Lightning, a Strikingly New Unconventional Electromagnetic Exploration Tool

Abstract:

Lightning occurs everywhere. It can now be used by petroleum and mining industries for exploration. Naturally occurring cloud to ground electrical discharges have now been used as a geophysical exploration tool. This technology that can be applied to resource exploration, large scale basin studies, and geo-hazard, geotechnical and environmental studies.

Although lightning is guided by meteorological conditions, the precise location and attributes of strikes appear to be guided by shallow, geologically related, perturbations of telluric currents. These electrical currents are influenced by lateral geological inhomogeneity caused by faults, fractures, mineralization, pore-fluids, and salinity variations.

Worldwide lightning data shows that lightning strikes are not uniformly distributed. Broad variations depend on weather, but details depend largely on geology. An analysis of sixteen years of recorded North American lightning data shows non-random patterns clearly dependent on geology.

After raw lightning data is edited and stacked, much like multi-fold seismic data, strike density and attribute maps show correlations to surface and subsurface geology. 3-D resistivity and permittivity volumes can also be generated from lightning data and displayed in the same manner as 3-D seismic data.

Evaluation shows how lightning clusters and lineations appear to correlate to fresh water, near-surface fluvial depositional patterns, hydrocarbon seeps, salt domes, and mineralization. Resource exploration case studies presented include two petroleum exploration case studies from the Texas Gulf Coast and a porphyry copper example from Arizona.

This is a new, effective, quick, and inexpensive reconnaissance and near surface geophysical tool. With proper subsurface calibration, potentially powerful 3-D resistivity and permittivity volumes can be generated.