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Retreating sectional type hydraulic cracking method

A hydraulic fracturing and segmented technology, applied in the field of hydraulic fracturing, can solve problems such as difficulty in meeting the effect of on-site hydraulic fracturing, easy blockage of gas migration channels, increase in gas content and pressure, etc. The effect of avoiding gas excess and improving air permeability

Active Publication Date: 2015-06-17
CHINA UNIV OF MINING & TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The inhomogeneous spatial expansion of hydraulic fractures will make the driving effect of gas in the coal body area with small hydraulic pressure gradient poor, or even unable to drive, resulting in gas retention; the inhomogeneous spatial expansion of hydraulic fractures will easily block the migration of gas in the coal body channels, and even trap coal gas, causing local gas content and pressure to rise
At the same time, the conventional hydraulic fracturing process will also cause stress redistribution in the coal body, and local stress concentration will also affect the permeability of the coal body, which is unfavorable for gas migration.
In addition, since the expansion direction of hydraulic fracturing fractures in coal and rock mass is affected by the stress field around the fracturing borehole, the fracturing range is affected by the drilling depth, water injection pressure and water injection displacement; especially in the deep hole hydraulic fracturing method The hydraulic pressure attenuation in the deep part of medium-fracturing drilling is serious, resulting in the hydraulic fractures of deep-hole fracturing appearing "dense on the outside and sparse on the inside" and extremely uneven. The single-hole or multi-hole single-time fracturing in conventional hydraulic fracturing methods is difficult to meet the field conditions. hydraulic fracturing effect

Method used

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  • Retreating sectional type hydraulic cracking method

Examples

Experimental program
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Effect test

Embodiment 1

[0022] Embodiment one: The average thickness of the coal seam in a certain mine is about 2.51 m, and the buried depth is about 800 m. The coal seam is stable in occurrence and simple in structure. The inclination angle of the coal seam is about 0°-6°, with an average of 4°. It occurs in the middle and lower part of the Shanxi Formation, about 50 m away from the limestone at the top of the Carboniferous Taiyuan Formation, 36.6 m away from the sandstone at the bottom of the coal seam, and about 50 m away from the K 4 The aluminum mudstone is 51.51 m, the roof is sandy mudstone or sandstone, the floor is sandy mudstone and siltstone, and the coal seam is relatively stable. The gas content is about 11.15m 3 / t, gas drainage radius is 5 m, coal seam permeability coefficient is 0.0861 m 3 / (MPa 2 .d). The damage type of the coal seam belongs to the type III-IV coal, the relative gas pressure is 1.12-1.7 MPa, the firmness coefficient is 0.22-0.4059, the initial gas emission vel...

Embodiment 2

[0025] Embodiment two: The average thickness of the coal seam in a mine is 1.5 m, the average inclination angle is 6°, and the hardness of the coal seam f=2; the immediate roof is light gray medium-grained sandstone with an average thickness of 2.28 m; the old roof is gray-black sandy mudstone with an average thickness of 5.33 m. According to the actual situation on site, it is necessary to construct several hydraulic fracturing boreholes 9 with an inclination angle of 90°, linear, and vertical roof upward arrangement on the 30 m ahead of the working face of the wind tunnel, that is, the linear arrangement of the elevation angle. The diameter of the fracturing drilling is 32 mm, the hole depth is 4 m, and the drilling distance is 0.5 m. The construction is carried out along the advancing direction of the working face in sequence, and the directional cutting of the roof is carried out along the gob-side entry. A special fracturing installation rod 3 in the threaded connection...

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Abstract

The invention relates to a retreating sectional type hydraulic cracking method. In the invention, a mounting rod specially used for cracking is adopted to convey a hole sealer to a set position of a cracking hole, hole sealing is carried out, and the hydraulic cracking method is implemented for one time; after cracking is completed, the hole sealer is externally moved at a set step pitch towards an orifice direction, and the hydraulic cracking method is continuously implemented; and with such a repeated way till the hole sealer is moved to the minimum hole sealing depth of the cracking hole, the integral retreating sectional type hydraulic cracking method is completed. With the retreating sectional type hydraulic cracking method disclosed by the invention, the defect of nonuniform deep drill hole cracking gap caused by deep hole cracking is effectively overcome, and therefore, the problem of external denseness and internal sparseness of the cracking gap is solved; the cracking position of a crack inside a drill hole is controlled, and the extended range of the cracking gap is enlarged, and therefore, the stress cracking effect of the retreating sectional type hydraulic cracking method for a deep hole is especially outstandingly improved; if the retreating sectional type hydraulic cracking method is simultaneously adopted for multiple holes, the cracking position of the crack inside the drill hole and the extending direction of the cracking gap can be effectively controlled, and therefore, the effect of directional cracking is achieved; and the retreating sectional type hydraulic cracking method has the advantages of simplicity, convenience for construction, easy operation, safety and reliability.

Description

technical field [0001] The invention relates to a hydraulic fracturing method, in particular to a retreat segmented hydraulic fracturing method. Background technique [0002] Hydraulic fracturing technology was first applied in petroleum engineering to increase the production of poor oil wells, and is now widely used in modern coal mining, geothermal resource development, nuclear waste storage and other fields, showing a wide range of industrial application values. With the help of the basic concept of hydraulic fracturing, the research and development of hydraulic fracturing weakening and anti-permeability technology of coal and rock mass is one of the key technologies to solve the problem of coal mining rock formation control and gas prevention and control. [0003] In the process of hydraulic fracturing of conventional coal seams, because the expansion of hydraulic fractures is affected by in-situ stress and coal cleat-pore system, the expansion of fractures shows inhomog...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): E21B43/26
Inventor 黄炳香程庆迎张统
Owner CHINA UNIV OF MINING & TECH
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