Relative permeability profile is one of the most uncertain parameters and challenging requirements in field performance models. It is a mandatory element for multi-phase flow calculations and has a significant impact on development schemes, expected hydrocarbon recovery factor and the related revenues. Moreover, it impacts the surface facilities decision based on predicted produced fluids and recycling requirements, which might affect the economics of any related projects. Accordingly, obtaining representative relative permeability profile is a historical continuous challenge in the industry through common laboratory methods of steady state and unsteady state along with other numerical modeling approaches.
Experimental relative permeability profiles using both methods of steady state and unsteady state have been obtained for one of the main reservoir rock types (RRT A) from a giant carbonate field in the Middle East. Comprehensive characterization and detailed numerical modeling for mixed wettability carbonates at full reservoir conditions has been studied covering all the details of rock properties, capillary pressure coupled with relative permeability profiles. The analysis revealed the uncertainty associated with each measurement method and surprisingly the limited data range of unsteady state method. Moreover, for the selected reservoir rock types, non-unique relative permeability profiles have been obtained using various experimental approaches and empirical correlations within the numerical modeling process in which different produced relative permeability profiles matched reasonably the laboratory reference measurements.
The resultant relative permeability profiles associated with uncertainty range presented in this paper has shown the significant influence of the measurement method selection, which impact the dynamic simulation models predictions and the eventually field development options. This work provides insight on experimental methods selection and optimum conditions to acquire representative relative permeability profiles with emphasis on possible sources of uncertainties and errors. It clearly demonstrates the relative permeability accuracy levels of various numerical modeling processes and the potential of non-unique profiles which dictate the reservoir dynamics, performance as well as economics.