CN114412433A - Deep coal in-situ fluidization mining method based on heat extraction power generation - Google Patents
Deep coal in-situ fluidization mining method based on heat extraction power generation Download PDFInfo
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- CN114412433A CN114412433A CN202210066834.7A CN202210066834A CN114412433A CN 114412433 A CN114412433 A CN 114412433A CN 202210066834 A CN202210066834 A CN 202210066834A CN 114412433 A CN114412433 A CN 114412433A
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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
- E21B43/295—Gasification of minerals, e.g. for producing mixtures of combustible gases
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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
- E21B41/00—Equipment or details not covered by groups E21B15/00 - E21B40/00
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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
- E21B41/00—Equipment or details not covered by groups E21B15/00 - E21B40/00
- E21B41/0085—Adaptations of electric power generating means for use in boreholes
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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
- E21B43/25—Methods for stimulating production
- E21B43/26—Methods for stimulating production by forming crevices or fractures
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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
- E21B43/285—Melting minerals, e.g. sulfur
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21C—MINING OR QUARRYING
- E21C37/00—Other methods or devices for dislodging with or without loading
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21F—SAFETY DEVICES, TRANSPORT, FILLING-UP, RESCUE, VENTILATION, OR DRAINING IN OR OF MINES OR TUNNELS
- E21F17/00—Methods or devices for use in mines or tunnels, not covered elsewhere
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/10—Geothermal energy
Abstract
The invention provides a deep coal in-situ fluidization mining method based on heat extraction power generation, which comprises the steps of determining a coal seam needing fluidization mining, and arranging a U-shaped well group in the coal seam; performing secondary transformation on the horizontal well to form a fishbone well; fracturing a coal seam around the fishbone well; injecting air into the fishbone well; igniting or detonating a methane-air mixture in the complex crack in an electric shock ignition mode to enable coal and oxygen decomposed from potassium permanganate to generate a combustion reaction; in the coal bed combustion process, water is injected into the horizontal well through the water injection pipe column, and simultaneously oxygen-enriched air is injected through an annular space between the water injection pipe column and the horizontal well; through the high temperature environment that forms among the coal combustion process, heat the moisture in the water injection tubular column, produce a large amount of vapor, the straight well in the middle of the rethread is with the vapor flowback to ground. The method can provide an environment-friendly fluidized mining process, effectively improve the mining efficiency and realize an integrated development and utilization process.
Description
Technical Field
The invention belongs to the technical field of deep coal mining, and particularly relates to a deep coal in-situ fluidization mining method based on heat extraction power generation.
Background
Because the problems of frequent safety accidents, damage to ground ecological environment and the like commonly exist in the deep coal resource exploitation, the xi hei academy in 2016 proposes a fluidization exploitation technical idea of converting the deep coal resource into gaseous or liquid energy in situ under the condition that people do not go into a well through a series of physical, chemical and biological technical means. The method subverts the existing coal resource mining concept and system, so that the coal resources can be fluidized and developed like oil gas mining, and further solves the problems of environmental pollution, ground collapse, ecological damage, low development and utilization efficiency and the like in the coal mining process. However, the technology of fluidization development is still not mature enough, and a specific supporting technology is lacked, so that large-scale field application is not realized yet.
The coal resource in-situ fluidization mining concept has rich scientific connotation and comprises a multi-level theoretical framework and a technical system. In the technical aspect, physical fluidization, chemical fluidization and biological fluidization mining methods are all important components of a fluidization mining technical system and also are technical guarantees for promoting deep coal resources to realize in-situ fluidization development and landing conversion. Therefore, a technical framework for in-situ fluidized mining of coal needs to be continuously perfected and filled, the existing mature engineering technology and the in-situ fluidized mining concept are combined, the development and innovation of the existing technology are continuously promoted, and further the industrial application of underground in-situ fluidized mining of deep coal resources is realized early.
Disclosure of Invention
The invention provides a deep coal in-situ fluidization exploitation method based on heat extraction and power generation, aiming at the problems in the prior art of deep coal exploitation, and the method can provide a green and environment-friendly fluidization exploitation process, not only can solve the problems of frequent safety accidents, serious environmental pollution, low exploitation efficiency and the like in the prior deep coal exploitation technology, but also can effectively improve the fluidization exploitation efficiency, and can realize an integrated exploitation and utilization process.
