oa Enhancement of Simulation Models Using Petrophysical Facies

If you ask a group of geoscientists and engineers “What is Facies?” you will definitely get very different<br>answers. The strange thing, but funny, is that they are working for long period of time, at the same<br>office, on modeling the same reservoir within the same field. One more strange (still funny) is that<br>both of them are exchanging a lot of data and most of these data are facies data (type, properties, categories…).<br>The wrong definition of facies affects negatively not only on the definition of the reservoir geometry but<br>also on the population of the reservoir properties. Geoscientists define facies from the geological point<br>of view based mainly on the lithology, depositional environment, diagenitic history, fossil contents and<br>other geological criteria. Based on these parameters geoscientists subdivide the facies into lithofacies,<br>biofacies, microfacies, icnofacies, electrofacies and seismic facies. Engineers look at the facies as a<br>different group of rocks that have different flow regime. Hence, if the flow of fluids within a body of the<br>reservoir is consistent this can be considered as one facies. Both definition need to be fine-tuned to get<br>the best results out of our reservoir models.<br>This paper suggests starting using the Petrophysical facies where the reservoir modeler uses all basic<br>Petrophysical reservoir rock properties (porosity, permeability, wettability, capillary pressure and<br>relative permeability) to differentiate between the different geological bodies within the reservoir rock.<br>This way we use the factors that control the fluid flow in a rock as a base for differentiating different<br>geological sittings. That will definitely give us a better chance to define the geometry of each facies<br>and then help us populate its properties within the defined reservoir bodies.<br>Out of 21 modeling projects in the Middle East and North Africa region, 16 of them did not obtain the<br>anticipated history matching because of the wrong definition of facies. Several case studies including<br>both carbonate and sandstone reservoirs showed a much better history matching after correcting the definition of facies.