Patent ID: 6968900
Filing Date: 2005-11-29
Classification: E21B

Abstract:
1. A closed system drill string compensator comprising: a cylinder having a cylinder inner wall surface, a cylinder outer wall surface and a cylinder cavity; a piston; a piston rod having a first piston rod end and a second piston rod end, the first piston rod end being connected to the piston; an accumulator surrounding the cylinder, the accumulator having a first accumulator inner wall surface, a second accumulator inner wall surface, an accumulator outer wall surface, and an accumulator cavity, the accumulator cavity being in fluid communication with the rod side cavity, the accumulator cavity containing a second portion of hydraulic fluid and a gas under pressure; at least one air pressure vessel radially disposed around the cylinder and the accumulator, each of the at least one air pressure vessel being in fluid communication with the accumulator cavity.