Pore structure and fractal characteristics of ultralow-permeability sandstone reservoirs in the Upper Triassic Yanchang Formation, Ordos Basin

Zhang, Quanpei; Jiao, Tao; Huang, Hao; Qi, Zhao; Jiang, Tao; Chen, Gang; Zhu, Yushuang; Jia, Na

doi:10.1190/int-2020-0185.1

Cited by 5 publications

(2 citation statements)

References 55 publications

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“…Therefore, the application of these methods in tight reservoirs is limited. The fractal theory proposed by Mandelbrot [30] has been widely used to characterize the heterogeneity of porous media [31,32]. Within a certain range of pore sizes, the pore space of tight sandstone is self-similar; that is, there is 'scale invariance'.…”

Section: Model Name Expressionmentioning

confidence: 99%

A New Model for Predicting Permeability of Chang 7 Tight Sandstone Based on Fractal Characteristics from High-Pressure Mercury Injection

Yang,

Wen,

Tian

et al. 2024

Energies

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Accurately predicting permeability is important to elucidate the fluid mobility and development potential of tight reservoirs. However, for tight sandstones with the same porosity, permeability can change by nearly three orders of magnitude, which greatly increases the difficulty of permeability prediction. In this paper, we performed casting thin section, scanning electron microscopy and high-pressure mercury injection experiments to analyze the influence of pore structure parameters and fractal dimensions on the permeability of Chang 7 tight sandstones. Furthermore, the key parameters affecting the permeability were optimized, and a new permeability prediction model was established. The results show that the pore throat structure of Chang 7 tight sandstone exhibits three-stage fractal characteristics. Thus, the pore throat structure was divided into large pore throat, medium pore throat and small pore throat. The large pore throat reflects the microfracture system, whose fractal dimension was distributed above 2.99, indicating that the heterogeneity of the large pore throat was the strongest. The medium pore throat is dominated by the conventional pore throat system, and its fractal dimension ranged from 2.378 to 2.997. Small pore throats are mainly composed of the tree-shaped pore throat system, and its fractal dimension varied from 2.652 to 2.870. The medium pore throat volume and its fractal dimension were key factors affecting the permeability of Chang 7 tight sandstones. A new permeability prediction model was established based on the medium pore throat volume and its fractal dimension. Compared to other models, the prediction results of the new model are the best according to the analysis of root mean square value, average absolute percentage error and correlation coefficient. These results indicate that the permeability of tight sandstones can be accurately predicted using mesopore throat volume and fractal dimension.

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Section: Model Name Expressionmentioning

confidence: 99%

A New Model for Predicting Permeability of Chang 7 Tight Sandstone Based on Fractal Characteristics from High-Pressure Mercury Injection

Yang,

Wen,

Tian

et al. 2024

Energies

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“…In 1975, Mandelbort and Wheeler (1998) came up with a fractal theory. At present, the fractal dimension theory has been widely applied to medicine (Cai and Wang, 2014; Chen and Bao, 2003; Zhang and Wei, 2010), geography (Huang et al, 2021; Zhang et al, 2021; Zhang et al, 2020), architecture (Hu et al, 2010; Li et al, 2018; Luan and Fan, 2015), and other fields. In 1988, Katz (1988) firstly raised the concept of Katz fractal dimension and pointed out that fractal features are especially suitable for the analysis of complicated waveforms, like electroencephalogram.…”

Section: Introductionmentioning

confidence: 99%

Compound faults feature extraction of inter-shaft bearing based on vibration signal of whole aero-engine

Fang

Chen

et al. 2021

Journal of Vibration and Control

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To effectively extract the information of compound faults of inter-shaft bearing of an aero-engine based on casing vibration signals, the paper has introduced the concept of weighted Katz fractal dimension and proposed the method combining information fusion, wavelet transform (WT), singular value decomposition (SVD), and Katz fractal dimension, the cross-correlation function (CCF-WT-SVD-Katz algorithm). The method includes homologous information fusion achieved by the CCF of horizontal and vertical vibration signals of the rotor from the same section; signal separation and denoising of blended signals through WT and SVD; reinforcement of fault characteristics of signals according to weighted Katz fractal dimension; and extraction of characteristic frequencies of compound faults of inter-shaft bearing by frequency spectrum of weighted and reconstructed signals. The result indicates that the proposed CCF-WT-SVD-Katz algorithm is capable of effectively extracting compound fault characteristics of inter-shaft bearing and precisely identifying a fault type based on whole casing vibration signals and will be of very good application value in engineering.

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Research on pore structure and classification evaluation of tight oil reservoirs based on fractal theory

Li,

Bian,

Zhang

et al. 2024

Acta Geophys.

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Chang 8 section of Yanchang Group in Yuancheng area of Ordos Basin is a typical tight oil reservoir in China, which is characterised by low porosity and low permeability, strong non-homogeneity and high difficulty in evaluating reservoir parameters. In order to clarify the microscopic pore structure characteristics of the Chang 8 section, this study uses cast thin section, scanning electron microscope, combined with the core physical properties test data, to analyse the basic characteristics of the reservoir rock mineralogy, pore permeability and other basic characteristics, and uses the shape of piezo-mercury curves to study the pore structure characteristics of the 17 samples. Based on the fractal dimension of the NMR T2 spectrum, the reservoir is classified into four categories, and a conversion model for the relationship between the NMR T2 spectrum and the capillary pressure curve is established by using the segmented power function method, which is applied to the interpretation of the NMR logging to obtain the continuous pseudo-capillary pressure curve for the whole well section. Three effective parameters reflecting the microscopic pore structure, namely, the expulsion pressure, median pressure, and sorting coefficient of the core samples, were extracted, and the relationship between the reservoir parameters and the reservoir category was established by using the generalised regression neural network. The pseudo-capillary pressure curve reservoir parameters of the whole well section were processed to obtain the classification profile of the reservoir, and the classification results were consistent with the results of the mercury pressure experiment with good results. The study shows that this method can provide an important basis for the study of pore structure of tight oil reservoirs and the evaluation of reservoir classification.

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Pore structure and fractal characteristics of ultralow-permeability sandstone reservoirs in the Upper Triassic Yanchang Formation, Ordos Basin

Cited by 5 publications

References 55 publications

A New Model for Predicting Permeability of Chang 7 Tight Sandstone Based on Fractal Characteristics from High-Pressure Mercury Injection

A New Model for Predicting Permeability of Chang 7 Tight Sandstone Based on Fractal Characteristics from High-Pressure Mercury Injection

Compound faults feature extraction of inter-shaft bearing based on vibration signal of whole aero-engine

Research on pore structure and classification evaluation of tight oil reservoirs based on fractal theory

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