Sub-regional multi-section gas extraction method for long borehole

Abstract

The present application relates to a kind of regional multi-section gas extraction methods for long borehole, using multi-channel gas extraction combined screen pipe to carry out zoned segmental closed extraction to borehole, the multi-channel gas extraction combined screen pipe includes several screen pipe groups of different lengths, screen pipe group is connected and fixed as a whole by packer between screen pipe group, each screen pipe group forms an extraction channel, screen pipe group of different lengths is located at different positions in borehole, after the section of borehole is separated by packer, segmented gas extraction is carried out.Can according to the depth of borehole and negative pressure decay law, extraction section is reasonably divided, segmented gas extraction to borehole is realized, and gas extraction efficiency and safety are improved.The present application can flexibly adjust the length and quantity of extraction section according to the actual situation of borehole, so that each section can be effectively subjected to negative pressure effect, segmented gas extraction to borehole is realized, and gas extraction efficiency and safety are improved.

Description

Technical Field

[0001] This invention belongs to the field of coal mine gas extraction technology, and relates to a multi-stage gas extraction method for long boreholes. Background Technology

[0002] Coal mine gas refers to methane gas in coal seams. It is a combustible, green energy source, but also a significant factor threatening coal mine safety. Methane extraction is a crucial means of ensuring safe production and utilizing coal mine gas. It can effectively reduce gas concentration, prevent gas explosions, and provide clean energy for the coal mine.

[0003] Currently, underground coal mines primarily rely on drilling for gas drainage. Normally, after drilling is completed, the borehole is sealed using a two-plug-one-injection method. Then, the drainage pipeline is connected to the sealing flange, and gas is drained from the borehole through the negative pressure of the drainage system. Under low-pressure, low-permeability, and low-saturation coal seam conditions, the negative pressure at the borehole opening determines the effectiveness of gas drainage. However, due to limitations of the drainage system, the negative pressure at the borehole opening has a limit. As the drilling depth increases, the negative pressure decreases, resulting in a limited range of influence within the borehole, significantly impacting the efficiency of borehole gas drainage. Especially with the widespread application of directional long-bore drilling technology, many coal mines are capable of drilling boreholes exceeding 500 meters in depth. However, based on the existing negative pressure parameters of the drainage system, it is impossible to generate a negative pressure effect in borehole sections of 200-500 meters, thus failing to fully utilize the gas drainage capabilities of long boreholes. Summary of the Invention

[0004] In view of this, the present invention proposes a multi-segment gas extraction method for long boreholes, which divides the long borehole into segments to form mutually spaced extraction borehole segments, and uses multi-channel screens to extract gas from each segment separately, thereby achieving segmented gas extraction.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A method for segmented, multi-stage gas extraction in long boreholes employs a multi-channel gas extraction combined screen pipe system to perform segmented, sealed gas extraction from the borehole. The multi-channel gas extraction combined screen pipe system comprises several screen pipe groups of different lengths, which are connected and fixed as a whole by a sealing device. Each screen pipe group includes a connecting pipe and an extraction pipe, which are connected to the extraction pipeline via the connecting pipe. The extraction pipe has screen holes, and each screen pipe group forms an extraction channel. Screen pipe groups of different lengths are located at different positions within the borehole. After the borehole is segmented by the sealing device, segmented gas extraction is performed.

[0007] Furthermore, the regional multi-stage gas extraction method for long boreholes specifically includes the following steps:

[0008] S1: After drilling and sealing the hole, use a directional drilling rig to drill a long directional hole. After drilling and cleaning the hole, retract the drill.

[0009] S2: Based on the borehole formation parameters and the negative pressure parameters of the wellhead extraction, the attenuation law of the negative pressure in the borehole is tested by numerical simulation or similar simulation analysis, and the maximum influence range of the negative pressure in the borehole is calculated.

