Permeability improvement technology for coal bed gas reservoir cap by using three-dimensional fracture network modification

A technology of coal bed methane and storage cap, applied in the direction of mining fluid, gas discharge, safety devices, etc., can solve the problems of prolonging the extraction time, failing to achieve the extraction effect, and increasing the gas permeability of coal storage caprock

Inactive Publication Date: 2012-03-28
HENAN COAL CHEM IND GROUP INST
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, due to the serious influence of the low permeability characteristics of the coal seam, when the conventional drilling arrangement is used to pre-drain coal seam gas, the required drainage effect is often not achieved; therefore, improving the permeability of the coal seam has become the key to improving the gas drainage effect
For the problem of gas drainage in low-permeability coal seams, the traditional methods only rely on measures such as reducing the drilling distance, increasing the amount of drilling, and prolonging the drainage time

Method used

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  • Permeability improvement technology for coal bed gas reservoir cap by using three-dimensional fracture network modification
  • Permeability improvement technology for coal bed gas reservoir cap by using three-dimensional fracture network modification
  • Permeability improvement technology for coal bed gas reservoir cap by using three-dimensional fracture network modification

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Experimental program
Comparison scheme
Effect test

Embodiment 1

[0032] The thickness of the coal seam is 6 m, and the burial depth is 600 m. The soft and outburst coal seam 6 is nearly horizontal. The damage type of this seam is type IV or type V, and the coal body structure is mylonitic coal; the gas content is 25 m 3 / t, the gas pressure is 1.8 MPa; the coal seam roof 4 is medium sandstone and siltstone, 0.95-10.32m thick, with an average of 6.55m; the coal seam floor 7 is sandy mudstone or siltstone, with a thickness of 0.88-19.33 m, with an average of 7.00 m, There is a limestone aquifer on the floor of the coal seam, 20-30m above the coal seam, and the development of karst and fissures is uneven.

[0033] The implementation steps are as follows:

[0034] (1) Select a suitable location on the surface 1 and determine the well location;

[0035](2) Drill wells to the roof 4 and floor 7 of the coal seam with a three-shape shaft structure. Two horizontal wells 5 are constructed on the roof at an angle of 30°, and two horizontal wells 8 ...

Embodiment 2

[0039] For the soft, low-permeability, outburst coal seam 6 with a thickness of 8 m and a burial depth of 640 m, the failure type of this seam is Class IV, and the coal body structure is crushed coal; the gas content is 28 m 3 / t, the gas pressure is 1.9MPa; the coal seam roof 4 is sandy mudstone, 3.2-15.9m thick, with an average of 7.8m, and the coal seam floor 7 is siltstone, 2.6-17.6m thick, with an average of 7.6m. Unbalanced development of fissures.

[0040] The implementation steps are as follows

[0041] (1) Select a suitable location on the ground 1 and determine the well location;

[0042] (2) The horizontal well is constructed to the coal seam roof 4 and the coal seam floor 7 by adopting the three-shaft shaft structure. Firstly, the horizontal well constructed in the coal seam roof 4 has a diameter of 311.1 mm in the first opening hole 2 of the branch horizontal well, and is drilled into Φ244. 5mm N80 steel grade technical casing, the surface layer casing is open...

Embodiment 3

[0048] For the soft, low-permeability, outburst coal seam 6 with a thickness of 8 m and a burial depth of 640 m, the failure type of this seam is Class IV, and the coal body structure is crushed coal; the gas content is 28 m 3 / t, the gas pressure is 1.9MPa; the coal seam roof 4 is sandy mudstone, 3.2-15.9m thick, with an average of 7.8m, and the coal seam floor 7 is siltstone, 2.6-17.6m thick, with an average of 7.6m. Unbalanced development of fissures.

[0049] The implementation steps are as follows:

[0050] (1) According to the conditions and requirements of the roadway engineering, select the opening positions of drilling holes 9 and 10.

[0051] (2) Use a high-power drilling rig to construct a set of bedding-long drill holes 9 and 10 on the top plate 4 and bottom plate 7 of the working face, with a diameter of 120 mm and a depth of 200 m.

[0052] (3) The bedding-long drilling 9 of the top plate and the bedding-long drilling 10 of the bottom plate form an included a...

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Abstract

The invention relates to a permeability improvement technology for a coal bed gas reservoir cap by using three-dimensional fracture network modification. The technology is as follows: building a bedding horizontal well from ground to top and bottom plates of the coal bed of an area not mined; building bedding, three-dimensional cross-type or multi-branch long boreholes on the top and bottom plates of the coal bed of the area not mined through perforation and segmented fracturing or existing sinking and driving engineering, and then carrying out hydraulic fracturing; modifying the coal bed gas reservoir cap into a crisscross fracture network system to form a modified volume; building various types of drainage boreholes in the modified volume; and carrying out negative pressure extraction together with a fractured well, so that coal bed gas can be continuously desorbed and dispersed and then extracted out in large scale through the modified volume. According to the invention, the crisscross fracture network system is formed in the coal bed gas reservoir cap, so that the coal bed gas can be continuously desorbed and dispersed at negative pressure and then extracted out in large scale through the modified volume, thus the content of coal bed gas in the modified bed can be quickly reduced to be below the safety standard in the outburst prevention formulation, and safe and high-efficiency production of mines can be realized on the basis of forming scale coal bed gas development.

Description

technical field [0001] The invention relates to the technical field of enhancement and anti-permeability of coalbed methane (gas) reservoir caprock, in particular to a new technology for reconstruction and antireflection of three-dimensional fracture network of coalbed methane (gas) reservoir caprock. Background technique [0002] In recent years, mine mining has developed to the deep, and the mining depth of some mines has exceeded 1000 m. With the increase of mining depth, the gas content of coal seams gradually increases, and the gas pressure of coal seams increases. Some low-gas mines or high-gas mines are gradually upgraded to outburst mines, resulting in frequent gas accidents and has become a bottleneck restricting the improvement of coal mine safety. Therefore, gas control is the primary task of the current coal mine safety work, and this problem needs to be solved urgently. [0003] The twelve-character policy of my country's gas control "pumping first, monitoring ...

Claims

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Application Information

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IPC IPC(8): E21F7/00E21B43/26E21B7/00
Inventor 马耕陶云奇苏现波李伍成杨程涛丁建础刘三钧王峰
Owner HENAN COAL CHEM IND GROUP INST
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