CN-121719527-B - Coal bed gas and synthetic gas co-production method based on pre-space release blasting fracturing

CN121719527BCN 121719527 BCN121719527 BCN 121719527BCN-121719527-B

Abstract

The invention discloses a coalbed methane and synthesis gas CO-production method based on pre-space release blasting fracturing, belonging to the technical field of coalbed methane exploitation; the method comprises the steps of drilling a plurality of drilling holes in a deep coal bed, sequentially and alternately arranging the drilling holes into supercritical CO 2 holes and oxidant holes, injecting oxidant into a first oxidant hole and igniting the oxidant holes, igniting peripheral coal bodies in the oxidant holes to form strip-shaped cavities, providing space and heat energy for coal blasting, simultaneously extracting synthetic gas generated by burning in real time, injecting supercritical CO 2 into adjacent supercritical CO 2 holes and performing blasting and fracturing, and extracting the coal bed gas which is desorbed after the blasting and fracturing to the ground surface.

Inventors

QIU PENG
HU JIE
LIANG WEIGUO
YUE ZHONGWEN
FAN YUANHANG
WU SHIWEI

Assignees

太原理工大学

Dates

Publication Date: 20260508
Application Date: 20260213

Claims (9)

1. The coalbed methane and synthesis gas co-production method based on the pre-space release blasting fracturing is characterized by comprising the following steps of: firstly, selecting a deep coal seam (6) according to investigation, arranging a supercritical CO 2 injection pipeline (1) and a coal-bed gas extraction pipeline (10) on one side of the deep coal seam (6), and arranging an oxidant injection pipeline (4) and a synthetic gas extraction pipeline (11) on the other side of the deep coal seam (6); Then dividing the whole deep coal seam (6) into a plurality of independent mining blocks, constructing a plurality of horizontal directional drilling holes along the trend of the deep coal seam (6) in each independent block, and sequentially and alternately arranging the drilling holes into supercritical CO 2 holes (7) and oxidant holes (8), communicating a supercritical CO 2 injection pipeline (1) with the supercritical CO 2 holes (7) in the first block, and communicating an oxidant injection pipeline (4) with the oxidant holes (8) in the first block; Then quantitatively injecting an oxidant into a first oxidant hole (8) in a first block through an oxidant injection pipeline (4) and igniting the oxidant, gradually forming strip-shaped cavities (12) distributed along the extending direction of the oxidant hole (8) in the coal combustion process, providing space and heat energy for subsequent coal blasting and fracturing by the strip-shaped cavities (12), and simultaneously extracting synthetic gas generated by combustion to the ground surface through a synthetic gas extraction pipeline (11); Injecting supercritical CO 2 into one supercritical CO 2 hole (7) adjacent to the first oxidant hole (8), and starting a blasting device in the supercritical CO 2 hole (7) to perform blasting fracturing after the injection amount of the supercritical CO 2 reaches a preset value; Then, injecting an oxidant into the supercritical CO 2 holes (7) subjected to blasting and fracturing through an oxidant injection pipeline (4) to fully burn the blasted and fractured coal, and extracting the synthesis gas formed by burning the coal to the ground surface through a synthesis gas extraction pipeline (11); extracting other drilling holes in the first block according to the same method, and extracting other blocks according to the extraction method of the first block.
2. The coalbed methane and synthetic gas co-mining method based on the pre-space release blasting fracturing according to claim 1, wherein the physical and mechanical parameters are tested by exploring and collecting coal samples, and the physical and mechanical parameters comprise density, porosity, compressive strength, tensile strength and elastic modulus of the coal samples, combustion characteristic parameters and coalbed methane occurrence parameters of the coal samples, and the deep coal bed (6) is selected through the physical and mechanical parameters.
3. The coalbed methane and synthetic gas CO-production method based on space release explosion fracturing in advance according to claim 1 is characterized in that shafts are drilled at two ends of two sides of a deep coal bed (6), horizontal wells are drilled in the bottoms of the shafts along the trend of the deep coal bed (6), a supercritical CO 2 injection pipeline (1) and a coalbed methane extraction pipeline (10) are respectively built in two shafts and corresponding horizontal wells on one side, an oxidant injection pipeline (4) and a synthetic gas extraction pipeline (11) are respectively built in two shafts and corresponding horizontal wells on the other side, and pressure flow, a temperature sensor (2) and a leakage monitoring device are arranged along the pipelines.
4. The coalbed methane and synthesis gas co-production method based on pre-space release blasting fracturing according to claim 1, wherein the combustion temperature of the peripheral coal body in the oxidant hole (8) is controlled to be 600-850 ℃ by dynamically adjusting the injection flow of the oxidant, and the injection flow of the oxidant is 8-12m 3 /min.
5. The coalbed methane and synthesis gas co-production method based on pre-space release blasting fracturing according to claim 1, wherein the volume of the strip-shaped cavity (12) is regulated and controlled by controlling the combustion time and the supply amount of the oxidant, so that the volume of the strip-shaped cavity (12) is 35% -40% of the volume of the corresponding raw coal body.
6. The coalbed methane and synthesis gas CO-production method based on pre-space release blasting fracturing according to claim 1, wherein the oxidant injection pipeline (4) is communicated with the synthesis gas extraction pipeline (11) through a second extraction pipeline (9) and is communicated with the oxidant hole (8), and a plate heat exchange device is arranged in the second extraction pipeline (9) connected with the synthesis gas extraction pipeline (11) and is used for transferring heat absorbed from the synthesis gas to the supercritical CO 2 hole (7) adjacent to the oxidant hole (8) through a conduction assembly.
7. The coalbed methane and synthesis gas co-production method based on pre-space release blasting fracturing according to claim 1, wherein when the synthesis gas extraction rate of the whole block reaches a preset target, continuously injecting oxidant into the coalbed through all oxidant holes (8) of the block, igniting residual coal and extracting the generated coalbed methane.
8. The coalbed methane and synthesis gas co-production method based on the pre-space release blasting fracturing is characterized in that the length of each block is 300-350m, the width of each block is 140-160m, an isolation coal pillar is reserved between adjacent blocks, an expansion type sealing device is arranged at the tail end of each drilling hole in a matched mode, the sealing length is more than or equal to 5m, and meanwhile an electromagnetic valve is arranged at the connecting position of each drilling hole and a corresponding pipeline.
9. The coalbed methane and synthesis gas CO-production method based on pre-space release blasting fracturing according to claim 1, wherein a temperature and pressure control device (5) integrating temperature monitoring and pressure control is arranged in a supercritical CO 2 hole (7), and CO 2 is regulated and controlled to be always maintained in a supercritical state of 31-40 ℃ and 7.5-10MPa before and after blasting.

Description

Coal bed gas and synthetic gas co-production method based on pre-space release blasting fracturing Technical Field The invention belongs to the technical field of coalbed methane exploitation, and particularly relates to a coalbed methane and synthesis gas co-production method based on pre-space release blasting fracturing. Background In the current coalbed methane exploitation method, the main mode is hydraulic fracturing, high-pressure water is injected into a coalbed, and the coalbed is broken by utilizing water pressure, so that the coalbed methane is released. However, in some areas, hydraulic fracturing operations are not suitable due to geological conditions, ecological environmental or other factors, and hydraulic fracturing requires a large amount of water resources, and in general, a coal-bed gas well may require thousands of cubic meters or more of water for hydraulic fracturing operations. This can create significant pressure on the local water supply in areas where the water resources are scarce, and the fracturing fluids (including bactericides, lubricants, surfactants, etc.) used in hydraulic fracturing processes contain chemical additives that, if improperly treated, can contaminate surface, soil and groundwater and thereby affecting the surrounding ecological environment and resident health, and in addition, although the purpose of hydraulic fracturing is to increase the permeability of the coal seam, some of the components in the fracturing fluid may remain in the pores and cracks of the coal seam after blasting. These residues can plug pores and cracks, resulting in a decrease in permeability of the coal seam over time. Therefore, various defects and problems of the technology need to be comprehensively and deeply considered in the hydraulic fracturing operation process, and effective measures are formulated and adopted in a targeted manner so as to reduce the negative effects caused by the defects and the problems to the greatest extent. In this context, it has become urgent to develop and apply a more optimized blasting method. Disclosure of Invention The invention overcomes the defects of the prior art and provides a coalbed methane and synthesis gas co-production method based on pre-space release blasting fracturing. The method of the invention uses the burning coal as the supercritical CO 2 blasting release space in advance, so that the blasting and breaking are more sufficient, the desorption capacity of the coal bed gas is improved, the CO-production of the synthetic gas and the coal bed gas is realized, and the problems of later reduction of permeability and insufficient coal bed gas exploitation caused by hydraulic fracturing in the existing coal bed gas exploitation process are solved. The invention is realized by the following technical scheme: According to the coal bed gas and synthetic gas CO-mining method based on the pre-space release blasting and fracturing, supercritical CO 2 holes and oxidant holes are sequentially drilled in a deep coal bed at intervals, oxidant is injected into the oxidant holes and ignited, peripheral coal bodies in the oxidant holes are ignited, strip-shaped cavities are gradually formed, the strip-shaped cavities provide space and heat energy for subsequent coal body blasting and fracturing, then supercritical CO 2 is injected into supercritical CO 2 holes adjacent to the strip-shaped cavities, blasting and fracturing are carried out, and coal bed gas and synthetic gas generated in the mining process are pumped. Further, the method comprises the following steps: Firstly, selecting a deep coal seam according to investigation, and arranging a supercritical CO 2 injection pipeline and a coal seam gas extraction pipeline on one side of the deep coal seam; then dividing the whole deep coal seam into a plurality of independent exploitation blocks, constructing a plurality of horizontal directional drilling holes along the trend of the deep coal seam in each independent block, and sequentially and alternately arranging the drilling holes into supercritical CO 2 holes and oxidant holes; Then quantitatively injecting oxidant into the first oxidant hole in the first block through an oxidant injection pipeline and igniting the oxidant, gradually forming strip-shaped cavities distributed along the extending direction of the oxidant hole in the coal combustion process, and simultaneously extracting the synthesis gas generated by combustion to the ground surface through a synthesis gas extraction pipeline; Injecting supercritical CO 2 into a supercritical CO 2 hole adjacent to the first oxidant hole, and starting a blasting device in the supercritical CO 2 hole to perform blasting fracturing after the injection amount of the supercritical CO 2 reaches a preset value; Then injecting an oxidant into the supercritical CO 2 holes which are subjected to blasting and fracturing through an oxidant injection pipeline to fully burn the blasted and fractured coal, and extr