FIELD: oil and gas industry.
SUBSTANCE: double drilling string comprises an outer pipe, an inner pipe mounted within the outer pipe, the drilling string bottomhole assembly fluidly connected to the outer and inner pipes and a discharge reducer connected to the inner pipe. The discharge reducer is configured to selectively operate in the normal drilling mode and the high flow mode. In normal drilling mode, the fluid is directed to the wellhead via the inner pipe. In the high flow mode, the returning fluid is directed to bottomhole via the inner pipe. The discharge reducer includes a return tube, wherein in the normal drilling mode, the returning fluid passes into the inner pipe via the return tube.
EFFECT: increased fluid management efficiency in well drilling and processing.
18 cl, 6 dwg
