What are microbial surveys?
The concept of microbial surveying for oil deposits is based on the observation of HC leakage towards the surface and specific microbial species in association with this seepage. These microbes have enzymes specific to HC metabolism, i.e. they thrive in seep environments with seep HC as their food source. Thus, the presence or frequent occurrence of these specific microbial communities is considered to be a prime indicator for subsurface HC occurrences, similar to high gas yields in soils observed over fields. In the past the occurrence of these HC-microbes was considered to be very diagnostic until later research found out the ubiquitous occurrence of these specific microbes (Schlegel, 1992). The reason for this is the ubiquitous occurrence of HC gases and HC liquids in the soil, and the fact that many of these organisms have the ability to switch the food source in lack of HC constituents. Thus, anomalous microbial surface readings operate on a relative scale; point-blank “presence”
