Artificial geothermal reservoir construction and development method based on oil shale reverse oxidation

Abstract

The invention discloses an artificial geothermal reservoir construction and development method based on oil shale reverse oxidation, and belongs to the technical field of resource exploitation, the method comprises the following steps: reservoir well construction: arranging an injection well, an exploitation well and a heat recovery well in a target layer section; an initial high-temperature environment is formed through manual heating, so that the oil shale is pyrolyzed to generate fixed carbon; injecting air to form an oxygen-enriched environment, initiating a fixed carbon oxidation self-heating reaction, and continuously pyrolyzing the oil shale; terrestrial heat is exploited through a circulating working medium, the air flow and components are dynamically controlled, and temperature control and safe operation are achieved; and finally reinjecting and sealing the carbon dioxide. The device can convert low-grade oil shale into clean geothermal energy, and has the advantages of energy conservation and environmental protection.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of resource exploitation, in particular to an artificial geothermal reservoir construction and development method based on oil shale reverse layer oxidation. BACKGROUND

[0002] Oil shale is an important unconventional oil and gas resource, which is rich in reserves and buried at a depth of 300-1500 meters. The traditional oil shale development technology mainly includes surface dry distillation technology and oil shale in-situ conversion technology. The surface dry distillation technology is suitable for shallow oil shale resource development, and the oil shale in-situ conversion technology is suitable for medium-deep oil shale. The oil shale in-situ conversion technology needs to be pre-constructed for reservoir permeability improvement, and then the target reservoir is artificially heated. The pyrolysis oil and gas is recovered to the surface after migrating through the formation. Due to the low oil content (generally 5-10%) and low permeability of oil shale, the technology has technical bottlenecks such as complex process control, difficult reservoir reconstruction, and low oil and gas recovery rate, and has not yet realized commercial development. In addition, current geothermal energy development relies on natural geothermal reservoirs, and the reservoir temperature is low (60-200℃). Generally, a 200℃ reservoir needs to be 4000 meters deep.

[0003] Therefore, oil shale resource development and geothermal energy development both face different technical bottlenecks. In view of the above problems, the present application proposes a new technical path combining oil shale resource development and artificial geothermal reservoir construction. By utilizing the characteristics that the pyrolysis products of oil shale can be further oxidized to generate heat in a high-temperature oxygen-containing environment, a chain self-heating reaction mechanism is formed to construct an ultra-high temperature artificial geothermal reservoir in the oil shale in-situ reservoir, and then the reservoir heat energy is collected through the heat exchange well. The invention of the technology can realize the conversion of low-grade oil shale and other fossil energy into green geothermal energy, improve the efficiency of oil shale resource development, and enrich China's geothermal resources. SUMMARY

[0004] In view of the deficiencies of the prior art, the purpose of the embodiments of the present application is to provide an artificial geothermal reservoir construction and development method based on oil shale reverse layer oxidation to solve the problems in the background art.

[0005] To achieve the above-mentioned purpose, the present application provides the following technical scheme:

[0006] The artificial geothermal reservoir construction and development method based on oil shale reverse layer oxidation comprises the following steps:

[0007] Step 1: Reservoir well construction, at least one group of injection wells, production wells and heat recovery wells are arranged in the target oil shale section. The injection well is used for injecting oxidizing agents such as air, the production well is used for producing pyrolysis products, and the heat recovery well is used for reservoir heat energy recovery;

[0008] Step two: Preheating the formation around the production well, heating the target layer at the bottom of the production well by artificial heating, heating the reservoir around the wellbore to above 300℃, forming an initial high-temperature pyrolysis environment, and making the oil shale around the well pyrolyze to form fixed carbon;

[0009] Step three: Air injection into the injection well, injecting normal temperature air into the injection well to form an oxygen-rich environment in the reservoir of the production area;

[0010] Step four: Start and promote the oxidation of fixed carbon in the well, the oil shale between the injection well and the production well occurs continuous pyrolysis under high temperature conditions, and the pyrolysis products occur oxidation reaction in the presence of oxygen, releasing heat to heat the surrounding reservoir, triggering the next layer of pyrolysis-oxidation reaction;

[0011] Step five: Pyrolysis oil and gas product displacement and oxidation, the oil and gas products produced by the pyrolysis of oil shale flow from the injection well to the production well under the driving of air, pass through the high-temperature reservoir that has been pyrolyzed, and the fixed carbon and organic matter generated by pyrolysis between the injection well and the production well continuously occur oxidation exothermic reaction with oxygen;

[0012] Step six: Artificial geothermal reservoir construction, through the above chain oxidation self-heat reaction and partition self-heat reaction, the temperature of the entire reservoir is increased, and an artificial geothermal reservoir is formed;

[0013] Step seven: Artificial geothermal reservoir heat energy development, a double-wall closed heat exchange system is arranged in the production well, and the circulating working medium absorbs the heat of the artificial geothermal reservoir and takes the heat energy to the ground surface;

[0014] Step eight: Process and safety control, temperature and pressure monitoring devices are arranged at the wellhead and wellbore to dynamically control the injection air flow and composition;

[0015] Step nine: Carbon dioxide product reinjection and sequestration, the products produced by the production well include water and carbon dioxide, and the pore space released by the pyrolysis of organic matter in the reservoir and the high-temperature decomposition of minerals, as well as the alkali metal ions in the backflow water of the reservoir after production, can provide an alkaline space and environment for the carbon dioxide reinjection and sequestration, and thus realize the self-generation and self-storage of carbon dioxide.

[0016] As a further scheme of the present application, the injection well and the production well in step one are in a one-injection and one-production mode and a one-injection and multiple-production mode, and the production well is arranged between the injection well and the production well and is arranged as a vertical well and a horizontal well.

[0017] As a further scheme of the present application, the artificial heating method in step two is well bottom heating or well bottom combustion heating.

[0018] As a further scheme of the present application, the normal temperature air in step three is an oxygen-containing gas, and the oxygen-containing gas gradually diffuses in the in-situ reservoir between the injection well and the production well.

[0019] As a further scheme of the present application, the pyrolysis product in step four is residual carbon.

[0020] As a further scheme of the present application, the fixed carbon and organic matter generated by pyrolysis between the injection well and the production well in step five continuously undergoes oxidation exothermic reaction with oxygen to further release heat, so that the overall temperature of the reservoir is higher than 200℃.

[0021] As a further scheme of the present application, the reservoir center temperature of the artificial geothermal reservoir in step six reaches 500℃.

[0022] As a further scheme of the present application, the double-wall closed heat exchange system in step seven adopts a closed-circuit water system or a carbon dioxide circulation system.

[0023] As a further scheme of the present application, the minerals in step nine include carbonates, and the alkali metal ions include calcium and magnesium.

[0024] In summary, the present application has the following beneficial effects compared with the prior art:

[0025] (1) A stable ultra-high temperature artificial geothermal reservoir is constructed, which has a temperature significantly higher than that of a conventional geothermal reservoir and has high energy density and continuous heat output capacity;

[0026] (2) The utilization efficiency of oil shale resources is effectively improved;

[0027] (3) The present application has the functions of energy development and green geothermal energy utilization, and promotes the transformation and upgrading of traditional fossil energy to clean energy;

[0028] (4) It is also suitable for the development of low-grade unconventional oil and gas resources, and reduces the cost of exploitation, such as oil-rich coal, medium-low mature shale oil, and post-production old oil fields.

[0029] In order to more clearly illustrate the structural features and effects of the present application, the present application will be described in detail below with reference to the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The basic principle diagram of the artificial geothermal reservoir construction and development method based on oil shale in-situ reverse layer oxidation self-generated heat according to the present application is shown in FIG. 1.

[0031] Figure 2 The one-injection and five-production well pattern diagram according to the present application is shown in FIG. 2.