In order to achieve the aim, the invention provides a deep coal in-situ fluidization exploitation method based on heat extraction power generation, which specifically comprises the following steps;
the method comprises the following steps: constructing a multi-plane U-shaped well;
determining a coal seam needing fluidized mining according to geological parameters and exploration data of an underground coal seam, and then arranging a well pattern in the coal seam, wherein the well pattern is composed of a straight well arranged at the center of the coal seam and a plurality of horizontal wells uniformly distributed around the straight well in the circumferential direction, the tail end of the straight well extends to the position near the bottom of the coal seam, the horizontal wells penetrate through the bottom of the coal seam, the tail ends of the horizontal wells are mutually communicated with the tail ends of the straight wells, after the drilling operation is finished, the straight well and the horizontal wells respectively form U-shaped wells in different planes, all the U-shaped wells share the same straight well, and a U-shaped well group is formed in a three-dimensional space of the coal seam;
step two: constructing a fishbone well;
performing secondary transformation on the horizontal well, drilling a plurality of horizontal branch wells at different positions along the length direction of the horizontal well, wherein the axes of the horizontal branch wells and the horizontal well are positioned on the same plane; the horizontal wells and the horizontal branch wells connected with the horizontal wells are integrally distributed in a fishbone shape, so that fishbone wells are built; after the drilling operation is finished, the coal bed is divided into a plurality of areas by a plurality of horizontal wells and fishbone wells, and the fishbone wells, the horizontal wells and the vertical wells integrally form a space which is communicated with each other, so that a complex well pattern is formed in the coal bed;
step three: hydraulic fracturing of the fishbone well;
after the fishbone well is constructed, fracturing a coal bed around the fishbone well in a manner of injecting high-pressure fluid into the fishbone well, and forming complex cracks, namely performing hydraulic fracturing operation in the fishbone well; in the fracturing process, a potassium permanganate solution is selected as a fracturing fluid, and the fluid injection pressure is reasonably controlled to ensure that the fluid pressure in the fishbone well is greater than the fracture pressure of the coal bed and lower than the fracture pressure of the upper rock stratum and the lower rock stratum, and the fracture is controlled to only extend in the coal bed;
step four: squeezing air;
after pumping the potassium permanganate solution with the designed dosage, injecting air into the fishbone well through the horizontal well, enabling the injected air to enter the complex fracture, and mixing the air with methane in the complex fracture to form a methane-air mixture;
step five: a water injection pipe column is arranged;
firstly, putting a water injection pipe column into a horizontal well, and enabling an outlet of the water injection pipe column to be positioned near the tail end of the horizontal well; then an annular plugging device is used for plugging an annular region at the tail end of the water injection pipe column, so that the fluid in the annular of the horizontal well cannot enter a middle vertical well;
step six: coal in-situ gasification;
igniting and detonating a methane-air mixture in the complex crack in an electric shock ignition mode, promoting the potassium permanganate solution in the complex crack to release oxygen by utilizing a high-temperature environment generated by combustion and explosion of methane and air, and simultaneously heating moisture in the potassium permanganate solution to form water vapor; under the high-temperature condition, oxygen released by the potassium permanganate can continuously ignite coal around the complex cracks, so that the coal and the oxygen decomposed from the potassium permanganate generate combustion reaction, and meanwhile, the coal combustion promotes the water evaporation to continuously propagate to the tips of the complex cracks;
step seven: injecting oxygen-enriched air and water;
in the coal bed combustion process, water is injected into the horizontal well through the water injection pipe column, and simultaneously oxygen-enriched air is injected through an annular space between the water injection pipe column and the horizontal well, so that the oxygen-enriched air injected into the annular space enters the complex cracks through the fishbone well connected with the horizontal well, and a combustion improver is provided for the combustion of coal, so that the sufficient combustion of the coal is ensured; meanwhile, water in the water injection pipe column is heated through a high-temperature environment formed in the coal combustion process to generate a large amount of water vapor, the water vapor is returned to the ground through the middle vertical well, and the water vapor is introduced into the steam turbine to drive the generator set to generate power or introduced into heating equipment to be used by residents for heating or simultaneously used for generating power and heating.
