Microseeps, or smaller scale macroseeps, also occur and are usually detectable only by sensitive instruments. These microseeps, although perhaps not as obvious or dramatic as macroseeps, are just as valid for the exploration of undiscovered reserves.
The stratigraphic and structural mapping of geological and seismic data, coupled with the measurement of microseeps in the shallow subsurface, provide powerful means of evaluating and ranking prospective trends and traps.
The close association of near-surface geochemical anomalies to faults and fractures is well known. These fractures act as preferential pathways, focusing the flow of hydrocarbons from the source beds to the reservoir, and from there on towards the surface. Anomalous hydrocarbon concentrations are always real seeps, since active flux is necessary to overcome near surface interfering effects.
The most useful detection technique involves the measurement of the light hydrocarbons: methane, ethane, propane, iso-butane and n-butane. PGES offers geochemical exploration technology for hydrocarbon and geothermal applications.