Fractal Properties of Various Clay Minerals Obtained from SEM Images

Abstract

Clay minerals significantly alter the pore size distribution (PSD) of the gas hydrate-bearing sediments and sandstone reservoir rock by adding an intense amount of micropores to the existing intragranular pore space. Therefore, in the present study, the internal pore space of various clay groups is investigated by manually segmenting Scanning Electron Microscopy (SEM) images. We focused on kaolinite, smectite, chlorite, and dissolution holes and characterized their specific pore space using fractal geometry theory and parameters such as pore count, pore size distribution, area, perimeter, circularity, and density. Herein, the fractal properties of different clay groups and dissolution holes were extracted using the box counting technique and were introduced for each group. It was observed that the presence of clays complicates the original PSD of the reservoir by adding about 1.31-61.30 pores/100 μm2 with sizes in the range of 0.003-87.69 μm2. Meanwhile, dissolution holes complicate the pore space by adding 4.88-8.17 extra pores/100 μm2 with sizes in the range of 0.06-119.75 μm2. The fractal dimension ( D ) and lacunarity ( L ) values of the clays’ internal pore structure fell in the ranges of 1.51-1.85 and 0.18-0.99, respectively. Likewise, D and L of the dissolution holes were in the ranges of, respectively, 1.63-1.65 and 0.56-0.62. The obtained results of the present study lay the foundation for developing improved fractal models of the reservoir properties which would help to better understand the fluid flow, irreducible fluid saturation, and capillary pressure. These issues are of significant importance for reservoir quality and calculating the accurate amount of producible oil and gas.

Evaluating the Effect of New Gas Solubility and Bubble Point Pressure Models on PVT Parameters and Optimizing Injected Gas Rate in Gas-Lift Dual Gradient Drilling

“…Besides, there are still many unknown aspects of applying the new interdisciplinary investigation techniques in assessing the gas solubility, bubble point pressure, bottom hole pressure or temperature, gas injection rate, etc., throughout dual gradient drilling or other deepwater drilling tasks. These techniques include fractal geometry theory [52][53][54][55], digital rock technology [56][57][58], one-dimensional [59][60][61][62] and two-dimensional nuclear magnetic resonance [63,64], numerical methods [65][66][67], artificial intelligence [68][69][70][71][72] especially the deep learning technique [73][74][75], which could be used individually or in a joint manner during well planning, design, engineering, operations, and technology application, etc. This wide range of topics is suggested as the potential areas of future research.…”

Microscopic Conductivity Mechanism and Saturation Evaluation of Tight Sandstone Reservoirs: A Case Study from Bonan Oilfield, China

“…Energies 2022, 15, 1368 2 of 27 cast thin section (CTS) [13], scanning electron microscope (SEM) [14][15][16], focused ion beam microscope (FIB-SEM) [17], micro/nano CT scanning and the resulting digital rock technology [18,19]. It has been recognized that the advantages and limitations for each test technique exist at the same time, and only one testing technique cannot fully reveal the pore structure characteristics of tight sandstone.…”

Quantitative characterization of organic and inorganic pores in shale based on FIB-SEM

“…The commonly used experimental methods to study pore structure include high pressure mercury injection (MICP), gas (N 2 or CO 2 ) adsorption, nuclear magnetic resonance (NMR), scanning electron microscope (SEM) and CT scanning method, etc. (Tian et al, 2012;Tiwari et al, 2013;Liu et al, 2015;Wu et al, 2019b;Cui et al, 2020;Li et al, 2022;Golsanami et al, 2021 and. High pressure mercury injection method and gas adsorption method are indirect means to obtain pore structure and morphology information.…”