MWD North Sea Field Use, Aug. 1978-Feb. 1979 (With 1982 Update) (includes associated papers 11865 and 11929 )
- W.H. Griffin (Teleco Oilfield Services Inc.) | F.A.J. Keith (Teleco Oilfield Services Ltd.)
- Document ID
- Society of Petroleum Engineers
- Journal of Petroleum Technology
- Publication Date
- December 1982
- Document Type
- Journal Paper
- 2,888 - 2,898
- 1982. Society of Petroleum Engineers
- 1.5 Drill Bits, 2.4.3 Sand/Solids Control, 1.6.6 Directional Drilling, 1.9.4 Survey Tools, 1.10 Drilling Equipment, 1.10.1 Drill string components and drilling tools (tubulars, jars, subs, stabilisers, reamers, etc), 1.12.1 Measurement While Drilling, 4.1.6 Compressors, Engines and Turbines, 1.11 Drilling Fluids and Materials, 1.6.1 Drilling Operation Management, 1.6 Drilling Operations, 1.4.1 BHA Design, 4.5 Offshore Facilities and Subsea Systems, 1.6.2 Technical Limit Drilling
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The use of the Teleco Oilfield Services Ltd. measurement-while-drilling(MWD) system has grown fivefold in the North Sea since 1979, when this paper was written. As of Sept. 1982. our service has been provided to more than 400 wells drilled by 17 operators from some 60 rigs in the U.K., Norwegian, Danish, and Dutch sectors. The operational procedures, case examples, and the like are still accurate as presented in the paper in 1979, but, of course, a wider range of drilling conditions has been experienced since. For instance, surveys have been transmitted from measured depths greater than 16,800 ft, inclinations higher than 72 degrees, and at flow rates exceeding 1,000 gal/min. As we have gained more experience and understanding of the North Sea drilling environment, the reliability of our system has nearly doubled. On the average, only one tool failure per 250 circulating hours is experienced in North Sea operations now. From the operators'standpoint, the direct time savings resulting from MWD have materialized as expected. Second-tier benefits also have been revealed and quantified. The years between 1979 and 1982 mark a turning point in directional surveying. During this period, MWD made the transition from being simply a new way of surveying to becoming the standard way of surveying in the North Sea. Our system now is being used on nearly every North Sea platform where directional wells are drilled. The remainder of the paper appears as originally presented.
Teleco Oilfield Services Ltd. was formed in May 1978 as a subsidiary of Teleco Oilfield Services Inc., a joint venture of Raymond Industries Inc., and Soc. Natl. Elf Aquitaine. The firm's primary function is to provide a directional drilling MWD service to customers in the North Sea. We began commercial service in the North Sea in Aug. 1978 and in the Gulf of Mexico in Sept. 1978.
The MWD System
This system uses mud-pulse telemetry to transmit data; hence, there is no wireline. Mud-pulse telemetry is a method of transmitting information from the bottom of a borehole to the surface by using a downhole valve to induce coded pressure pulses in the mud. The MWD system consists of a downhole assembly containing a sensor and transmitter mounted in a nonmagnetic drill collar (Fig. 1) and surface display equipment (Fig. 2) located on the drilling platform. The collar is a self-contained unit that remains in the drillstring near the drill bit. The sensor incorporates a magnetometer to measure direction and accelerometers to measure inclination and tool facing. Electrical power for the downhole assembly is produced by a mud-driven turbine in the transmitter. After taking a survey, the sensor tells the transmitter to encode the directional data into a series of positive pressure pulses by periodically moving a valve that partially restricts mud flow. The increase in pressure propagates upward inside the drillstring through the mud to the surface, where it is detected by a pressure transducer in the standpipe. The presence or absence of a pulse in a given time interval forms a binary number code that is decoded into a directional angle and displayed on the surface equipment.
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