Structural characteristics and porosity estimation of organic matter‐hosted pores in gas shales of Jiaoshiba Block, Sichuan Basin, China

Abstract

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Fractal Characteristics and Significance of Different Pore Types of the Wufeng–Longmaxi Formation, Southern Sichuan Basin, China, Based on N2 Adsorption and Image Analysis

“…Various types of reservoir spaces were observed by FE-SEM, of which organic pores, intergranular pores, dissolution pores, and microfractures were the most common, and the morphology, size, and content of different types of pores are quite different (Figures and ). ,− In previous studies, the pore size extracted by image software was usually converted into a diameter of a circle of equal area to study size distribution characteristics. ,, However, pores are more like ellipses with different long and short axis lengths when compared to circles. Therefore, the lengths of the major axis and minor axis of ellipses with the same area as pores and the same long/minor axis ratio are used to accurately characterize the true pore size in this paper.…”

“…4,7−9 In previous studies, the pore size extracted by image software was usually converted into a diameter of a circle of equal area to study size distribution characteristics. 4,25,67 However, pores are more like ellipses with different long and short axis lengths when compared to circles. Therefore, the lengths of the major axis and minor axis of ellipses with the same area as pores and the same long/minor axis ratio are used to accurately characterize the true pore size in this paper.…”

“…Pore structure characteristics (pore size, volume, area, shape, connectivity, and spatial distribution) are key parameters to evaluate the quality of shale gas reservoirs because they play an important role in controlling the gas content and permeability. ,, Previous studies have been carried out by a variety of methods, such as field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), nm and μm CT, etc., which are mainly based on microscopic imaging techniques. ,− In addition, high-pressure mercury injection (HPMI), − nuclear magnetic resonance (NMR), − CO 2 and N 2 gas adsorption (N 2 -GA), ,,− and other quantitative techniques were also used widely. In addition, the semiquantitative technology based on a combination of high-resolution imaging technology and image software is another useful method. ,,, However, the results of FE-SEM, TEM, and CT methods are significantly affected by the size of the observation field. , Although HPMI, NMR, and CO 2 and N 2 gas adsorption could quantitatively describe pore size distribution, they are not suitable for microscopic observations . The semiquantitative method is also affected by the image resolution and the number of statistical samples .…”

“…In addition, the semiquantitative technology based on a combination of highresolution imaging technology and image software is another useful method. 4,13,14,25 However, the results of FE-SEM, TEM, and CT methods are significantly affected by the size of the observation field. 8,26 Although HPMI, NMR, and CO 2 and N 2 gas adsorption could quantitatively describe pore size distribution, they are not suitable for microscopic observations.…”

Pore Structure Characterization and Reservoir Quality Evaluation of Analcite-Rich Shale Oil Reservoir from the Bohai Bay Basin

“…The observed OM-hosted pores present in this work are much smaller than those found in the marine overmature siliceous shale from Wufeng and Longmaxi Formations. 60,61 Inorganic mineral-related pores, including intergranular pores, intraparticle pores, and intercrystal pores, are tens of nanometers to a few micrometers in diameter with irregular, slim, or triangular shapes. Similar to siliceous shale, inorganic mineral-related pores are the dominant pore types, with few OM-hosted pores found in analcite-rich siliceous shale.…”