CN113216908A

CN113216908A - Coal bed gas mining method and horizontal drilling equipment

Info

Publication number: CN113216908A
Application number: CN202110564056.XA
Authority: CN
Inventors: 王博洋; 李晶晶; 柳波; 刘琦; 刘淼
Original assignee: Northeast Petroleum University
Current assignee: Northeast Petroleum University
Priority date: 2021-05-24
Filing date: 2021-05-24
Publication date: 2021-08-06
Anticipated expiration: 2041-05-24
Also published as: CN113216908B

Abstract

The application relates to the technical field of coal bed gas exploitation, and particularly provides a coal bed gas exploitation method and horizontal drilling equipment, wherein the coal bed gas exploitation method comprises the following steps: exploring the coal bed gas and determining a target mining area; drilling a first vertical well at a center of a target production zone; drilling a plurality of radial horizontal wells at the bottom of the first vertical well, enabling one ends of the radial horizontal wells to be located at the bottom of the first vertical well, and enabling the other ends of the radial horizontal wells to extend to the edge of the target exploitation area; drilling at least one second vertical well at the edge of the target production area; drilling an annular horizontal well at the bottom of the second vertical well; injecting fracturing fluid into the coal bed through the radial horizontal well to perform coal bed fracturing; and collecting the coal bed gas through the annular horizontal well. The coal bed gas exploitation method utilizes the improved horizontal drilling equipment to perform coal reservoir fracturing through the radial horizontal well, so that the coal bed gas is enabled to be changed from an adsorption state to a free state, and then the coal bed gas is acquired through the annular horizontal well, so that the yield of coal bed gas exploitation is improved.

Description

Coal bed gas mining method and horizontal drilling equipment

Technical Field

The application relates to the technical field of coal bed gas exploitation, in particular to a coal bed gas exploitation method and horizontal drilling equipment.

Background

The coal bed gas is a gas resource associated with coal and symbiotic with the coal, refers to hydrocarbon gas stored in a coal bed, takes methane as a main component, and belongs to unconventional natural gas. The coal bed gas mainly adsorbs the surfaces of coal matrix particles, and part of the hydrocarbon gas is dissociated in coal pores or dissolved in coal bed water, is an associated mineral resource of coal, and is a clean and high-quality energy and chemical raw material.

The coal bed gas resource in China has great potential, and the quantity of coal bed gas geological resources with the burial depth of 2000m or less is about 37 multiplied by 10¹²m³And the amount of the natural gas is equivalent to that of the conventional natural gas resource. Therefore, the development of coal bed gas can relieve the shortage situation of conventional oil gas energy in China, reduce the occurrence probability of coal mine gas accidents, reduce the emission of greenhouse gas in coal mine production, and generate remarkable economic, environmental, safety and social benefits. Because coal reservoirs in China generally have the characteristics of low porosity and low permeability, strong heterogeneity, complex coal body structure and the like, the low-yield well has a high occupation ratio, and about 35 percent of daily gas of production wells is lower than 500m³And the development benefit is lower.

In the existing coal bed gas mining method, a horizontal well drilling and mining process is one of the more common construction processes, but the existing horizontal well drilling and mining process mostly adopts a plurality of horizontal wells to simultaneously mine gas, the horizontal wells are not communicated with each other in an underground target coal reservoir, each horizontal well is in an independent gas mining state, and the yield increasing effect of the coal bed gas is still not ideal. In addition, the difficulty of adjusting the drilling track of the existing coal bed gas drilling equipment is high, so that the horizontal well cannot be drilled at a target position according to a preset track, particularly, a steeply inclined coal reservoir with suddenly reduced thickness is encountered, the drilling angle cannot be adjusted timely by a drill bit, and once the drill bit penetrates out of the target coal reservoir, the construction quality of the horizontal well can be seriously influenced, and further the exploitation amount of the coal bed gas is influenced.

Disclosure of Invention

In view of the above analysis, the present application aims to provide a coal bed methane mining method and a horizontal drilling device, so as to solve the problems of low gas production rate and poor control accuracy of a horizontal drilling trajectory of the existing coal bed methane.

The purpose of the application is mainly realized by the following technical scheme:

in a first aspect: the application provides a coal bed gas mining method, which comprises the following steps: exploring the coal bed gas and determining a target mining area; drilling a first vertical well at a center of a target production zone; drilling a plurality of radial horizontal wells at the bottom of the first vertical well, enabling one ends of the radial horizontal wells to be located at the bottom of the first vertical well, and enabling the other ends of the radial horizontal wells to extend to the edge of the target exploitation area; drilling at least one second vertical well at the edge of the target production area; drilling an annular horizontal well at the bottom of the second vertical well, wherein all the second vertical wells in the same target mining area are communicated through the annular horizontal well; injecting fracturing fluid into the coal bed through the radial horizontal well to perform coal bed fracturing and seam building; and collecting the coal bed gas through the annular horizontal well.

In one embodiment of the present application, the target mining area includes a reference circle, and projections of the target mining area on a plane of the reference circle are all located within the reference circle; the center of the reference circle coincides with the center of the target mining area.

In one embodiment of the present application, the plurality of radial horizontal wells are located at the same horizontal level.

In one embodiment of the application, the plane of the annular horizontal well is parallel to the plane of the radial horizontal well; the plane of the annular horizontal well is higher than that of the radial horizontal well.

In one embodiment of the present application, the input Q of the fracturing fluid satisfies:

wherein n is the number of the radial horizontal wells, R is the radius of the radial horizontal wells, D is the distance between the plane of the annular horizontal well and the plane of the radial horizontal well,

and L is the length of the radial horizontal well.

In one embodiment of the present application, the fracturing fluid employs a mixed gas foam fracturing fluid system.

In one embodiment of the present application, the radial horizontal well and the annular horizontal well are drilled by a horizontal drilling apparatus.

In a second aspect: the application provides horizontal drilling equipment, which is used in the coal bed methane mining method of the embodiment of the application; the horizontal drilling equipment comprises a steering mechanism and a drill bit; the steering mechanism comprises a first connecting block, a second connecting block and a connecting shaft; the drill bit is connected with the first connecting block; the first connecting block is hinged with the second connecting block through a connecting shaft.

In one embodiment of the present application, the connecting shaft includes a connecting shaft, a first expansion portion and a second expansion portion; the connecting shaft is vertical to the axis of the drill bit; two ends of the first telescopic part and the second telescopic part are respectively hinged with the first connecting block and the second connecting block; the telescopic directions of the first telescopic part and the second telescopic part are parallel to the axis of the drill bit.

In one embodiment of the present application, the horizontal drilling device further comprises a rotating mechanism, and the rotating mechanism is connected with the second connecting block; the rotating mechanism is used for driving the second connecting block to rotate around the axis of the drill bit.

Compared with the prior art, the invention has at least one of the following beneficial effects:

(a) the coal bed gas mining method comprises the steps of fracturing a target coal bed through a radial horizontal well to form seams, artificially increasing the permeability of the coal bed, promoting the coal bed gas to be converted from an adsorption state to a free state, accelerating desorption, and being beneficial to coal bed gas mining, wherein all second vertical wells in the same target mining area are communicated through annular horizontal wells, the coal bed gas is collected through the annular horizontal wells, the free coal bed gas in the target coal bed can be mined from the second vertical wells simultaneously, so that the coal bed gas mining efficiency is obviously improved, and the coal bed gas yield is greatly improved.

(b) The horizontal drilling equipment is simple in structure, and the steering mechanism is arranged on the drill bit, so that the drill bit can be bent towards any direction in the drilling process, the tunneling in any direction in the horizontal plane is realized, and the accurate control of the drilling track can be realized.

