Cloud-to-Ground Lightning: A Newly Recognized Natural Resource Exploration Tool

Lightning data, first documented as an electrical phenomenon by Benjamin Franklin in Pennsylvania, has been collected for decades for insurance, meteorological, and safety reasons. Geophysicists have indirectly used lightning data as part of the electrical source for magnetotellurics (MT) and other electrical telluric measurements since the 1950's. Until recently geophysicists, who are the primary scientists exploring for new natural resource deposits, have missed the fact there are databases with both locations and attributes of billions of lightning strikes, which databases are available to data mine and to integrate with other exploration data. We recognized these lightning databases as a new geophysical data type, which can be integrated with gravity, magnetic, electrical, seismic, and satellite based geophysical tools to enhance exploration for natural resources that are resistive (oil, gas, water, salt, etc.) and conductive (mineralization and minerals, brines and geothermal water, kimberlite pipes where diamonds are found, etc.).

In the early 1980's new measurement technologies enabled accurate identification of lightning strike locations.  This led to defining nearly all cloud-to-ground (CG) lightning strike locations and related lightning physical characteristics across the continental United States starting in 1989. The result was the creation of the National Lightning Detection Network (NLDN), and recent advances in measuring ability has opened the door to new lightning-based technologies worldwide.

Lightning is a meteorological phenomenon. However, lightning strike location and lightning strike attributes appear to be influenced, if not controlled, by geology. Telluric currents are electrical currents in the subsurface, typically at 20-30,000 foot depths, which have been recognized since the 1950's to be charged by worldwide thunderstorms and the auroras at either pole. The flow of these currents and particularly shallow extensions of these telluric currents (terralevis currents) are modified by faults, mineralization, fluids like resistive fresh water or oil or gas or like conductive brines and geothermal waters, and by the conductivity or resistivity of lithology and geology like clays (conductive) and salt (resistive), etc.

Data mining and mapping millions of lightning strikes has shown geology influences lightning strike locations and attributes. When we mapped the various attributes recorded in the lightning databases from Florida, Louisiana, Michigan, New York, North Dakota, and several places in Texas we found the similar spatial variations and temporal consistencies. Lightning strike density varies spatially, and these variations are somewhat consistent over time. Two maps showing lightning strike Density (Figure 1) and average Rise-Time (Figure 2) of lightning strikes between 1998 and 2014 on the Louisiana coastline highlight our results. Note the 3 resistive salt domes in the area are highlighted in the Rise-Time maps.

 

Figure 1. Lightning Strike Density on Louisiana Coast		Figure 2. Average Lighting Strike Rise-Time

Data mining lightning strike databases provides a new geophysical data type, which data type can be integrated with other potential field geophysical data types and with seismic data to explore for natural resources. A dozen lightning analyses over the last five years show lightning strike locations are not random. From this work faults have been mapped, relationships have been made to sediment thickness, possibly we are predicting seeps, maps of anisotropy (fault density and orientation) have the potential to differentiate between ductile and brittle shales in the significant new shale resource plays like the Bakken, Eagle Ford, Marcellus, Vicksburg, Bossier, Fredricksburg, Mississippian Lime, etc. It has been demonstrated lightning strike location and attributes are not predominantly tied to infrastructure (tall objects, wells and pipelines), nor are locations controlled only by topography or vegetation or water depth. We were granted United States Patent 8344721 B2 in January 2013; A method for locating sub-surface natural resources. The method utilizes lightning data to discern relatively likely locations for finding the sub-surface natural resources.