Xinjiang Petroleum Geology ›› 2025, Vol. 46 ›› Issue (6): 762-772.doi: 10.7657/XJPG20250612

• APPLICATION OF TECHNOLOGY • Previous Articles     Next Articles

NMR Effective Porosity Spectrum Prediction and Resolution Matching Based on ReliefF and LSBoost Ensemble Tree

DU Xuebiao1(), ZHANG Jinfeng1(), XIAO Dianshi2, RAN Yang1, LIU Yingjie2, QIN Jiamin1, WANG Liangzhe1   

  1. 1. Jiqing Oilfield Operation District, Xinjiang Oilfield Company, PetroChina, Jimsar, Xinjiang 831700, China
    2. School of Geosciences, China University of Petroleum (East China), Qingdao, Shandong 266580, China
  • Received:2025-04-22 Revised:2025-09-08 Online:2025-12-01 Published:2025-12-05
  • Contact: ZHANG Jinfeng E-mail:dxb_zy@petrochina.com.cn;zhjf@petrochina.com.cn

Abstract:

Nuclear magnetic resonance (NMR) logging is a critical method for obtaining the porosity of shale oil reservoirs, but the varying vertical resolutions of different logging tools severely affect the division of oil layer thickness and the characterization of sweet spots. The spectral characteristics of different NMR effective porosity curves were analyzed through the Fourier transform. With the spectral amplitudes of the logs including microspherically focused resistivity, acoustic, neutron porosity, and P-type NMR effective porosities selected using the ReliefF algorithm as the input features for the machine learning (ML) model, and the spectral amplitude of CMR-type NMR effective porosity log as the target value, a prediction model for the spectral amplitude of NMR effective porosity was constructed using decision tree (DT) and LSBoost ensemble tree. The prediction results of different ML models were compared, showing that the LSBoost ensemble tree model is the most accurate. For purpose of resolution matching among different NMR logs, the time-frequency analysis was innovatively integrated with the resolution matching to form a method for improving the resolution of NMR effective porosity log through spectral amplitude transplantation. This method has been validated to significantly enhance the resolution of low-resolution NMR effective porosity logs. The reconstructed NMR effective porosity logs are significantly superior in oil layer thickness division, fully proving that this resolution matching method is highly promising, laying a foundation for the precise characterization of sweet spot distribution and the efficient extraction of shale oil in the Permian Luocaogou formation in the Jimsar sag of the Junggar Basin. However, this method is limited when applied in strata with high pyrite content or small thickness.

Key words: Junggar Basin, Jimsar sag, Lucaogou formation, NMR effective porosity, Fourier transform, spectral amplitude, vertical resolution, LSBoost ensemble tree

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