Further, in order to effectively treat CO generated by deep coal combustion2In order to avoid the greenhouse effect caused by direct discharge into the atmosphere, in the seventh step, CO generated by deep coal combustion is carried out through a horizontal well2Pumping to ground, collecting, and recycling CO from waste mine2And carrying out geological sequestration.
Further, in order to realize the purpose of recycling the waste resources, in the seventh step, when the generator set is driven by the water vapor to generate electricity, the generated electricity resources are stored through an underground energy storage system, and the underground energy storage system is reconstructed by the abandoned mine in the mining area.
Further, in order to effectively improve the fluidized mining and conversion efficiency, in the step one, the number of the horizontal wells is four, the phase angles of the four horizontal wells are 90 degrees, and the distance between each horizontal well and the vertical well on the ground is equal.
Further, in order to significantly improve the fracturing effect and enable the generated cracks to stably exist, the specific steps in the hydraulic fracturing process in the third step are as follows;
s31: firstly, dissolving potassium permanganate particles into special slick water for fracturing, and fully dissolving the potassium permanganate particles to prepare a plurality of potassium permanganate solutions, wherein the concentrations of the potassium permanganate solutions are respectively 10%, 15%, 20% and 25%;
s32: sequentially injecting multiple parts of potassium permanganate solution with the concentration rising in a stepped manner into a fishbone well through a horizontal well by using a ground high-pressure pump set, and performing fracturing operation on a coal bed, wherein the injection amount of the multiple parts of potassium permanganate solution is the same; in the process, when the concentration of the potassium permanganate is increased to 20%, starting to mix a certain volume of fracturing propping agent into the potassium permanganate solution for propping the formed complex fracture and preventing the complex fracture from closing; along with the continuous injection of the potassium permanganate solution, the pressure in the fishbone well is continuously increased, and when the injection pressure of the potassium permanganate solution exceeds the coal bed fracture pressure, cracks begin to be generated around the fishbone well; meanwhile, in the fracturing process, the concentration of the potassium permanganate solution is continuously increased, the potassium permanganate content in the area close to the tip of the crack is lower, and the potassium permanganate content in the position close to the fishbone well is highest.
Furthermore, in order to limit the fracturing range in the region where the bottom of the current U-shaped well group is located, adverse effects on the next operation region are avoided, meanwhile, in order to guarantee the fracturing effect of the bottom region of the current U-shaped well group, in the second step, the included angle between the drilling direction of the horizontal branch well and the drilling direction of the horizontal well connected with the horizontal branch well is 30-60 degrees, the horizontal branch wells in the same horizontal well are distributed along the two sides of the horizontal well in a staggered mode, and the number of the horizontal branch wells on the two sides is the same.
Furthermore, in order to ensure that the propping agent can enter the tip of the complex fracture, and simultaneously, in order to ensure the propping effect, the particle size of the propping agent is 0.147-0.210 mm.
Further, in order to ensure the sufficient combustion of coal, in the seventh step, the volume concentration of oxygen in the oxygen-enriched air is more than 50%.
