| 摘要 |
A method for maintaining pressure in a wellbore during drilling operations is disclosed. The method includes the steps of providing fluid from a reservoir through a drill string, circulating the fluid from the drill string to an annulus between the drill string and the wellbore, isolating pressure in the annulus, measuring pressure in the annulus, calculating a set point backpressure, applying back pressure to the annulus based on the set point back pressure, diverting fluid from the annulus to a controllable choke, controllably bleeding off pressurized fluid from the annulus, separating solids from the fluid, and directing the fluid back to the reservoir. An apparatus for maintaining pressure in a wellbore during drilling operations, comprising: a pressure transducer in the drill string to measure pressure in the annulus; rotating control device isolating pressure in the annulus and communicating fluid from the reservoir to the drill string and diverting fluid and solids from the annulus; an adjustable choke in fluid communication with the rotating control device controllably bleeding off pressurized fluid from the annulus; solids control equipment receiving fluid and solids from the adjustable choke and removing the solids from the fluid; wherein the fluid from the solids control equipment is directed to the reservoir; a processor receiving the measured pressure from the pressure transducer and calculating a set point backpressure; and a backpressure pump in fluid communication with the reservoir and applying a backpressure between the rotating control device and the automatic choke based on the calculated set point backpressure. |
