An Improved Fractal Model for Characterizing Spatial Distribution of Undiscovered Petroleum Accumulations

Study of a mature petroleum play in the Western Canada Sedimentary Basin (WCSB) indicates that the spatial distribution of petroleum accumulations exhibits a self-affinity characteristic. This characteristic motivated the examination of a fractal model for a quantitative description of petroleum resource spatial distribution. The proposed approach transforms the spatial information with respect to discovered petroleum accumulations into a frequency domain, represented by an amplitude map and a phase spectrum. The amplitude map is then calibrated using a fractal model, inferred from exploration data, to account for the sampling bias in exploration procedure. The information in the obtained phase spectrum provides no clue with respect to the locations of undiscovered accumulations, and cannot be enhanced by the established fractal model either. If the calibrated amplitude map and a random phase map are transformed back to the spatial domain and conditioned on the discovered petroleum accumulations, the resulting map is equivalent to one of equal-probable realisations from a conditional simulation. Improvement can be made by extracting information with respect to locations of undiscovered petroleum deposits from geological factors controlling the formation of petroleum accumulations in a petroleum system. Using additional quantitative models, such as a geological favorability map or a map of probability of petroleum occurrence, allows an improved characterisation of spatial distribution of petroleum accumulations by the fractal model. An example from the Western Canada Sedimentary Basin illustrates the application of the method.