AXIALLY EXTENDED DOWNHOLE SEISMIC SOURCE

摘要

An axially extended downhole seismic source is disclosed. In one embodiment, the seismic source includes multiple pressure storage chambers, each having an inlet valve and an outlet valve. The inlet valve is coupled between the pressure storage chamber and the interior of the drill string (8), and the outlet valve is similarly coupled between the pressure storage chamber and t he annular space (20) around the drill string. The use of multiple pressure storage chambers allows the pressure front from the seismic source to be extended axially to advantageously increase the fraction of seismic energy transmitted into the formation while preventing damage to the formation.