Research on hole protection technology of screen pipe for hydraulic transportation and automatic butt joint in high position directional borehole

Ensuring the stable extraction of high position directional long boreholes in the mining process of working face is the premise of realizing ' replacing the roadway with the boreholes', and the use of screen pipe completion is an effective hole protection measure to maintain the stability of boreholes. In order to realize the engineering application of full-hole segment screen pipe protection in high position directional borehole, the technology of automatic butt joint technology of grouping screen pipe for hydraulic transportation in the borehole has been developed, and the ø95 mm screen pipe Hanging unit, ø95 mm fiberglass screen pipe, ø100 mm water flow blocking short section, ø140 mm drilling bit plug with passable water and ø95 mm grouping screen pipe connecting device have been developed, In addition, the field test of hydraulic transportation grouping screen pipe hole completion was carried out in the high level boreholes of different working faces in two coal mines in the northern Anhui mining area. The test results show that the weight of the GRP screen pipe is light and the resistance to push is small. The ø95 mm GRP grouping screen pipe with a length of ø100 m can be manually connected in the borehole with an inclination of 17°−26°. The water pressure in the grouping screen pipe transportation process is about 1.0−1.5 MPa, and the water pressure drops below 0.5 MPa when it is transported in place. Under the pump capacity of 200-390 L/min, the average hydraulic transportation speed of the grouping screen pipe can reach 150-260 m/min. The pump pressure changes significantly when the grouping screen tube is transported in place during the test. The front and rear sets of screen pipes are connected reliably, which can effectively realize the message in place, and successfully achieve the full hole protection of ø95 mm screen pipes in the ø153 mm high position directional borehole. The hydraulic transportation test depth of screen pipes in the two boreholes reaches 501 and 522 m respectively and the cumulative pure gas extracted from the two boreholes in 120 d working face mining is 139 945 and 176 139 m³ respectively. The technology of screen pipe for hydraulic transportation and automatic butt joint in the borehole provides an achievable technical solution for the large-diameter screen pipe hole protection in the full-hole section of the high-position directional long borehole, helps to ensure the gas drainage effect of the high-position directional long borehole, and provides technical support for the innovation of the gas control mode of ‘replacing the roadway with the boreholes’ in the coal mine.