--> ABSTRACT: Five Year Look Back at Risk Assessment and Estimation of Hydrocarbon Volumes, by Robert M. Otis; #91020 (1995).

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Five Year Look Back at Risk Assessment and Estimation of Hydrocarbon Volumes

Robert M. Otis

The process used by Chevron Overseas Petroleum, Inc. for evaluating international exploration ventures includes an annual comparison of predicted and actual values for assessed geologic risk and estimated hydrocarbon volumes. Risk histograms constructed from the yearly data show a previous tendency for explorationists to assess risk in a narrow range, i.e., they overestimate risk in low risk ventures and underestimate risk in high risk ventures. Data indicate a wide range of risk in three main categories: Low risk (1:1 - 1:4) for proven plays in producing areas, moderate risk (1:4 - 1:8) for unproven plays in producing areas and high risk (> 1:8) for unproven plays in non-producing areas. This examination helped focus on critical geological issues resulting in assessme ts more consistent with historical evidence. Volumetric histograms indicate estimates of reserve ranges and individual volumetric parameter ranges were too narrow or overly optimistic. Modifications to the process for assigning ranges to areal extent, geometric factors, and reservoir parameters have been implemented and recent results indicate more accurate representations of volumetric ranges are being made. Utilization of this feedback loop is considered an integral part of our evaluation process and has helped build credibility in the overall risk and volumetric processes.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995