Geophysical prospecting using transitory currents - incorporating many repetitions of emission current of particular pulse form and particular dipole configuration

摘要

A method of geophysical prospecting comprises applying a pulsing electric current consisting of a group of pulses of alternating polarity followed by zero current repetitively to an emitting dipole placed in the subsoil and detecting the resulting transitory signal at a receiving dipole also placed in the subsoil. The method incorporates defining intervals of time of predetermined duration following the excitation pulses and simultaneously with the period of zero excitations current. The transitory signals detected during these intervals are treated statistically to give a rough representation of the transitory response which is then smoothed and normalised. The operations are repeated with implantation of the emitting-receiving device successively at different stations of the zone being prospected, and a number of smoothed and normalised local curves is obtd. A regional curve is determined from the set of local curves and residual representations are determined by difference. The residual representations are used to give final figurative representations in map form, which the geophysicist can use to obtain indications of deep anomalies, e.g. petroleum deposits.. The invention improves existing technique by reducing interference levels and simplifying the interpretation of the data.