WO2020113870A1

WO2020113870A1 - Method for cooperatively draining roof separation water and mining coal-measure gas

Info

Publication number: WO2020113870A1
Application number: PCT/CN2019/080733
Authority: WO
Inventors: 吴财芳; 房孝杰; 刘宁宁; 刘小磊; 张和伟
Original assignee: 中国矿业大学
Priority date: 2018-12-07
Filing date: 2019-04-01
Publication date: 2020-06-11
Also published as: CN109339746A; KR102369397B1; CN109339746B; KR20200070214A; JP2021510398A; JP6868747B2; AU2019323218A1

Abstract

A method for cooperatively draining roof separation water and mining a coal-measure gas. The section structure of a coal stratum comprises: a vertical well (1), a horizontal well (2), a horizontal section (3) of the horizontal well, a vertical section (4) of the horizontal well, an inclined section (5) of the horizontal well, a sealing device (6), a goaf (7), a coal seam (8), a curve subsidence zone (9), a working face (10), a hard stratum (11), a soft stratum (12), a separation space (13), and an unmined area (14). Said method comprises the following steps: a stage of only mining coal-measure gas; a stage of synchronously draining water and mining gas; and a stage of only draining roof separation water. Said method combines coal-measure gas mining, coal production, and mine separation water disaster prevention and control, reduces the mash gas content in the coal seam, the working face, the goaf and a roadway during coal stoping so as to reduce the harm from mash gas on mine safe production, and promotes the desorption and production of methane under the effect of coal mining, increases the yield of coal-measure gas, and also controls the separation water in the separation space in the roof of the goaf, so as to prevent the occurrence of a secondary roof separation water disaster.

Description

Method for synergic drainage of roof separation water and coal system gas

Technical field

The present invention relates to the technical field, and in particular to a method for cooperative drainage of roof delamination water and coal-based gas.

Background technique

Coal mine water hazards occur frequently in China. Although conventional water hazard prevention technologies and prevention capabilities are at the international advanced level, it is still difficult to prevent and control secondary secondary delamination water hazards that occur without strong aquifers. Such water hazards are harmful The characteristics of large, instantaneous water influx, unclear precursors, small total water volume, and periodicity have become a hidden danger to the safety of mine production. However, the prevention and control of delaminated water hazards is currently more difficult, and the research results are still concentrated in the delaminated layer The formation mechanism, distribution law and other aspects, and the cost of prevention and treatment are relatively high. Therefore, it is of great theoretical and practical significance to propose a cost-effective method for mine delamination water treatment.

Existing coal-based gas drainage and production methods are diverse, including straight wells, cluster wells, U-shaped wells, multi-branch horizontal wells, etc. However, coal seams in China are generally characterized by low porosity and permeability, so their production is low. The economic benefits are poor.

Patent document CN10481131A, the patent title is "A CBM Well Up and Down Stereo Combined Extraction Method" does not disclose the simultaneous stage of hydrophobic gas production and the stage of single-thin roof water separation, only a single drainage of coal bed methane, the patent Although it is possible to realize three-dimensional combined drainage of coalbed methane up and down the well, it cannot solve the problem that the casing of the horizontal well caused by coal mining is damaged by the surrounding rock and cannot continue to discharge coalbed methane, nor can it be compatible with mine safety. Other issues related to production.

Summary of the invention

In order to overcome the above-mentioned shortcomings of the prior art, the present invention provides a method for cooperative drainage of roof delaminated water and coal-based gas, which combines coal-based gas drainage, coal production, and mine delamination water hazard prevention to reduce coal The gas content in the coal seam, working face, goaf and roadway during mining is to reduce the harm of gas to the safety production of coal mines. It can also promote the desorption output of methane under the influence of coal mining and increase the output of coal system gas. It can prevent and control the delamination water in the delamination space in the roof of the coal mine goaf, and prevent the occurrence of secondary roof delamination water hazard accidents, which has great economic and social benefits.

The technical scheme adopted by the present invention is: a method for cooperative drainage of roof separation water and coal-based gas. The coal-rock layer profile structure includes a U-shaped well and a drainage device, a goaf, a coal bed, a curved subsidence zone, Working face, hard rock layer, weak rock layer, separation space and unmined area, the U-shaped well includes vertical well, horizontal well, horizontal section of horizontal well, vertical section of horizontal well and inclined section of horizontal well, the drainage and production device Including tube pump, tubing, sucker rod, conventional casing, glass fiber reinforced plastic casing, plastic butt pipe and sealing device, the drainage method includes the following steps: ①Single coal bed methane stage, before coal recovery The horizontal section of the horizontal well is subjected to conventional casing directional perforation and segmented hydraulic fracturing. The perforation direction is vertically downward. The vertical well is mainly used for drainage operations. The horizontal well is used for gas extraction, and the fracturing fractures affect the coal in the coal seam and the coal roof. The system gas is used for extraction. The extraction method is negative pressure extraction. According to the statistical results of U-type wells with a general gas recovery period of 8 to 10 years, in order to ensure gas recovery efficiency, the discharge time is set to 8 years;

②Synchronized stage of hydrophobic gas production. After 8 years of independent gas production, the coal seam starts to recover. After the mined-out area is formed, the conventional well casing corresponding to the working face position in the horizontal section of the horizontal well is sealed with a sealing device to separate the horizontal well. The horizontal section is divided into two sections, which are the drainage section of the mined-out area and the gas extraction section of the un-mined area. The coal-series gas in the unmined area is continuously discharged, and the delaminated water in the delaminated space in the curved subsidence zone of the mined-out area Drainage is carried out. At this time, the coal seam on the side of the unmined area close to the goaf is affected by mining at the working face, and further depressurization and desorption to increase the daily gas production of the horizontal well;

③Single alienation layer water stage, continue to advance on the working face until the working face is close to the corresponding position of the vertical section of the horizontal well, close the sealing device, at this time, formed in the horizontal section of the horizontal well and the curved subsidence zone There are multiple sets of delamination spaces. The delamination water in the upper delamination space is led by the fissures to conduct water into the delamination space below it. At this time, the vertical section of the vertical well, the horizontal section of the horizontal well and the water that has not been destroyed by the surrounding rock The horizontal section of the horizontal well is drained at the same time to prevent the occurrence of water inrush accidents from the layer, to ensure the safety of the underground working face.

Further, the horizontal section of the horizontal well is set in the area between the rock system where the first layer that appears at the bottom end of the curved subsidence zone of the mined-out area is a hard rock layer above and a weak rock layer below, and the vertical well is close to the working face On one side, the horizontal well is away from the working face, and the horizontal section of the horizontal well is connected to the vertical section of the horizontal well through the horizontal well deflection section. The horizontal section of the horizontal well is set on the side of the return air lane close to the working face. When the coal seam is high, a group of U-shaped wells with the same structure are arranged at the corresponding positions close to the intake roadway of the mining face.

Further, in the curved sinking zone of the goaf roof formed behind the mining face, it is easy to stratify successively the delamination space and collect delamination water, and arrange the horizontal section of the horizontal well in the lowest layer may form the delamination space. In the top of the weak rock layer immediately adjacent to the bottom of the hard rock layer, this interval first forms the first set of delaminated space, which is also the lowermost delaminated space. As the mining work progresses, after the delaminated space is formed, the delaminated space is directed The first sealing device on the side of the unmined area is opened to seal the horizontal section of the horizontal well into two parts. The unmined area is still drained of coal system gas, and the goaf area is drained for the purpose of draining the delaminated water , And taking into account the extraction of coal system gas in the mined-out area, with the progress of the mining work, open the newly formed delamination space to the first sealing device immediately adjacent to the side of the unmined area, and close the opened delamination space to the The sealing device of the vertical well makes the horizontal section of the horizontal well divided into two sections of hydrophobic and gas production, until the coal seam is recovered to the corresponding position of the vertical section of the horizontal well, and the last sealing device is closed. The horizontal section of the damaged horizontal well is simultaneously drained.

Further, the installation position of the sealing device is determined according to the length of each section of the caving coal mining design. The number of installation of the sealing device is n-1 (n is the number of caving sections). To connect plastic butt joints at the butt joints, a total of m-1 plastic butt joints (m is the number of conventional casings) need to be connected.

