ABSTRACT
Well logging is the practice of measuring the properties of the geologic strata through which a well has been or is being drilled. A well log is the trace or record of the data from a downhole sensor tool plotted versus well depth. Its most common application is by the oil and gas industries that seek out recoverable hydrocarbon zones. For oil and gas production, companies would like to have several kinds of information about a geologic layer, such as the hydrocarbon content. To measure these properties, sources and sensors loaded into housings called sondes can be lowered into an existing borehole (a technique called wireline logging) or can be mounted on a collar behind the drilling head for taking measurements while the well is being drilled (called logging while drilling [LWD]). LWD records bottomhole data acquired incrementally from sensors located in the drill string near the bit in a drilling well. Recording LWD is done during drilling. Data can be transmitted to the surface in real time by pressure pulses through the mud inside the drill pipe. Large data les (e.g., waveforms) are temporarily stored in the memory of the tool for later recovery.
