Schlumberger was born of an idea—that if an electric field could be generated below ground, voltage measurements at the surface could be mapped to reveal subsurface structure. Following two years of lab and field testing, the first map of equipotential curves was recorded in 1912 using very basic equipment. The result confirmed the method while revealing underground features, such as bed boundaries and the direction of formation layer dips. This was crucial because the technique provided extra information that might be useful for locating subsurface structures forming traps for minerals such as oil and gas.
Two decades and a world war would intercede before those seeds of logging would sprout, cultivating an entirely new approach to identifying geological formations consistent with oil- and gas-bearing structures, launching nearly a century-long legacy of innovation and precision.