Determination of Porous Medium Structure by NMR Technique
Dr. Qingwen Ni 倪慶文 博士
Southwest Research Institute, San Antonio, TX
摘要：
Recent a new generation of pulsed Nuclear Magnetic Resonance (NMR) logging tools have increased the interest in using NMR for measuring properties of porous media. The NMR technique yields valuable petrophysical information from the well logs; for example, the porosity, total fluid content, water saturation, permeability, wettability, and pore size distribution of the reservoir rock. Most of these properties are determined from the pore size distribution. This NMR measurement relies on excitement of the proton spins in aqueous phase followed by measurement of their relaxation back to equilibrium. The relaxation time of the proton spins near the pore surface is faster than that in the bulk because the spin interactions between the liquid phase and the solid phase are much stronger than those in the bulk liquid. Previous study has showed that the surface-to-volume ratio of pore can be estimated from the spin-lattice relaxation time (T1) or spin-spin relaxation time (T2). Because of the surface effect, surface to volume ratio and hence pore-size distribution can be extracted from a NMR measurement with the longer relaxation times corresponding to the larger pores. The advantages of this approach includes: (1) a wide range of pore sizes from nm to μm can be analyzed, (2) the method is non-destructive, (3) it is independent of the pore shape, and (4) it can be used with wet materials. This NMR technique has been used extensively to measure pore sizes and pore-size distributions in various meaterials, such as membrances, different kinds of rocks, silica gel and hydrogels, wood fibers, concrete, and the other porous media.
簡歷：
Dr. Ni is an experimental solid state physicist with expertise experience in Nuclear Magnetic Resonance (NMR). His primary expertise is the application of NMR to the industrial process. The range of NMR applications includes using 1H, 13C, 23Na, 31P NMR, and magic-angle-spinning (MAS) NMR. He has experimentally and theoretically developed the cross-relaxation proton NMR to analyze the structure and dynamical motions of molecule in multiphasic materials. Recently he has involved several projects related to characterization of porous media. PROFESSIONAL CHRONOLOGY: Teaching Assistant, University of North Texas, 1984-1985, M.S. in physics; Research Assistant, UNT, 1986-1991, Ph.D. in physics; Postdoctoral Associate, Purdue University, 1991-1993; Postdoctoral Fellow, Southwest Research Institute, 1993-1994; Research Scientist 1994-1996; Senior Research Scientist 1996-present.