A note on dynamic rock typing and TEM-function for grouping, averaging and assigning relative permeability data to reservoir simulation models

Abstract

For years, rock typing based on two-phase flow characteristics was mainly founded on grouping primary drainage capillary pressure curves, while rock classification based on relative permeability measurements and its practical applications were overlooked. Recently, a dynamic rock typing approach was proposed by defining a True Effective Mobility tool (TEM-function) to convert relative permeability data to fluid flow indicators. This technical note sheds further light on the concept of dynamic rock typing and TEM-function. Moreover, in previous studies the fact that how identified petrophysical dynamic rock types (PDRTs) and their corresponding average relative permeability tables should be assigned to simulation grid cells was not addressed. We accordingly investigate whether a general property can be found to assign average relative permeability data to grid cells. For this purpose, we apply TEM-function to identify PDRTs and present average relative permeability tables using gas-oil relative permeability experiments on a subset of carbonate samples. We also analyze the PDRTs in a counter-part water-oil system and investigate their relationship with gas-oil PDRTs. Results show that the recent dynamic rock typing approach incorporates forward and inverse processes that are physically meaningful and consistent with laboratory analysis and reservoir simulation processes. The strong dependency of TEM-function on the ratio of permeability to porosity enables us to introduce a general property to assign average relative permeability data to grid cells. Furthermore, while PDRTs in the gas-oil systems were almost identical, PDRTs in the water-oil system were dissimilar and different from the gas-oil counterpart. This confirms that each saturation function needs its specific rock typing scheme.