Abstract: How to Reduce Risk in Prospect and Field Appraisal by Uncertainty Modeling

Marek Kacewicz

There is direct link between risk and uncertainty. The higher the uncertainty related to data and processes, the more risk is involved in basin, prospect, and field appraisal. Therefore risk assessment should always be preceded by a thorough analysis of sources of uncertainty. Uncertainty and risk related to prospects or fields should not be analyzed in separation from the uncertainty and risk related to basins. Actual reserves can be better assessed after a detailed basin modeling study is performed. This is especially true in the case of long distance migration and complex charging systems. Among different sources of uncertainty in basin, prospect, and field assessment, the following are worth mentioning: basin geometry as a function of time, erosion, timing and potenti l of generation, direction of expulsion and expulsion efficiency, timing of trap formation, four dimensional aspect of reservoir properties (x, y, z, time), diagenesis, development and activity of fracture systems and faults, migration conduits and sealing systems, and migration directions. Charging potential of prospects and fields, spatial distribution of fields and accumulated hydrocarbons should be assessed as a function of the factors mentioned above.

In this paper some real-world examples of appraisal, which start from regional studies and are followed by more detailed block and prospect studies are presented. We show how our approach helps to highlight prospects and to calculate reserves taking into account uncertainty. Mathematical methods which have been applied involve stochastic processes, geostatistics, and differential equations.

AAPG Search and Discovery Article #90956©1995 AAPG International Convention and Exposition Meeting, Nice, France