Fractured horizontal well position deployment construction method giving consideration to mine pressure treatment and gas extraction

Abstract

The invention provides a well position deployment construction method for a fractured horizontal well considering mine pressure treatment and gas extraction. The well position deployment construction method comprises the steps that firstly, a target key layer is determined; secondly, a ground L-shaped horizontal well is constructed; thirdly, hydraulic staged fracturing is conducted; step 4, reinjection; step 5, filling; sixthly, gas is extracted in a high extraction roadway; and 7, high-position drilling gas extraction is carried out. The method has the advantages of being controllable in drilling track, wide in influence area, low in construction cost and the like, rock burst can be effectively prevented and controlled, the problem that gas in a mining area and a goaf exceeds the limit is solved, meanwhile, the roadway tunneling work amount is reduced, and the purposes of reducing cost and improving efficiency are achieved. According to the method, multiple purposes are achieved through one well, treatment of the rock burst area of the deep coal seam is achieved, the gas extraction effect of a mining area in stoping and the gas extraction effect of a goaf after stoping are improved, and safe production of a mine is guaranteed.

Description

Technical Field

[0001] The present invention belongs to the technical field of coal mining, relates to a fracturing horizontal well, and specifically relates to a well site deployment and construction method for a fracturing horizontal well that takes into account both mine pressure control and gas extraction. Background Art

[0003] Directional blasting and short-bore hydraulic fracturing are often used to prevent and control the overlying roof pressure of coal seams. Practice has proved that underground directional blasting and short-bore hydraulic fracturing are relatively effective means of preventing and controlling hard roof within a short distance from the coal seam, but there are problems such as small range of danger relief, limited underground construction conditions, large workload, and prominent contradictions with production, which cannot achieve regional prevention and control of the overlying roof within the entire working face and higher layers.

[0004] In order to deal with the disaster of excessive gas in mines, the method of arranging high-extraction lanes and high-position drilling holes to extract gas is often used. The high-extraction lane is a special extraction lane excavated in the fracture zone formed by mining at the top of the mining layer. The underground gas extraction system is used to extract the gas from the mining face at a high position, reduce the gas concentration during the mining process of the working face, and reduce gas exceeding the limit. The high-position drilling hole is to drill a hole from the return air lane to the roof of the coal seam, and use the fracture space formed by the caving zone of the mining stress field as a gas flow channel. Under the action of the negative pressure of extraction, the gas flows to the borehole, thereby solving the problem of excessive gas in the upper corner of the goaf and the return air flow.

[0005] The above-mentioned governance methods are only single-factor disaster governance, and have not formed a set of technical methods for the simultaneous governance of multiple disaster factors. Summary of the invention

[0006] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for deploying and constructing a fractured horizontal well that takes into account both mine pressure control and gas extraction, so as to solve the technical problem that the method for deploying and constructing a fractured horizontal well in the prior art is difficult to take into account both mine pressure control and gas extraction.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions to achieve the above problems:

[0008] A method for deploying and constructing a fracturing horizontal well that takes into account both mine pressure control and gas extraction, the method comprising the following steps:

[0009] Step 1: Determine the target key layer:

[0010] Collect exploration and mine data of the target mining area, analyze the distance between the key layers above the coal seam and the coal seam, and obtain the range of the fracture zone through the working face mining height and working face mining depth. Finally, select the key layer in the fracture zone as the target key layer.

[0011] Step 2: Construction of L-shaped horizontal well on the ground:

[0012] A surface L-shaped horizontal well is constructed in the target key layer obtained in step 1. The surface L-shaped horizontal well adopts a two-opening structure including a first horizontal well opening and a second horizontal well opening. The second opening horizontal section is drilled along the target key layer.

[0013] Step 3: Hydraulic staged fracturing:

[0014] The L-shaped horizontal well obtained in step 2 is hydraulically fractured.

[0015] Step 4: Make up shot:

[0016] After the hydraulic fracturing in step three is completed, hydraulic sandblasting perforation is used for supplementary perforation.

[0017] Step 5: Filling:

[0018] The horizontal section is pebble filled during well completion.

[0019] Step 6: Extract gas from high-pressure tunnels:

[0020] During the mining process, as coal is mined, the overlying rock strata move and deform, forming a banded structure. The banded structure will enter the coal seam, surrounding rock and adjacent coal seams above and below, becoming a gas migration channel for the migration of gas released by the pressure relief disturbance of the working face. The gas enters the wellbore through the gas migration channel and is pumped to the ground.

[0021] Step 7: High-level drilling to extract gas:

[0022] After mining, the gas released from the residual coal pillars and surrounding rocks will accumulate in the goaf due to the concentration difference and pressure difference. These accumulated gases will also enter the wellbore through the gas migration channel and be pumped to the ground.