According to the method, the multi-plane U-shaped well is taken as a basis, then a plurality of fishbone wells are drilled in the horizontal well section of the U-shaped well, and then hydraulic fracturing operation is performed in the fishbone wells, so that a fracture network with better complexity can be formed in a coal bed more efficiently, the fracture network can be effectively ensured to cover all spaces where the bottoms of the U-shaped well groups are located, and further the formation of complex fractures with higher complexity in the subsequent fracturing process can be ensured. The potassium permanganate solution is used as the fracturing fluid, so that the medium pressure can be realized in the coal bed around the fishbone wellThe complex crack is formed, so that the contact area of a coal bed and a combustion improver can be increased, a high-flow-conductivity channel can be provided for conveying the combustion improver, the physical characteristics of the combustion improver can be fully utilized, the potassium permanganate ingredient can release oxygen for combustion assistance after being heated at high temperature under the high-temperature condition, and then coal can be sufficiently combusted under the combustion assistance of the oxygen released by the potassium permanganate, so that more heat can be released, the temperature of ground steam is remarkably improved, and the power generation efficiency can be guaranteed. The annular region at the tail end of the water injection pipe column is plugged by the annular plugging device, so that oxygen-enriched air injected into the annular region can only enter a complex crack through a fishbone well connected with a horizontal well, and therefore after the oxygen-enriched air is injected, the combustion improver can be continuously provided for the combustion of coal, and the sufficient combustion of the coal can be ensured, so that a more ideal high-temperature environment can be generated. When the generated electric energy needs to be stored, the underground energy storage system formed by reforming the abandoned mine is used for storing, so that the abandoned mine resources in the mine area can be effectively stocked, and the reutilization of the abandoned resources is realized. At the same time, CO generated by coal combustion is carried out through a horizontal well2The waste mine is pumped to the ground and then is sealed and stored on site, so that adverse effects on the environment caused by direct discharge into the air can be avoided. The method can realize the in-situ fluidized mining, power generation, energy storage, heat extraction and CO extraction of deep coal2The sealing and abandoned mine utilization integrated utilization process can provide a novel deep coal resource mining process with environmental protection and high efficiency.
Drawings
FIG. 1 is a schematic view of a multi-planar U-shaped well of the present invention;
FIG. 2 is a schematic view of a fishbone well of the invention;
FIG. 3 is a schematic diagram of the present invention for fracturing and creating seams in a coal seam surrounding a fishbone well;
FIG. 4 is a schematic diagram of in situ fluidized mining of a deep coal resource in accordance with the present invention;
FIG. 5 is a cross-sectional view taken at m-m of FIG. 4 according to the present invention;
FIG. 6 is a schematic view of the injection of water and oxygen-enriched air in the present invention;
figure 7 is a schematic diagram illustrating wellbore heat extraction and power generation.
In the figure: 1. the system comprises a coal seam, 2 horizontal wells, 3 vertical wells, 4 horizontal branch wells, 5 fishbone wells, 6 complex cracks, 7 underground energy storage systems, 8 hair areas, 9 water injection pipe columns, 10 annular stoppers, 11 water, 12 oxygen-enriched air, 13 and a generator set.
Detailed Description
The invention will be further explained with reference to the drawings.
The invention provides a deep coal in-situ fluidization exploitation method based on heat extraction power generation, which specifically comprises the following steps;
the method comprises the following steps: constructing a multi-plane U-shaped well;
determining a coal seam 1 needing fluidized mining according to geological parameters and exploration data of an underground coal seam, and then arranging a well pattern in the coal seam 1, wherein the well pattern is composed of a straight well 3 arranged at the center of the coal seam 1 and a plurality of horizontal wells 2 uniformly distributed around the straight well 3 in the circumferential direction, as shown in fig. 1, the tail end of the straight well 3 extends to the position near the bottom of the coal seam 1, the horizontal wells 2 penetrate through the bottom of the coal seam 1, the tail ends of the horizontal wells are mutually communicated with the tail ends of the straight well 3, after the drilling operation is finished, the straight well 3 and the horizontal wells 2 respectively form U-shaped wells in different planes, all the U-shaped wells share the same straight well 3, and a U-shaped well group is formed in a three-dimensional space of the coal seam 1;
in order to effectively improve the fluidized mining and conversion efficiency, the number of the horizontal wells 2 is four, the phase angle of the four horizontal wells 2 is 90 degrees, and the distance between each horizontal well 2 and the vertical well 3 on the ground is equal.
