Patent ID: 7468679
Filing Date: 2008-12-23
Classification: E21B,G01V

Abstract:
1. A telemetry apparatus for transmitting information from a drill string positioned at a down hole location in a bore hole to a surface location, the drill string having a flow passage through which a drilling fluid flows, the telemetry apparatus comprising: a pulser positioned within the flow passage approximate the down hole location for generating a series of positive pressure pulses in the drilling fluid which are encoded to contain the information to be transmitted, said pulser comprising: a rotor capable of at least partially blocking the flow passage; a motor positioned within an internal housing defined by said pulser, said housing being filled by a gas at atmospheric pressure; a drive shaft extending from said drive motor to a position external of said internal housing, said drive shaft connected to said rotor; a seal positioned about said drive shaft such that said seal seals said internal housing; wherein said seal comprises: a plurality of seal elements; a plurality of seal carriers holding said plurality of seal elements; and wherein said plurality of seal elements include a first group of seal elements of a first seal diameter and a second group of seal elements of a second seal diameter, and wherein said plurality of seal elements are held by said plurality of seal carriers such that first and second group of seals are arranged in an alternating pattern.