Title: Fractal study on pore structure of tight sandstone based on full-scale map

Authors: X. Zhao; Z. Yang; W. Lin; S. Xiong; Y. Luo; X. Liu; D. Xia

Addresses: Institute of Porous Flow and Fluid Mechanics, University of Chinese Academy of Sciences, Langfang, 065007, China; Department of Porous Flow and Fluid Mechanics, Research Institute of Petroleum Exploration and Development, PetroChina Company Limited, Langfang, Hebei, 065007, China ' Department of Porous Flow and Fluid Mechanics, Research Institute of Petroleum Exploration and Development, PetroChina Company Limited, Langfang, Hebei, 065007, China ' Institute of Porous Flow and Fluid Mechanics, University of Chinese Academy of Sciences, Langfang, 065007, China; Department of Earth and Planetary Science, University of California, Berkeley, CA 94720, USA ' Department of Porous Flow and Fluid Mechanics, Research Institute of Petroleum Exploration and Development, PetroChina Company Limited, Langfang, 065007, China ' Department of Porous Flow and Fluid Mechanics, Research Institute of Petroleum Exploration and Development, PetroChina Company Limited, Langfang, 065007, China ' Department of Porous Flow and Fluid Mechanics, Research Institute of Petroleum Exploration and Development, PetroChina Company Limited, Langfang, 065007, China ' Institute of Porous Flow and Fluid Mechanics, University of Chinese Academy of Sciences, Langfang, 065007, China

Abstract: The pore characteristics of tight sandstones are of great significance for studying the size distribution, surface roughness and seepage mechanism. In order to evaluate the pore size distribution and pore comprehensive fractal characteristics of tight sandstone in Y Basin, the pore structure of tight sandstone is characterised by low temperature nitrogen adsorption (LTNA) and high pressure mercury intrusion (HPMI), and fractals of different scales are fitted and calculated. We calculate the pore comprehensive fractal dimension of tight sandstone based on the full-scale map and discuss the difference in pore roughness from the shale in the Qinshui Basin. Finally, we also studied the relationship between comprehensive fractal dimension and permeability and porosity. Our results suggest that the pore radius of tight sandstones is distributed between 2 nm to 1,000 nm, and the surface of the macropores (> 100 nm) is rougher and more complex than the small pores (< 100 nm). The pore structure of the tight sandstone in the Y Basin is generally simpler than that of the shale in the Qinshui Basin. Besides, there is no significant correlation between the comprehensive fractal dimension and the permeability and porosity, suggesting the fractal dimension is not affected by porosity and permeability. [Received: September 11, 2018; Accepted: December 17, 2018]

Keywords: tight sandstone; pore-throat structure; full-scale map; fractal dimension.

DOI: 10.1504/IJOGCT.2019.102788

International Journal of Oil, Gas and Coal Technology, 2019 Vol.22 No.2, pp.123 - 139

Received: 11 Sep 2018
Accepted: 17 Dec 2018
Published online: 07 Oct 2019 *

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