[0032] Figure 3 The horizontal well heat production development method diagram of the artificial geothermal reservoir according to the present application is shown in FIG. 3.

[0033] Figure 4 The vertical well heat production development method diagram of the artificial geothermal reservoir according to the present application is shown in FIG. 4. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application.

[0035] The specific implementation of the present application is described in detail below in combination with specific examples.

[0036] In one embodiment, the artificial geothermal reservoir construction and development method based on oil shale reverse layer oxidation includes the following steps: Figures 1-4

[0037] Step one: reservoir well construction, at least one set of injection wells, production wells and heat extraction wells are arranged in the target oil shale section, the injection wells are used to inject oxidants such as air, the production wells are used to produce pyrolysis products, and the heat extraction wells are used to recover heat energy from the reservoir;

[0038] Step two: preheating the formation around the production well, the target section at the bottom of the production well is artificially heated, the reservoir around the wellbore is heated to above 300℃, an initial high-temperature pyrolysis environment is formed, and the oil shale around the well is pyrolyzed to form fixed carbon;

[0039] Step three: air injection into the injection well, normal temperature air is injected into the injection well to form an oxygen-rich environment in the reservoir of the production area;

[0040] Step four: start and promote of the self-generated heat reaction of the oxidation of fixed carbon around the well, the oil shale between the injection well and the production well continuously pyrolyzes under high temperature conditions, the pyrolysis products undergo oxidation reaction in the presence of oxygen, heat the surrounding reservoir, and trigger the next layer of pyrolysis-oxidation reaction;

[0041] Step five: displacement and oxidation of pyrolysis oil and gas products, the oil and gas products produced by the pyrolysis of oil shale flow from the injection well to the production well driven by air, pass through the high-temperature reservoir that has been pyrolyzed, and the fixed carbon and organic matter generated by pyrolysis between the injection well and the production well continuously undergo oxidation exothermic reaction with oxygen, further release heat, and at the same time improve the temperature and insulation performance of the cracked area, so that the overall temperature of the reservoir is higher than 200℃;

[0042] Step six: construction of high-temperature artificial geothermal reservoir, through the above chain oxidation self-generated heat reaction and partition self-generated heat reaction, the temperature of the entire reservoir is increased, and an artificial geothermal reservoir is formed;

[0043] Step seven: development of heat energy of the artificial geothermal reservoir, a double-walled closed heat exchange system is arranged in the heat extraction well, and the circulating working medium absorbs the heat of the artificial geothermal reservoir and takes the heat energy to the ground surface;

[0044] ​Step eight: process and safety control, by setting temperature and pressure monitoring devices at the wellhead and wellbore, dynamically controlling the injection air flow and composition;

[0045] Step nine: carbon dioxide product reinjection and sealing, the products produced by the production well include water and carbon dioxide, the pore space released by the pyrolysis of reservoir organic matter, the high temperature decomposition of minerals, and the alkali metal ions of the post-production reservoir water can provide alkaline space and environment for carbon dioxide reinjection and sealing, and further realize the self-generation and self-storage of carbon dioxide.

[0046] Further, referring to Figures 1-4 , the injection well and the production well in step one are in one injection and one production mode and one injection and multiple production mode, and the heat production well is arranged between the injection well and the production well, and is set as a vertical well and a horizontal well.

[0047] Further, referring to Figures 1-4 , the artificial heating method in step two is bottom heating or bottom combustion heating.

[0048] Further, referring to Figures 1-4 , the normal temperature air in step three is an oxygen-containing gas, which gradually diffuses in the in-situ reservoir between the injection well and the production well.

[0049] Further, referring to Figures 1-4 , the pyrolysis product in step four is residual carbon.

[0050] Further, referring to Figures 1-4 , the fixed carbon and organic matter generated by pyrolysis between the injection well and the production well in step five continuously undergoes oxidation and exothermic reaction with oxygen to further release heat, so that the overall temperature of the reservoir is higher than 200℃.