[0010] S3: Based on the influence range of the negative pressure during extraction and the borehole trajectory, the directional long borehole is divided into n extraction sections, where n is a natural number;

[0011] S4: Lower the multi-channel gas extraction combined screen pipe from the orifice until the designed orifice depth; where the number of channels is n and the number of sealing devices is n-1.

[0012] S5: Through primary ball throwing and pumping pressure, the final sealing device is expanded and sealed to the borehole wall;

[0013] S6: Then, through secondary ball throwing and pumping pressure, the second sealing device at the bottom of the hole is expanded and sealed to the borehole wall;

[0014] S7: Sequentially throw balls and pump pressure until the first sealing device at the orifice expands and seals it against the borehole wall;

[0015] S8: Connect the connecting pipes of different channels to the multi-channel flange assembly of the orifice, and then connect them to different negative pressure extraction pipelines respectively;

[0016] S9: Open the negative pressure extraction pipeline, drain the gas from the borehole, and observe and record the gas extraction data of each channel.

[0017] Furthermore, the drilling parameters for directional drilling in S2 are hole depth, hole diameter, drilling inclination angle, and azimuth angle.

[0018] Furthermore, the cross-sectional shape of both the connecting pipe and the extraction pipe is circular, arc-shaped, annular, or polygonal.

[0019] Furthermore, the length and number of the screen tube group are determined based on the borehole depth and extraction design.

[0020] The beneficial effects of this invention are as follows:

[0021] This invention solves the problem of insufficient negative pressure influence range at the borehole opening by dividing and segmenting long boreholes and connecting them with multiple extraction channels that are individually linked to the extraction sections. Ultimately, it achieves segmented gas extraction from long boreholes, significantly improving the gas extraction efficiency per borehole and shortening the coal mine gas control cycle.

[0022] This invention can flexibly adjust the length and number of extraction sections according to the actual situation of the borehole, so that each section can be subjected to effective negative pressure, thereby realizing segmented gas extraction of the borehole and improving gas extraction efficiency and safety.

[0023] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0024] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein:

[0025] Figure 1 This is a schematic diagram of the multi-segment gas extraction method for long boreholes according to the present invention.

[0026] Figure 2 This is a schematic diagram of the overall structure of the multi-channel gas extraction combined screen pipe in this invention.

[0027] Figure 3 for Figure 2 A schematic diagram of the structure of the middle sieve tube assembly.

[0028] Reference numerals: 1-Multi-channel flange assembly; 2-Coal wall; 3-First sealing device; 4-Second sealing device; 5-First screen tube assembly; 6-Second screen tube assembly; 7-Third screen tube assembly; 8-Connecting pipe; 9-Extraction pipe. Detailed Implementation

[0029] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0030] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0031] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0032] Please see Figures 1-3 This invention relates to a multi-segment gas extraction method for long boreholes. It employs a multi-channel gas extraction combined screen pipe system to perform segmented, sealed gas extraction from the borehole. The multi-channel gas extraction combined screen pipe system comprises several screen pipe groups of different lengths, which are connected and fixed as a whole by a sealing device. Each screen pipe group includes a connecting pipe 8 and an extraction pipe 9. The extraction pipe 9 is connected to the extraction pipeline through the connecting pipe 8 and has screen holes. Each screen pipe group forms an extraction channel. Screen pipe groups of different lengths are located at different positions within the borehole. After the borehole is divided into segments by the sealing device, segmented gas extraction is performed.

[0033] The cross-sectional shapes of both the connecting pipe 8 and the extraction pipe 9 are circular, arc-shaped, annular, or polygonal. The length and number of screen pipe groups are determined according to the drilling depth and extraction design. The connecting pipe 8 is a hollow solid pipe and is connected to the extraction pipe 9 by means of threads, plugs, etc.

[0034] In this embodiment, a 3-channel borehole is used as an example. The borehole is divided into 3 sections by 2 sealing devices. The first screen tube group 5, the second screen tube group 6, and the third screen tube group 7 are used to extract water from the three sections separately. The specific implementation includes the following steps:

[0035] S1: After drilling and sealing the hole, use a directional drilling rig to drill a long directional hole. After drilling and cleaning the hole, retract the drill.

