Abstract:
Deep coalbed methane (CBM) horizontal wells with long horizontal sections demonstrate significant advantages in enhancing single-well production and reducing drilling costs. Long horizontal section drilling technology has gradually become a key factor in achieving efficient extraction. To address the challenges encountered in drilling long horizontal sections in deep CBM wells in the eastern margin slope zone of the Ordos Basin, including wellbore instability, difficulties in trajectory control, and high friction and torque, this study optimized and determined the offset distance for safe obstacle avoidance by simulating the relationship between the well trajectory offset distance and friction/torque. The wellbore configuration was optimized as “conductor + three spud” design from “conductor + two spud”. The trajectory was optimized by using six-segment “vertical-build-hold-turn-build-hold” profile on the basis of “dual 2D + minor 3D” mode. The trajectory was precisely controlled by combining a “PDC bit + 1.25° single-bend single-stabilizer screw + hydraulic oscillator” building assembly and a “PDC bit + near bit azimuth gamma +1.25° single-bend double-stabilizer screw + hydraulic oscillator”holding assembly in drilling operation. The drilling fluid system was prepared with strong sealing, inhibition, and lubrication properties, focusing on such three key aspects as sealing to prevent collapse, chemical hydrophobicity, and lubrication to prevent sticking. Ultimately, an integrated drilling technology system for long horizontal sections in deep coalbed methane wells was developed, centered on geology-engineering integrated design, trajectory control, anti-collapse drilling fluid, and wellbore cleaning. Field trials conducted at the JS6-3 well pad successfully completed three wells with horizontal sections exceeding 2,000 meters, setting a record of
2104 m in one trip for horizontal section. The average drilling and completion cycle was reduced by 21.3% compared to the original design, with an average composite rate of penetration of 93.8% in the horizontal section and an average target penetration rate of 96.0% for the "black gold" reservoir. This technology provides crucial technical support for the efficient development of deep CBM in the eastern margin slope zone of the Ordos Basin. Moreover, it serves as a valuable reference for long horizontal section drilling technologies in similar deep CBM wells across China.