PRESSURE AND FLOW CONTROL IN CONTINUOUS FLOW DRILLING OPERATIONS

摘要

A method of providing substantially continuous circulation of fluid through a drill string and an annulus can include sealing off the annulus from atmosphere, regulating flow of the fluid from the annulus, thereby controlling pressure in the wellbore, and diverting flow of the fluid from a pump to an uppermost connector of the drill string and an inlet extending in a sidewall of the drill string, the regulating and the diverting being performed concurrently. A pressure and flow control system can include one or more flow control devices which divert flow from a pump to a valve which selectively permits and prevents communication between an uppermost connector of the drill string and a flow passage extending longitudinally through the drill string, and to a valve which selectively permits and prevents communication between the flow passage and an inlet extending in a sidewall of the drill string.