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Unformatted text preview: struments. • Inner Wire: to provide electric power to downhole equipments & for data telemetry. 54 Wireline Cable Geology & Geophysics in Oil Exploration Mahmoud Sroor Geology & Geophysics in Oil Exploration Wireline Unit: The cabin that contains the surface hardware needed to make wireline logging measurements. The logging unit contains at the minimum the surface instrumentation, a winch, a depth recording system and a data recorder. The surface instrumentation controls the logging tool, processes the data received and records the results digitally and on hard copy. The winch lowers and raises the cable in the well. A depth wheel drives the depth recording system. The data recorder includes a digital recorder and a printer. 1-Onshore: The logging company sends Truck Logging Unit which contains the computers, winch and recorders. 2-Offshore: The logging unit is stored as small house on the rig.
Offshore Onshore Logging While Drilling (LWD): In the 1980s, a new technique, logging while drilling (LWD), was introduced which provided similar information about the well. Instead of sensors being lowered into the well at the end of wireline cable, the sensors are integrated into the drill string and the measurements are made while the well is being drilled. While wireline well logging occurs after the drill string is removed from the well, LWD measures geological parameters while the well is being drilled. However, because there are no wires to the surface, data are recorded downhole and retrieved when the drill string is removed from the hole. A small subset of the measured data can also be transmitted to the surface in real time via pressure pulses in the well's mud fluid column. This mud telemetry method provides a bandwidth of much less than 100 bits per second, although, as drilling through rock is a fairly slow process, data compression techniques mean that this is an ample bandwidth for real-time delivery of information. Measuring While Drilling (MWD): It is the evaluation of physical properties, usually including pressure, temperature and wellbore trajectory in...
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- Spring '10