--> ABSTRACT: Compositional Modeling of Petroleum Generation and Expulsion--3-D Mass Balance, by P. L. Forbes, P. Ungerer, A. B. Kuhfuss, F. Riss, S. Eggen; #91003 (1990).

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ABSTRACT: Compositional Modeling of Petroleum Generation and Expulsion--3-D Mass Balance

P. L. Forbes, P. Ungerer, A. B. Kuhfuss, F. Riss, S. Eggen

Prediction of hydrocarbon composition is of great economic importance but very few models have considered that it requires an accounting of transport processes. An early expulsion of petroleum from source rocks favors formation of liquid, whereas late expulsion increases the extent of cracking and factors gas formation. We propose a compositional kinetic model that addresses primary cracking, secondary cracking, and simultaneous expulsion.

The application deals with the Smorbukk ß structure, Haltenbanken area, Norway. The composition of generated, unexpelled or expelled hydrocarbons is computed for the different source rocks throughout the drainage area, leading to a three-dimensional balance of expelled and unexpelled products.

The model produces a synthesis consistent with geological and geochemical data. The coal-bearing source rock is found to be the main source providing hydrocarbons mainly during the last 5 m.y.. The actual accumulations account for less than 10% of the total expelled hydrocarbon, which suggests major loss through the structural spillpoint. In contrast, the accumulations are comparable, in mass and composition, to the hydrocarbons expelled during the last 0.5 m.y. This suggests that the effect of drainage on the composition of hydrocarbons in the reservoir formation dominates in comparison to other phenomena such as diffusion, water solution, or segregation.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990