Patent ID: 7083008
Filing Date: 2006-08-01
Classification: E21B

Abstract:
1. An apparatus for pressure-compensated telemetry and power generation in a borehole, the apparatus comprising: a stator adapted for being secured within the drill collar against rotation relative to the drill collar; a shaft rotatably carried within the stator so as to define a fluid-conducting annular gap between the shaft and the stator, the shaft having a fluid-conducting channel extending axially therethrough; a rotor secured about the shaft for rotation therewith, a portion of the rotor being disposed adjacent a portion of the stator so as to define an inlet therebetween through which drilling fluid in the drill collar is conducted, the rotor portion cooperating with the stator and the shaft to define a first annular cavity that fluidly communicates with the gap and the inlet; a rotary seal disposed in the first cavity for isolating the gap from the inlet; a first compensating chamber within one of the rotor, the shaft, and a combination thereof, for holding a compensating fluid, the first compensating chamber fluidly communicating with the gap; a movable barrier disposed in the first compensating chamber for isolating the compensating fluid; and at least one port extending through the rotor for communicating drilling fluid pressure to the compensating fluid via the movable barrier, the port being positioned at a location not downstream of the inlet, such that the drilling fluid conducted through the port has a nominal pressure at least as great as the nominal pressure of the drilling fluid conducted through the inlet.