Section 1: Wireline Logging Measurements of Subsurface Geology
Conrad and Marcel Schlumberger were French geophysicists from Alsace, who originally worked with surface electrical prospecting techniques in the search for ore bodies and petroleum. In 1927, as a result of a conversation with the manager of a Franco-Belgian drilling company, Conrad arranged for his son-in-law, Henri Doll to attempt the first experimental resistivity survey in a well.
In the Pechelbronn oilfield in Alsace, the top of the Hydrobiae marls was used as a stratigraphic marker, but was sometimes missed or misidentified in drilling. Consequently, the problem the resistivity survey would attempt to solve was whether the technique could be an effective means to recognize subsurface formations for use in correlation and mapping.
Doll put together a four-electrode (lateral) resistivity device and drove out to the well Diefenbach 2905, Tower 7, together with Scheibli and Jost on September 5, 1927. There, they linked the sonde weighted with lead to three conductive cables spliced together with insulating tape, loaded it onto a hand-operated winch, and attached it to batteries and a potentiometer. The first run was to 140 meters and took 15 hours largely because of interruptions caused by breaks in the cable. A new and longer cable was brought in by taxi to allow them to reach the full well depth of 600 meters. Resistivity readings were taken at one-meter intervals in a slow process that gradually speeded up as they became more practiced.
Doll took the logging data back to Paris and plotted the resistivity readings as a function
Figures & Tables
This manual was created in 1994 to assist the geologist to interpret logs. In the not too distant past, the reading of geology from wireline logs was highly interpretive. The ability of a rock to conduct electrical current or sound waves is several steps removed from traditional outcrop descriptions based on the eye and hammer. However, the range of logging measurements has expanded markedly over the years. In particular, the addition of nuclear tools has introduced log traces that reflect both rock composition and geochemistry in a more direct manner. Taken together, both new and old logs contain a host of keys to patterns of rock formation and diagenesis. The majority of books on log analysis focus on the reservoir engineering properties of formations penetrated in the borehole. The promise of potential porous and hydrocarbon-saturated rocks generally pays for both the hole and the logging run. There are many examples of common log types from a variety of sequences.