Abstract: A telemetry system for a downhole tool positionable in a wellbore penetrating a subterranean formation is provided. The telemetry system includes a telemetry tool engageable within the downhole tool. The telemetry tool including a telemetry unit, the unit being interchangeable between a mud pulse telemetry unit and an electromagnetic telemetry unit.

Abstract: An apparatus and related method are useful for compensating the pressure of drilling fluid in a drill collar disposed in a borehole. The apparatus includes a stator adapted for being secured within the drill collar against rotation relative to the drill collar, and a shaft rotatably carried within the stator so as to define a fluid-conducting annular gap between the shaft and the stator. The shaft has a fluid-conducting channel extending axially therethrough. A rotor is secured about the shaft for rotation therewith. A portion of the rotor is disposed adjacent a portion of the stator so as to define an inlet between the rotor and stator portions through which drilling fluid in the drill collar will be conducted. The rotor portion further cooperates with the stator and the shaft to define a first annular cavity that fluidly communicates with the gap and the inlet. A rotary seal is disposed in the first cavity for isolating the gap from the inlet.

Abstract: An apparatus and related method are useful for compensating the pressure of drilling fluid in a drill collar disposed in a borehole. The apparatus includes a stator adapted for being secured within the drill collar against rotation relative to the drill collar, and a shaft rotatably carried within the stator so as to define a fluid-conducting annular gap between the shaft and the stator. The shaft has a fluid-conducting channel extending axially therethrough. A rotor is secured about the shaft for rotation therewith. A portion of the rotor is disposed adjacent a portion of the stator so as to define an inlet between the rotor and stator portions through which drilling fluid in the drill collar will be conducted. The rotor portion further cooperates with the stator and the shaft to define a first annular cavity that fluidly communicates with the gap and the inlet. A rotary seal is disposed in the first cavity for isolating the gap from the inlet.

Abstract: A while drilling system and method for determining downhole parameters is provided. The system includes a retrievable while drilling tool positionable in a downhole drilling tool, a sensor chassis and at least one sensor. The while drilling tool is positionable in the downhole drilling tool and has a first communication coupler at an end thereof. The sensor chassis is supported in the drilling tool. The sensor chassis has a second communication coupler at an end thereof for operative connection with the first communication coupler. The sensor is positioned in the chassis and is adapted to measure internal and/or external parameters of the drilling tool. The sensor is operatively connected to the while drilling tool via the communication coupler for communication therebetween. The sensor may be positioned in the while drilling tool and retrievable with the drilling tool. Preferably, the system is operable in high temperature and high pressure conditions.

Abstract: A modulated bias unit is provided for controlling the direction of drilling of a rotary drill bit when drilling boreholes in subsurface formations. The unit comprises a plurality of hydraulic actuators spaced apart around the periphery of the unit and having movable thrust members hydraulically displaceable outwardly for engagement with the formation of the borehole being drilled. Each actuator has an inlet passage for connection to a source of drilling fluid under pressure and an outlet passage for communication with the annulus. A selector control valve connects the inlet passages in succession to the source of fluid under pressure, as the unit rotates, and a choke is provided to create a pressure drop between the source of fluid under pressure and the selector valve. A further choke is provided in the outlet passage from each actuator unit. The actuators and control valve arrangements may take a number of different forms.