Quantitative NMR imaging of multiphase flow in porous media.

Quantitative description of multiphase flow in porous media and local saturation distributions at steady states are of fundamental importance for petroleum recovery. The use of MRI provides an unprecedented means for obtaining such information. In this paper, profile imaging techniques for quantitative evaluation of fluid saturations during flow experiments in porous media are developed. The procedures for overcoming problems arising from very short, fluid saturation-dependent and spatial variation of T2, which are common in porous media, were addressed. The general methods developed should also be applicable to similar inhomogeneous biological systems. Experimental NMR imaging measurements of two-phase displacement were conducted in several limestones and sandstones representing various different types of pore structures, including a macroscopically homogeneous structure, a laminated structure, and a sample that exhibits porosity at different scales. The advantages of using each different type of profile imaging sequence to investigate flow in different types of porous structures are demonstrated. Images showing many features of multiphase flow, including nonuniform flow through different bedding structures, are obtained during the flow experiments. The use of profile images for obtaining many important petrophysical properties, such as permeability, porosity, saturation, and pore structural information, is discussed.