Downhole valve device

摘要

A downhole valve device ( 1 ) in a drill string ( 14 ) in a petroleum well ( 2 ) and method for maintaining optimal annular fluid velocity and wellbore pressure. The device comprises a valve housing ( 20 ) connected between adjacent segments ( 12, 13 ) of the drill string. The valve housing is further provided with at least one valve ( 23 ) arranged to open and close to the flow of drilling fluid based on measured values of downhole physical parameters or on signals from the surface in order to permit the through-flow of a sufficient volume of drilling fluid necessary to adjust and maintain the annular fluid velocity of the drilling fluid and the wellbore pressure within optimal operating conditions.