Compared with the prior art, the beneficial effects of the present invention are: using this method of cooperative drainage of roof delaminated water and coal-based gas, it can combine coal-based gas drainage, coal production, and prevention of mine delamination water damage. , Can not only reduce the gas content in coal seam, working face, goaf and roadway during coal mining, reduce the harm of gas to coal mine safety production, but also promote the desorption output of methane and increase coal under the influence of coal mining The gas production can also prevent the delamination water in the delamination space in the roof of the coal mine goaf and prevent the occurrence of secondary delamination water damage accidents.

BRIEF DESCRIPTION

FIG. 1 is a schematic diagram of a stage in which hydrophobic gas production is synchronized in a method for cooperating drainage of roof layer separation water and coal system gas;

2 is a schematic diagram of the single-bed coal bed methane phase in the present invention;

Fig. 3 is a schematic diagram of the water stage of a single alienation layer in the present invention.

Among them: 1-straight well, 2-horizontal well, 3-horizontal well horizontal section, 4-horizontal well vertical section, 5-horizontal well deviating section, 6-sealing device, 7-goaf area, 8-coal seam, 9 -Bending subsidence zone, 10-working face, 11-hard rock formation, 12-weak rock formation, 13-separation space, 14-uncut area, 15-tube pump, 16-oil pipe, 17-sucker rod, 18 -Conventional casing, 19-fiberglass casing, 20-plastic butt joint.

detailed description

In order to deepen the understanding of the present invention, the present invention will be further described below in conjunction with the drawings and embodiments. This embodiment is only used to explain the present invention and does not limit the protection scope of the present invention.

As shown in FIG. 1, in the present invention, the hydrophobic gas production is divided into three stages, including: ①Single coal bed methane production stage, ②Synchronized hydrophobic gas production stage, ③Single roof separation layer water stage; ①If Figure 1: The single-bed coal bed methane stage is the conventional casing 18 directional perforation and segmented hydraulic fracturing of the horizontal section 3 of the horizontal well of the U-shaped well before coal recovery. The perforation direction is vertically downward, and the vertical well 1 is mainly Carry out drainage operations, gas production in horizontal well 2, fracturing fractures to extract coal system gas in coal seam 8 and coal seam roof, the extraction method is negative pressure extraction, and the general gas production period of U-type wells is 8 to 10 years In order to ensure the efficiency of gas production, the discharge time is set to 8 years. ②As shown in Figure 2: The synchronized stage of hydrophobic gas production is that after 8 years of separate gas production, coal seam 8 begins to recover, and after the formation of goaf 7, the use of sealing device 6 in the horizontal section of horizontal well 3 corresponds to the position of working face 10 The casing 18 is sealed to divide the horizontal section 3 of the horizontal well into two sections, which are the drainage section of the mined area 7 and the gas production section of the unmined area 14 respectively. The empty zone 7 bends the sinking zone 9 and the delamination water in the delamination space 13 is drained. At this time, the coal seam 8 on the side of the unmined zone 14 close to the goaf 7 is affected by the mining of the working face 10, and further depressurization and desorption. Increase the gas production of horizontal wells for 2 days. ③ As shown in Figure 3: The single-separation layer water stage is to continue to move forward in the working face 10 until the working face 10 is close to the corresponding position of the vertical section 4 of the horizontal well, and the sealing device 6 is closed. At this time, in the horizontal section 3 of the horizontal well and its Multiple sets of delamination spaces 13 are formed within the upper curved subsidence zone 9, and the delamination water in the upper delamination space 13 is conducted by the fissure, and conducts water into the delamination space 13 underneath. 3. The vertical section 4 of the horizontal well and the horizontal section 3 of the horizontal well that are not damaged by the surrounding rock are simultaneously drained to prevent the occurrence of water inrush from the layer, to ensure the safety of the underground working face 10, and to close the well after the recovery of the working face 10 is completed.

In the above embodiment, the design position of the extraction well is determined according to the plan layout drawing of the mining excavation project, a vertical well is constructed at the starting end of the mining area, a horizontal well 2 is constructed along the advancing direction of the working face 10, and the horizontal well is vertical at the end point of the mining Section 4, horizontal well Horizontal section 3 is located in the area between the first series of hard rock layers 11 and soft rock layers 12 at the bottom of the curved subsidence zone 9 from bottom to top. The vertical well 1 is slightly deeper than Horizontal section 3 of horizontal wells, but not deep into the fracture zone, both horizontal well 2 and vertical well 1 adopt negative pressure extraction.