In the present application, the above technical solutions may be combined with each other to realize more preferable combination solutions. Additional features and advantages of the application will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the application. The objectives and other advantages of the application may be realized and attained by the structure particularly pointed out in the written description and drawings.

Drawings

The drawings are only for purposes of illustrating particular embodiments and are not to be construed as limiting the application, wherein like reference numerals are used to designate like parts throughout.

FIG. 1 is a flow chart of a method for coal bed methane mining in accordance with an embodiment of the present disclosure.

FIG. 2 is a schematic illustration of a first vertical well, a second vertical well, a radial horizontal well, and an annular horizontal well according to an embodiment of the present application.

FIG. 3 is a schematic representation of dimensions of a first vertical well, a second vertical well, a radial horizontal well, and an annular horizontal well of an embodiment of the present application.

FIG. 4 is a schematic view of a horizontal drilling apparatus according to an embodiment of the present application.

FIG. 5 is a side view of a horizontal drilling apparatus according to one embodiment of the present application.

Reference numerals:

1. a first vertical well; 2. a second vertical well; 3. radiating a horizontal well; 4. an annular horizontal well; 5. a drill bit; 6. a first connection block; 7. a second connecting block; 8. a connecting shaft; 9. a first telescopic part; 10. a second telescopic part; 11. and a rotating mechanism.

Detailed Description

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate preferred embodiments of the application and together with the description, serve to explain the principles of the application and not to limit the scope of the application.

In the description of the embodiments of the present application, it should be noted that the term "connected" is to be understood broadly, and may be, for example, a fixed connection, a detachable connection, or an integral connection, which may be a mechanical connection, an electrical connection, which may be a direct connection, or an indirect connection via an intermediate medium, unless explicitly stated or limited otherwise. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art as appropriate.

The terms "top," "bottom," "above … …," "below," and "on … …" as used throughout the description are relative positions with respect to components of the device, such as the relative positions of the top and bottom substrates inside the device. It will be appreciated that the devices are multifunctional, regardless of their orientation in space.

Example 1

In an embodiment of the present application, a method for exploiting coal bed methane is disclosed, and fig. 1 is a flowchart of a method for exploiting coal bed methane according to an embodiment of the present application.

Referring to fig. 1, a coal bed methane mining method includes the steps:

and S1, exploring the coal bed gas and determining a target mining area.

Before coal bed gas exploitation is carried out, a mining area containing coal bed gas is explored, multiple factors such as thickness, gas content, permeability, coal body structure, reservoir pressure and reservoir remodelability are comprehensively considered, the production potential of the coal bed gas reservoir is reasonably evaluated, a coal bed gas accumulation area is obtained, a coal bed gas development favorable area is defined, and therefore a target exploitation area of the coal bed gas is determined. During exploration, the spatial distribution characteristics of a target coal seam and coal reservoir characteristic parameters need to be determined, specifically, the spatial distribution characteristics of the target coal seam include the depth, the plane distribution range, the inclination and the dip angle of the target coal seam, and the coal reservoir characteristic parameters include the porosity, the permeability and the like of the target coal seam. It should be noted that the target mining area in the present application refers to a coal bed methane development advantageous area, the target mining area may be a whole advantageous area, or may be a plurality of small target mining areas divided by a large-scale target mining area.

Because the coal seam has roof and bottom plate, in most cases, roof and bottom plate are not the horizontal plane or the inclined plane in the strict sense, and in the plane direction, there will also be the difference in the distance between roof and the bottom plate, and the coal seam is the thickness and the inclination difference of angle on the plane distribution.

In this embodiment, when the horizontal well drills, the drilling trajectory needs to be controlled in combination with the space spread characteristics of the target coal seam, so that the drill bit drills along the middle of the coal seam all the time, the radial horizontal well 3 and the annular horizontal well 4 are guaranteed to be in the middle of the target coal seam, and the top plate and the bottom plate of the coal seam are not drilled through.

