Ball seat with controlled releasing pressure and method setting a downhole tool ball seat with controlled releasing pressure and method setting a downholed tool

摘要

An improved ball seat is described for downhole use. The ball seat can be held in place by one or more shear pins or other fixation devices or by the nature of assembly. A breakable device, such as a rupture disc, is in communication above the ball and with an enlarged piston area below. When the breakable member or rupture disc breaks, the applied pressure is translated to a far larger piston area, and the shear rating of the shear pin or pins is almost instantaneously overcome. Thus, the pressure at which the ball seat releases is determined by the design and rating of the breakable member or rupture disc. The cavity behind the breakable member is preferably grease-filled with a small weep hole to avoid trapping pressure during assembly.