Importance

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Abstract

A downhole tool containing instruments and a pulser is landed within a string of drill pipe. The pulser has a pulser body and an orifice on a lower end. A piston slides within a bore in the body and has a signal poppet on a lower end. In an extended position, the signal poppet extends into and obstructs the orifice to reduce the flow of drilling fluid. In an open position, the signal poppet does not obstruct the orifice to increase the flow of drilling fluid. A bidirectional solenoid valve is located above the piston and has upper and lower electromagnetic coils and an axially moveable rod. The rod is movable between a closed position in an opening in the body and an open position away from the opening. The rod is moved to both positions in response to the instruments which sends signals to the coils. The mud pulser also has an on/off flow switch which is actuated by the commencement of mud circulation. Initially, the rod is in the closed position. The instruments take various measurements which are communicated through the pulser to the surface in the form of mud pulses. A mud pulse is generated when a coil is energized to move the rod to the open position. This forces the piston and signal poppet into the extended position to restrict mud flow. The rod is moved to the closed position when the other coil is energized. The signal poppet creates pulses which are detected at the surface.

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First Claim