Before step S1, space spread information of a target coal seam in an exploration area is obtained in advance by means of drilling, geophysical prospecting, earthquake and the like, a space three-dimensional rectangular coordinate system is constructed in a target mining area range with a ground borehole as an origin of coordinates, a space coordinate set of a top plate and a bottom plate of the coal seam in the target mining area is obtained, a data set of inclination angles of the top plate and the bottom plate of the coal seam is obtained according to the space coordinate information of the top plate and the bottom plate of the coal seam, a position of thinning and steep dip development of the coal seam is calibrated according to the change situation of the thickness of the coal seam, and a coordinate set of a sudden change boundary line of the top plate and the bottom plate of the coal seam is extracted. Therefore, the three-dimensional coordinate system is constructed in the range of the target mining area, the space distribution characteristics of the target coal bed are obtained in detail, data support is provided for track control of horizontal drilling, the drill bit is guaranteed to be located in the coal bed all the time to drill, and the construction effect is guaranteed.

When the spatial coordinate sets of the top plate and the bottom plate of the coal seam in the target mining area are obtained, the plane of the top plate and the plane of the bottom plate of the coal seam in the target mining area are subjected to grid division in a grid division mode to obtain the central coordinate of each grid, so that the spatial coordinate sets of the top plate and the bottom plate of the target coal seam and the inclination angle data of the top plate and the bottom plate are obtained.

With continuing reference to fig. 1, the method for mining coal bed methane according to the embodiment of the present application further includes:

s2, drilling a first vertical well 1 at the center of the target production area.

Fig. 2 is a schematic diagram of a first vertical well 1, a second vertical well 2, a radial horizontal well 3, and an annular horizontal well 4 according to an embodiment of the present application.

Referring to fig. 2, a first vertical well 1 is drilled at the center of the target production area according to the target production area determined at step S1. Optionally, the target mining area is circular, the target mining area includes a reference circle, and projections of the target mining area on a plane where the reference circle is located are all located in the reference circle. The center of the reference circle coincides with the center of the target mining area. The first vertical well 1 now extends into the target production zone. The first vertical well 1 is used for injecting fracturing fluid into the target mining area, so that the coal seam of the target mining area is fractured, a seepage channel of gas is increased, carbon dioxide competes for adsorption effect to promote the conversion of the adsorption state coal bed gas to the free state, and the mining performance of the target coal bed gas is improved.

It should be noted that the "reference circle" in the present application does not mean a circle in a strict geometric sense, and may be a circle in a geometric sense, an ellipse, or an approximate circle or ellipse.

and S3, drilling a plurality of radial horizontal wells 3 at the bottom of the first vertical well 1, wherein one end of each radial horizontal well 3 is positioned at the bottom of the first vertical well 1, and the other end of each radial horizontal well 3 extends to the edge of the target exploitation area.

With continued reference to fig. 2, a first vertical well 1 extends into the target production zone. A plurality of radial horizontal wells 3 are drilled at the bottom of the first vertical well 1. In the plane of the radial horizontal well 3, a plurality of radial horizontal wells 3 are formed radially with the bottom of the first vertical well 1 as the center. The first vertical well 1 and the radial horizontal well 3 are used for injecting fracturing fluid into the coal seam to fracture and form seams of the coal seam, and the effects of increasing permeability and promoting desorption are achieved.

Further, in step S3, a plurality of radial horizontal wells 3 are evenly distributed in the plane in the circumferential direction, so that fracturing fluid can be uniformly injected into the coal bed to the periphery of the first vertical well 1, the coal bed in the target mining area is uniformly fractured, the fracture is more uniform, the coal bed gas in the coal bed in the target mining area is enabled to be converted from an adsorption state to a free state, the desorption of the coal bed gas is accelerated, the content of the free coal bed gas in the target coal bed is greatly improved in a short time, and the mining efficiency is improved.

s4, drilling at least one second vertical well 2 at the edge of the target production area.

