Reverse circulation pressure control method and system

摘要

A system for reverse circulation in a wellbore includes equipment for supplying drilling fluid into the wellbore bit via at least an annulus of the wellbore and returning the drilling fluid to a surface location via at least a bore of a wellbore tubular. The system also includes devices for controlling the annulus pressure associated with this reverse circulation. An active pressure differential device may increase the pressure wellbore annulus to at least partially offset a circulating pressure loss. Alternatively, the system may include devices for decreasing the pressure in the annulus of the wellbore.