Capillary Pressure Curves from Nuclear Magnetic Resonance Log Data in a Deepwater Turbidite Nigeria Field - A Comparison to Saturation Models from SCAL Drainage Capillary Pressure Curves

Abstract

Abstract The DW Turbidite field in Deepwater Nigeria has limited SCAL data on drainage capillary pressure curves used, traditionally, in building saturation-height functions for application in 3D static and dynamic models. An alternative approach to derive capillary pressure curves from Nuclear Magnetic Resonance (NMR) T2 distributions, developed by Volokitin et al, has been tested in one of the key reservoirs in the DW Turbidite North field and compared to mercury injected capillary pressure (MICP) data from a full-bore core across the reservoir. The alternative approach relies on an underlying assumption that a relationship exists between porebody radius (as represented by the NMR T2 distribution) and pore-throat radius (which drives capillary behavior). An algorithm has been applied that uses a T2 cutoff such that the sum of the bound and moveable fluid spectra amplitudes matches the water porosity to correct for the presence of hydrocarbons. The hypothesis is the resulting relationship (between the NMR T2 distribution and pore-throat distribution) embedded within a proportionality parameter, κ. The hypothesis was tested on the three key facies (CSA - Channel Storey Axis, CSM - Channel Storey Margin & ICTB - Inter-Channel Thin Beds) identified in the reservoir. Field-specific proportionality parameters were determined from which NMR T2 capillary pressure curves have been derived. Comparison between the derived capillary pressure curves and the SCAL (MICP) data provide confidence that this technique can be applied in the absence of SCAL data.