Petrophysics and Nuclear Magnetic Resonance (NMR) Study of Low-Resistivity Pay in Lower Silurian Sandstone Reservoir

Knowledge of reservoir evaluation is helpful in the interpretation of well-logging data, where the hydrocarbon saturation is expected as the final result by Archie equation. It is calculated from the deep resistivity, water formation resistivity and porosity. Porosity is calculated from the bulk density, neutron and sonic are measured directly in the well. The Archie evaluation, in the low resistivity layers, is characterized by high water saturation. The MDT tests in the low resistivity pay prove several oil samples. For this incompatibility interpretation of low-resistivity-contrast pay zones needs an analysis of the reservoir composition in the study area. The divergence results between Archie and well test allow integrating a new evaluation approach. However, the proposed interpretation framework does allow the incorporation of new logging technology as this becomes established. Nuclear magnetic resonance (NMR) is a useful tool in reservoir evaluation. The objective of this study is to predict petrophysical properties from NMR T2 distributions. The evaluation of NMR relaxation time distributions estimates of pore-size distributions. Irreducible water-saturation estimates from NMR-based pore-size distributions. In this study, we look at the downhole NMR measurements to determine pore geometry and volumetrics within a reservoir (free fluid index). NMR measures the net magnetization of a hydrogen atom (H) in the presence of an external magnetic field. Hydrogen has a relatively large magnetic moment and is abundant in both the water and hydrocarbons that exist in the pore space of sedimentary rocks. NMR measurements provide information about the pore structure (Sp), the amount of fluid in situ (FFI), interactions between the pore fluids, and surface of pores and provide important information for evaluation of low-resistivity layers.