In the above embodiment, on the plane, the horizontal section 3 of the horizontal well is preferentially arranged on the side of the return air lane 10 close to the recovery face. If the recovery coal seam is a coal seam with a higher gas content, the air intake lane near the recovery face 10 can be used. A group of U-shaped wells with the same structure are arranged at the corresponding positions.

In the above embodiment, both the horizontal well 2 and the vertical well 1 are drilled with a large-diameter drilling tool, and a glass fiber reinforced plastic casing 19 is provided at the junction of the horizontal section 3 of the horizontal well and the vertical well 1, and the butt section of the vertical well 1 is mechanically expanded. The diameter of the section is 0.5m, which is convenient for the docking of the horizontal section 3 of the horizontal well and the vertical well 1.

In the above embodiments, conventional casing 18 is used to cement the vertical section 4 of the horizontal well, the deflection section 5 of the horizontal well and the vertical well 1 except for the butting section. The conventional casing 18 has an inner diameter of 200 mm and 3 sets of horizontal sections The tube assembly is a conventional casing 18 connected with a plastic butt joint tube 20. The plastic butt joint tube 20 can plastically expand and contract when the surrounding rock is deformed to ensure the horizontal connectivity of the horizontal section 3 of the horizontal well.

In the above embodiment, a tubular pump 15 is installed in the lower part of the butt joint section of the vertical well 1 and the horizontal section 3 of the horizontal well and the bottom of the vertical section 4 of the horizontal well. The tubing pump 15 is connected to the tubing 16 above the tubing 16 and the inside of the tubing 16 is a sucker rod 17. Determine the installation position of the sealing device 6 according to the length of each section of the caving coal mining design. The number of installations of the sealing device 6 is n-1 (n is the number of caving sections). In the horizontal section of the horizontal well 3 two conventional casings The butt joint between 18 is connected to the plastic butt joint pipe 20, and a total of m-1 plastic butt joint pipes 20 (m is the number of casing roots) need to be connected.

The embodiment of the present invention discloses a preferred embodiment, but it is not limited to this. Those of ordinary skill in the art can easily understand the spirit of the present invention and make different extensions and changes based on the above embodiments. But as long as it does not deviate from the spirit of the present invention, it is within the protection scope of the present invention.

Claims

A method for collaborative drainage of roof separation water and coal-series gas. The coal-rock layer profile structure includes a U-shaped well and a drainage device, a mined-out area (7), a coal seam (8), a curved subsidence zone (9), Working face (10), hard rock layer (11), weak rock layer (12), delamination space (13) and unmined area (14), the U-shaped well includes vertical well (1), horizontal well (2), water The horizontal section (3) of horizontal wells, the vertical section (4) of horizontal wells and the deflection section (5) of horizontal wells, characterized in that the drainage device includes a tubular pump (15), an oil pipe (16), and a sucker rod (17), conventional casing (18), glass fiber reinforced plastic casing (19), plastic butt pipe (20) and sealing device (6), the drainage method includes the following steps: ① single coal bed methane production stage, in coal Before recovery, the horizontal section (3) of the horizontal well is subjected to conventional casing (11) directional perforation and staged hydraulic fracturing, the perforation direction is vertically downward, the vertical well (1) is mainly used for drainage operations, and the horizontal well (2) is Gas and fracturing cracks are used to extract the coal-series gas in the coal seam (8) and the roof of the coal seam (8). The extraction method is negative pressure extraction, and the set drainage time is 8 years;

②The stage of synchronous production of hydrophobic gas recovery. After 8 years of independent gas recovery, coal seam (8) starts to recover. After the goaf (7) is formed, the horizontal section (3) of the horizontal well corresponds to the working face using the sealing device (6) (10) The conventional casing (18) at the location is isolated, and the horizontal section (3) of the horizontal well is divided into two sections, which are the mined-out area (7) and the non-mined area (14). The unmined area (14) continues to discharge coal system gas, and drains the delaminated water in the gob area (7) curved subsidence zone (9) delamination space (13), and the unmined area (14) Further depressurization and desorption;

③In the phase of water separation of the single thin roof, continue to advance on the working face (10) until the working face (10) is close to the corresponding position of the vertical section of the horizontal well (4), close the sealing device (6), at this time, in the water A plurality of sets of delamination spaces (13) are formed within the horizontal section (3) of the flat well and the curved subsidence zone (9) above, and the delamination water in the upper delamination space (13) is led by the fissure to the bottom Water is conducted in the delaminated space (13). At this time, the vertical well (1), the vertical section of the horizontal well (4) and the horizontal section of the horizontal well (3) that are not damaged by the surrounding rock are simultaneously drained, and the working face (10 ) After completion of mining, seal the well.
The method for cooperative drainage of roof delamination water and coal measures gas according to claim 1, characterized in that the horizontal section (3) of the horizontal well is set at the bottom of the curved sinking zone (9) in the mined-out area (7) The first layer that appears from the bottom is the area between the rock series with the hard rock layer (11) above and the weak rock layer (12) below. The vertical well (1) is close to the working face (10) side and the horizontal well (2) Far from the working face (10), the horizontal section of the horizontal well (3) communicates with the vertical section of the horizontal well (4) through the horizontal well deflection section (5), and the horizontal section of the horizontal well (3) is set close to the mining face (10) On the side of the return airway, when the coal seam is a coal seam with a high gas content, a group of U-shaped wells with the same structure are arranged at the corresponding positions near the intake airway of the mining face (10).
The method for cooperative drainage of roof layer delamination water and coal system gas according to claim 1, characterized in that: the mined-out area (7) formed behind the mining face (10) is in the curved roof sinking zone (9) , It is easy to stratify successively the delamination space (13) and collect delamination water, arrange the horizontal section of the horizontal well (3) at the bottom of the hard rock layer (11) that may form the delamination space and the top of the weak rock layer (12) Within the boundary, the lowermost layer of delamination space (13) is first formed in this interval, and the mining work will be carried out. After the delamination space is formed, the delamination space will be directed to the first immediately adjacent to the side of the unmined area (14) The sealing device (6) is opened to seal the horizontal section (3) of the horizontal well into two parts. The un-mined area (14) is still discharging coal-series gas, and the mined-out area (7) is used to drain the delaminated water as The purpose of drainage operation, taking into account the extraction of coal gas in the mined-out area (7), as the recovery work progresses, open the newly formed delamination space (13) to the first adjacent to the side of the unmined area (14) A sealing device (6), which closes the sealing device (6) of the opened delamination space (13) and points to the vertical well (1), so that the horizontal section (3) of the horizontal well is always divided into two sections of hydrophobic and gas production until coal seam recovery To the corresponding position of the vertical section of the horizontal well (4), close the last sealing device (6), the vertical well (1), the vertical section of the horizontal well (4) and the horizontal section of the horizontal well (3) that has not been damaged by the surrounding rock Hydrophobic operation.
The method for cooperative drainage of roof separation water and coal system gas according to claim 1, characterized in that the tubular pump (15) is arranged at the lower part of the butt joint section of the vertical well (1) and the horizontal section (3) of the horizontal well Connected to the bottom of the vertical section (4) of the horizontal well, the tubing (15) is connected above the tubing pump (15), and the tubing (16) has a sucker rod (17) inside, according to the length of each section of the top coal recovery design Determine the installation position of the sealing device, the number of installation of the sealing device (6) is n-1 (n is the number of topping section), and connect the plastic butt pipe at the butt joint between the two conventional casings (11) in the horizontal section (3) of the horizontal well (20), it is necessary to connect m-1 plastic butt joint pipes (20) (m is the number of conventional casing).
The method for cooperative drainage of roof layer delamination water and coal measures gas according to claim 1, characterized in that both horizontal wells (2) and vertical wells (1) are drilled with large-diameter drilling tools, and the horizontal section (3 ) FRP casing (19) is set at the joint with the vertical well (1), and the diameter of the joint section of the vertical well (1) is mechanically expanded to make the diameter of this section 0.5m, which is convenient for the horizontal section (3) of the horizontal well and the vertical well (1) )'S docking.