A gas drainage method for underground water-sand fracturing in low-permeability coal seams

Abstract

The invention provides a hydraulic sand fracturing gas extraction method for an underground coal seam with low air permeability, and aims at enabling gas cavity fracture surfaces to be communicated with each other, so that the permeability of a coal seam is improved. The method comprises the steps that hydraulic sand fracturing drilling is conducted from a floor rock pre-pumping lane to a working face crossheading, wherein drilling drainage is conducted after hydraulic sand fracturing; if the highest pressure is 35 MPa or below, a capsule sealing method is adopted to seal holes; after a fracturing pump is started, prepad fluid is injected into a construction coal seam; after coal seam cracks are formed and meet the requirements, injection of sand-carrying fluid is started, injection is stopped when construction pressure rises rapidly; injection of the prepad fluid is continued for coal seam pressure compensation again, the sand-carrying fluid is injected again when liquid construction pressure is reduced to 10 MPa, and injection is stopped when the pressure rises rapidly; then displacement fluid is injected; the well mouth is closed, the fracturing holes are flushed with high pressure water after the coal seam pressure releases slowly; the water is drained from the area; if capsule sealing is adopted when fracturing, capsules are taken out for hole sealing, and extraction pipelines are introduced for extraction.

Description

technical field [0001] The invention relates to a method for pressing high-pressure fracturing liquid and proppant into a coal seam through a fracturing process in underground to enhance the gas permeability of the coal seam and improve the gas drainage effect. Background technique [0002] For a long time, coal mine gas disasters have been an important factor restricting the safe and efficient production of coal enterprises. The number of deaths due to gas accidents accounts for more than 70% of the total number of deaths in coal mines, and major and extraordinarily serious accidents are mostly related to gas. At present, with the gradual mining of coal mines in my country, the gas pressure and gas content in mines are increasing, and the proportion of high-gas mines and outburst mines is increasing. According to the current technology, the most effective method of gas control is to drain first and then mine. However, low permeability coal seam seriously restricts the effe...

AI Technical Summary

Problems solved by technology

Judging from the current technology, the most effective method of gas control is to drain first and then mine. However, low-permeability coal seams seriously restrict the effect of gas drainage and affect the safety of coal mine production.