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 ... read more
