Oil & Gas Geology ›› 2020, Vol. 41 ›› Issue (1): 15-25.doi: 10.11743/ogg20200102

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Characteristics of intra-platform rift in ancient small-scalecratonic platform of China and its implications for hydrocarbon exploration

Anjiang Shen1,2(), Yana Chen1,3,*(), Jianyong Zhang1,3, Xinfeng Ni1,2, Jingao Zhou1,2, Xingning Wu1,2   

  1. 1. Hangzhou Research Institute of Geology(HIPG), PetroChina, Hangzhou, Zhejiang 310023, China
    2. Key Laboratory of Carbonate Reservoirs, CNPC, Hangzhou, Zhejiang 310023, China
    3. Research Center of Sichuan Basin, Research Institute of Petroleum Exploration & Development, PetroChina, Chengdu, Sichuan 610094, China
  • Received:2019-03-17 Online:2020-02-01 Published:2020-01-19
  • Contact: Yana Chen E-mail:shenaj_hz@petrochina.com.cn;chenyn_hz@petrochina.com.cn
  • Supported by:
    国家科技重大专项(2016ZX05004-002);中国石油天然气股份有限公司直属院所基础研究和战略储备技术研究基金项目(2018D-5008-03);中国石油科技重大专项(2018A-0103)

Abstract:

The intra-platform carbonate rock is another potential for hydrocarbon exploration in addition to reef-shoal at the platform margins.The study focuses on the elucidation of petroleum geologic characteristics and origin of intra-platform rifts in the Deyang-Anyue area during the Upper Sinian-Lower Cambrian, Sichuan Basin, and analysis of analogues of the intra-platform rifts such as the Tarim Basin during the Nanhua Period and the Ordos Basin during the Changcheng Period, based on the outcrop, core, and thin section observation, as well as single-well, seismic and testing data.The results show that (1) the breakup of Rodinia Pangaea provides the regional geological setting for the development of Deyang-Anyue intra-platform rifts.Tensional or strike-slipping faulting and differential subsidence are key to the formation of intra-platform rifts; (2) The Deyang-Anyue intra-platform rifts have gone through four stages of evolution, namely, the erosional stage during the deposition of the 2nd member of Dengying Formation, the rifting stage during the 4th member of Dengying Formation, the rifting climax-filling stage during the Maidiping -Canglangpu Formations, and the development of ramp-platform during the deposition of Longwangmiao Formation.In turn, the rift controlled the development of two sets of source rocks (Qiongzhusi and Maidiping Formations) and two reservoirs (the 4th member of Dengying Formation and Longwangmiao Formation); (3) Two types of hydrocarbon accumulation assemblages formed according to the spatial configuration of source rocks and reservoirs, with reservoir either alongside the source rock on the same depth level or above it; (4) The intra-platform rifts in the Tarim Basin during Nanhua Period and in the Ordos Basin during Changcheng Period share similar geological features with those in Deyang-Anyue area, indicating good hydrocarbon exploration potential.These results suggest that the region of hydrocarbon exploration can be extended from platform margin to intra-platform.This may shed a guiding light to the hydrocarbon exploration of marine carbonate reservoirs in ancient small-scale cratonic platforms in China.

Key words: marine carbonate rock, intra-platform rift, Sinian, Cambrian, Changcheng Period, Sichuan Basin, Tarim Basin, Ordos Basin

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