Efficient gas extraction method for up-and-down combined fracturing area of broken soft low-permeability coal seam well

Abstract

The invention provides an efficient gas extraction method for an up-and-down combined fracturing area of a broken soft low-permeability coal seam well. The method comprises the following steps that amining area main roadway or an operation roadway is formed under a coal mine, and a place is provided for construction operation and gas extraction; secondly, a group of directional long drill holes capable of covering a plurality of working surfaces of a mining area are constructed along a certain distance between a coal seam roof and a coal seam top boundary or between a coal seam floor and a coal seam bottom boundary under a coal mine; then, a roadway penetrating well communicates with the underground mining area main roadway or the operation roadway on the ground, so that a ground fracturing manifold is connected with a ground well-underground long drill hole high-pressure connecting device; and then staged fracturing construction is alternately carried out on the underground long drill hole of the coal mine through ground large-scale fracturing equipment, staged fracturing operation is mainly completed in an underground roadway, and finally grid-connected extraction is carried outthrough a special extraction pipeline for underground gas of the coal mine. According to the method, the transformation strength and the extraction effect of the underground broken soft low-permeability coal seam reservoir of the coal mine are effectively improved, and underground regionalized dead-corner-free low-cost efficient gas extraction of the coal mine is achieved.

Description

technical field [0001] The invention belongs to the technical field of gas drainage in coal mines, and relates to a high-efficiency gas drainage method in an upper and lower combined fracturing area of ​​a fractured soft low-permeability coal seam. Background technique [0002] At present, the coal mine gas extraction methods are mainly based on surface coalbed methane development and underground borehole negative pressure extraction, but the gas extraction effect is poor and the extraction cost is high in broken, soft, low-permeable, high-gas outburst coal seams. [0003] The coal mine methane drainage method based on surface coalbed methane development has disadvantages such as high operating cost, low extraction efficiency, long extraction cycle, large land occupation, and severe terrain restrictions. [0004] Coal mine gas drainage mainly based on underground borehole negative pressure drainage is limited by underground fracturing equipment and construction conditions, w...

AI Technical Summary

Problems solved by technology

[0002] At present, coal mine gas extraction methods are mainly based on surface coalbed methane development and underground borehole negative pressure extraction, but the gas extraction effect of broken, soft, low-permeable, high-gas outburst coal seams is poor and the extraction cost is high

[0003] The coal mine gas drainage method based on surface coalbed methane development has disadvantages such as high operating costs, low drainage efficiency, long drainage cycle, large land occupation, and severe terrain restrictions.

[0004] Coal mine gas drainage mainly based on underground borehole negative pressure drainage is limited by underground fracturing equipment and construction conditions, which has the advantages of small fracturing pump injection and displacement, difficult sand addition, difficult equipment transportation, and enhanced permeability of coal seams. Poor disadvantages lead to poor gas drainage effect

[0005] In the prior art, there is disclosed a coal mine underground gas drilling and fracturing method (Patent No. ZL201010252178.7). Ground drilling and fracturing equipment is used to perform full-hole fracturing on long boreholes in the coal seam. This drainage method exists The following limitations are manifested in the following limitations: (1) Drilling into broken and soft coal seams is easy to collapse and bury the drill, and the length of the drill hole is limited; (2) Open-hole drilling is used for full-hole fracturing, and the initiation and extension of cracks are random, which is easy to form a drainage blank area. , direct fracturing in relatively plastic broken soft coal seams, the expansion and extension of fracturing fractures is not long, and the effect of stimulation is not good; therefore, technical defects limit the application of this method in broken soft low permeability coal seams

Also disclosed in the prior art is a ground-assisted downhole long borehole gas enhanced drainage method (patent number CN108661697 A), in which ground fracturing equipment is used to perform segmental fracturing on long boreholes in the coal seam. Although ground fracturing equipment has been used to achieve segmental fracturing of underground drilling, since the horizontal drilling is arranged in the coal seam, in addition to the impact on the length of the drilling hole and the fracturing effect of the coal seam, there are also difficulties in the middle and lower screens of the coal seam and mining problems. Problems such as the treatment of screen pipes in front of the coal are still unable to solve the problem of advanced gas control in the soft and low-permeability coal seam area from a technical perspective

[0006] To sum up, in view of the broken soft low permeability coal seam, the current surface coalbed methane development technology, downhole drilling negative pressure drainage technology and combined upper and lower well drainage methods are all unsatisfactory, and it is difficult to quickly reduce the broken soft low permeability at low cost. CBM Content and Gas Pressure Targets

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