Estimates of potential volume, composition and phase of petroleum charges to traps are an integral part of petroleum prospect evaluation. Such estimates are directly sensitive to the timing and efficiency of petroleum expulsion from the source rock.
To date, geochemists have adopted two approaches to prediction of expulsion behaviour. The first is an heuristic approach based on a limited number of case studies. The second, a theoretical approach based on extrapolation of permeability concepts used in reservoir engineering, has popular appeal but may be of limited application to the pores of fine-grained petroleum source rocks, where the behaviour of interstitial water is rather different. Consequently the processes controlling expulsion are still a subject for debate.
It remains possible to challenge established relative permeability models, and to argue that the concepts of petroleum saturation and discrete-phase flow are either unimportant in the expulsion process, or else involve such low concentrations of petroleum within the pore volume that they can be considered negligible. Instead, kerogen itself may exert the prime control on expulsion behaviour by retaining (adsorbing) generated petroleum. If so, a simple quantitative model can be devised to predict expulsion efficiency of both oil and gas as a function of the initial kerogen composition (proportions of petroleum-generative versus petroleum-retentive kerogen).
Expulsion behaviour modelled in this way compares favourably with previously observed behaviour of a wide variety of source rocks. In particular, a case history presented demonstrates the capability of the model in predicting the differences in the expulsion behaviour of different coals, and the consequences in terms of composition of the expelled products.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.