... sticky formations such as coal, oil shale, tarsands, and shallow oil and gas.PDC bit : 56, 60, 76, 96 ... 116, T2 131 and so on.China Drilling Geological Equipment ltd., is the main manufacturer of drilling tool ... in china, and specializing in the design and manufacture of premium ... NQ NQ2 NQ3 HQ HQ3 PQ PQ3 & head assembly and assembly 3.AQ,BQ,NQ,HQ,PQ, T2, T6 ...