Pressure pulse detection having noise reduction - has downstream facing Pitot tube surrounded by adjustable venturi

摘要

Appts. is used for detecting signals conveyed up a column of drilling mud in a drill string from a downhole signal source. Also it is subjected to noise from an upstream source such as a noisy mud pump and can be connected in the mud flow path at a selected location. A Pitot tube with an open end is positioned in the mud flow path and pointed downstream. A serially connected venturi is positioned about the Pitot tube adjacent its open end and includes an arrangement for altering the venturi through adjacent the Pitot tube open end. Pref. the venturi consists of an elongate, resilient, expandable and shrinkable diaphragm in a pipe coupling. The coupling has a fluid receiving chamber around the diaphragm for receiving fluid under pressure.