[0023] The present invention also has the following technical features:

[0024] In step 2, the drilling direction of the second horizontal section is opposite to the mining direction of the working face.

[0025] In step six, the belt-like structure includes a span zone, a fracture zone and a curved subsidence zone.

[0026] Compared with the prior art, the present invention has the following technical effects:

[0027] (I) The present invention proposes a ground staged fracturing horizontal well technology that takes into account both underground mine pressure control and high-drawing lane and high-position drilling gas extraction. The method of the present invention has the advantages of controllable drilling trajectory, wide affected area, and low construction cost. It can effectively prevent and control rock bursts and solve the problem of excessive gas in mining areas and goafs. At the same time, it also reduces the amount of tunnel excavation engineering, achieving the goal of reducing costs and increasing efficiency.

[0028] (II) The present invention proposes a well site deployment and construction method for ground staged fracturing horizontal wells that takes into account both underground mine pressure control and gas extraction from high-extraction lanes and high-position boreholes, thereby realizing "one well for multiple uses" and achieving regional control of impact ground pressure in deep coal seams, improving the gas extraction effect in the mining area during mining, and the gas extraction effect in the goaf area after mining, thereby ensuring safe production in mines.

[0029] (III) The present invention can treat the rock burst in deep coal seams through L-shaped segmented fracturing horizontal wells on the ground, while extracting gas from the mining area and goaf of the working face; improve the communication between the formation and the wellbore through hydraulic fracturing supplementary injection technology; and fill pebbles into the horizontal well section through pebble filling technology to ensure that the extraction channel is not deformed by mining, thereby extending the extraction service life of the horizontal well.

[0030] (IV) The present invention can treat the rock burst in deep coal seams through L-shaped segmented fracturing horizontal wells on the ground, while replacing high-extraction lanes and high-position drilling holes to extract gas from the mining area and goaf of the working face; improve the communication between the formation and the wellbore through hydraulic sandblasting supplementary injection technology; and fill pebbles into the horizontal well section through pebble filling technology to ensure that the extraction channel is not deformed by mining, thereby extending the extraction service life of the horizontal well. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of the well location deployment of the ground staged fracturing horizontal well of the present invention.

[0032] The meanings of the numbers in the figure are: 1-first opening of horizontal well, 2-second opening of horizontal well, 3-target key layer, 4-coal seam, 5-starting mining line of working face.

[0033] The specific contents of the present invention are further explained in detail below in conjunction with embodiments. DETAILED DESCRIPTION

[0034] It should be noted that, unless otherwise specified, all components and equipment in the present invention are components and equipment known in the prior art.

[0035] Specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent changes made on the basis of the technical solution of this application fall within the protection scope of the present invention.

[0036] Example:

[0037] This embodiment provides a method for deploying a horizontal well location for fracturing that takes into account both mine pressure control and gas extraction. Figure 1 As shown, the method comprises the following steps:

[0038] Step 1: Determine the target key layer:

[0039] The exploration and mine data of the target mining area are collected, and the distance between the key layers above the coal seam 4 and the coal seam 4 is analyzed according to the key layer theory and the "three-zone" theory known in the art. The range of the fracture zone is obtained through the working face mining height and working face mining depth, and finally the key layer in the fracture zone is selected as the target key layer 3.

[0040] Specifically, in this embodiment, a fracture zone with a range of 10 to 15 times the mining height is obtained, and a key layer in the fracture zone is selected as the target layer for well layout.

[0041] Step 2: Construction of L-shaped horizontal well on the ground:

[0042] A surface L-shaped horizontal well is constructed in the target key layer 3 obtained in step 1. The surface L-shaped horizontal well adopts a two-opening structure including a horizontal well first opening 1 and a horizontal well second opening 2. The second opening horizontal section is drilled along the target key layer 3.

[0043] Specifically, in this embodiment, the first vertical well section and the second inclined well section are conventionally designed for a surface L-shaped well, the landing point is located in the target key layer 3, and the second horizontal well section extends along the top of the fracture zone.

[0044] In step 2, the direction of drilling the second horizontal section is opposite to the mining direction of the working face, so as to ensure that the wellbore is not damaged by formation collapse during the mining process.

[0045] Step 3: Hydraulic staged fracturing:

[0046] The L-shaped staged fracturing horizontal well obtained in step 2 is hydraulically staged fracturing to prevent and control rock burst.

