Fluid flow conduit vibrator and method

Claim 1

A gravel packing apparatus for placing a gravel pack within a portion of a wellbore comprising: a) a fluid flow path comprising a work string within which a slurry comprising a carrier fluid and gravel pack solids can be transported to near the portion of the wellbore within which the gravel pack is to be placed, a cross over tool capable of directing slurry flow from the drill string to the portion of the wellbore to be packed, a screen defining a sand free volume within the wellbore through which the carrier fluid but not the gravel pack solids can pass into the same free volume from the portion of the wellbore to be packed, and a means to direct the carrier fluid from the sand free volume to the wellbore above the portion of the wellbore to be gravel packed; and b) within the fluid flow path, a vibrator constrained within the fluid flow path comprising a movable bluff hammer capable of moving between a plurality of positions wherein fluid flow through the fluid flow path causes the bluff hammer to move between positions and change direction of the movement of the bluff hammer after the bluff hammer impacts a wall of the fluid flow path.