Analysis of Light Hydrocarbons in Soil Gases, Lost River Region, West Virginia: Relation to Stratigraphy and Geological Structures* By

Analyses of near-surface soil-gas samples for light methane through butane hydrocarbons and ethylenepropylene over the Lost River gas field in Hardy County, West Virginia, has revealed sites containing anomalously high concentrations of gases directly above the faulted, eastern limb of the Whip Cove anticline that defines the productive structure. Statistical analysis suggests that approximately 10 % of the samples (forty-five out of a total of 471) contain anomalously high concentrations of light hydrocarbons. Fairly active seepage is suggested by the very large saturate to olefin ratios exhibited by the largest magnitude soil gas anomalies. Grids placed on botanically defined anomalies (maple trees in a Climax Oak forest) suggest a seepage-related correlation. Compositional variations divide the soil gas data into two different domains, with gassier compositions to the east and oilier compositions to the west. The gassier anomalies, which are very similar to the Oriskany production gases, are above near-vertical beds of Devonian and older formations, and appear to be sourced by thermal gases derived from these more mature rocks. The oilier compositions of the soil-gas anomalies that follow the strike of the eastern, faulted limb of the Lost River gas field suggests that the dry gases from the Oriskany reservoir are probably mixing with oilier gases derived from less mature organic-rich strata contained in the overlying Devonian shales. Although the soil gas signatures would not have predicted th