Research on wireline sealed coring equipment and technology for coalbed methane content determination

Coalbed methane content is an important technical parameter for the development and utilization of coalbed methane resources and the prevention and control of mine gas. In order to solve the problem of deviation of coalbed methane content measurement results caused by inaccurate estimation of coal core loss gas volume in the process of surface well coalbed methane content determination, the wireline sealing coring device for surface well coal seam is developed, and the wireline sealing coring technology for surface well coal seam is proposed. The upper end of the coal seam wireline sealing coring device is designed with wireline fishing interface, wireline fishing tool string and rope lifting system to realize the rapid lowering and lifting of coring inner cylinder components; the hydraulic driving head is used to directly push down the coring inner cylinder, and the coring bit is matched with the coring inner cylinder to achieve the purpose of rotating closing the ball valve, so as to ensure sufficient coring inner cylinder volume and annulus, at the same time, the outer diameter of the closed coring device is minimized(only ø114 mm), and a ø127 mm coring bit is equipped to make the whole set of closed coring device suitable for more well types. The surface wells in Jincheng mining area(medium hard, high metamorphic and high gas coal seam) were selected to carry out wireline sealed coring test in coal(rock) layer. The field coring and sample test results show that the coalbed methane content of wireline sealed coring is about 1.12-1.17 times of that of conventional(wireline) coring gas content, the lifting speed of the wireline is 63.60-66.92 m/min. The determination wireline sealed coring technology improved the accuracy of coalbed methane content determination and realized rapid core lifting and accurate determination coalbed methane content in surface wells.