Patent attributes
A crossover sub includes a tubular housing connected to a drill string in a wellbore, a sealing structure to seal against a wellbore wall, and a sleeve valve disposed within the housing and movable between a closed position and an open position in response to a fluid pressure in a first flow chamber or second, separate flow chamber of the housing. The first flow chamber fluidly connects an upper annulus of the wellbore to a central bore of the drill string downhole of the crossover sub. The second flow chamber fluidly connects a central bore of the drill string uphole of the sealing structure to a lower annulus of the wellbore. The sleeve valve closes the second flow chamber in response to the sleeve valve being in the closed position, and opens the second flow chamber in response to the sleeve valve being in the open position.
