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ORIGINAL RESEARCH article

Front. Earth Sci.

Sec. Solid Earth Geophysics

Volume 13 - 2025 | doi: 10.3389/feart.2025.1657687

This article is part of the Research TopicFrontiers in Borehole Multi-Geophysics: Innovations and ApplicationsView all articles

Radial inversion method of oil saturation Using Combined NMR and Resistivity Logging with Application to Low-Resistivity-Contrast Reservoirs

Provisionally accepted
Weibiao  XieWeibiao Xie1*Qiuli  YinQiuli Yin1Yanghu  LiYanghu Li2Xueping  DaiXueping Dai1Jingbo  ZengJingbo Zeng3Pan  ZhangPan Zhang1
  • 1China University of Petroleum Beijing, Karamay Campus, Karamay, China
  • 2Xinjiang Oilfield Company, Karamay, China
  • 3China Petroleum Logging Co Ltd, Xi'an, China

The final, formatted version of the article will be published soon.

Estimation of oil saturation in low resistivity-contrast reservoirs using resistivity-log analysis is inherently challenging. Nuclear Magnetic Resonance (NMR) logging, on the other hand, is less sensitive to formation-water salinity and rock matrix variations when predicting fluid properties. Integrating a greater volume of well logging data to effectively address the issue of reservoir parameter calculation represents the trend of big data development.This characteristic gives NMR logging a significant advantage over conventional resistivity-based methods in evaluating low resistivity-contrast reservoirs. The proposed method for estimating oil saturation integrates both NMR and resistivity logging data and involves two key steps. First, the oil saturation of the invaded zone is estimated using an NMR-based oil saturation model, which has been validated through experimental NMR data obtained from oil-bearing rock samples. Second, the oil saturation of the uninvaded zone is derived by inverting a resistivity-based oil saturation model. Based on the analysis of experimental data and thin sections, the primary cause of low resistivity contrast in the study area is attributed to the presence of montmorillonite and illite-montmorillonite mixed-layer minerals. Application results demonstrate that the calculated oil saturation using this new method aligns well with both experimental measurements and production test data. Compared to the Archie model applied in resistivity-contrast reservoirs, the new method shows improved accuracy, indicating its effectiveness for such reservoir evaluations.

Keywords: Oil saturation, NMR analysis, Low resistivity-contrast reservoir, Archie model, Radial inversion

Received: 01 Jul 2025; Accepted: 01 Aug 2025.

Copyright: © 2025 Xie, Yin, Li, Dai, Zeng and Zhang. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Weibiao Xie, China University of Petroleum Beijing, Karamay Campus, Karamay, China

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