The Oil-Water Distribution During Flooding in High Temperature and High Salt Reservoir Using NMR T1-T2 Maps

The oil-water distribution is essential for evaluating the oil displacement effect and development potential during flooding in high temperature and high salt reservoir. Low-field nuclear magnetic relaxometry(NMR) T1-T2 maps is one of the methods for analyzing oil- water distribution. In order to analysis oil-water distribution at different displacement stage, two-dimension NMR T1-T2 map, and oil-water two-phase displacement experiments were employed on sandstone samples and oil collected in Gasi Reservoir, Qinghai Oilfield. Combining NMR and core displacement results data analysis, the reason for whether oil is produced and the entire flow process of oil and water in the displacement experiments were explained, distribution characteristics of oil and water in the NMR T1-T2 map were analyzed, and evaluate the crude oil production characteristics during the flooding. The results indicated that the pore structure of the sandstone samples is single and show weak heterogeneity according to the NMR T2 spectrum, and the distribution of sandstone pore size is the main factor determining whether there is oil in the sandstone core in the displacement experiment. NMR T1-T2 map is an effective way to identify different components (oil and water) of sandstone samples and the oil-water distribution, and Hydrogen signal distribution regions of oil and water changed after the oil and the brine of 152144 mg/L injected into the sandstone core successively, and the recovery rate increased by approximately 71.3%. Along with the surfactant injected into the sandstone core, the changes of NMR T1-T2 map were slight, and the recovery rate increased by approximately 8.8%. Therefore, T1-T2 map provides another effective method for describing the displacement process.