Mud pulse telemetry is a method of transmitting information from the vicinity of the drill bit to the surface drilling platform while drilling. Information can be conveyed through a flowing column of drilling mud by the presence or absence of pressure pulses arranged in a binary code. Pressure in the flowing mud column is periodically modulated at a point downhole by mechanical means, and the resulting periodic pressure pulses appearing at the surface end of the mud column are detected by a pressure transducer conveniently located in the standpipe. Although the concept of mud-pulse telemetry is not new, only recently have sophisticated systems embodying mud-powered turbine generators and solid-state electronics been developed to the point of being able to withstand the hostile downhole environment. After ten years of active technology development and over $10 million of R and D expenditures, Teleco has demonstrated through field tests carried out in the Gulf of Mexico during 1977, that equipment reliability necessary for commercial operation is essentially at hand. Three generations of prototype systems were tested under actual drilling conditions during 1968 through 1977. Using eight new production systems, Teleco began a Pilot Service Demonstration in August 1977, under a contract with the U.S. Department of Energy and six major oil companies. Each system consisting of a sensor assembly and mud pulse telemetry transmitter measures borehole azimuth, inclination, and tool facing. Accurate directional measurements have been provided from kick-off through to target depth with minimum interruption to the drilling operation. Tool face information has been used to successfully kick-off directional wells using both mud motor and jet deflection techniques. Equipment reliability, as indicated by recent test runs of 254 and 272 hours of drilling with two separate systems, without failure, is approaching the level needed for commercial service. (ERA citation 04:000204)
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