It is well known that NMR is already used in various core laboratory analyses to characterize rock and fluids, obtain pore-size distribution, determine porosity and even evaluate rock wettability qualitatively using different numerical methods. The development of A SINGLE ANALYTICAL expression relating the porosity, permeability, diffusion coefficient, NMR/MRI relaxation parameters and the transverse magnetization will significantly enhance the present understanding of these petro physical properties. Our goal is to apply a generally applicable and simple approach which may yield useful information from NMR signals of different petro-physical properties useful in Petroleum and Gas industry. This presentation is based on a model of the Bloch NMR diffusion equation for complex pore geometries in which the transverse magnetization is obtained as a function of reservoir chemical (relaxation) and physical properties. The NMR signal is also shown to be dependent on the tortuosity and relaxation rate of rocks fluid so that reservoirs comprised of mixed lithology and mineralogy can be easily evaluated. The novel model may open up new research opportunities which can be jointly explored with any Oil and gas Company. For example, it can be used to visualize and track the saturation front during displacement experiments (dynamic measurements). The difficulty in estimating permeability from grain-size distributions or from well logs can be reduced very significantly if the simple analytical expression obtained from the Bloch NMR flow equation as a function of permeability, porosity, tortuosity and diffusion coefficient is fully explored.