Title: Lithofacies identification and prediction of Chang 7₃ shale oil reservoirs in Ordos Basin: insights from the multi-resolution graph-based clustering analysis

Authors: Ruiliang Guo; Junhong Jia; Guangjun Xu; Fei Liu; Jingzhou Zhao; Yubin Bai; Weitao Wu; Lei Cao

Addresses: National Engineering Laboratory for Exploration and Development of Low-Permeability Oil and Gas Fields, Xi'an 710018, China; School of Earth Sciences and Engineering, Xi'an Shiyou University, Xi'an 710065, China ' National Engineering Laboratory for Exploration and Development of Low-Permeability Oil and Gas Fields, Xi'an 710018, China; Exploration and Development Research Institute of PetroChina Changqing Oilfield Company, Xi'an 710018, China ' No. 2 Gas Production Plant, PetroChina Changqing Oilfield Company, Xi'an, Shaanxi 710200, China ' National Engineering Laboratory for Exploration and Development of Low-Permeability Oil and Gas Fields, Xi'an 710018, China; Exploration and Development Research Institute of PetroChina Changqing Oilfield Company, Xi'an 710018, China ' School of Earth Sciences and Engineering, Xi'an Shiyou University, Xi'an 710065, China ' School of Earth Sciences and Engineering, Xi'an Shiyou University, Xi'an 710065, China ' School of Earth Sciences and Engineering, Xi'an Shiyou University, Xi'an 710065, China ' School of Earth Sciences and Engineering, Xi'an Shiyou University, Xi'an 710065, China

Abstract: The Chang 7 member of Yanchang formation of the Ordos Basin contains abundant shale oil resources, making it the core area for exploration and exploitation of lacustrine shale oil in China recent years. However, the strong spatial heterogeneity makes lithofacies identification and prediction a key challenge in shale oil reservoir development. This study divides the lithofacies of the Chang 7₃ shale oil reservoir into four types based on sedimentary structure, mineral composition, and TOC content, namely high TOC tuffaceous laminated shale, high TOC argillaceous laminated shale, moderate TOC felsic laminated shale, and moderate TOC felsic bedded mudstone. Multi-resolution graph-based clustering analysis (MRGC) was used to perform cluster analysis on lithofacies sensitive logging, including GR, AC, DEN, RT, and SH, and the electrofaices was compared with single well lithofacies to establish the logging value range model for different lithofacies.. This study validates the applicability of MRGC in shale lithofacies division and rapid prediction. [Received: January 4, 2024; Accepted: February 13, 2024]

Keywords: Ordos Basin; Yanchang formation; shale oil; lithofacies; MRGC.

DOI: 10.1504/IJOGCT.2024.139534

International Journal of Oil, Gas and Coal Technology, 2024 Vol.36 No.1, pp.77 - 94

Received: 27 Dec 2023
Accepted: 13 Feb 2024
Published online: 03 Jul 2024 *

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