[0051] Further, referring to Figures 1-4 , the reservoir center temperature of the artificial geothermal reservoir in step six reaches 500℃.

[0052] Further, referring to Figures 1-4 , the double-wall closed heat exchange system in step seven adopts a closed-loop water system or a carbon dioxide circulation system.

[0053] Further, referring to Figures 1-4 , the minerals in step nine include carbonates, and the alkali metal ions include calcium and magnesium.

[0054] In this embodiment, step 1: reservoir well construction. At least one set of injection well, production well and heat production well is arranged in the target oil shale section. The injection well is used for injecting oxidizing agents such as air; the production well is used for producing pyrolysis products; and the heat production well is used for reservoir heat energy recovery.

[0055] Step 2: Preheat the formation around the production well. By artificially heating the target layer at the bottom of the production well, the reservoir around the wellbore is heated to above 300℃ in a short time, forming an initial high-temperature pyrolysis environment and causing the oil shale around the well to pyrolyze and form fixed carbon.

[0056] In the above steps, the artificial heating method can be conduction heating by a downhole electric heater or downhole combustion heating.

[0057] Step 3: Air injection into the injection well. Normal temperature air is injected into the injection well, and the oxygen-containing gas gradually diffuses in the original reservoir between the injection well and the production well, forming an oxygen-rich environment in the production zone reservoir.

[0058] Step 4: Start and promote self-generated heat. The oil shale around the production well pyrolyzes under high temperature conditions, and its products (mainly residual carbon) oxidize in the presence of oxygen, releasing a large amount of heat. This heat further heats the surrounding reservoir, triggering the next layer of pyrolysis-oxidation reaction, forming a self-sustaining, layer-by-layer advancing reverse layer oxidation self-generated heat reaction front, gradually expanding from the production well to the injection well.

[0059] Step 5: Pyrolysis oil and gas product displacement and oxidation. The oil and gas products produced by oil shale pyrolysis flow from the injection well to the production well under the driving of air, passing through the high-temperature reservoir that has been pyrolyzed along the way. The fixed carbon and organic matter generated by pyrolysis between the injection well and the production well continue to undergo exothermic oxidation with oxygen, further releasing heat and improving the temperature and insulation performance of the cracked region, making the overall reservoir temperature higher than 200℃.

[0060] In the above steps, when the pyrolysis oil and gas products migrate in the already pyrolyzed reservoir, the heavy oil components with high viscosity and poor flowability will undergo exothermic oxidation near the high-temperature pyrolysis front, and the highly flowable light oil and gas components will migrate a long distance and undergo exothermic oxidation near the production well area. Thus, a zonal self-generated heat reaction of residual carbon oxidation exothermic reaction-heavy component oxidation exothermic reaction-light component oxidation exothermic reaction is formed in the reservoir, which cooperatively improves the temperature of the pyrolyzed reservoir.

[0061] Step 6: High-temperature artificial geothermal reservoir construction. Through the above chain oxidation self-generated heat reaction and zonal self-generated heat reaction, the temperature of the entire reservoir gradually increases, forming a stable super-high-temperature artificial geothermal reservoir with a center temperature of up to 500℃ or above, good thermal stability and continuous heat energy output capacity, and a reservoir temperature much higher than that of conventional medium-deep geothermal reservoirs.

[0062] Step 7: Artificial geothermal reservoir heat energy development. A double-walled closed heat exchange system, such as a closed-loop water system or a carbon dioxide circulation system, is installed in the production well to absorb the heat of the artificial geothermal reservoir and bring the heat energy to the surface for power generation, heating or industrial heat, realizing the effective development and heat energy utilization of the artificial geothermal reservoir.

[0063] Step 8: Process and safety control. During the operation of the system, by setting temperature and pressure monitoring devices at the wellhead and wellbore, the injection air flow and composition are dynamically controlled to prevent risks such as overheating and local deflagration, while ensuring stable reaction progress and reservoir temperature balance, improving the efficiency of organic matter utilization and reservoir heat energy development in the target reservoir.

[0064] Step 9: Carbon dioxide product reinjection and sequestration. The main products produced from the production well are water and carbon dioxide. Due to the release of a large amount of reservoir space in the developed reservoir, the high-temperature decomposition of carbonate minerals in the reservoir, and the enrichment of calcium and magnesium alkali metal ions in the reservoir after recovery, abundant alkaline space can be provided for carbon dioxide reinjection and sequestration, thereby achieving self-generation and self-storage of carbon dioxide and achieving the goal of clean and efficient development of oil shale resources.

[0065] Step 1: Well placement. The oil shale reservoir in a certain area has a burial depth of about 800 m and a thickness of about 20 m, with an oil content of 5%. Referring to the figure below, the oil shale reservoir is divided into 11 wells, including 5 injection wells A, 1 production well B, and 5 heat production wells C. The horizontal distance between the injection wells and the production well is about 50 m, arranged in a five-pointed letter shape. Figure 2 In this block, 11 wells are arranged, including 5 injection wells A, 1 production well B, and 5 heat production wells C. The horizontal distance between the injection wells and the production well is about 50 m, arranged in a five-pointed letter shape.

[0066] In the above steps, the injection well and the production well can be in one injection and one production mode, or in one injection and multiple production modes, as shown in the figure below. Figures 2-4 The heat production well is arranged between the injection well and the production well, which can be a vertical well or a horizontal well.

[0067] Step 2: Formation preheating and reverse layer oxidation start. An electric heater is lowered into the production well B and controlled to heat to a reservoir temperature of 320°C, with a heating time of about 72 hours. At the same time, normal temperature air is continuously injected through the injection well A, with a flow rate of about 50-100 Nm³ / h per injection well, triggering the pyrolysis of oil shale around the production well and the reverse layer oxidation of pyrolysis products, releasing heat.

[0068] Step 3: Reverse layer oxidation zoning reaction establishment: As the reaction front gradually advances, it extends from the production well B to the injection well A, and the pyrolysis water and other tail gas are recovered in the production well B. The pyrolysis products in the reservoir flow along the oxygen flow and gradually oxidize in the already pyrolyzed area, forming a residual carbon oxidation zone (temperature > 500°C), a heavy component oxidation and heat generation zone, and a light component oxidation and heat generation zone (temperature > 200°C), forming a high-temperature artificial geothermal reservoir, and realizing in-situ oxidation and heat generation of hydrocarbon gases in the pyrolysis mixed gas without reinjection.

[0069] Step 4: Reservoir heat production. Start the double-wall pipe closed heat exchange system in the heat production well C, inject deionized water from the ground to the bottom of the well along the outer annulus, and return to the ground through the center pipe after heat absorption at the bottom, to realize heat production and collection. The single well circulating water flow is 5-10 m³ / h, and the ground temperature of circulating water is higher than 80℃.

[0070] Low-grade oil shale formation can realize sustained reverse layer oxidation self-generated heat, build an ultra-high temperature artificial geothermal reservoir, and recover reservoir heat through closed heat exchange process. The present technology revolutionizes the development and utilization of oil shale resources, breaks through the bottleneck of low temperature in shallow layer and high development parameters in deep layer of conventional geothermal reservoirs, and can build an ultra-high temperature artificial geothermal reservoir within 1000m, realizing the transformation of low-grade oil shale resources into clean geothermal energy.

[0071] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for constructing and developing artificial geothermal reservoirs based on oil shale reverse oxidation, characterized in that, Includes the following steps: Step 1: Well construction in the reservoir. At least one set of injection wells, production wells and thermal wells are laid in the target oil shale formation. Injection wells are used to inject air, production wells are used to produce pyrolysis products, and thermal wells are used to recover thermal energy from the reservoir. Step 2: Preheating of the formation around the wellbore. The target section at the bottom of the wellbore is heated by artificial heating to raise the temperature of the reservoir around the wellbore to above 300°C, creating an initial high-temperature pyrolysis environment and causing the oil shale around the well to pyrolyze and form fixed carbon. Step 3: Air injection into the injection well. At room temperature air is injected into the injection well to create an oxygen-rich environment in the reservoir of the production area. Step 4: Initiation and advancement of the autogenous heating reaction of fixed carbon oxidation around the well. The oil shale between the injection well and the production well undergoes continuous pyrolysis under high temperature conditions. The pyrolysis products undergo oxidation in the presence of oxygen, releasing heat to heat the surrounding reservoir and triggering the next layer of pyrolysis-oxidation reaction. Step 5: Displacement and oxidation of pyrolysis oil and gas products. The oil and gas products generated by the pyrolysis of oil shale flow from the injection well to the production well under the drive of air. After passing through the high-temperature reservoir that has been pyrolyzed, the fixed carbon and organic matter generated by pyrolysis between the injection well and the production well continue to undergo exothermic oxidation reactions with oxygen. Step Six: Construction of High-Temperature Artificial Geothermal Reservoirs. Through the above-mentioned chain oxidation autogenous heating reaction and zoned autogenous heating reaction, the temperature of the entire reservoir increases, forming an artificial geothermal reservoir. Step 7: Development of thermal energy from artificial geothermal reservoirs. A double-walled closed heat exchange system is installed in the heat extraction well to absorb heat from the artificial geothermal reservoir through circulating working fluid and bring the heat energy to the surface. Step 8: Process and safety control, by installing temperature and pressure monitoring devices at the wellhead and wellbore to dynamically control the injection air flow and composition; Step Nine: Carbon Dioxide Product Reinjection and Sequestration. The products produced by the production well include water and carbon dioxide. The pore space released by the pyrolysis of reservoir organic matter and the high-temperature decomposition of minerals, as well as the alkali metal ions in the post-production reservoir return water, can provide an alkaline space and environment for carbon dioxide reinjection, solidification, and sequestration, thereby achieving self-generation and self-storage of carbon dioxide.

2. The method for constructing and developing artificial geothermal reservoirs based on reverse oxidation of oil shale according to claim 1, characterized in that, In step one, the injection well and the production well are in a one-injection-one-production mode or a one-injection-multiple-production mode. The heat production well is arranged between the injection well and the production well, and is set as a vertical well and a horizontal well.

3. The method for constructing and developing artificial geothermal reservoirs based on reverse oxidation of oil shale according to claim 2, characterized in that, In step two, the artificial heating method is bottom heating or bottom combustion heating.

4. The method for constructing and developing artificial geothermal reservoirs based on reverse oxidation of oil shale according to claim 3, characterized in that, In step three, the ambient air is oxygen-containing gas, which gradually diffuses in the in-situ reservoir between the injection well and the production well.

5. The method for constructing and developing artificial geothermal reservoirs based on reverse oxidation of oil shale according to claim 4, characterized in that, The pyrolysis product in step four is residual carbon.

6. The method for constructing and developing artificial geothermal reservoirs based on reverse oxidation of oil shale according to claim 5, characterized in that, In step five, the fixed carbon and organic matter generated by pyrolysis between the injection well and the production well continue to undergo an exothermic oxidation reaction with oxygen to further release heat, making the overall reservoir temperature higher than 200°C.

7. The method for constructing and developing artificial geothermal reservoirs based on reverse oxidation of oil shale according to claim 6, characterized in that, In step six, the reservoir center temperature of the artificial geothermal reservoir reaches 500°C.

8. The method for constructing and developing artificial geothermal reservoirs based on reverse oxidation of oil shale according to claim 7, characterized in that, In step seven, the double-wall closed heat exchange system adopts a closed-loop circulating water system or a carbon dioxide circulating system.

9. The method for constructing and developing artificial geothermal reservoirs based on reverse oxidation of oil shale according to claim 8, characterized in that, The minerals in step nine include carbonates, and the alkali metal ions include calcium and magnesium.

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