Method for quantitatively evaluating oil washing effect of rock core by using nuclear magnetic resonance (NMR) technology

Abstract

The invention relates to the technical field of rock core oil washing effect evaluation, and in particular relates to a method for quantitatively evaluating the oil washing effect of a rock core by using a nuclear magnetic resonance (NMR) technology. The method comprises the following steps: (1) volatilizing an oil washing solvent and drying; (2) measuring gas porosity and gas void volume; (3) measuring the NMR T2 spectrum of the rock core and the NMR T2 spectrum of a standard sample; (4) obtaining residual oil volume; (5) obtaining residual oil porosity; and (6) obtaining residual oil saturation, thereby evaluating the oil washing effect of the rock core. According to the method, the time of a measurement process is short, and the efficiency of measurement is effectively improved; during measurement, the measurement is non-contact and non-destructive measurement, no damage to the rock core can be caused, and the measured rock core cannot affect the subsequent experiment measurement of the rock core; meanwhile, quantitative parameters, such as the porosity of the rock core, the residual oil volume, the residual oil porosity, the residual oil saturation and the NMR T2 spectrum of residual oil, can be simultaneously obtained, so that the applicable range is wide.

Description

technical field

[0001] The invention relates to the technical field of evaluating the oil-washing effect of rock cores, and relates to a method for quantitatively evaluating the oil-washing effect of rock cores by using nuclear magnetic resonance technology. Background technique

[0002] At present, the inspection method of core oil washing effect at home and abroad is usually the fluorescence analysis method, which can be divided into qualitative and quantitative analysis methods according to its accuracy. The principle is to use a fluorescence analyzer to detect the fluorescence color and intensity of rock samples, cuttings, or organic solvents soaked in rock samples, and evaluate the residual oil content qualitatively or quantitatively based on comparison with standard samples; in addition, there are indirect measurements Particle density comparison method, this method has strict requirements on lithology, large error, and poor applicability. In the fluorescence analysis...