Oil & Gas Geology ›› 2013, Vol. 34 ›› Issue (3): 323-331.doi: 10.11743/ogg20130307

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Distribution and significance of high-resistivity carbonates of Ordovician Yingshan Formation of northern slope of Tazhong area,Tarim Basin

Hua Xiaoli1,2,3, Luo Chunshu4, Lü Xiuxiang1,2, Yu Hongfeng4, Wang Xiang4, Zhang Jinhui3, Sun Xijia3, Hua Qiao5   

  1. 1. College of Geosciences, China University of Petroleum, Beijing 102249, China;
    2. State Key Laboratory of Petroleum Resource and Prospecting, China University of Petroleum, Beijing 102249, China;
    3. Tianjin Branch, CNOOC (China) Ltd., Tianjin 300452, China;
    4. Petroleum Exploration and Development Research Institute, Tarim Oilfield Company, PetroChina, Korla, Xinjiang 841000, China;
    5. Linpan Oil Production Plant, Shengli Oilfield Company, SINOPEC, Dezhou, Shandong 251509, China
  • Received:2012-12-01 Revised:2013-03-04 Online:2013-06-28 Published:2013-07-17

Abstract: The Ordovician oil reservoirs in Tarim Basin are highly heterogeneous with a complex distribution pattern of fluids.Drilling data,mud logging and well logging data were integrated to analyze the lithology and thickness of high-resistivity layers in the Yingshan Formation.Well tie profiles of each wellblock and inner-outer zones based on single well histograms were generated and the distribution patterns of these high-resistivity carbonates were mapped.The lithology of high resistivity layers in the Yingshan Formation is mainly micritic limestone.They occur as layered bright yellow on imaging logs and show spatial distribution featuring in "lateral unstableness and vertical superimposition".Examination of rock mineral cast thin sections of high resistivity layers indicates that the high resistivity layers were formed mainly by mechanical-chemical filling and selective dissolution by atmospheric water.In addition,the thickness of high resistivity layer correlate well with properties of oil in the underlying reservoir,daily oil/gas production and gas/oil ratio.With increasing thickness of high resistivity layer,daily oil/gas production and gas/oil ratio increase,while density and viscosity of oil decrease,suggesting that high resistivity layers could have a certain control on underlying oil and gas distribution.The high resistivity layers in the Yingshan Formation could act as a set or multiple sets of subtle local seals for the underlying reservoir.

Key words: high resistivity layer, carbonate rock, Yingshan Formation, northern slope of Tazhong area, Tarim Basin

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