[0047] Specifically, in this embodiment, pumped perforation and cable-delivered bridge plug and perforation joint technical service process are used for fracturing, with a perforation interval of 50m, and one-third of the fracturing section is selected for crack monitoring during fracturing. The downhole perforating gun and the bridge plug tool string are connected by cables, and the tool string is lowered into the well under a closed construction state. After reaching the high-angle section, the wellhead is pressurized to push the tool string downward. By adjusting the pump displacement, a local pressure difference is formed before and after the tool string, pushing the tool string to the target layer section, lifting the cable to ignite and seal the bridge plug, and lifting the cable again to complete the perforation.

[0048] Step 4: Make up shot:

[0049] After the hydraulic fracturing in step three is completed, hydraulic sandblasting perforation is used for supplementary perforation to improve the communication effect between the formation and the wellbore.

[0050] Specifically, in this embodiment, hydraulic sandblasting perforation technology is used for supplementary perforation, and the perforation interval is 5m. The oil pipe with bottom seal is selected to drag the hydraulic sandblasting perforation construction.

[0051] Step 5: Filling:

[0052] When completing the well, the horizontal section is filled with pebbles to improve the casing's anti-smear strength, prevent casing deformation, protect the smooth flow of the extraction channel, and extend the service life of the horizontal well.

[0053] Specifically, in this embodiment, the bottom hole tool is connected and lowered; the screen pipe is connected, and the inside of the screen pipe is filled with pebbles; and the screen pipes filled with pebbles are lowered in sequence to prevent the casing from being deformed and increase the compressive strength of the casing.

[0054] Step 6: Extract gas from high-pressure tunnels:

[0055] During the mining process, as the coal is mined, the overlying rock strata move and deform, forming a banded structure. The banded structure will enter the coal seam, surrounding rock and the adjacent coal seams above and below, becoming a gas migration channel for the migration of a large amount of gas released by the pressure unloading disturbance of the working face. The gas enters the wellbore through the gas migration channel and is pumped to the ground, achieving the purpose of extracting gas in a high-extraction lane.

[0056] In step six, the belt structure includes the span zone, the fracture zone and the curved subsidence zone.

[0057] Step 7: High-level drilling to extract gas:

[0058] After mining, a large amount of gas released from the residual coal pillars and surrounding rocks will accumulate in the goaf due to the concentration difference and pressure difference. These accumulated gases will also enter the wellbore through the gas migration channel and be pumped to the ground, thus achieving the purpose of gas extraction through high-position drilling.

[0059] The above embodiment provides a ground L-shaped segmented fracturing horizontal well location deployment and construction method that can carry out regional prevention and control of deep rock burst before mining, while taking into account the extraction of gas during mining and gas in goaf areas, thereby achieving "one well for multiple uses" and providing a new method for rock burst and gas disaster management.

Claims

1. A method for deploying and constructing a horizontal well for fracturing that takes into account both mine pressure control and gas extraction, characterized in that: The method comprises the following steps: Step 1: Determine the target key layer: Collect exploration and mine data of the target mining area, analyze the distance between each key layer above the coal seam (4) and the coal seam (4), and obtain the range of the fracture zone through the working face mining height and working face mining depth, and finally select the key layer in the fracture zone as the target key layer (3); Step 2: Construction of L-shaped horizontal well on the ground: Constructing a surface L-shaped horizontal well in the target key layer (3) obtained in step 1, the surface L-shaped horizontal well adopts a two-opening structure including a horizontal well first opening (1) and a horizontal well second opening (2), and the second opening horizontal section is drilled along the target key layer (3); Step 3: Hydraulic staged fracturing: Performing hydraulic staged fracturing on the surface L-shaped staged fracturing horizontal well obtained in step 2; Step 4: Make up shot: After the hydraulic fracturing in step 3 is completed, hydraulic sandblasting perforation is used for supplementary perforation; Step 5: Filling: Pebble filling of horizontal sections during well completion; Step 6: Extract gas from high-pressure tunnels: During the mining process, as the coal is mined, the overlying rock strata move and deform, forming a banded structure. The banded structure will enter the coal seam, surrounding rock and upper and lower adjacent coal seams, becoming a gas migration channel for the gas released by the pressure relief disturbance of the working face. The gas enters the wellbore through the gas migration channel and is pumped to the ground. Step 7: High-level drilling to extract gas: After mining, the gas released from the residual coal pillars and surrounding rocks will accumulate in the goaf due to the concentration difference and pressure difference. These accumulated gases will also enter the wellbore through the gas migration channel and be pumped to the ground.

2. The method for deploying and constructing a horizontal well for fracturing that takes into account both mine pressure control and gas extraction as claimed in claim 1, characterized in that: In step 2, the drilling direction of the second horizontal section is opposite to the mining direction of the working face.

3. The method for deploying and constructing a horizontal well for fracturing that takes into account both mine pressure control and gas extraction as claimed in claim 1, characterized in that: In step six, the belt-like structure includes a span zone, a fracture zone and a curved subsidence zone.

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