With continued reference to fig. 2, among the circles concentric with the reference circle, the circle with the smallest radius is taken as the edge of the target mining area. A second vertical well 2 is drilled at the edge of the target production area. The second vertical well 2 is used for collecting coal bed gas. After the coal bed is fractured, the hole fractures are expanded, the connectivity is enhanced, and free coal bed gas in the coal bed in the whole target mining area range is collected from the target mining area through the second shaft, so that the gas production efficiency is greatly improved, and the gas production amount is obviously increased in the same time.

and S5, drilling an annular horizontal well 4 at the bottom of the second vertical well 2, wherein the second vertical well 2 is communicated through the annular horizontal well 4.

With continued reference to fig. 2, the annular horizontal well 4 has the same shape as the circle of the smallest radius in step S4, taking into account that the second vertical well 2 is located at the edge of the target production zone. When the annular horizontal well 4 is drilled, the plane of the annular horizontal well 4 is parallel to the plane of the radial horizontal well 3; the annular horizontal well 4 is located on a plane higher than the radial horizontal well 3.

The height difference between the plane of the annular horizontal well 4 and the plane of the radial horizontal well 3 is smaller than the length of a crack for fracturing and seam making, and the annular horizontal well 4 can be communicated with the radial horizontal well 3 through the crack. The specific height difference of the two planes is related to rock mechanical parameters such as coal quality, coal rank, porosity, permeability, hardness, brittleness and the like and the fracture forming capability of the fracturing equipment.

and S6, injecting fracturing fluid into the coal seam through the radial horizontal well 3 to fracture the coal seam.

When the fracturing fluid is injected into the coal bed through the radial horizontal well 3, a large number of fractures are generated in the coal bed, so that the coal bed gas in the target mining area is converted from an adsorption state into a free state. Fig. 3 is a schematic size diagram of a first vertical well 1, a second vertical well 2, a radial horizontal well 3, and an annular horizontal well 4 according to an embodiment of the present application.

Referring to fig. 3, after the drilling of the first vertical well 1, the second vertical well 2, the radial horizontal well 3 and the annular horizontal well 4 is completed, the fracturing fluid is injected into the coal bed through the first vertical well 1 and the radial horizontal well 3, and the high pressure action can cause the coal bed to crack, accelerate the desorption of the coal bed gas, and rapidly improve the content of the coal bed gas in a free state in the coal bed.

Furthermore, the fracturing fluid adopts a mixed gas foam fracturing fluid system, the mixed gas foam fracturing fluid system comprises a gas phase and a liquid phase, and the volume ratio of the gas to the liquid is 3: 1. Wherein, the gas phase is nitrogen, and the liquid phase comprises the following components in percentage by weight: 60-65% of liquid carbon dioxide, 1.0% of foaming agent, 0.2-0.5% of thickening agent, 0.9-1.0% of foam stabilizer, 0.1-0.2% of bactericide, 0.2-0.4% of anti-swelling agent and the balance of clear water, wherein the total weight of the liquid phase is 100%.

In this embodiment, the main component of the coal bed gas is CH₄Coal reservoir bed base pair CO₂Has stronger adsorption capacity of CO₂By promoting CH₄Desorption can effectively prolong the gas well extraction period and CO in a supercritical state₂The surface tension (the temperature is 364.2K and the pressure is 7.28MPa) is approximate to 0, and the porous and micro-crack system is easy to enter so as to improve sweep efficiency and gas well drainage and production capacity. The carbon dioxide content in the fracturing fluid is designed to be 60-65%, so that the coal bed gas desorption can be accelerated, andthe cost is reduced.

