Quantitative Comparison of T2 Spectra from 1D and 2D Nuclear Magnetic Resonance Methods in Monitoring Imbibition Behavior of Tight Reservoirs

Nuclear magnetic resonance (NMR) has been widely used in monitoring the imbibition behavior of oil/gas reservoirs, especially the T-2 spectrum. Most T-2 spectra are obtained from one dimensional (1D) NMR, but less research is related to T-2 spectra from two dimensional (2D) NMR. Understanding the difference between these two methods helps take advantage of NMR in monitoring imbibition behavior. The main experiment is the imbibition behavior monitored by 1D and 2D NMR. Samples are tight sand from the Upper Paleozoic Taiyuan and Shihezi formations in the eastern Ordos Basin, which is full of natural gas, and the testing liquid is distilled water. The T-2 spectra from 1D and 2D NMR increase with imbibition time, which shows that liquid increases among pore spaces. More peaks are in 2D T-2 spectra than in 1D T-2 spectra, which shows that 2D T-2 spectra can differentiate more types of H1 proton signal. In dry state, a higher signal is 0.01-0.1 ms in 2D T-2 spectra than in 1D T-2 spectra, whereas the signal 0.1-1 ms is the opposite. This indicates that more signals are interpreted as short T-2 values in 2D T-2 spectra, and these signals mainly correspond to crystal water. In spontaneous imbibition with 30 min and 1 h, the signal of 0.01-0.1 ms in 2D T-2 spectra is much higher than in 1D T-2 spectra, because of the crystal water and water film effect. The signals in 1-10 ms are close between 1D and 2D T-2 spectra, which indicates that imbibed liquid in this interval is interpreted the same. Overall, compared with 1D T-2 spectra, 2D T-2 spectra can differentiate more types of H1 proton and are suggested to monitor the imbibition behavior of tight reservoirs. (C) 2022 American Society of Civil Engineers.