Fractal Analysis of Shale Pore Structure of Continental Gas Shale Reservoir in the Ordos Basin, NW China

Jiang, Fujie; Chen, Di; Chen, Jian; Li, Qianwen; Liu, Ying; Shao, Xinhe; Hu, Tao; Dai, Jinxiong

doi:10.1021/acs.energyfuels.6b00574

Cited by 135 publications

(132 citation statements)

References 62 publications

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“…The Langmuir volumes of the shale samples had a positive relationship with fractal dimension (Figure 14), which was consistent with many previous studies of coal and shale [13,14,37,45]. The higher fractal dimension values represented a rough and irregular surface, which provided more adsorption sites and resulted in higher adsorption capacity.…”

Section: Effects Of Fractal Dimension On the Adsorption Capacity Of Ssupporting

confidence: 89%

“…Compared with continental shale and marine-continental transitional shale, the fractal dimension of the marine shale is much higher, indicating that these marine shales have a more heterogeneous pore system. The fractal dimension of the continental shales or transitional shales is generally less than 2.70 [43][44][45]53]. …”

Section: Fractal Dimensions From N 2 Physisorptionmentioning

confidence: 99%

“…Many methods, including the Langmuir model, thermodynamic method and the Frenkel-Halsey-Hill (FHH) model, are used to calculate fractal dimension [41][42][43]. Among these, the FHH model is widely used and has been shown to be the most effective method for describing the irregular geometric and structural properties of shale [44][45][46]. Fractal dimension D can be calculated independently via the FHH equation combined with N 2 adsorption isotherm data and the detailed process to derive fractal dimension D is discussed in Qi et al [47].…”

Section: Fractal Theorymentioning

confidence: 99%

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Pore Structure and Fractal Characteristics of Niutitang Shale from China

Tang

Wang

et al. 2018

Minerals

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A suite of shale samples from the Lower Cambrian Niutitang Formation in northwestern Hunan Province, China, were investigated to better understand the pore structure and fractal characteristics of marine shale. Organic geochemistry, mineralogy by X-ray diffraction, porosity, permeability, mercury intrusion and nitrogen adsorption and methane adsorption experiments were conducted for each sample. Fractal dimension D was obtained from the nitrogen adsorption data using the fractal Frenkel-Halsey-Hill (FHH) model. The relationships between total organic carbon (TOC) content, mineral compositions, pore structure parameters and fractal dimension are discussed, along with the contributions of fractal dimension to shale gas reservoir evaluation. Analysis of the results showed that Niutitang shale samples featured high TOC content (2.51% on average), high thermal maturity (3.0% on average), low permeability and complex pore structures, which are highly fractal. TOC content and mineral compositions are two major factors affecting pore structure but they have different impacts on the fractal dimension. Shale samples with higher TOC content had a larger specific surface area (SSA), pore volume (PV) and fractal dimension, which enhanced the heterogeneity of the pore structure. Quartz content had a relatively weak influence on shale pore structure, whereas SSA, PV and fractal dimension decreased with increasing clay mineral content. Shale with a higher clay content weakened pore structure heterogeneity. The permeability and Langmuir volume of methane adsorption were affected by fractal dimension. Shale samples with higher fractal dimension had higher adsorption capacity but lower permeability, which is favorable for shale gas adsorption but adverse to shale gas seepage and diffusion.

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Section: Effects Of Fractal Dimension On the Adsorption Capacity Of Ssupporting

confidence: 89%

Section: Fractal Dimensions From N 2 Physisorptionmentioning

confidence: 99%

Section: Fractal Theorymentioning

confidence: 99%

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Pore Structure and Fractal Characteristics of Niutitang Shale from China

Tang

Wang

et al. 2018

Minerals

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“…The micropore PV and SSA increased with increasing temperature to a maximum value at 600 • C, and micropore PV and SSA decreased toward the highest maturity sample M-750 (Ro = 4.87%) (Figure 2). The evolutionary characteristics of micropores do not follow a linear increasing trend as suggested by previous studies [29] and there was a reduction in micropore content above 600 • C. There was also a reduction in shale porosity in the oil window as indicated by many previous studies [30,31], and the primary reason was pore blocking by liquid hydrocarbon [32]. Then, there was a rapid increase in pore content after the oil window due to OM cracking, which formed a large number of pores, and the OM pores were mostly micropores and fine mesopores [5,21].…”

