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The Use of Windowed Radiometrics (WR) and high Resolution Magnetotellurics (HRMT) to Reduce Exploration Risk

Robert Olsen

Total count radiometrics has been used in oil and gas exploration since the early 1950s. Improved instrumentation has allowed the identification of the individual gamma emitting radioelements (WR). The increased concentration of uranium and the decreased concentration of potassium over a microseeping hydrocarbon accumulation reflects the geochemistry of these two elements. Line processing of the WR data often shows a periodic mutual divergence of the concentrations of these two elements when compared to regional background (the potassium - uranium couplet: the K - U Couplet). This suggests some hydrocarbon liquids in the reservoir. Aerial data can cover a large area but is surface only. The modern controlled-source electromagnetics (CSEM) systems used offshore by ExxonMobil and others generate the input energy source at specified frequencies. CSEM data processing uses much of the same stacking technology as modern seismic data processing. This "stacks out" the "noise" of electromagnetic phase, possibly losing fluid content information. The input energy source for HRMT is generated by the interaction of the solar wind with the earth's electric and magnetic fields. This input energy source contains all frequencies. The HRMT system must tune to the necessary frequencies. Both of these electromagnetic systems investigate depth as a function of frequency. HRMT is point specific. The recorded HRMT data maintain frequency and phase. WR data give location, size and an indication of hydrocarbon liquids (the K - U Couplet). HRMT data give depth and thickness (frequency) and fluid content (phase: oil-gas-water). These two technologies together provide the basic information for the initial economic analysis of the prospect. The HRMT success ratio is 49% for commercial production. The do-not-drill prediction ratio is 100%. 

AAPG Search and Discovery Article #90176©AAPG Mid-Continent Meeting, Wichita, Kansas, October 12-15, 2013