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Geological Journal of China Universities ›› 2023, Vol. 29 ›› Issue (5): 726-734.DOI: 10.16108/j.issn1006-7493.2022029

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Structural Characteristics and Deformation Mechanisms of Multipledetachments in Luzhou area, Southeastern Sichuan Basin

ZHAO Shengxian1,XU Wenqiao2*,YANG Xuefeng1,YIN Hongwei2,LI Bo1,WANG Wei2,ZHANG Chenglin1,JIA Dong2,LIU Yongyang1,XIE Wei1,ZHANG Dongjun1,LI Changsheng3#br#   

  1. 1. Shale Gas Institute of PetroChina Southwest Oil & Gasfield Company, Chengdu 610056, China;
    2. School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China;
    3. School of Earth Science, East China University of Technology, Nanchang 330013, China
  • Online:2023-10-11 Published:2023-10-10

Abstract: In recent years, shale gas exploration and development in southeastern Sichuan has gradually expanded to the deep areas. The Luzhou area shows great potential of shale gas exploration and development with the depth over 3500 m. In order to further clarify the characteristics and evolution mechanism of various structural deformation in Luzhou area, the main controlling factors of fold belt were explored by using discrete element numerical simulation based on structural analysis of seismic data, and the evolution process of Mesozoic and Cenozoic was restored. And the following research results show that multiple detachment layers and regional tectonic compression are the main controlling factors of structural deformation in Luzhou area. Influenced by multiple detachment layers, Luzhou area has developed low steep thin-skinned structure and obvious vertical stratification, forming complex structure such as fault-propagation folds, detachment folds, buried folds and duplex structures between detachment layers. Among them, the lower Cambrian gypsum rock plays a major role in controlling the deformation, and the gypsum rock and shale slippage coordinate and accumulate towards the core of the anticlines. Since the late Yanshanian, the multi-detachment allochthonous succession with regional compression in Luzhou area were developed the thin-skinned comb-shaped folds. The fold belt rose again in Himalayan, the displacement of the original fault sand shear zones increased, and a series of secondary faults and buried folds formed between the detachment layers. The reservoirs are easy to be destroyed at anticline zones, while the syncline areas are a favorable area for shale gas exploration. The relatively simple deformation for syncline composed of ramp thrusts results in comparable stable internal stress distribution.

Key words: Luzhou area, structural deformation, tectonic analysis, multi -detachment, discrete element method

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