This paper discusses issues related to the choice of total or effective porosity as the porosity basis for geostatistical model construction. Distributions of variables are different depending on the porosity basis. The distribution of variables has a strong effect on the performance of collo-cated simulation techniques. This paper presents the two porosity approaches and demonstrates some of the issues that may arise. In the examples shown here, total porosity appears to generate better behaved porosity-permeability co-distributions. Regardless of the porosity basis, upscaling methods are shown to potentially move hydrocarbon from low quality rock into more accessible coarser cells which means that any application of cutoffs is more meaningfully applied prior to upscaling if this movement is considered unrealistic for large-scale flow simulation.