Step two: constructing a fishbone well 5;
carrying out secondary transformation on the horizontal well 2, and drilling a plurality of horizontal branch wells 4 at different positions along the length direction of the horizontal well 2, wherein as shown in fig. 2, the axes of the horizontal branch wells 4 and the horizontal well 2 are positioned on the same plane, the included angle between the drilling direction of the horizontal branch well 4 and the drilling direction of the horizontal well 2 connected with the horizontal branch well 4 is 30-60 degrees, the horizontal branch wells 4 in the same horizontal well 2 are distributed along the two sides of the horizontal well 2 in a staggered manner, and the number of the horizontal branch wells 4 at the two sides is the same; by the technical means, the fracturing range can be effectively limited in the area where the bottom of the current U-shaped well group is located, so that adverse effects on the next operation area are avoided, and meanwhile, the area at the bottom of the current U-shaped well group can have a good fracturing effect; the horizontal well 2 and the horizontal branch well 4 connected with the horizontal well are integrally distributed in a fishbone shape, so that a fishbone well 5 is built; after the drilling operation is finished, the coal seam 1 is divided into a plurality of areas by a plurality of horizontal wells 2 and fishbone wells 5, and the fishbone wells 5, the horizontal wells 2 and the vertical wells 3 integrally form a space which is communicated with each other, so that a complex well pattern is built in the coal seam 1;
step three: hydraulic fracturing of the fishbone well 5;
after the fishbone well 5 is constructed, fracturing the coal seam 1 around the fishbone well 5 in a manner of injecting high-pressure fluid into the fishbone well 5 to form a complex crack 6, namely performing hydraulic fracturing operation in the fishbone well 5, as shown in fig. 3; in the fracturing process, a potassium permanganate solution is selected as a fracturing fluid, the fluid injection pressure is reasonably controlled, the fluid pressure in the fishbone well 5 is ensured to be greater than the fracture pressure of the coal seam 1 and lower than the fracture pressure of the upper rock stratum and the lower rock stratum, and the complex fracture 6 is controlled to only extend in the coal seam 1;
in order to obviously improve the fracturing effect and enable the generated cracks to stably exist, the specific steps in the hydraulic fracturing process are as follows;
s31: firstly, dissolving potassium permanganate particles into special slick water for fracturing, and fully dissolving the potassium permanganate particles to prepare a plurality of potassium permanganate solutions, wherein the concentrations of the potassium permanganate solutions are respectively 10%, 15%, 20% and 25%;
s32: sequentially injecting multiple parts of potassium permanganate solution with the concentration rising in a stepped manner into a fishbone well 5 through a ground high-pressure pump set, and performing fracturing operation on a coal seam 1, wherein the injection amount of the multiple parts of potassium permanganate solution is the same; during the process, when the potassium permanganate concentration increases to 20%, a volume of fracturing proppant begins to be mixed into the potassium permanganate solution; in order to ensure that the propping agent can enter the tip of the complex fracture and ensure the propping effect, the particle size of the propping agent is 0.147-0.210 mm, and the propping agent is used for propping the formed complex fracture 6 and preventing the complex fracture 6 from closing; with the continuous injection of the potassium permanganate solution, the pressure in the fishbone well 5 is continuously increased, and when the injection pressure of the potassium permanganate solution exceeds the fracture pressure of the coal seam 1, cracks are generated around the fishbone well 5; meanwhile, in the fracturing process, the concentration of the potassium permanganate solution is continuously increased, the potassium permanganate content in the area close to the tip of the crack is lower, and the potassium permanganate content in the position close to the fishbone well 5 is highest.
