Optimum design and application of directional coalbed methane wells with small curvature radius in Weibei area, eastern Ordos basin

The traditional directional wells in Weibei area, eastern Ordos gas field are faced with the technical bottleneck of eccentric wear of sucker rod, poor effect of fracturing reconstruction and low production of single well. Through in-depth analysis and evaluation on the characteristics of coal geology of the area, small radius directional well drilling scheme suitable for Weibei coal seam gas wells transformation was put forward. Considering the special conditions of CBM wells such as drainage and gas recovery, the optimal design model of small radius directional well trajectory was established, and the optimization of directional drilling tools was also carried out. The results show that through the integrated application of staged fracturing technique, directional wells with small curvature radius could use seams 3, 5 and 11 vertically, an effective pressure fracture network could be formed in the main coal seam 11 horizontally, controlled area of single well increased by 37.76% and gas production increased by 25% compared to conventional directional wells; From the point of view of CBM drainage technology, submergence depth could meet the requirements of normal discharge operation of conventional rod pump if the wellhead produced stable casing pressure of 1.5 MPa; The optimal slope of small curvature radius directional well was 11.5°/30 m, and it is necessary to configure directional drilling with single curve screw drill assembly of 1.55 degree or more, and the 139.7 mm casing can be tripped in smoothly.