Experimental Study on Longmaxi Shale Breaking Mechanism with Micro-PDC Bit

China has abundant shale gas resource, but its geological conditions are complicated. This work sought to find the shale breaking mechanism with the polycrystalline diamond compact (PDC) bit when drilling the shale that is rich in stratification. Therefore, a laboratory-scale drilling device based on a drilling machine is developed. The influences of Longmaxi shale stratification on drilling parameters in the drilling process with micro-PDC bit are investigated. Six groups of drilling experiments with six inclination angles (beta = 0A degrees, 15A degrees, 30A degrees, 45A degrees, 60A degrees and 90A degrees), total thirty-six groups, are carried out. The weight on bit reaches the maximum value at beta = 30A degrees and reaches the minimum value at beta = 0A degrees. The biggest torque value is at beta = 30A degrees, and the smaller torque values are at beta = 15A degrees, beta = 45A degrees and beta = 60A degrees. When the inclination angle is between 30A degrees and 60A degrees, the shale fragmentation volume is larger. The inclination angle beta = 0A degrees is beneficial, and beta = 15A degrees and beta = 60A degrees are detrimental to controlling the drilling direction in the Longmaxi shale gas formation.