[0036] S2: Based on the borehole formation parameters and borehole extraction negative pressure parameters of directional borehole A, including borehole depth, borehole diameter, borehole inclination angle, and azimuth angle; use numerical simulation or similar simulation and other analytical methods to test the attenuation law of negative pressure in the borehole and calculate the maximum influence range of negative pressure in the borehole.

[0037] S3: Based on the influence range of the negative pressure during extraction and the borehole trajectory, the directional long borehole A is divided into 3 extraction sections;

[0038] S4: Lower the multi-channel gas extraction combined screen pipe from the orifice until the designed orifice depth;

[0039] S5: Through the first-stage ball throwing and pumping pressure, the second sealing device 4 at the very end is expanded and sealed to the borehole wall;

[0040] S6: Then, through secondary ball throwing and pumping pressure, the first sealing device 3 at the orifice is expanded and sealed to the borehole wall; the first sealing device 3 and the second sealing device 4 divide the directional borehole A into three extraction sections: B, C and D.

[0041] S8: Connect the connecting pipes 8 with different channels to the multi-channel flange assembly 1, and then connect them to different negative pressure extraction pipelines respectively.

[0042] S9: Open the negative pressure extraction pipeline, and use the first screen tube group 5, the second screen tube group 6, and the third screen tube group 7 to extract gas from the borehole, and observe and record the gas extraction data of each channel.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for multi-segment gas extraction in long boreholes, characterized in that: A multi-channel gas extraction combined screen pipe is used to perform segmented closed gas extraction from the borehole. The multi-channel gas extraction combined screen pipe includes several screen pipe groups of different lengths, which are connected and fixed as a whole by a sealing device. Each screen pipe group includes a connecting pipe and an extraction pipe. The extraction pipe is connected to the extraction pipeline through the connecting pipe. The extraction pipe is provided with screen holes. Each screen pipe group forms an extraction channel. Screen pipe groups of different lengths are located at different positions in the borehole. After the borehole is divided into sections by the sealing device, segmented gas extraction is performed. Includes the following steps: S1: After drilling and sealing the hole, use a directional drilling rig to drill a long directional hole. After drilling and cleaning the hole, retract the drill. S2: Based on the borehole formation parameters and the negative pressure parameters of the wellhead extraction, the attenuation law of the negative pressure in the borehole is tested by numerical simulation or similar simulation analysis, and the maximum influence range of the negative pressure in the borehole is calculated. S3: Based on the influence range of the negative pressure during extraction and the borehole trajectory, the directional long borehole is divided into n extraction sections; S4: Lower the multi-channel gas extraction combined screen pipe from the orifice until the designed orifice depth; where the number of channels is n and the number of sealing devices is n-1. S5: Through primary ball throwing and pumping pressure, the final sealing device is expanded and sealed to the borehole wall; S6: Then, through secondary ball throwing and pumping pressure, the second sealing device at the bottom of the hole is expanded and sealed to the borehole wall; S7: Sequentially throw balls and pump pressure until the first sealing device at the orifice expands and seals it against the borehole wall; S8: Connect the connecting pipes of different channels to the multi-channel flange assembly of the orifice, and then connect them to different negative pressure extraction pipelines respectively; S9: Open the negative pressure extraction pipeline, drain the gas from the borehole, and observe and record the gas extraction data of each channel.

2. The method for multi-segment gas extraction in long boreholes according to claim 1, characterized in that: The drilling parameters for directional drilling in S2 are hole depth, hole diameter, drilling inclination angle, and azimuth angle.

3. The method for multi-segment gas extraction in long boreholes according to claim 1, characterized in that: The cross-sectional shapes of the connecting pipe and the extraction pipe are both circular, arc-shaped, annular, or polygonal.

4. The method for multi-segment gas extraction in long boreholes according to claim 1, characterized in that: The length and number of the screen tube groups are determined based on the borehole depth and extraction design.

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