Pressure pulse detection apparatus - eliminates pulses from mud pump and enhances pulses from downhole equipment

摘要

A mud delivery system used in drilling an oil well has mud delivered from a pump through a pipe connected to a drill string extending to a downhole signalling apparatus. Signals are propogated up the mud column standing in the drill pipe. An apparatus is arranged to measure and null to a minimum value variations in mud flow velocity and pressure from the mud pump traveling through the mud column. An output signal is formed representative of variations from the downhole signal apparatus. Pref. there are arrangements for measuring pressure and velocity variations in the mud column and forming output signals. Weighted portions of these signals are summed and an output sum formed where mud pump noise is accompanied by pressure and velocity increases which are weighted and summed to cancel a range of specified variations. Signals from the downhole signalling apparatus are summed and weighted resulting in additive enhancement. With the apparatus of the invention the pump pressure pulses are eliminated while pressure pulses from the downhole equipment are markedly increased.