Oil & Gas Geology ›› 2024, Vol. 45 ›› Issue (1): 200-214.doi: 10.11743/ogg20240114

• Petroleum Geology • Previous Articles    

Karst paleogeomorphology and reservoir control model of the 2nd member of Dengying Formation in Penglai gas area, Sichuan Basin, China

Zhili ZHANG1(), Yanping QIAO1, Shuang DOU1, Kunyu LI1(), Yuan ZHONG1, Luya WU1, Baoshou ZHANG1, Xin Dai1, Xin JIN2, Bin WANG2, Jinmin SONG2   

  1. 1.Research Institute of Exploration and Development,Southwest Oil & Gas Field Company,PetroChina,Chengdu,Sichuan 610041,China
    2.State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation,Chengdu University of Technology,Chengdu,Sichuan 610059,China
  • Received:2023-09-02 Revised:2023-12-07 Online:2024-02-01 Published:2024-02-29
  • Contact: Kunyu LI E-mail:zzl_kyy@petrochina.com.cn;likunyu2018@petrochina.com.cn

Abstract:

An integration of core and thin section observation, log and 3D seismic data is applied to systematically analyze the epigenetic karst paleogeomorphology and reservoir development pattern of the 2nd member of the Dengying Formation (hereafter referred to as Deng 2 Member) in the Penglai gas area, Sichuan Basin, China. Key findings are summarized as follows. First, the Deng 2 Member in the Penglai gas area can be vertically divided into the epigenetic karst zone, vertical vadose zone, superimposed zone, horizontal phreatic zone, and deep tranquil flow zone. Notably, the horizontal phreatic zone exhibits the thickest reservoirs; second, the karst paleogeomorphology of the Deng 2 Member was restored using the dual interface method. The results indicate that it can be categorized into four types of first-order paleogeomorphic units, namely karst highland, karst slope, karst depression, and karst basin, exhibiting one karst highland, one karst slope, and two karst depressions overall; third, the karst highland is situated in the Gaoshiti-Moxi area in the east, the karst slope is present in the central part of the study area, and the karst depressions are found on the northwest and southwest sides of the study area. The karst highland and karst slope primarily contain vertical vadose zones and horizontal phreatic zones, respectively. It is proposed that reservoirs in the Deng 2 Member of the Penglai gas area are jointly influenced by karst paleogeomorphology and sedimentary facies; fourth, epigenetic karst reservoirs emerge as the predominant reservoir type in the study area, with high-quality reservoirs occurring in the karst slope with superimposed microfacies of mound-shoal complexes.

Key words: epigenetic karst, karst zonation, karst paleogeomorphology, Deng 2 Member, Sinian, Penglai gas area, Sichuan Basin

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