Hydraulic fracturing overlying key layer pressure relief and permeability increasing method

Abstract

The invention belongs to the field of gas control and geological strata, and relates to a hydraulic fracturing overlying key layer pressure relief and permeability increasing method which comprises the following steps: determining the positions of a main key layer and a sub-key layer in an overlying rock layer according to a key layer theory, and determining the lithologic property of the key layer; determining the pressure control and fracturing range of the hydrofracture key layer according to the lithologic property, determining and analyzing the rock mechanical parameters of the overlying key layer through uniaxial tensile and compression experiments to obtain uniaxial compressive strength and uniaxial tensile strength, and performing mechanical calculation on the fracture pressure of the roof sandstone by adopting an H-W model to determine the influence range of the hydrofracture destroyed key layer; the method comprises the following steps: determining an arrangement scheme of hydraulic fracturing drill holes, arranging observation holes according to a fracturing range, determining a fracturing position, determining a fracturing drill hole arrangement scheme, fully fracturing and destroying an overlying key layer by adopting a segmented hydraulic fracturing technology, and effectively cutting off a stress transmission path between the key layer and coal seam roofs on two sides of a roadway to achieve the purposes of pressure relief and permeability improvement.

Description

technical field [0001] The invention belongs to the technical field of gas treatment and geological strata, and in particular relates to a pressure relief and permeability enhancement method for a hydraulic fracturing overlying key layer. Background technique [0002] In the process of gas extraction, excavation, and coal mining in soft coal, the stress concentration of the overlying stratum causes gas, the coal is soft (high gas content, high gas pressure, low gas permeability), complex geological conditions, and high in-situ stress. , The comprehensive effect of stress and gas leads to: frequent occurrence of coal cannons during excavation; easy occurrence of stuck drills, collapsed holes, blowholes, etc.; abnormal gas gushing; hydraulic caverns have relatively poor pressure relief and permeability enhancement effects. The effect of digging and pumping is not good, and the amount of gas gushing during the mining process is too large. SUMMARY OF THE INVENTION [0003] Th...

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Problems solved by technology

[0002] In the process of gas drainage, tunneling, and coal mining in the soft coal body, the stress concentration of the overlying strata leads to gas, the coal body is soft (high gas content, high gas pressure, low permeability), complex geological conditions, high ground stress , the combined effects of stress and gas lead to: frequent coal blasting during excavation; drill sticking, hole collapse, and injection holes are prone to occur; abnormal gas gushing out; hydraulic cavitation has relatively poor pressure relief and anti-reflection effects

The effect of pumping while digging is not good, and the amount of gas gushing out during the mining process is too large

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