An Integrated Deterministic/Probabilistic Approach to Reserve Estimations(includes associated papers 31056 and 35248 )

Abstract

Abstract Mobil Oil Exploration and Producing Corporation utilizes a unique methodology for reserve and resource evaluation. The approach integrates both deterministic and probabilistic methods to evaluate externally reported reserves and establish the full hydrocarbon potential of our projects. There are three basic classifications for hydrocarbons in our reserve/resource system; Reserves (appropriated projects that are economic at today's prices), Contingent Resources (projects being appraised or not viable with today's prices and technology), and Speculative Potential (yet to be drilled). In addition, the Reserves and Contingent Resources classifications each have three categories: Proved, Probable, and Possible. Proved and Probable are calculated deterministically utilizing in house definitions which conform to SEC and SPE guidelines. Monte-Carlo simulation is then run to establish the cumulative probability distribution for recoverable hydrocarbons. This distribution and the deterministic results are used to define the possible category and to establish the project expected value. Average risk factors are calculated for each of the categories to ensure they meet Mobil guidelines. These average risk factors (truly confidence factors) are reported in association with their category value. The ultimate or EV is then used for economic assessment of the field and equals the projected ultimate recovered amount.