Under-balanced drilling fluid separation at reduced pressures.

摘要

During the drilling of a hydrocarbon well in an under-balanced condition, the returning stream materials 40 are separated at a first reduced pressure P1 stage 50 to remove gas and the majority of cuttings 32. The remaining fluids exit the first stage at 58 to continue to a second separation stage 70 at a pressure P2, that is lower than P1. A recovered drilling base fluid 20 exits from stage 2 to be returned back to the well 26 after the pressure has been raised once again. A further feature involves the measuring of the separated quantity of drilling fluid 20, supplying drilling fluid to the well, mixing a quantity of gas 22 with the drilling fluid to vary the specific gravity, and determining the quantity of added gas.