according to claim 1 or 2, characterized in that: In the step four, the heating device (100) is extended to correspond to the fracture area of ​​the target oil shale layer (7).

5. The method for mining oil shale formation according to claim 1 or 2, characterized in that: In step five, the fluid generated by the reaction between the high-pressure water flow and the alkali powder includes critical water, alkaline solution and hydrogen. A portion of the heat released by the reaction is directly transferred outward to heat the target oil shale layer (7), and the other portion is transferred with the fluid generated by the reaction and then to the hydraulic fracture to heat the target oil shale formation (7) again.

6. The method for mining oil shale formation according to claim 5, characterized in that: The heat released by the reaction between the high-pressure water flow and the alkali powder can heat the target oil shale layer (7) to 300-500°C, the concentration of the generated alkaline solution is 0.1-1 mol / L, and the pressure of the high-pressure water flow is 3-20 MPa.

7. A production system for use in a production method for an oil shale formation according to any one of claims 1 to 6, comprising: A heating device (100) comprising a water injection unit (1), an alkali thermal reaction unit (2) and a heat injection unit (3) connected in sequence from top to bottom, wherein the water injection unit (1) comprises a high-pressure water flow channel (15) and an alkali powder injection channel (25); The high-pressure water flow and alkali powder can be respectively injected into the alkali thermal reaction unit (2) through the high-pressure water flow channel (15) and the alkali powder injection channel (25), and come into contact in the alkali thermal reaction unit (2) to produce a chemical reaction to release heat, and the fluid generated by the reaction enters the fracture through the heat injection unit (3).

8. The mining system according to claim 7, characterized in that: The water injection unit (1) comprises a main pipe body, a first axial through hole is provided at the center of the main pipe body to form the alkali powder injection channel (25), and a first axial annular through portion is provided radially outside the alkali powder injection channel (25) to form the high-pressure water flow channel (15), and a pressure valve (14) is provided at the lower end of the high-pressure water flow channel (15).

9. The mining system according to claim 7 or 8, characterized in that: The alkali thermal reaction unit (2) comprises an alkali thermal reaction chamber outer tube (22), a baffle (23) arranged inside the alkali thermal reaction chamber outer tube (22), and a bottom filter plate (24) fixedly connected to the lower end of the baffle (23).

10. The mining system according to claim 7 or 8, characterized in that: The heat injection unit (3) comprises a heat injection chamber outer tube (31), a heat injection chamber (33) is formed inside the heat injection chamber outer tube (31), and a plurality of through heat injection holes (32) are evenly opened on the side wall of the heat injection chamber outer tube (31), and the fluid generated by the reaction enters the fracture through the heat injection holes (32).

11. The mining system according to claim 7 or 8, characterized in that: It also includes a ground auxiliary equipment device (4) for injecting high-pressure water flow and alkali powder into the heating device (100), which includes a water supply unit connected to the high-pressure water flow channel (15) and an alkali powder supply unit connected to the alkali powder injection channel (25).

12. The mining system according to claim 11, characterized in that: The water supply unit comprises a water source (45), a water pump (41) and a booster pump (42). The water source (45), the water pump (41) and the booster pump (42) are connected via a water injection pipe (44), and the tail end of the water injection pipe (44) is connected to the high-pressure water flow channel (15).

13. The mining system according to claim 11, characterized in that: The alkali powder supply unit comprises a high-pressure conveyor (43) and a high-pressure conveying pipeline (47), and the high-pressure conveyor (43) is connected to the alkali powder injection channel (25) through the high-pressure conveying pipeline (47).

14. The mining system according to claim 7 or 8, characterized in that: It also includes an extraction device, which includes an oil storage tank (52) installed at the wellhead of the extraction well (92), an oil extraction pipeline (53) arranged in the extraction well (92) and extending to the bottom, and an oil extraction pump (51) connected between the oil storage tank (52) and the oil extraction pipeline (53).

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