Oil & Gas Geology ›› 2021, Vol. 42 ›› Issue (3): 557-569.doi: 10.11743/ogg20210303

• Petroleum Geology • Previous Articles     Next Articles

Sedimentary configuration and reservoir distribution in the Cambrian mound-shoal complexes at platform margins of Gucheng area, Tarim Basin

Junlong Zhang1,2(), Mingyi Hu1,*(), Aiyun Wang3, Bin Zhang2, Bo Yan2, Xiangiang He2   

  1. 1. School of Geosciences, Yangtze University, Wuhan, Hubei 430100, China
    2. Exploration and Development Research Institute, Daqing Oil Field Company, PetroChina, Daqing, Heilongjiang 163712, China
    3. Daqing Branch under China Petroleum Logging Co., Ltd., Daqing, Heilongjiang 163412, China
  • Received:2020-04-13 Online:2021-06-28 Published:2021-06-23
  • Contact: Mingyi Hu E-mail:zhangjunlong@petrochina.com.cn;humingyi65@163.com

Abstract:

The four stages of massive Cambrian platform-margin mound-shoal complexes in Gucheng area are the new exploration targets in the Tarim Basin with some promising reservoirs encountered during wildcatting.However, a lack of understanding on the complexity in sedimentary models and reservoir distribution as well as other reservoir forming factors has limited further exploration.Based on core observation, thin section identification, petrographical and geochemical characterization of reservoirs, seismic facies description, and etc., this paper expounds on the identification of sedimentary configuration patterns of the complexes and major factors controlling the reservoirs, and the establishment of a reservoir distribution model under constructive diagenesis constrained by sedimentary configuration.The results show that there are four microfacies (i.e.mound base, mound core, mound flank and mound flat) developed inside the complexes with the sedimentary energy gradually increasing upward, and two types of sedimentary configurations (i.e."accretion type" and "progradation type").The facies belts formed during stages 1 and 2 are "accreted" mound-shoal complexes of vertical superimposition, and those during stages 3 and 4 are "progradational" mound-shoal complexes of lateral stacking.High-quality reservoirs with dissolved pores and cavities are well developed in multiple cyclic distribution with high-energy facies belts as the basis and meteoric water dissolution as an indispensable factor.Generally, the top of the mound-shoal complexes are better in physical properties compared with the bottom, core and flank.The frequently exposed mound-shoal complexes of accretion type contain large-scale reservoirs in a vertically "sandwich-shaped" superimposition distribution; while the long-term exposed progradation type has reservoirs of better physical properties in a laterally "inverted toothbrush-shaped" staggered distribution.The results may be of geological value to the prediction of potential hydrocarbon play fairways in exploration deployment.

Key words: sedimentary configuration, reservoir, mound-shoal complex, Cambrian, Gucheng platform-margin zone, Tarim Basin

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