Three Common Source Rock Evaluation Errors Made by Geologists

Harry Dembicki
Anadarko Petroleum Corp, Houston, TX

Geologists are frequently called upon to evaluate the source rocks associated with their exploration prospects or plays. While assessing the hydrocarbon generating potential of these sediments, they will look at a sediment's capacity for hydrocarbon generation, the type of organic matter present, and its thermal maturity.

The techniques most frequently used to appraise these characteristics of source rocks are TOC, Rock-Eval pyrolysis, and vitrinite reflectance. So it is not surprising that when a prospect goes through a project review the most common questions asked and answered about the source rock are "What's the TOC?", "What kerogen type does Rock-Eval indicate?", and "What maturity level does the vitrinite data point to?"

The answers to these seemingly innocuous questions may in fact be providing a false sense of security about the source rock in question. It is important to understand how this line of questioning can lead you astray and make you the victim of The TOC Myth (“If I have high TOC, I have a good source rock.”), The Rock-Eval Fallacy (“The Rock-Eval data tells me what kind of kerogen is in my source rock."), and The Vitrinite Reflectance Shortcoming ("Vitrinite reflectance will tell me if my source rock is generating.”). The roots of these hazards are examined as well as ways to avoid them.