The reason why the annular horizontal well 4 is located at a level higher than the radial horizontal well 3 in step S5 is that: in the step S6, fracturing fluid is injected into the coal seam through the radial horizontal well 3, so that the coal seam around the radial horizontal well 3 is fractured, and the fracturing fluid contains liquid CO₂And will change into gaseous CO within a certain time after injection₂High pressure CO₂The annular horizontal well 4 is higher than the plane of the radial horizontal well 3, so that the annular horizontal well 4 can be positioned in the methane concentration enrichment region, and the gas production efficiency is improved. In addition, from the perspective of the drilling engineering cost, and considering that the density of the main component methane of the coal bed gas is low, the coal bed gas in a free state should be located in an upper space, so that the height of the plane of the annular horizontal well 4 is higher than that of the radial horizontal well 3.

At present, the influence of microorganisms on the fracturing effect of a coal reservoir is not considered in coal bed gas exploitation, and the bactericide is added into the fracturing fluid of the embodiment to inhibit the survival of the microorganisms, prevent the mass propagation of the microorganisms, induce the damage of the coal reservoir and damage the performance of the fracturing fluid.

Considering that a certain amount of expansive clay minerals are commonly contained in a coal seam and in order to prevent the water-sensitive damage in the injection process of the fracturing fluid, the fracturing fluid of the embodiment is added with an anti-swelling agent to prevent the clay minerals from absorbing water and expanding to block cracks, so that the cracks are kept in a communicated state for a long time, and the gas production effect is guaranteed.

In one embodiment of the present application, the wellbore is formed to full bore after dissolution by a dissolvable bridge plug at the time of fracturing.

The input quantity Q of the fracturing fluid meets the following conditions:

wherein the content of the first and second substances,n is the number of the radial horizontal wells 3, R is the radius of the radial horizontal wells 3, D is the distance between the plane of the annular horizontal well 4 and the plane of the radial horizontal well 3,

and L is the length of the radial horizontal well 3, which is the porosity of the coal seam.

Through the limit value of the input amount of the fracturing fluid, the length of the crack can be ensured, the generated crack is ensured to be communicated with the annular horizontal well 4, the crack can be effectively prevented from being closed, and meanwhile, CO in the fracturing fluid is utilized₂Further promote coal bed gas desorption, effectively prolong gas well extraction cycle, continuously ensure that free gas enters annular horizontal well 4 through the crack, is pumped out to ground by second vertical well 2, improves coal bed gas output.

and S7, collecting coal bed gas through the annular horizontal well 4.

After the fracturing and seam making of the coal seam are completed, a large amount of free coal bed gas exists in the target coal seam, and the free coal bed gas in the target mining area is collected by the annular horizontal well 4. The coal bed gas can be extracted by negative pressure equipment such as an air pump, and the coal bed gas can also be obtained by extracting fracturing fluid mixed with the coal bed gas by a liquid pump.

In summary, compared with the prior art, the coalbed methane mining method provided by the embodiment of the application fractures and forms seams on a target coalbed through the radial horizontal well, so that the permeability of the coalbed is artificially increased, the coalbed methane is promoted to be converted from an adsorption state to a free state, desorption is accelerated, and coalbed methane mining is facilitated.

Example 2

In yet another embodiment of the present application, a horizontal drilling apparatus is disclosed, which is used in the coal bed gas exploitation method of embodiment 1, that is, when the coal bed gas exploitation method of embodiment 1 of the present application is used, a radial horizontal well 3 and an annular horizontal well 4 are drilled by the horizontal drilling apparatus of the present embodiment. FIG. 4 is a schematic view of a horizontal drilling apparatus according to an embodiment of the present application. FIG. 5 is a side view of a horizontal drilling apparatus according to one embodiment of the present application.

Referring to fig. 4 and 5, the horizontal drilling apparatus includes a steering mechanism and a drill bit 5; the steering mechanism comprises a first connecting block 6, a second connecting block 7 and a connecting shaft 8; the drill bit 5 is connected with the first connecting block 6; the first connecting block 6 is hinged with the second connecting block 7 through a connecting shaft 8. The drill bit 5 is used for tunneling, and the steering mechanism is used for adjusting the tunneling direction of the drill bit 5. The angle between the first connecting block 6 and the second connecting block 7 is adjusted by the connecting shaft 8, thereby adjusting the heading direction of the drill bit 5.

