Key Technologies for Safe Drilling in Horizontal Section of Deep Coal and Rock Gas Horizontal Well in the Ordos Basin

The target layer of the deep coal rock gas horizontal well in the eastern gas field of the Ordos Basin is the 8 # coal seam of the Benxi Formation, which is deeply buried and has strong heterogeneity. During the drilling process, when encountering coal gangue and carbonaceous mudstone interlayers, it faces technical difficulties such as low ROP, easy instability and collapse of the wellbore, complex and frequent underground faults, difficulty in extending the horizontal section, and difficulty in running the completion casing. Therefore, on the basis of analyzing the characteristics of drilling benxi formation 8# coal-rock stratum and drilling technical difficulties, The optimization of high-efficiency PDC bit and speed-up tool for reverse reaming, optimization of steering drilling tool assembly without sticking prevention, fine steering trajectory control technology for horizontal section, rotary casing running technology and micro-nano strong inhibition of high-efficiency water-based drilling fluid system technology were carried out, and the safe drilling technology for deep coal gas horizontal section in eastern basin was formed. This technology was applied to 10 deep coal gas horizontal wells in Suide-Mizhi block of eastern basin gas field, with an average completion depth of 4231 m. The average drilling period is 77.29 d, the average horizontal section length is 1344 m, the average drilling period of horizontal section is 11.67 d, the average ROP of horizontal section is 9.0 m/h, the average coal and rock reservoir is 1 192 m, and the average reservoir drilling rate is 88.68%, among which the horizontal section length of well S47-62YH4 is 2 222 m, which creates the longest horizontal well of coal and rock gas in the deep layer of 8# coal bed reservoir in Benxi formation, Ordos Basin. The successful application of safe drilling technology in deep coal-gas horizontal section of gas field in eastern basin provides technical support for safe and rapid drilling and large-scale and efficient development of deep coal-gas horizontal wells in this block.