The Evaluation Method Of Petrophysical Parameter In Reservoir Using NMR

Core analysis is the most basic and accurate method to measure reservoir parameters. As harder and harder the exploitation becomes, conventional methods are no longer meet the needs of the research in tight oil and gas reservoirs, especially for the cores with complicated pore structure and strong heterogeneity. While as a potential method, nuclear magnetic resonance(NMR) can use less time to measure physical parameters of reservoir, such as permeability, pore distribution and oil saturation. The application is not only convenient and rapid, as well as non destructive, it is also less effected and has higher precision to deal with all kinds of state of reservoir prediction.Based on the laboratory core analysis research with NMR method, this paper discusses the evaluating methods of reservoir basic parameter. In the case of unchanged experiment conditions, we study the effect of porosity by changing echo interval in different permeability in order to formulate echo interval range, increasing NMR porosity measurement precision. In combination with the conventional analysis of cores in a certain area, undetermined coefficient in SDR or Coates calculation model can be determined using numerical simulation.The applicability can be estimated in the way of comparing with the conventional permeability. A new method is put forward to determine the T2 cutoff value by using the T2 spectrum data of cores with completely saturated water and bound water saturation in order to calculate irreducible water saturation. In the meantime, the results of(T2-D) two-dimensional spectrum measurement and centrifuge experiment can be used to verify the reliability of the method. In terms of the relationship between T2 spectrum and capillary pressure curve, we build a new idea which uses a two-dimensional array to store conversion coefficient to calculate the pseudo capillary pressure value. Finally we achieve the technique in measurement of physical property parameters to evaluate porosity, permeability, irreducible water saturation and pseudo capillary pressure curve in reservoir.