Step four: squeezing air;
after pumping of the potassium permanganate solution with the designed dosage is finished, injecting air into the fishbone well 5 through the horizontal well 2, enabling the injected air to enter the complex fracture 6, and mixing the injected air with methane in the complex fracture 6 to form a methane-air mixture;
the air extrusion has two functions: firstly, the residual potassium permanganate solution in the horizontal well 2 and the fishbone well 5 can be displaced into a complex fracture 6 in the stratum; secondly, a certain amount of air can be put into the space near the inlet of the complex crack 6, and a methane-air mixed zone is formed in the area along with the desorption of the coal bed methane;
step five: a water injection pipe column 9 is arranged;
as shown in fig. 4 and 5, firstly, a water injection string 9 is put into the horizontal well 2, and an outlet of the water injection string 9 is positioned near the tail end of the horizontal well 2; an annular plugging device 10 is used for plugging an annular area at the tail end of the water injection pipe column 9, so that the fluid in the annular of the horizontal well 2 cannot enter the middle vertical well 3;
step six: coal in-situ gasification;
igniting and detonating a methane-air mixture in the complex crack 6 in an electric shock ignition mode, promoting the potassium permanganate solution in the complex crack 6 to release oxygen by utilizing a high-temperature environment generated by combustion and detonation of methane and air, and simultaneously enabling moisture in the potassium permanganate solution to form water vapor by heating; under the high-temperature condition, the oxygen released by the potassium permanganate can continuously ignite the coal around the complex crack 6, so that the coal and the oxygen decomposed from the potassium permanganate generate combustion reaction, and meanwhile, the coal combustion promotes the water evaporation to continuously propagate to the tip of the complex crack 6;
step seven: injecting oxygen-enriched air 12 and water 11;
as shown in fig. 6, in the coal seam combustion process, water 11 is injected into the horizontal well 2 through the water injection pipe column 9, and simultaneously oxygen-enriched air 12 (the oxygen volume concentration is more than 50%) is injected into an annular space between the water injection pipe column 9 and the horizontal well 2, because the annular space region at the tail end of the water injection pipe column 9 is blocked, the oxygen-enriched air 12 injected into the annular space can only enter the complex crack 6 through the fishbone well connected with the horizontal well 2, so that a combustion improver is provided for the combustion of coal, and the sufficient combustion of the coal is ensured; due to the continuous combustion of coal, a high-temperature environment is formed in the coal seam, and the water 11 in the injection pipe column 9 can be heated into steam. As shown in fig. 7, the water vapor is discharged back to the ground through the middle vertical shaft 3 to drive the generator set 13 to generate power, meanwhile, the generated power resource is stored through the underground energy storage system 7, and the water vapor discharged back to the ground can be used for heating the residential area 8 in winter. In order to effectively treat CO generated by deep coal combustion2To avoid direct emission into the atmosphere to produce greenhouse effect, and to avoid the generation of CO by deep coal combustion2The water can be pumped to the ground through the horizontal well 2, collected and then geologically sealed and stored by using a waste mine. In order to realize the purpose of recycling waste resources, the underground energy storage system 7 is formed by rebuilding a waste mine in a mining area to build a water pumping energy storage or compressed air energy storage system of the waste mine, and finally deep coal in-situ fluidized mining, power generation, energy storage, heat extraction, CO is formed2The sealing and abandonment mine is used as an integrated technology.
According to the method, the multi-plane U-shaped well is taken as a basis, then a plurality of fishbone wells are drilled in the horizontal well section of the U-shaped well, and then hydraulic fracturing operation is performed in the fishbone wells, so that a fracture network with better complexity can be formed in a coal bed more efficiently, the fracture network can be effectively ensured to cover all spaces where the bottoms of the U-shaped well groups are located, and further the formation of complex fractures with higher complexity in the subsequent fracturing process can be ensured. The potassium permanganate solution is used as the fracturing fluid, so that complex cracks can be pressed in the coal bed around the fishbone well, the contact area of the coal bed and the combustion improver can be increased, and combustion can be supportedThe agent is conveyed to provide a high-flow-conductivity channel, and the physical characteristics of the agent can be fully utilized, so that the potassium permanganate component can release oxygen for combustion assistance after being heated at high temperature, and further, coal can be sufficiently combusted under the combustion assistance of the oxygen released by the potassium permanganate, so that more heat can be released, the temperature of ground water vapor is remarkably improved, and the power generation efficiency can be guaranteed. The annular region at the tail end of the water injection pipe column is plugged by the annular plugging device, so that oxygen-enriched air injected into the annular region can only enter a complex crack through a fishbone well connected with a horizontal well, and therefore after the oxygen-enriched air is injected, the combustion improver can be continuously provided for the combustion of coal, and the sufficient combustion of the coal can be ensured, so that a more ideal high-temperature environment can be generated. When the generated electric energy needs to be stored, the method is carried out through an underground energy storage system formed by modifying the abandoned mine, so that the abandoned mine resources in the mine area can be effectively stocked, and the reutilization of the abandoned resources is realized. At the same time, CO generated by coal combustion is carried out through a horizontal well2The waste mine is pumped to the ground and then is sealed and stored on site, so that adverse effects on the environment caused by direct discharge into the air can be avoided. The method can realize the in-situ fluidized mining, power generation, energy storage, heat extraction and CO extraction of deep coal2The sealing and abandoned mine utilization integrated utilization process can provide a novel deep coal resource mining process with environmental protection and high efficiency.
