David M Richers¹, Victor T Jones², Douglas E Wyatt³, Earl Detra⁴
(1) Mt Evans Geosciences, Inc, Thornton, CO
(2) Exploration Technologies, Inc, Houston, TX
(3) Westinghouse Savannah River Co, Aiken, SC
(4) Mt. Evans Geosciences, Thornton, CO

Abstract: Some applications of geochemistry for basin evaluation,exploration target assessment, and environmental screening

Soil gas geochemical methods, when applied properly, can assist in evaluating basin hydrocarbon potential, facilitate ranking hydrocarbon targets, and can be useful in delineating hydrocarbon-related plumes in near surface groundwater studies. Presented will be three separate studies depicting such uses. The first example, evaluates the source rock character and hydrocarbon potential in the Dunbarton and Riddlesville basins under the coastal plain in South Carolina and Georgia. At least two different suites of source rock are apparent from soil gas evaluations: 1) a normal oil-prone, marine source, and 2) a more gas-prone, terrigenous source. In the second example, ten potential exploration targets were identified on seismic on the Zarzis peninsula of southeastern Tunisia. By utilizing soil gas geochemical methods, it was possible to build a discriminant function that accurately identified known end-member (i.e. barren versus hydrocarbon-bearing) compartments in the Cretaceous Zebag Limestone. This model was then applied to the exploration targets to rank them on the relative probability of containing hydrocarbons. Upon drilling, one of the higher ranked targets had significant, albeit noncommercial hydrocarbon shows, while one of the lesser ranked targets had no hydrocarbon shows. Finally, the third example shows the use of shallow multi-profile soil gas data being used to delineate contaminant plumes in the vadose and phreatic zones downgradient from a leaking petroleum product storage facility. Subsequent investigation of multisensor satellite imagery over the area shows a strong affinity of a spectral anomaly mapping the extent of the groundwater plume. This suggests that at least in areas of suspected contamination, the use of remote sensing could facilitate the placement and design of environmental studies. This could result in substantial savings in the collection and analysis phase of similar studies.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana