Patent ID: 6412614
Filing Date: 2002-07-02
Classification: E21B

Abstract:
A shock absorber for absorbing the energy generated by a downhole shock generating device, comprising: a housing tube; a shock mandrel telescopically disposed within the housing tube; a spring assembly disposed between the housing tube and the shock mandrel to resist axial movement of the shock mandrel within the housing tube, the spring assembly including at least a first spring and a second spring, the first spring having a stiffness greater than the second spring, the first and second springs being contained between first and second shoulders on the shock mandrel and between first and second shoulders on the housing tube and compressible by any one of the shoulders; a damper assembly to dampen axial movement of the shock mandrel within the housing tube, the damper assembly includes a valve permitting two way flow of fluid therethrough but providing a greater dampening effect against axial movement of the shock mandrel out of the housing tube than that against axial movement of the shock mandrel into the housing tube; an end of the shock mandrel extending at the first end of the shock absorber and adapted for connection into a downhole assembly; and an end of the housing tube extending at the opposite end of the shock absorber and adapted for connection into the downhole assembly.