ABSTRACT: A new top-down approach to evaluating prospects with dependent layers and compartments

Stabell, Charles¹, Francis Rollins², Espen Langli¹
(1) GeoKnowledge AS, Sandvika, Norway
(2) Statoil Exploration (US) Inc, Houston, TX

A main challenge for wildcat risk and resource assessment of prospects with complex, multiple layers and compartments is handling explicitly and consistently both risk and volume dependencies. In this paper we present a new top-down approach that generalizes the marginal play, conditional prospect approach to prospect level risking to a 3-level model where we introduce a conditional segment level risk. The conditional prospect risk is then an estimate of the common risk across all segments in the prospect. Each segment has a conditional segment risk that is an estimate of the risk of success given that at least one other segment in the prospect is a hydrocarbon accumulation. The un-risked prospect level resource estimate is the segment resources weighted by their respective conditional segment risks. Intra- and inter-segment correlation coefficients model volume dependencies.

We illustrate the application of the methodology with an example of a deep marine clastic prospect. In the review of the application we present a group evaluation procedure that fuses the expertise of the exploration team when estimating marginal and conditional risk factors. We also review how the top down approach advocated in this paper compares and contrasts with alternative approaches that have been presented in the literature.

AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia