Abstract

Geochemical prospecting for oil and gas comprises the study of hydrocarbon induced surface alterations which are indicative of subsurface accumulations in seepage dominant areas. The light gaseous hydrocarbons migrate upward towards the shallow surface (microseepage) from the subsurface oil/gas reservoirs and reside as free gases in the soil pores, interstitial gases occluded in pore spaces between sediment grains, gases adsorbed on to the soil particles and dissolved gases in the water column. The detection of the anomalous concentrations of the gases such as methane, ethane, propane and butane serves as a direct evidence for the presence of a working petroleum system in an area.