Based On The Core Analysis Experiment And Application Of Nuclear Magnetic Resonance (nmr) Research

Core analysis is one of the most necessary means to recognize the geological characteristics of reservoirs. Compared with conventional core analysis, NMR core analysis have some characteristics such as nondestructive testing, one machine with multiple parameters, fast detection, no pollution, low cost, simple operation and so on. Fluid content on NMR relaxation time curve shape are analyzed in the present paper on the basis of NMR core analysis experiments. NMR relaxation time spectrums can be acquired which rich information of different fluid, and then be processed and analyzed. Based on this, one method has been developed to identify the fluid type in rock pores. In order to study the effect of echo spacing on NMR porosity, the NMR porosity is calculated with different echo spacing. Applicability of empirical formula for the calculation of NMR permeability has been studied. A new method for calculating NMR permeability has been established to improve the reliability of calculation on NMR permeability. Pore structure has been studied using NMR transverse relaxation time distribution combined with the pore structure information obtained from mercury porosimetry.The traditional method for fluid identification of NMR is based on the difference of longitudinal relaxation time Ti and diffusion rate. This paper puts forward a new method for fluid identification according to the value of T1/T2. Some experiments have been carried out with mixtures of different percentages of crude oil and dodecane in order to study the effect of fluid content on the NMR relaxation time curve. The measurement of transverse relaxation time can be affected by the internal magnetic field gradients and the difference of diffusion rate. We only study the effects of fluid content on the longitudinal relaxation time in order to eliminate effects of the internal magnetic field gradient and the difference of diffusion rate on the experimental results. NMR relaxation time spectrums can be acquired which rich information of different fluid, and then be processed and analyzed. Based on this, one method has been developed to identify the fluid type in rock pores.NMR porosity is calculated when the echo spacing is respectively0.3,0.6,1.2ms in order to analyze the effects of echo spacing on NMR porosity. The results show that the NMR porosity will decrease with the increasing of echo spacing. The NMR porosity is close to the conventional porosity when the echo spacing is0.3ms.So far, the estimation for the permeability is indirectly. Applicability of the empirical formula for calculating the magnetic is analyzed in this paper. The results show that the calculation is inaccurate. The applicability of the new method is well compared with the empirical formula. The reason is that the new method reduces the error by avoiding the use of NMR porosity and geometric mean of transverse relaxation time when the permeability is calculated.Pore structure has been studied using NMR transverse relaxation time distribution combined with the pore structure information obtained from mercury porosimetry. The result shows that the geometric mean of transverse relaxation time have obvious relationship with the parameters obtained from mercury porosimetry such as mean radius of pore throat, sorting coefficient, coefficient of homogeneity, displacement pressure, mean pressure and so on.