Play Risk and Uncertainty -- Probabilistic Modelling of Plays in the Western Desert and the Kom Ombo Areas of Egypt

By

R. C. Coskey¹, M. W. Titus¹, J. E. Leonard¹, T. El Azhary², M. Said²

(1) Platte River Associates, Inc, Boulder, CO (2) Stratochem Services, Cairo, Egypt

 The hydrocarbon potential of the Western Desert has been exploited for the last three decades and a substantial base of knowledge has been gathered to constrain models. Even so, geologic uncertainties exist that have a dramatic effect on the modeled timing of hydrocarbon generation and expulsion. Deterministic basin models of wells suggest a 53 mW/m^2 heat flow in the area. The resulting calculated maturity is in good agreement with measured Ro. Yet subtle changes in other parameters using stochastic techniques can vary expulsion timing by up to 80 million years. Clearly, analysis of the whole petroleum system (trap formation, etc.) is necessary to constrain the solutions.

Alternatively, in the sparsely drilled Kom Ombo area of Upper Egypt, the heat flow history is much more uncertain. Furthermore, other uncertainties abound, from facies distributions to source rock properties. In this data poor areas, stochastic modeling is much more efficacious. Here, the full range of geologic uncertainties must be addressed in a petroleum system analysis.

Traditionally modelers have dealt with geologic uncertainties by performing sensitivity analyses, creating multiple scenarios and noting the effects on charge timing; a slow and, oftentimes, limited technique. A stochastic approach to volumetric basin modeling provides an alternative that tests thousands of constrained assumptions creating a probabilistic response. The results that best calibrate with measured data may be extracted yielding the best results from all possible scenarios. The range of calculated hydrocarbon resources resulting from this risk analysis for the Kom Ombo area will be presented.