Abstract: The drilling operation is very difficult in shallowmid superthick gravel beds in western China, where the beds exist widely; accidents are frequent, which leads to long drilling cycle and the high cost. Aimed at the poor consolidation, loosen texture, easy collapse and sloughing, cationic gelbentonite drilling fluid should be chosen, and the ratio of dynamic shear force value to plastic viscosity should be≥1 . For the lower gravel formation which is better consolidated, highly mineralizedanti sloughing fluid system should be used to reduce the sloughing of the gravel beds. The research summarizes some successful experience and provides useful reference for the gravel beds drilling.

Key words: gravel bed, well drilling, countermeasures, drilling fluid system, China Western Region