Nuclear magnetic resonance (NMR) is a useful tool in reservoir evaluation. The objective of this study is to predict petrophysical properties from NMR T 2 distributions. A series of laboratory experiments including core analysis, capillary pressure measurements, NMR T 2 measurements and image analysis were done on sixteen greensand samples from two formations in the Nini field of the North Sea. Hermod Formation is weakly cemented, whereas Ty Formation is characterized by microcrystalline quartz cement. The surface area measured by BET method and the NMR derived surface relaxivity are associated with the micro-porous glauconite grains. The effective specific surface area as calculated from Kozeny's equation and as derived from petrographic image analysis of Backscattered Electron Micrograph's (BSE), as well as the estimated effective surface relaxivity is associated with macro-pores. Permeability may be predicted from NMR by using Kozeny's equation when surface relaxivity is known. Capillary pressure drainage curves may be predicted from NMR T 2 distribution when pore size distribution within a sample is homogeneous.

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The effects of porosity and pore geometry on the fluid saturation and immiscible displacement of greensand reservoir rocks were investigated on eight samples from the North Sea basin. Dynamic Neutron Radiography (DNR) was used to image the front stability during displacement experiments where oil was infiltrating water-saturated samples. The flow characteristics were related to petrography and pore geometry, which may be determined by image analysis of backscattered electron (BSE) micrographs. The fluid saturation observed in each DNR image was modelled in a corresponding BSE image as a means of evaluating the effect of pore geometry on front stability. Piston-like displacement and channelling were observed and these flow patterns were found to reflect variations in pore geometry. The samples with piston-like displacement have homogeneous pore space, whereas the samples with channelling have heterogeneous pore space, with spatial variations in porosity and pore size. The modelled saturation distribution was interpreted using results from petrographic and petrophysical analyses. The results suggest that the micropores of the glauconite grains and clay minerals contain water, whereas the oil is moving through the intergranular pore space during the displacement experiment.