Abstract Valuable geologic information can be obtained by utilizing wireline conveyed measurements. Generally referred to as “logs," these readings probably derive their name from the general term meaning a “record" of a series of events. In the context used here, the term log refers to a particular measurement in a well that is recorded as a function of well depth. It often refers to a measurement of one or more physical properties as a function of well depth. From these physical properties, the rock properties are inferred. Results are not limited to rock property measurements, though. Examples of other types of logs are fluid flow, cement quality, casing corrosion, etc. Having defined the term log , why the term wireline? This is to differentiate between logs made from instruments lowered into the well on a cable, and logs made in the oil field by noncable means such as mud logs (drilling mud characteristics), drilling time logs (bit penetration rates), etc. The term cable, as used in the foregoing comment, should be clarified. Cables, in their most familiar form, are strong, flexible "ropes" made of spiraled metal strands. "Wireline" denotes a special form of metal stranded cable that contains electrical conductors on the inside (core). These conductors generally serve dual purposes: to power the downhole instrument (tool) and to convey the tool signal back to the surface for display on the log. The "wireline" cable causes some difficult obstacles for the logging service company. Because of the small diameter conductors, line resistance tends