AN ANALYSIS OF OIL FIELD SIZE DISTRIBUTIONS IN CONSANGUINEOUS BASINS (RESOURCE ASSESSMENT, RICHARDS FUNCTION)

When assessing the amount of ultimately producible petroleum from an unexplored region, two things are important. First, the size distribution of sampled oil fields in the region will indicate the fraction of oil fields which are likely to be found for a given field size. Second, the richness of the region, or ultimately producible oil per unit area, indicates the amount of oil in that region and is directly related to the total number of oil fields in the region. In some instances, it is possible to use geological analogy to transfer the sampled oil field size distribution from a mature region to an unexplored region within a similar tectonic setting. But the richness of a region is generally unrelated to the tectonic setting of the region and invalidates the use of geological analogy as a resource assessment tool.;Classical Multidimensional Scaling was used to reduce the dimensionality of the distance matrix between the parameterizations of the basins. This technique revealed that only the craton interior and foreland basins had a parameterization that was constrained enough to allow a distribution to be transferred from a mature region to an unexplored region in the same tectonic setting.;The estimated ultimately producible oil in each province was used to create a richness factor for the province. While Craton interior basins are constrained from having a high richness factor and rifted convergent margin basins seem to always have a high richness factor, in general, richness was found to be extremely variable both within and across basin types. The richness is not related to the tectonic setting of the basin and indicates that a province must be at least partially explored before any petroleum resource assessment technique can be of any use.;The Klemme basin classification system was used to place each petroleum producing basin of the U.S. into its appropriate tectonic setting. A 1981 excerpt of the Petroleum Data System was used to obtain the distributions of sampled oil field sizes. These distributions were modeled very precisely by the Richards cumulative growth function, whose parameters were then used to compare the oil field size distributions between basins. The parameters of the Richards function were found to be related to the tectonic setting of the basin to some extent.