MUD LIFT DRILLING SYSTEM USING EJECTOR ASSEMBLY IN MUD RETURN LINE

摘要

A method is described for controlling pressure in a wellbore drilled below the bottom of a body of water wherein the wellbore has a fluid outlet in communication with a working fluid inlet of an ejector assembly to return drilling fluid to a drilling platform on the water surface. The method includes pumping drilling fluid into a drill string extending from the drilling platform into the wellbore and at least one of, (i) introducing fluid into a power fluid inlet of the ejector assembly at a rate selected to remove fluid from the wellbore fluid outlet at a selected rate and (ii) operating a controllable flow restriction in a flow path from the wellbore fluid outlet to the working fluid inlet of the ejector assembly, in order to maintain a selected wellbore pressure.