| 摘要 |
A method of operating a drilling system, the drilling system comprising: a drill string which extends into a wellbore, a driver operable to rotate the drilling string, a pump operable to pump drilling fluid down the drill string, a well head mounted at the top of the wellbore, a riser extending up from the wellhead around the drill string, a blowout preventer which is mounted on the well head and which is operable to close around the drill string to substantially prevent flow of fluid from the annular space around the drill string in the wellbore into the annular space around the drill string in the riser (the riser annulus), the BOP having a sealing element which engages with the drill string when the BOP is operated to close around the drill string, a riser closure device which is mounted in the riser and which is operable to close around the drill string to substantially prevent flow of fluid along the riser annulus, a return conduit, a flow outlet which is provided in the riser below the riser closure device and which connects the riser annulus to the return conduit, wherein the method comprises the steps of, after determining that there is or may be a need to close the BOP, implementing a control procedure comprising the following steps: a) operating the driver to stop rotation of the drill siring, b) closing the riser closure device (if not already closed), c) operating the pump to stop the pumping of mud into the drill string, d) closing the blowout preventer, characterised in that the method further includes the step of e) increasing the wellbore pressure by controlling the rate of flow of fluid along the return conduit. |
