Abstract: A shear assembly used downhole to actuate a work string function includes a dampening subassembly to dampen the momentum of moving parts following shearing to avoid excessive acceleration and resulting jarring forces within the work string. A dual shear assembly is provided, in which the dampening subassembly prevents inertial force resulting from a first shear from exceeding the threshold for actuating the second, higher threshold, shear mechanism thereby allowing more precise control of the forces applied to the work string to prevent premature shearing of the second shear mechanism. In a specific embodiment, the dampening subassembly is a hydraulic dampening subassembly. The dual shear assembly may be used, for example, to first open a wash port above a tool lodged within the wellbore to loosen debris above the lodged tool, and then to shear the tool from the work string if necessary.
December 8, 2008
June 11, 2009
Robert Bohuslav Kratochvil, Scott Oliver Kirk, Daniel Schofield, Darko Smolcic