NMR derived capillary pressure and relative permeability curves as an aid in rock typing of carbonate reservoirs

Abstract

Capillary pressure together with relative permeability curves are key parameters in carbonate reservoirs characterization. They serve as fundamental inputs in petrophysical and reservoir engineering studies such as rock typing, fluid contacts determination and saturation height function generation. In the current study, the NMR-T2 distribution diagrams were inverted to the synthetic capillary pressure and relative permeability curves. The results were compared to the laboratory-derived MICP and Kr curves and a satisfactory agreement was achieved between them. Afterwards, the reservoir rock types were determined from the integration of Conventional Core Analysis(CCAL) results with the NMR-derived Pc and Kr curves. Accordingly, the studied carbonate rocks were classified into four hydraulic flow units. Subsequently, a representative capillary pressure and relative permeability curve was derived for each hydraulic flow unit. The methodology is investigated through a case study of the upper Cretaceous Ilam Formation in the Abadan Plain. The results of this study demonstrated that NMR log contributes to a more precise carbonate reservoirs characterization and reducing uncertainty in reservoir rock typing. Through performing some additional computations and calibration with the core results, worthy information is extractable from NMR log.