Claims (8)
1. A deep coal in-situ fluidization exploitation method based on heat extraction power generation is characterized by comprising the following steps;
the method comprises the following steps: constructing a multi-plane U-shaped well;
determining a coal seam (1) needing fluidized mining according to geological parameters and exploration data of an underground coal seam, and then arranging a well pattern in the coal seam (1), wherein the well pattern is composed of a straight well (3) arranged at the center of the coal seam (1) and a plurality of horizontal wells (2) uniformly distributed circumferentially around the straight well (3), the tail end of the straight well (3) extends to the position near the bottom of the coal seam (1), the horizontal wells (2) penetrate through the bottom of the coal seam (1), the tail ends of the horizontal wells are mutually communicated with the tail ends of the straight well (3), after the drilling operation is finished, the straight well (3) and the horizontal wells (2) respectively form U-shaped wells in different planes, all the U-shaped wells share the same straight well (3), and a U-shaped well group is formed in the three-dimensional space of the coal seam (1);
step two: constructing a fishbone well (5);
carrying out secondary transformation on the horizontal well (2), drilling a plurality of horizontal branch wells (4) at different positions along the length direction of the horizontal well (2), wherein the axes of the horizontal branch wells (4) and the horizontal well (2) are positioned on the same plane; the horizontal well (2) and the horizontal branch well (4) connected with the horizontal well are integrally distributed in a fishbone shape, so that a fishbone well (5) is built; after the drilling operation is finished, the coal seam (1) is divided into a plurality of areas by a plurality of horizontal wells (2) and fishbone wells (5), and the fishbone wells (5), the horizontal wells (2) and the vertical wells (3) integrally form a space which is communicated with each other, so that a complex well pattern is built in the coal seam (1);
step three: hydraulic fracturing of the fishbone well (5);
after the fishbone well (5) is constructed, fracturing a coal seam (1) around the fishbone well (5) in a manner of injecting high-pressure fluid into the fishbone well (5) and forming a complex crack (6), namely performing hydraulic fracturing operation in the fishbone well (5); in the fracturing process, a potassium permanganate solution is selected as a fracturing fluid, the fluid injection pressure is reasonably controlled, the fluid pressure in the fishbone well (5) is ensured to be greater than the fracture pressure of the coal seam (1) and lower than the fracture pressures of the upper rock stratum and the lower rock stratum, and the complex fracture (6) is controlled to only extend in the coal seam (1);
step four: squeezing air;
after pumping of the potassium permanganate solution with the designed dosage is finished, injecting air into the fishbone well (5) through the horizontal well (2), enabling the injected air to enter the complex fracture (6) and mixing with methane in the complex fracture (6) to form a methane-air mixture;
step five: a lower water injection pipe column (9);
firstly, a water injection pipe column (9) is arranged in the horizontal well (2), and an outlet of the water injection pipe column (9) is positioned near the tail end of the horizontal well (2); an annular plugging device (10) is used for plugging an annular region at the tail end of the water injection pipe column (9) so as to ensure that fluid in the annular of the horizontal well (2) cannot enter the middle vertical well (3);
step six: coal in-situ gasification;
igniting and detonating a methane-air mixture in the complex crack (6) in an electric shock ignition mode, promoting the potassium permanganate solution in the complex crack (6) to release oxygen by utilizing a high-temperature environment generated by combustion and detonation of methane and air, and simultaneously heating water in the potassium permanganate solution to form water vapor; under the high-temperature condition, oxygen released by the potassium permanganate can continuously ignite coal around the complex crack (6), so that the coal and the oxygen decomposed from the potassium permanganate generate combustion reaction, and meanwhile, the coal combustion promotes the water evaporation to continuously propagate to the tip of the complex crack (6);
step seven: injecting oxygen-enriched air (12) and water (11);
in the coal bed combustion process, water (11) is injected into the horizontal well (2) through the water injection pipe column (9), and meanwhile, oxygen-enriched air (12) is injected through an annular space between the water injection pipe column (9) and the horizontal well (2), so that the oxygen-enriched air (12) injected into the annular space enters the complex crack (6) through the fishbone well (5) connected with the horizontal well (2), and a combustion improver is provided for the combustion of coal, so that the sufficient combustion of the coal is ensured; meanwhile, water in the water injection pipe column (9) is heated through a high-temperature environment formed in the coal combustion process to generate a large amount of water vapor, the water vapor is returned to the ground through the middle vertical well (3), and the water vapor is introduced into a steam turbine to drive a generator set (13) to generate power or introduced into heating equipment to be used by residents for heating or simultaneously generate power and heat.
