Oil & Gas Geology ›› 2007, Vol. 28 ›› Issue (1): 110-115.doi: 10.11743/ogg20070116

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Pore structure study of low porosity and permeability reservoirs in MHM oilfield of Ordos Basin with fractal theory

Zhang Chenkai1, Shen Jinsong1,2, Fan Zhen3   

  1. 1. China University of Petroleum, Beijing 102249, China;
    2. Key Laboratory of Geophysical Exploration, PetroChina, Beijing 102249, China;
    3. Xinjiang Oilfield Company, PetroChina, Kelamayi, Xinjiang 834000, China
  • Received:2006-05-17 Online:2007-02-25 Published:2012-01-16

Abstract:

Fractal features of pore structure are studied by using analytic data of capillary pressure of core samples.The fitting relationship between the volume percentage(S)of pores with pore diameter smaller than a given value(r)and the pore diameter(r)is used to calculate the fractal dimension of pore structure of the low porosity and permeability reservoirs in the Triassic Yanchang Formation and Jurassic Yan'an Formation of MHM oilfield,Ordos basin.The capillary pressure curves of both formations have a scale interval,in which pore structure shows fractal features.The macropore and micropore intervals of same core sample show multi-fractal features.For the 10th member of Yan'an Formation(Yan 10 reservoir),the fractal dimension of pore structure in macropore interval is larger than that in micropore interval,while for the 6th member of Yanchang Formation(Chang 6 reservoir),the distribution of fractal dimension is just the opposite.In macropore interval,the fractal dimension of Yan 10 reservoirs is smaller than that in Chang 6 reservoirs,indicating that the pore structure of the latter is more complex than that of the former.Fractal dimension of pore structure,in conjunction with the other pore characteristic parameters,can well reflect the complexity of microscopic pore structure.It provides a convenient and effective method for study on the microscopic heterogeneity of reservoir pore structure,and a solid basis for further reservoir evaluation.

Key words: capillary pressure, fractal dimension, pore structure, low porosity and low permeability reservoir, Ordos Basin

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