A method and system for mud pulse telemetry through a compressible drilling fluid during underbalanced drilling

摘要

A mud pulse telemetry system comprises pressure sensor 92 mounted downstream of a reflector 110 which is mounted in a conduit 86 downstream of a gas injector 84. Pressure waves travelling to the surface in the compressible mud 106 are reflected 122 by the reflector 110 and have the same polarity as the incident waves 120. Pressure sensor 92 comprises a pressure transducer which detects the pulses and generates corresponding electric signals, these are then passed onto a processor 94. The processor 94 demodulates the signals and converts them into useable MWD data. The reflector may be a fixed orifice plate or have an adjustable aperture. A system is also disclosed wherein a pair of pressure transducers are positioned on either side of a flow restriction located in gas conduit 104. The flow restriction can be a valve 118 or it can be a separate venturi or orifice plate. This system may be combined with the first so as to have a reflector and flow restriction.