Geological Well Logs

When I joined Schlumberger in 1982 I was surprised to find very few geologists in the company, and the few there were worked more as log analysts than geol- ogists. The reason for this became soon clear to me: Except for the dipmeter there was no tool, and no other service, that was considered 'geological'. Schlumber- ger geologists were supposed to work with dipmeters, and, if they had a taste for it, the natural gamma-ray spectroscopy logs. It turned out that my timing was fortunate. At Schlumberger's research center, in Ridgefield, Connecticut, a prototype electrical imaging tool had been designed, and after having spent three years in the Middle East I was transferred there. The first field test results were just coming in, and the images were startling. We could see geological details that nobody had ever seen from a log: cross-beds, unconformities, pebbles, fractures, folds, faults. No cores were needed to confirm the reality of these data; they were too real to be artifacts.