GEOLOGICAL CONTROLS IN THE GEOSTATISTICAL SIMULATION OF HYDROCARBON RESERVOIRS

In many, if not most, reservoirs geological structures have an overrid ing and controlling effect on the continuity and heterogeneity of petr ophysical variables. In general terms, categorical variables influence the variability of quantitative variables. As this influence is signi ficant, and sometimes dominant, it is essential that it be incorporate d either explicitly or implicitly in reservoir models. This paper desc ribes a method of incorporating categorical control variables, such as lithology, in the geostatistical simulation of quantitative variables , such as porosity and permeability. The method described is basically a co-conditional co-simulation version of sequential gaussian simulat ion using a truncated gaussian distribution to model the category vari able(s). The method is applied to the simulation of porosities in carb onate rock in which lithology has a controlling influence on the spati al distribution of porosities.