Further, referring to fig. 4 and 5, the spindle includes a connecting shaft 8, a first telescopic part 9 and a second telescopic part 10; the connecting shaft 8 is vertical to the axis of the drill bit 5; both ends of the first telescopic part 9 and the second telescopic part 10 are respectively hinged with the first connecting block 6 and the second connecting block 7; the expansion and contraction directions of the first expansion and contraction part 9 and the second expansion and contraction part 10 are parallel to the axis of the drill bit 5. When the first telescopic part 9 is extended and the second telescopic part 10 is shortened, the first connecting block 6 is turned towards one side of the second telescopic part 10 relative to the second connecting block 7, namely the tunneling direction of the drill bit 5 is turned towards one side of the second telescopic part 10. Similarly, when the second expansion part 10 is expanded, the first expansion part 9 is shortened, and the first connecting block 6 is turned toward the first expansion part 9 side relative to the second connecting block 7, that is, the heading direction of the drill bit 5 is turned toward the first expansion part 9 side in the reverse direction.

In order to enable the drill bit 5 to turn in any direction, referring to fig. 4 and 5, in the embodiment of the present application, the horizontal drilling equipment further includes a rotating mechanism 11, and the rotating mechanism 11 is connected with the second connecting block 7; the rotating mechanism 11 is used for driving the second connecting block 7 to rotate around the axis of the drill bit 5.

Further, the rotation mechanism 11 includes a drive motor, an output gear, and a ring gear. An output shaft of the driving motor is connected with the output gear, and the gear ring is meshed with the output gear. The gear ring is connected with the second connecting block 7, and when the driving motor drives the output gear to rotate, the gear ring drives the second connecting block 7 to rotate. The drill bit 5 is turned by combining a turning mechanism, so that the drill bit 5 can be turned towards any direction, and the tunneling in any direction in the horizontal plane is realized.

In order to accurately control the drilling track of the horizontal well, a positioning tracker and a ground control system are arranged on the drill bit. The positioning tracker is used for acquiring real-time position coordinates of the drill bit 5 in a three-dimensional rectangular coordinate system constructed in the range of the target mining area and sending out drill bit position information. And the ground control system is used for receiving the drill bit position information sent by the positioning tracker and adjusting the tunneling direction of the drill bit 5 according to the drill bit position information.

The ground control system comprises a control subsystem and a database subsystem. The database subsystem is used for collecting and storing coal seam space spread characteristic data in the target mining area, wherein the coal seam space spread characteristic data comprises a top and bottom plate space coordinate set, a coal seam top and bottom plate inclination angle data set, a coal seam top and bottom plate abrupt change boundary coordinate set and a real-time position coordinate of a drill bit in a three-dimensional space rectangular coordinate system. The database subsystem also stores the safe distance between the drill bit and the top and bottom of the coal seam in advance. And the database subsystem compares the position of the spatial position coordinate of the drill bit in the three-dimensional rectangular coordinate system of the target coal seam in real time. The database subsystem will issue control signals depending on the position of the drill bit 5. The control subsystem receives the control signal sent by the database subsystem and adjusts the tunneling direction of the drill bit 5 according to the control signal. The control signals include a direction signal and an angle signal. The direction signal is used to control the rotation angle of the rotating mechanism 11. The direction signal is used to control the rotation angle of the steering mechanism. When the coal seam roof or floor is about to be drilled through or the coal seam is drilled to a steep development position, the control subsystem can adjust the tunneling direction of the drill bit 5 through controlling the steering mechanism according to the drilling speed, so that the coal seam roof or floor is prevented from being drilled through, the drill bit 5 is guaranteed to drill in the middle of the coal seam all the time, and accurate horizontal well track control is achieved.

In summary, compared with the prior art, the horizontal drilling equipment provided by the embodiment of the application has a simple structure, and the drill bit can be bent towards any direction in the drilling process by arranging the steering mechanism on the drill bit, so that the tunneling in any direction in the horizontal plane is realized, and the accurate control of the drilling track can be realized. Through set up the location tracker on the drill bit, combine the three-dimensional space rectangular coordinate system based on the regional institute of target exploitation, the drill bit is at the drilling in-process, can confirm the position of drill bit in the space coordinate system, prevent that the drill bit from wearing out the coal seam roof, the bottom plate, can also meet the coal seam steepness, the direction of creeping of adjustment drill bit, make drill bit and roof or bottom plate keep the safe distance all the time, in order to guarantee that the drill bit is located the coal seam middle part all the time, thereby realize the accurate control of horizontal well drilling orbit, guarantee the smooth construction of horizontal well, to improving coal bed gas exploitation efficiency, and the device has great significance.

The above description is only for the preferred embodiment of the present application, but the scope of the present application is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present application should be covered within the scope of the present application.

Claims

1. A coal bed gas mining method is characterized by comprising the following steps:

exploring the coal bed gas and determining a target mining area;

drilling a first vertical well at a center of the target production zone;

drilling a plurality of radial horizontal wells at the bottom of a first vertical well, enabling one end of each radial horizontal well to be located at the bottom of the first vertical well, and enabling the other end of each radial horizontal well to extend to the edge of the target mining area;

drilling at least one second vertical well at the edge of the target production area;

drilling an annular horizontal well at the bottom of the second vertical well, wherein the second vertical well is communicated through the annular horizontal well;

injecting fracturing fluid into the coal bed through the radial horizontal well to perform coal bed fracturing and seam building;

and collecting the coal bed gas through the annular horizontal well.

2. The method of claim 1, wherein the target mining area comprises a reference circle, and projections of the target mining area on a plane of the reference circle are all located within the reference circle; the center of the reference circle coincides with the center of the target mining area.

3. The method of mining coal bed methane according to claim 1, wherein the plurality of radial horizontal wells are located at the same horizontal level.

4. The coal bed gas mining method according to claim 3, wherein the plane of the annular horizontal well is parallel to the plane of the radial horizontal well; the plane of the annular horizontal well is higher than the plane of the radial horizontal well.

5. The coalbed methane mining method of claim 4, wherein the input Q of the fracturing fluid satisfies:

and L is the porosity of the coal seam, and the length of the radial horizontal well.

6. The coal bed methane mining method according to any one of claims 1 to 5, wherein the fracturing fluid adopts a mixed gas foam fracturing fluid system.

7. A coal seam gas mining method according to any of claims 1 to 6, characterized in that the radial horizontal well and the annular horizontal well are drilled by horizontal drilling equipment.

8. A horizontal drilling apparatus for use in a coal bed methane mining method according to any one of claims 1 to 7;

the horizontal drilling equipment comprises a steering mechanism and a drill bit;

the steering mechanism comprises a first connecting block, a second connecting block and a connecting shaft; the drill bit is connected with the first connecting block; the first connecting block is hinged to the second connecting block through a connecting shaft.

9. The horizontal drilling apparatus of claim 8, wherein the connection shaft comprises a connection shaft, a first telescoping portion, and a second telescoping portion;

the connecting shaft is vertical to the axis of the drill bit; two ends of the first telescopic part and the second telescopic part are respectively hinged with the first connecting block and the second connecting block; the telescopic directions of the first telescopic part and the second telescopic part are parallel to the axis of the drill bit.

10. The horizontal drilling apparatus as claimed in claim 8 or 9, further comprising a rotation mechanism connected with the second connection block; the rotating mechanism is used for driving the second connecting block to rotate around the axis of the drill bit.