WELL DEVIATION CONTROL TECHNOLOGY IN THE COALBED METHANE WELL IN HUAIBEI

Formation deflection tendency is distinctive in block SN of Huaibei area, and the conventional deviation control drilling assemblies and correction methods are inefficient in vertical drilling of this formation. Downhole motors are used for deviation control and correction, and it meets the requirement of maintaining the maximum inclination within 5°. Reverse direction adjustment in well SN-3 is described, which involves six drilling assembly adjustments. Pack-hole and pendulum assemblies are replaced with downhole motors, and 1.5° bent subs and 0.75° single bent screws are also changed. After adjustment, the inclination and direction are controlled within 3.5° and 260° respectively. Drilling assemblies adjustments in other three wells increase penetration rate from 5.36 m/h to 11.95~13.46 m/h, and drilling time is reduced to 37.81 h over the 75h used in well SN-3.