Numerical Investigations of NMR T1T2 Map in Two-Phase Fluid-Bearing Tight Sandstone


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Study of two-dimensional nuclear magnetic resonance (NMR) longitudinal and transverse relaxation time (T1T2) responses of tight reservoirs and optimization of T1T2 acquisition parameter are of significance for exploration and development of tight oil and gas reservoirs. In this paper, a tight sandstone digital model was generated using a micro-CT scanning technique, and the random-walk method was modified to simulate the T1T2 measurements in a two-phase fluid-bearing tight sandstone. The echo data of the saturation-recovery Carr–Purcell–Meiboom–Gill pulse sequence were acquired and processed to obtain a T1T2 map. We compared oil–water-bearing tight sandstone T1T2 maps with gas–water-bearing tight sandstone T1T2 maps, and analyzed how fluid types, various degrees of fluid saturation, acquisition parameters, and signal-to-noise ratio (SNR) of NMR data affected T1T2 maps. The research indicated that NMR T1T2 logging is more suitable for identifying gas-bearing reservoirs, rather than oil-bearing reservoirs. NMR-logging acquisition parameters have different influences on various fluid-bearing tight sandstone T1T2 maps. Increasing either the magnetic field gradient or echo spacing leads to a leftward shift of the gas signal, but does not affect the water signal and the oil signal in a T1T2 map; the T1T2 map with a mixed group of wait time is better than that with a long or short group of wait time in providing fluid relaxation information. The NMR data with lower SNR result in stronger divergence of fluid signal in T1T2 map, rendering it more difficult to identify the fluid according to the map, and a data SNR more than 21 is recommended.

作者简介

Jiangfeng Guo

State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum (Beijing); Key Laboratory of Earth Prospecting and Information Technology, China University of Petroleum (Beijing)

Email: xieranhong@cup.edu.cn
中国, Beijing, 102249; Beijing, 102249

Ranhong Xie

State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum (Beijing); Key Laboratory of Earth Prospecting and Information Technology, China University of Petroleum (Beijing)

编辑信件的主要联系方式.
Email: xieranhong@cup.edu.cn
ORCID iD: 0000-0003-1554-8450
中国, Beijing, 102249; Beijing, 102249

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