Oil & Gas Geology ›› 2015, Vol. 36 ›› Issue (3): 447-455.doi: 10.11743/ogg20150313

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Reservoir characteristics and influences on poroperm characteristics of the Lower Cretaceous fan-delta facies in Chagan Depression

Wei Wei1,2, Zhu Xiaomin1,2, Tan Mingxuan1,2, Guo Dianbin3, Su Hui3, Zhao Qilei3, Jiang Feihu3   

  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. Research Institute of Petroleum Exploration and Development, Zhongyuan Oilfield Company, SINOPEC, Puyang, Henan 457001, China
  • Received:2014-04-10 Online:2015-06-08 Published:2015-07-24

Abstract: In order to reveal the reservoir characteristics and their influences on poroperm characteristics of the Lower Cretaceous in Chagan Depression, core, thin-section, and reservoir analysis data were utilized to research the petrological characteristics, sedimentation and diagenesis of the reservoirs.The results show that the sandbodies of fan-delta facies in the Lower Cretaceous consist of lithicarkose and feldspathic litharenite with low compositional maturity, low maturity structure and high cement content, which are originated from proximal and rapid accumulation.The reservoir is relatively tight as a whole and is of ultra-low porosity and permeability reservoir type(with average porosity of 6.3% and permeability of 7.78×10-3 μm2).Thin-tiny throats are well developed and the reservoir spaces are dominated by residual primary and dissolved intergranular pores, and their development are controlled by particle size, compaction, cementation, content of carbonate and the origin of organic acid.The favorable reservoir is mainly distributed in the sandstones(conglomerates)of the subaqueous distributary channel of fan delta front, followed by fine sandstones in sand sheet and mouth bar.Vertically, the secondary porosity zone is mainly developed in the depth interval of 2 100-2 800 m, which corresponds to the maturity stage of organic matters.The mature organic matter released large amount of organic acid which strongly dissolved the feldspar particles and carbonate cement, enlarged intergranular and intragranular pores and effectively enhanced reservoir quality.Obviously, favorable sedimentary microfacies, strong dissolution zone and secondary porosity zone are the main factors controlling favorable reservoir distribution.

Key words: reservoir property, diagenesis, fan delta, Lower Cretaceous, Chagan Depression

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