Analysis Of Influence Of Displacement Fluid On Oil Displacement Efficiency Based On Nuclear Magnetic Resonance Method

Low-field nuclear magnetic resonance technology is a new type of detection technology with potential for development.It only responds to the hydrogen-containing fluid in the sample,and has the advantages of rapid detection,no damage to the sample,and high precision.Low-field NMR technology has the dual functions of field and laboratory analysis of cores,and has been widely used in the field of petroleum engineering to measure rock porosity,pore size distribution,permeability and other petrophysical properties,gradually replacing traditional rock analysis methods.In this thesis,the low-field nuclear magnetic resonance technology is used as the main research method,and the one-dimensional nuclear magnetic resonance technology is used to measure the T₂ spectrum of the sample,and then the total signal amplitude of the hydrogen-containing fluid and the porosity of the sample are obtained;The proportion of the oil signal in the total signal amplitude of the hydrogen-containing fluid was measured by two-dimensional nuclear magnetic resonance technology,and the oil displacement efficiency was evaluated by the residual oil content in the core.Based on low-field nuclear magnetic resonance technology,a multi-field coupled magnetic resonance experimental platform was first built to meet the confining pressure,displacement pressure and back pressure required by the experiment,and the simulated oil hydrogen index was calculated;secondly,NMR flooding experiments were carried out by using surfactants,polymers and compound flooding fluids to analyze the flooding mechanism;finally,through the analysis of the experimental results,the influence of different displacement fluids on the oil displacement efficiency was analyzed,the relationship between the oil displacement efficiency and the displacement fluid was obtained,and the optimal oil displacement efficiency system was obtained.The low-field NMR flooding experiment can avoid the influence of unclean oil-water separation and residual oil in the pipeline when the oil-water separation method is used to calculate the oil displacement efficiency,so that the experimental results obtained by the oil-water separation method are smaller than the actual oil displacement efficiency results.The experimental results show that the oil displacement effect of the binary composite flooding fluid is the best,and the enhanced oil recovery can reach 21.6%.