Radiometrics and Magnetotellurics a Combination Methodology to Reduce Exploration Risk

Robert W. Olson² and Daniel A. Woods^1
1Geophysical, DMT Technologies, Broken Arrow, OK
²Geology, DMT Technologies, Broken Arrow, OK

Micro-seepage and catalytic cracking of hydrocarbons in the subsurface produce a negative charge around a hydrocarbon accumulation, which in turn creates a relative positive charge at the surface. The micro-seepage process creates a relative reducing environment at the surface. This changes the Eh-pH potential which affects the solubility and precipitation of the remote sensing hydrocarbon indicators. This is the Pirson “fuel cell” (1981). With detail processing of surface radiometric data, we have observed periodic, semi-symmetrical “cross-over” on plots of the apparent radiological concentrations of potassium and the uranium series, associated with non-depleted oil and gas fields and potential prospects. We believe that due to geometric magnetic field stability considerations, the Pirson fuel cell breaks up into several adjacent vertical Pirson cells, each with an associated independent vertical magnetic field. These independent vertical magnetic fields are thought to be both the driving force and guiding force for vertical micro-seepage. The concept of multiple Pirson cells with their accompanying magnetic fields and the associated Eh-pH gradients away from the micro-seepage locus, completes the unified theory of Reed Tompkins (1990), and as such, explains the origin and physical placement of the vast majority of remote sensing hydrocarbon indicators. However, remote sensing hydrocarbon indicators still lack the critical elements of depth, thickness, and fluid content in a prospective hydrocarbon reservoir. High resolution magnetotellurics can provide information concerning depth (within 25 feet), thickness (within approximately 3 feet), and fluid content. Thus magnetotelluric attributes allow an economic quantification and ranking of the remote sensing prospect leads. Examples from Oklahoma, Kansas, Texas, and Utah will be shown.

AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas