Method and application of oil and water dynamic calibration method based on LF-NMR in core displacement experiment

Low-field nuclear magnetic resonance (LF-NMR) technique can be used to quantitatively monitor the contents and distribution of oil and water in cores in the process of water displacing oil and plays an important role in promoting the studies on EOR mechanisms. In order to ensure the accuracy of testing results, it is quite crucial to develop the oil and water calibration method and establish the corresponding relationships between NMR signals and oil/water quality. In this paper, the corresponding relationships between the area of T₂ relaxation spectrum peak and the quality or volume of water/oil in a core in the process of core displacement were established based on LF-NMR core displacement experiment. Then, a new dynamic calibration method was developed. It is experimentally indicated that as for oil and water calibration, the water quality/oil volume in homogeneous core and heterogeneous core is proportional to the area of the corresponding water peak/oil peak and the calibration results are more deviated from the ones of conventional samples. This method can determine the contents of water and oil in a core quickly and accurately based on the area of T₂ relaxation spectrum peak during core displacement. The successful application of this dynamic calibration method to evaluate the displacement effect of the YFP-2 foam system in the Well Block X of Baikouquan Oilfield indicates that it has good actual application value.