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Abstract

AAPG Bulletin, V. 107, No. 4 (April 2023), P. 539-551.

Copyright ©2023. The American Association of Petroleum Geologists. All rights reserved.

DOI: 10.1306/06282218185

An empirical method to correct nuclear magnetic resonance porosity of tight sandstone using low-field nuclear magnetic resonance data

Xinmin Ge,1 Yiren Fan,2 Jianyu Liu,3 Donghui Xing,4 Hongjun Xu,5 and Falong Hu6

1School of Geosciences, China University of Petroleum (East China), Qingdao, China; Laboratory for Marine Mineral Resources, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China; Key Laboratory of Marine Mineral Resources, Ministry of Land and Resources, Guangzhou, China; [email protected]
2School of Geosciences, China University of Petroleum (East China), Qingdao, China; Laboratory for Marine Mineral Resources, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China; [email protected]
3PetroChina Research Institute of Petroleum Exploration and Development-Northwest, Lanzhou, China; [email protected]
4Key Laboratory of Marine Mineral Resources, Ministry of Land and Resources, Guangzhou, China; [email protected]
5School of Geosciences, China University of Petroleum (East China), Qingdao, China; PetroChina Research Institute of Petroleum Exploration and Development, Beijing, China; [email protected]
6PetroChina Research Institute of Petroleum Exploration and Development, Beijing, China; [email protected]

Abstract

Low-field nuclear magnetic resonance (NMR) technology has been widely used in laboratory core analysis and formation evaluation since the recording signal is only sensitive to the number of hydrogens in fluid, and the rock matrix has no contribution to the NMR response. However, it is a challenge to obtain accurate porosity from NMR logging in tight sandstone formations due to the effect of echo spacing (TE) on short transverse relaxation time (T2) fluid components in T2 distribution. The aim of this paper is to establish an empirical method to correct NMR porosity of tight sandstone by using a multi-TE laboratory experiment, a dual T2 cutoff model, and graph-regulated nonnegative matrix factorization. The effect of TE on the transverse relaxation spectrum is investigated and corrected for different relaxation ranges, which are determined by the dual T2 cutoff model. The graph-regulated nonnegative matrix factorization is adopted to separate the relaxation components from the T2 spectrum, aiming to eliminate the effect of hydrocarbon. This study demonstrated that the corrected NMR porosity agrees well with the laboratory data. This method can be easily extended in other tight sandstone formations to realize NMR porosity correction.

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