Schumacher reported in 1996 that exploration methods based on what are assumed to be hydrocarbon-induced soil and sediment alterations have long been popular, but the processes that produce the observed effects are not well understood and even less well documented. The nature and extent of the alteration can vary significantly not only laterally and vertically but also temporally.
The cause of these altered soils and sediments may well be hydrocarbon related, but it is an indirect cause at best and may not be the most probable cause. We must evaluate seemingly “significant” alteration anomalies carefully to determine if they are related to hydrocarbon seepage. This requires answers to the following questions. Is the anomaly a function of geology or an artifact of culture? If geology, is the observed alteration syngenetic or authigenic? If authigenic, is the anomaly seep-related or of non-seep origin? If seep-related, does the anomaly result from an active hydrocarbon seep or a paleoseep?
Finally, if the anomaly at the surface is to be related to a drilling objective at depth, does the anomaly result from mainly vertical migration or does the migration path follow a more complex route? Numerous claims of success have been made for various exploration methods based on soil and sediment
alteration anomalies. Well-documented case studies are rare, however, and the claims are seldom substantiated by a scientifically rigorous program of sampling and analysis. Although the occurrence of hydrocarbon-induced alteration is well established, considerable scientific research is needed before we understand the formation of these anomalies in the near-surface and realize their full value for hydrocarbon exploration.
For a more recent review of the issues: (here).
Managed & Built by I2M Consulting, LLC | © 2010-
