Solving the ‘Enigma’ of Reserve Growth

As a good rule of thumb, when you have a promising model describing some physical process, you might as well put it through its paces. Not only do you shake out some stubborn corner cases, but you often find something new and revealing. We did that in the last post, The Derivation of “Logistic-shaped” Discovery, grinding out the derivation of the classic Logistic/Sigmoid-shaped Hubbert curve based on the generalized Dispersive Discovery model. With this post, I use the same discovery model to derive the upward climb of the cumulative reserve growth curve which we empirically observe on many oil reservoirs and oil-bearing regions.


Many analysts have found this reserve growth behavior both curious and ultimately very important. I know that Khebab and Rembrandt have spent much time on TOD tracking this behavior as it plays an important role in how the peak will play out. Furthermore, I believe that the practice of “back-dating” discoveries based on reserve growth updates has muddied the waters and stalled progress in the basic understanding of the fundamental growth process. Unless we have a good model for the reserve growth dynamics we have to resort to using the heuristics supplied by USGS geologists, including the modified Arrington equation that Khebab has successfully used in the past. I find nothing wrong with using a heuristic and Khebab has really kick-started the “un-back-dating” approach with some excellent results. Still, a heuristic lacks some of the predictive power and room for insight that a fundamental model can provide.

The Oil Drum