Oil & Gas Geology ›› 2020, Vol. 41 ›› Issue (4): 862-873.doi: 10.11743/ogg20200418

• Methods and Technologies • Previous Articles     Next Articles

Pore-throat heterogeneity in dolomite reservoirs based on CT imaging: A case study of the 3rd member of the Ordovician Yingshan Formation in Well GC601 in Gucheng area, eastern Tarim Basin

Kedan Zhu1(), You Zhang2, Tong Lin3, Yachun Wang1,*(), Xingping Zheng2, Lin Zhu4   

  1. 1. School of Earth Sciences, Northeast Petroleum University, Daqing, Heilongjiang 163318, China
    2. Hangzhou Research Institute of Geology, PetroChina, Hangzhou, Zhejiang 310023, China
    3. Exploration and Development Research Institute of Daqing Oilfield Company Ltd., PetroChina, Daqing, Heilongjiang 163712, China
    4. The 3 rd Oil Production Plant of Daqing Oilfield Company Ltd., PetroChina, Daqing, Heilongjiang 163113, China
  • Received:2019-04-19 Online:2020-08-01 Published:2020-08-11
  • Contact: Yachun Wang E-mail:redcloudszkd@163.com;dqpiwyc@163.com

Abstract:

The pore-throat heterogeneity of dolomite reservoirs is mainly reflected by their complex structure and distribution that are difficult to sufficiently and quantitatively analyze with conventional reservoir characterization methods.In this study, nine samples from dolomite reservoirs in the 3rd member of the Ordovician Yingshan Formation (Ying 3 member), Gucheng area, eastern Tarim Basin, were CT scanned to establish a 3D network model for the pore-throats.Such reservoir parameters as pore-throat radius, pore and throat numbers, total porosity, spatial connectivity, and etc., were calculated based on the model.The results show obvious differences among the pore-throat radius distribution curves for the samples.These curves can then be grouped into three categories in terms of shape features, that is, Type Ⅰ, the normal unimodal curve; Type Ⅱ, the unimodal curve for pores and multi-modal curve for throats; and Type Ⅲ, the multi-modal curve for both pores and throats.The genesis of the curves was analyzed and pore-throat radius distribution patterns were set up based on core observation and casting thin section identification of the samples.In conclusion, the pore-throat radius distribution curves for dolomite reservoirs dominated by intra-crystalline pores are generally evenly skewed unimodal distribution, except for some tinny peaks beside the main summits caused by the development of local micro-fractures.The curves may show obvious multiple summits with pores converging along some residual sedimentary structures such as bedding surfaces.All the curves may show the multi-modal distribution with increasing numbers of inter-crystalline dissolved pores under stronger dissolution that indicates high heterogeneity of reservoirs.

Key words: CT imaging technology, pattern of pore-throat radius distribution, pore-throat heterogeneity characterization, dolomite reservoir, Yingshan Formation, Tarim Basin

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