Patent ID: 6722452
Filing Date: 2004-04-20
Classification: E21B

Abstract:
An underreamer for forming a cavity within a well bore, comprising:a housing adapted to be rotatably disposed within the well bore; a piston slidably positioned in the housing, the piston comprising a fluid passage disposed in fluid communication with an internal passage of the housing; a deformable member disposed proximate the fluid passage, wherein an increase in the axial force deforms the member such that a fluid travels through the fluid passage; one or more first cutters each having a first end and a second end, the first end of each first cutter pivotally coupled to the housing; and one or more second cutters each having a first end and a second end, the first end of each second cutter pivotally coupled to the piston and the second end of each first cutter pivotally coupled to the second cutter such that an axial force applied to the piston is operable to slide the piston relative to the housing and extend the second end of each second cutter radially outward relative to the housing from a retracted position to form the cavity.