Xinjiang Petroleum Geology ›› 2022, Vol. 43 ›› Issue (2): 153-159.doi: 10.7657/XJPG20220204

• OIL AND GAS EXPLORATION • Previous Articles     Next Articles

Fractal Characteristics and Main Controlling Factors of Wufeng-Longmaxi Formation Shale in Luobu Syncline, Southern Sichuan Basin

DUAN Wengang1(), LIN Wen2(), TIAN Jijun1, MA Jinghui1, DU Meng1, LUO Jinchang1   

  1. 1. School of Geology and Mining Engineering, Xinjiang University, Urumqi, Xinjiang 830047, China
    2. Shale Gas Research Institute, Research Institute of Petroleum Exploration and Development, PetroChina, Beijing 100083, China
  • Received:2021-11-01 Revised:2021-12-07 Online:2022-04-01 Published:2022-03-24
  • Contact: LIN Wen E-mail:1425366986@qq.com;27193627@qq.com

Abstract:

In the Luobu syncline, southern Sichuan basin, the shale in the Upper Ordovician Wufeng formation (O3w)-Lower Silurian Longmaxi formation (S1l) is characterized by large thickness, high organic carbon content, wide distribution range and moderate thermal evolution of organic matter, making it an important target for subsequent shale gas exploration. In order to better characterize the heterogeneity of shale pore structure and clarify the influence of heterogeneity on shale gas enrichment in the study area, the fractal characteristics of the shale in layers of O3w-S1l11 in the study area were analyzed using the rock-mineral analysis, geochemical and well logging data, and CO2 and N2 adsorption analysis. The results show that the layers in the study area are very different in TOC content, mineral compositions and porosity, and the reservoir is highly heterogeneous. The fractal dimension of shale pores ranges from 2.711 0 to 2.794 8, with an average of 2.747 0; the value is relatively high for O3w and Layer #1 in S1l11, and the lowest for Layer #4 in S1l11. The organic carbon and bio-quartz can promote the development of shale micropores. The smaller the average pore size of shale, the more the pores, and the more complex the pore structure, and the larger the fractal dimension.

Key words: Sichuan basin, Dianqianbei depression, Luobu syncline, Wufeng formation, Longmaxi formation, shale, heterogeneity, pore structure, fractal characteristic

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