Oil & Gas Geology ›› 2016, Vol. 37 ›› Issue (5): 713-720.doi: 10.11743/ogg20160511

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Characterization of high-frequency sequences in the epicontinental carbonate platform of Jia 2 member in Moxi gas field and its controls over reservoirs

Liu Hong1, Wang Gaofeng1, Liu Nan3, Qiao Lin4, Ding Wei4, Ding Xiong1, Duan Hongzhen5, Tan Xiucheng1   

  1. 1. Sichuan Province Key Laboratory of Natural Gas Geology, School of Geoscience and Technology, Southwest Petroleum University, Chengdu, Sichuan 610500, China;
    2. PetroChina Deposition and Accumulation Department of Key Laboratory of Carbonate Reservoirs, Southwest Petroleum University, Chengdu, Sichuan 610500, China;
    3. Shenzhen Branch Company, CNOOC, Guangzhou, Guangdong 510240, China;
    4. Exploration Department of Southwest Oil & Gas Field Company, PetroChina, Chengdu, Sichuan 610041, China;
    5. CNPC Logging Qinghai Business Division, Dunhuang, Gansu 736202, China
  • Received:2015-05-20 Revised:2016-06-15 Online:2016-10-08 Published:2016-11-07

Abstract: High-frequency sequences,generally formed in basins with stable subsidence settings and correspond well to astronomical Milankovitch cycles,are vivid records of high-frequency eustatic flucturation.Such sequences developed in epicontinental platforms of non-coastal sedimentary environment are both representative and special in certain ways.By combining core observations,thin section analyses and logging facies studies with such factors as energy environment,eustatic fluctuation and sea water salinity cycle as well as reservoir genesis types under high-frequency sequential framework,we classified high-frequency sequences in the epicontinental carbonate platform of the Jia 2 member of the Moxi gas field into the following three types:platform flat type,intraplatform shoal type and lagoon type.The sequences are found to be characterized by widely-distributed gypsiferous rocks and grainstone with all kinds of exposure marks.As a whole,they consist of stratigraphic assemblages of shallowing upwards sequences.Within the framework,sequences are separated by clear boundaries and stratigraphic assemblages are stable and highly comparable.The paper also discussed the mechanisms behind the formation of early reservoirs in the high-frequency sequence framework and proposed that the high-frequency sequences controlled the order of lithofacies development and the syngenetic karstification,and thus controlled the development of different genetic types of reservoirs.

Key words: high-frequency sequence, carbonate rock, Jialinjiang Formation, epicontinental sea platform, Moxi gas field

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