Reality Checks for Prospect and Play Risk Assessment

Chris Wold¹, Jay Leonard¹, Marshall Titus¹, Robert Coskey¹, and P. Jeffrey Brown^2
1 Platte River Associates, Inc, Boulder, CO
² Decision Strategies, Inc, Houston, TX

To date, most of the industry has evaluated plays based on the probability assessment system published by White and others in the 1980's and 1990's. Play shared probability is based upon estimated adequacy of charge/migration/timing, play independent probability upon an “average” prospect geologic chance, and volumes are estimated from an analog field size distribution. Recent advances in map-based technology have made map presentations of variations in shared and independent probability a powerful (and routine) reality check of prospect probabilities. Such reality checks and linkages are critical to correct implementation of risk analysis.

Another advance is the capability to capture the uncertainty associated with petroleum system dynamics. A stochastic compaction, thermal, kinetic model can now be used to estimate the range in potential charge from one or more source rocks. Uncertainty of the quality and quantity of organic matter in the source rock are input to the simulator. Other important components include the extent of the pod of active source rock and amount of hydrocarbon retained by the source rock or lost during secondary migration. The calculated cumulative probability volume distribution of migrated and entrapped hydrocarbon is a reality check on play reserves estimated from the older approach, and the range in volumes charging an individual prospect is a powerful reality check for prospect risk analyses.