Temperature Effects on NMR Responses in Porous Media
Authors:   China University of Petroleum, Xie Zhen , Xiao Lizhi ,   China University of Petroleum, Liao Guangzhi ,   China University of Petroleum, Luo Sihui ,   China University of Petroleum, Zhang Lu ,   China University of Petroleum, Cheng Jiajie ,   China Oilfield Services Limited, Xu Danian ,   China Oilfield Services Limited, Wang Meng ,   China Oilfield Services Limited
Published: November 2024

Temperature affects the responses of 1D and 2D NMR spectra of fluids in porous media, which may cause errors in reservoir evaluation using downhole NMR data. The purpose of this paper is to study how temperature affects the NMR T2 spectrum and D-T2 spectrum of porous media. In this paper, the Monte Carlo-Random Walk method is used, and the simulation parameters are set according to the temperature sensitivity of surface relaxation in Korb surface relaxation theory and the temperature characteristics of bulk diffusion. The temperature response characteristics of the T2 spectrum, one-dimensional confined diffusion attenuation, and D-T2 spectra are studied, and the influencing factors are analyzed. Then, we measured the temperature dependence of the T2 spectrum and D-T2 spectrum of saturated water and 68-lb white oil of artificial sandstone with different physical properties by using a water bath circulating heating device. The numerical simulation results show that the obvious movement of the general sandstone T2 spectrum caused by temperature mainly comes from the influence of surface relaxation. Temperature can also increase the confined diffusion in porous media in the case of reinforcement diffusion, which causes the D- T2 spectrum to move up. The degree of upward migration is related to pore size and porosity. And the simulated D-T2 spectra at all temperatures are consistent with the Padé nterpolation equation, indicating that the simulation results are correct and applicability of the Padé interpolation equation when the bulk diffusion increases a lot. The experimental results show that the T2 spectrum of impure sandstone has a significant left shift with the change of temperature, and the T2 at the peak of macropore is consistent with Korb theory. The variation of D-T2 spectra of artificial sandstones with different porosity and pore size with temperature is consistent with the simulation results. Due to the different temperature sensitivity of surface relaxation and bulk relaxation of 68-lb white oil in artificial sandstone, the T2 spectrum in different pore structure cores shows different response characteristics with temperature. It is difficult to directly characterize the change of T2 with temperature. Based on the BT equation, we derive a method to rapidly determine the surface relaxation temperature sensitivity of oil in sandstone and the interconversion of transverse relaxation time at different temperatures. This method is basically consistent with the experimental results. We studied the temperature sensitivity of the T2 spectrum and D-T2 spectrum of saturated single-phase fluid porous media. The method of quantitative characterization of the T2 spectrum and D-T2 spectrum with temperature was established or verified. The above research results and cognition can be used to guide the subsequent reservoir high-temperature logging data correction so as to improve the accuracy of reservoir evaluation.