Patent ID: 6241031
Filing Date: 2001-06-05
Classification: E21B

Abstract:
A tractor for moving within a borehole, comprising:an elongated body having a thrust-receiving portion;a gripper longitudinally movably engaged with said body, said gripper having an actuated position in which said gripper limits relative movement between said gripper and an inner surface of said borehole, and a retracted position in which said gripper permits substantially free relative movement between said gripper and said inner surface;a flow channel extending to said thrust-receiving portion and configured to contain a first fluid flowing to said thrust-receiving portion;a chamber configured to contain a second fluid; anda pressure-regulator configured to control the pressure of said second fluid in said chamber;wherein said tractor is configured such that the pressure of said second fluid in said chamber controls the flowrate of said first fluid in said flow channel flowing to said thrust-receiving portion.