2. The deep coal in-situ fluidized mining method based on heat extraction power generation as claimed in claim 1, characterized in that in step seven, CO generated by deep coal combustion is processed through a horizontal well (2)2Pumping to ground, collecting, and recycling CO from waste mine2And carrying out geological sequestration.
3. The deep coal in-situ fluidization mining method based on heat extraction power generation as claimed in claim 1 or 2, characterized in that in step seven, when the generator set (13) is driven by steam to generate power, the generated power resource is stored by an underground energy storage system (7), and the underground energy storage system (7) is reconstructed by abandoned mines in the mining area.
4. The deep coal in-situ fluidization mining method based on thermal power generation is characterized in that in the step one, the number of the horizontal wells (2) is four, the phase angle of the four horizontal wells (2) is 90 degrees, and the distance between each horizontal well (2) and the vertical well (3) on the ground is equal.
5. The deep coal in-situ fluidization exploitation method based on thermal power generation as claimed in claim 4, wherein the specific steps in the hydraulic fracturing process in the third step are as follows;
s31: firstly, dissolving potassium permanganate particles into special slick water for fracturing, and fully dissolving the potassium permanganate particles to prepare a plurality of potassium permanganate solutions, wherein the concentrations of the potassium permanganate solutions are respectively 10%, 15%, 20% and 25%;
s32: injecting multiple parts of potassium permanganate solution with the concentration rising in a stepped manner into a fishbone well (5) through a ground high-pressure pump unit in sequence, and performing fracturing operation on a coal seam (1), wherein the injection amount of the multiple parts of potassium permanganate solution is the same; in the process, when the potassium permanganate concentration is increased to 20%, starting to mix a certain volume of fracturing propping agent into the potassium permanganate solution for propping the formed complex fracture (6) and preventing the complex fracture (6) from closing; the pressure in the fishbone well (5) is continuously increased along with the continuous injection of the potassium permanganate solution, and when the injection pressure of the potassium permanganate solution exceeds the fracture pressure of the coal bed (1), cracks are generated around the fishbone well (5); meanwhile, in the fracturing process, the concentration of the potassium permanganate solution is continuously increased, the potassium permanganate content in the area close to the tip of the crack is lower, and the potassium permanganate content in the position close to the fishbone well (5) is highest.
6. The deep coal in-situ fluidized mining method based on heat extraction and power generation as claimed in claim 5, characterized in that in the second step, the included angle between the drilling direction of the horizontal branch well (4) and the drilling direction of the horizontal well (2) connected with the horizontal branch well is 30-60 degrees, a plurality of horizontal branch wells (4) in the same horizontal well (2) are distributed along two sides of the horizontal well (2) in a staggered manner, and the number of the horizontal branch wells (4) on the two sides is the same.
7. The deep coal in-situ fluidization mining method based on heat extraction and power generation as claimed in claim 5, wherein the size of the proppant particles is 0.147-0.210 mm.
8. The deep coal in-situ fluidization mining method based on heat extraction power generation as claimed in claim 7, characterized in that in step seven, the oxygen-enriched air (12) has oxygen concentration greater than 50% by volume.
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