Oil & Gas Geology ›› 2012, Vol. 33 ›› Issue (2): 190-199.doi: 10.11743/ogg20120205

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Geological characteristics and hydrocarbon accumulation model of the Cenozoic Asmari-Gachsran play,Zagros Basin

Zhang Zhen1,2, Li Haowu3, Duan Hongzhen4, Xu Xiangkai5, Jiang Siqin6   

  1. 1. Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China;
    2. Key Laboratory of Saline Lake Resources and Environments, Ministry of Land and Resources, Beijing 100037, China;
    3. PetroChina Research Institute of Petroleum Exploration & Development, Beijing 100083, China;
    4. Qinghai Business Division, CNPC Logging, Dunhuang, Gansu 736202, China;
    5. Yingdong Oilfield Exploration and Development Department, PetroChina Qinghai Oilfield Company, Haixi National Municipality of Mongol and Tibetan, Qinghai 816400, China;
    6. No.6 Oil Production Plant, PetroChina Daqing Oilfield Company, Daqing, Heilongjiang 163114, China
  • Received:2011-10-10 Revised:2012-02-10 Online:2012-04-28 Published:2012-05-24

Abstract:

The Asmari-Gachsran play is an important play in Zagros Basin.We studied the paleogeography evolution,hydrocarbon source rocks,reservoir rocks,cap rocks and hydrocarbon accumulation process and model of the Asmari-Gachsran play.The Cretaceous Kazhdumi source rocks was more deeply buried due to the Noegene-Quarternary Zagoros folding and mostly reached peak hydrocarbon generation.Meanwhile,open fracture networks that penetrate the Cenozoic Asmari limestone,Pebdeh mudstone and the Cretaceous Sarvark limestone were also formed due to the tectonics,and they constitute vertical pathways for hydrocarbon migration the Kazhdumi source rocks to the above reservoirs.In most areas,the hydrocarbons in the Asmari play were directly charged from the Kazhdumi source rocks instead of the Sarvark play.The Asmari and the Sarvark reservoir share the same oil-water contact due to the connection of fractures,thus the shallow Asmari reservoirs were charged earlier than of the deeper Sarvark reservoir,and have higher filling degree.High quality source rocks,vertical open fractures connecting the source rocks and reservoirs,thick evaporate cap rock,and the good timing between peak hydrocarbon generation and trap-fracture development are the key factors controlling hydrocarbon accumulation in Asmari-Gachsran play.

Key words: fracture, Kazhdumi source rock, Gachsran evaporate, hydrocarbon accumulation model, Asmari-Gachsaran play, Zagros Basin

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