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...