Current issues in risk and uncertainty evaluations on petroleum system

Abstract

The development of risk and uncertainty evaluations on exploration prospects were initiated by major oil companies in 1960ʼs, which are now widely used in most of oil companies over the world. Dr. Peter Rose is one of main contributors to compile and introduce the methodology widely to oil industry. There are a few points（ rules） in his methodology; 1） Parameters related to Gross Rock Volume （GRV） such as accumulated area and net pay thickness should be given as log-normal distribution, so that calculated resources also have log-normal distribution, 2） Geological Success should be given as Chance of Success （CoS） corresponding to the probability that the minimum （P99） of resource distribution occurs.

In this paper, these points （rules） in the Roseʼs method are discussed to be convinced that it is not always necessary to stick on them, since oil and gas accumulated volume are better evaluated than before. If accumulated volume can be evaluated correctly, the resource distribution is not necessary as log-normal distribution. In addition, giving only the Geological Success becomes valid, if the resource distribution can be modified to include all the uncertainties as the results of the integration with accumulated volume.

Therefore, the key to improve the Roseʼs method is to be integrated with petroleum system analysis, especially for the evaluation of oil and gas accumulated volume by geochemistry and seismic attribute analysis. In second part of this paper, oil and gas migration efficiency that is the key parameter to calculate accumulated volume by static simple method is discussed in detail. Finally, the ratio of oil and gas accumulated volume against generated volume that corresponds to the migration efficiency is demonstrated using actual cases in petroleum systems and sedimentary basins over the world.