High-efficiency Sealing Technology And Equipment For High-pressure Water Injection In Gaojiapu Coal Seam

Coal seam water injection technology plays an important role in reducing dust concentration,fire prevention and cooling,prevention of underground rock pressure and prevention of coal and gas outburst,and can effectively improve the production environment of the working face.Since July 2014,since the construction of the Gaojiabao Mine,there have been many phenomena of impacting ground pressure dynamics during the excavation of the main road.The concrete performance is that the bottom plate is rapidly bulged,the two gangs suddenly bulge,the shoulder socket and the roof plate sink,the anchor rod(cable)appears to be broken,and accompanied by the loud coal cannon sound,the impact of the ground pressure disaster is very severe;at the same time,the mining is hard.A large amount of dust is also generated in the coal seam,and a large amount of dust particles are inhaled during mining,which threatens the physical and mental health of workers in the work area.Gaojiabao Coal Mine is a relatively new mine with a maximum ground stress of more than 30 MPa.It belongs to the ultra-high geostress area and requires coal seam water injection to prevent impact and earth pressure disasters.The development of hydraulic fracturing and coal seam high-pressure water injection technology in Gaojiabao Coal Mine is not mature enough.The drilling and sealing effect is difficult to meet the normal development of hydraulic fracturing and coal seam water injection.Sealing has become the key technology to prevent Gaojiapu disaster prevention and prevention.In order to solve the problem of difficulty in water sealing and sealing of Gaojiabao coal seam,this paper analyzes the stress distribution curve and plastic zone width of six kinds of elastic constitutive equations and establishes a reasonable sealing length by establishing a theoretical model of gas-bearing coal seam mechanics..Based on this research and development of the sealing device,the on-site sealing length and sealing pressure research,and finally the on-site coal seam high pressure water injection and hydraulic fracturing sealing test,and gradually carried out the "Gaojiabao coal seam high pressure water injection high efficiency sealing technology and equipment research "The study of this subject.Firstly,the plastic zone width is theoretically analyzed,the constitutive equation of the plastic zone and the elastic zone is constructed,and the formula of the plastic zone width is derived.The width of the plastic zone of the Gaojiapu coal seam is calculated to be 8.952 m,which provides a theoretical basis for the determination of the length of the site seal.Secondly,a series of physical experiments were carried out to develop a downhole quick-sealing device,and a capsule sealing device with high pressure resistance,high expansion performance and reusable use was developed.According to the production conditions of 202 working face of Gaojiabao Coal Mine,two sets of sealing schemes were designed,and the best solution was selected on site.The high pressure pump,high pressure hose and shut-off valve were selected,and the sealing length and sealing pressure were carried out.The test verified that the sealing hole length of 12 m can meet the requirements of high pressure water injection of 38 MPa,ensuring that the sealing device has no water leakage,and the sealing effect is good,which can effectively block high pressure water.Finally,the application of high-efficiency sealing technology was carried out in the 202 backwinding trough of Gaojiabao Coal Mine,and the hydraulic fracturing test and coal seam water injection test were carried out.During the whole water injection process,the sealing device and the inner wall of the test hole are well sealed,and no water leakage occurs.The sealing time can meet the water injection of the coal seam for 4 days,the sealing efficiency is high,the process time is greatly saved,and the sealing device can be recycled and reused.Reduced sealing costs.The sealing efficiency is increased by more than 70%,and the water content of the coal seam can be increased by 17.496%after water injection.During the hydraulic fracturing test,there was always a coal cannon sound,indicating that the hydraulic fracturing effect is better,and the fracturing radius can reach more than 6 m,which has a certain effect on anti-shocking and pressure relief.