Section: Evolutionary Characteristics Of Microporesmentioning

confidence: 67%

Experimental Investigation of Evolution of Pore Structure in Longmaxi Marine Shale Using an Anhydrous Pyrolysis Technique

Wang

Hu³

et al. 2018

Minerals

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Abstract:To better understanding the evolutionary characteristics of pore structure in marine shale with high thermal maturity, a natural Longmaxi marine shale sample from south China with a high equivalent vitrinite reflectance value (Ro = 2.03%) was selected to conduct an anhydrous pyrolysis experiment (500-750 • C), and six artificial shale samples (pyrolysis products) spanning a maturity range from Ro = 2.47% to 4.87% were obtained. Experimental procedures included mercury intrusion, nitrogen adsorption, and carbon dioxide adsorption, and were used to characterize the pore structure. In addition, fractal theory was applied to analyze the heterogeneous pore structure. The results showed that this sample suite had large differences in macropore, mesopore, and micropore volume (PV), as well as specific surface area (SSA) and pore size distributions (PSD), at different temperatures. Micropore, mesopore, and macropore content increased, from being unheated to 600 • C, which caused the pore structure to become more complex. The content of small diameter pores (micropores and fine mesopores, <10 nm) decreased and pores with large diameters (large mesopores and macropores, >10 nm) slightly increased from 600 to 750 • C. Fractal analysis showed that larger pore sizes had more complicated pore structure in this stage. The variance in pore structure for samples during pyrolysis was related to the further transformation of organic matter and PSD rearrangement. According to the data in this study, two stages were proposed for the pore evolution for marine shale with high thermal maturity.

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“…FHH method is relative simple and convenient, and it requires only adsorption isotherms. Apart from calculating fractal dimension of oil shale, FHH method has widely been applied in determining fractal dimension of coals and shale gas . The equation is as follows:

ln \frac{V}{V_{0}} = C + false(D - 3 false) ln [ln (\frac{P_{0}}{P})]

…”

Section: Methodsmentioning

confidence: 99%

Evaluation of different microwave heating parameters on the pore structure of oil shale samples

Zhu

Yang

et al. 2018

Energy Science & Engineering

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The pore structure of oil shale during microwave heating significantly determines the flow behavior, the transformation products and the ultimate recovery regardless of ex situ retorting or in situ development methods. In this experimental study, the effects of microwave heating parameters including heating time, reaction temperature and output power on the heating behavior, surface morphology and pore roughness of oil shale were investigated based on the nitrogen adsorption/desorption and scanning electron microscope (SEM) experiments. Fractal dimension D1 and D2 (at relative pressures of 0‐0.5 and 0.5‐1, respectively) were calculated according to the fractal Frenkel‐Halsey‐Hill model. The relationships between specific surface area, cumulative pore volume, average pore diameter, and fractal dimension have been studied. The results demonstrated that the pore structure of oil shale was greatly influenced by microwave heating parameters due to the decomposition of kerogen, the internal pressure caused by the steam and volatiles, the complicated reactions and the thermal stress induced by microwave. Moreover, fractal dimension also changed correspondingly with different heating parameters. The variations of fractal dimension D1 was consistent with the evolvement of specific surface area and the changes in fractal dimension D2 showed negative correlation with average pore volume. The relationships between D1 and surface roughness, D2 and pore structure were verified based on the comparison of SEM images. The fractal theory is reliable to describe the surface morphology and pore structure of oil shale and thus supports the application of microwave heating on the oil shale development.

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Fractal Analysis of Shale Pore Structure of Continental Gas Shale Reservoir in the Ordos Basin, NW China

Cited by 135 publications

References 62 publications

Pore Structure and Fractal Characteristics of Niutitang Shale from China

Pore Structure and Fractal Characteristics of Niutitang Shale from China

Experimental Investigation of Evolution of Pore Structure in Longmaxi Marine Shale Using an Anhydrous Pyrolysis Technique

Evaluation of different microwave heating parameters on the pore structure of oil shale samples

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