Investigation on the pore structure and multifractal characteristics of tight oil reservoirs using NMR measurements: Permian Lucaogou Formation in Jimusaer Sag, Junggar Basin

Zhao, Peiqiang; Wang, Zhenlin; Sun, Zhen; Cai, Jianchao; Wang, Liang

doi:10.1016/j.marpetgeo.2017.07.011

Cited by 218 publications

(116 citation statements)

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“…from greyscale image analyses 37 to pore structures of porous media, 38,39 and from fracture networks 40,41 to larger-scale sand body macroscopic characteristics. 6,42 It is also important for the evaluation of the reservoir quality. This paper separated pores from throats, as is shown in Fig.…”

Section: Constant-rate Mercury Injection-based Fractal Dimensionsmentioning

confidence: 99%

Pore-Throat Structure and Fractal Characteristics of Shihezi Formation Tight Gas Sandstone in the Ordos Basin, China

et al. 2018

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In order to better understand the impact of fractal features of pore-throat structures on effective physical properties of tight gas sandstones, this paper carried out constant-rate mercury ‡ ‡ Corresponding authors. This is an Open Access article published by World Scientific Publishing Company. It is distributed under the terms of the Creative Commons Attribution 4.0 (CC-BY) License. Further distribution of this work is permitted, provided the original work is properly cited. 1840005-1Fractals 2018.26. Downloaded from www.worldscientific.com by 13.66.222.141 on 04/01/19. Re-use and distribution is strictly not permitted, except for Open Access articles. H. Huang et al.injection tests, gas-water permeability analyses, helium-based porosity and nitrogen pulse decay permeability measurements, and SEM and casting thin-section analyses on 20 sandstone samples of the Shihezi Formation from 16 wells of the Sulige Gas Field in the Ordos Basin, China. The fractal dimensions of pores corresponding to two pore radius ranges, namely fractal dimensions D p2 and D p3 , and those of throats also corresponding to two throat radius ranges, namely fractal dimensions D t1 and D t2 , were then calculated using the constant-rate mercury injection data. Fractal dimensions D p2 and D p3 are negatively correlated with the average pore radius and pore volume as well as quartz content, and they are positively related to contents of clay minerals and lithic fragments. Compared with pore fractal dimensions, throat fractal dimensions have lower correlations with throat structural parameters, and show vague relations with mineral compositions. Although the effects imposed by mineral compositions upon throat structures are similar to those upon pore structures, the flake-like and curved shapes of throats result in irregularity of fractal dimensions. Tight gas sandstones, with smaller fractal dimensions D p2 and D p3 , have larger effective porosity, indicating that more gas volumes can be replaced by liquids. As for tight gas sandstones with lower fractal dimensions D p3 and D t2 , the effective gas permeability is relatively high. In such cases, gas can flow more easily through the reservoir.

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Section: Constant-rate Mercury Injection-based Fractal Dimensionsmentioning

confidence: 99%

Pore-Throat Structure and Fractal Characteristics of Shihezi Formation Tight Gas Sandstone in the Ordos Basin, China

et al. 2018

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“…The multifractal theory was introduced with the deepening of research . Compared with single fractal, the multifractal theory can decompose the self‐similarity measure into staggered fractal sets and decompose the complex fractal structure into several parts to characterize the local complexity and heterogeneity of pore distribution, so as to identify the micro‐local characteristics of pore distribution …”

Section: Introductionmentioning

confidence: 99%

“…Former researchers show that there is a close relationship between the PSD of rocks and multifractal parameters . In addition, some scholars have found that multifractal parameters (such as D min− D max and D min / D max , △α ) are closely related to the T 2 cutoff value in coal and sandstone reservoirs, The corresponding prediction models of T 2 cutoff value have been proposed based on the multifractal parameters. However, there are only multifractal parameters in the prediction model.…”

Section: Introductionmentioning

confidence: 99%

“…45 Compared with single fractal, the multifractal theory can decompose the self-similarity measure into staggered fractal sets and decompose the complex fractal structure into several parts to characterize the local complexity and heterogeneity of pore distribution, so as to identify the micro-local characteristics of pore distribution. 39,46,47 Former researchers show that there is a close relationship between the PSD of rocks and multifractal parameters. [47][48][49][50][51][52][53][54] In addition, some scholars have found that multifractal parameters (such as D min− D max and D min /D max , △α) are closely related to the T 2 cutoff value in coal and sandstone reservoirs, 47,50,52,54 The corresponding prediction models of T 2 cutoff value have been proposed based on the multifractal parameters.…”

Section: Introductionmentioning

confidence: 99%

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A method to determine nuclear magnetic resonance T₂ cutoff value of tight sandstone reservoir based on multifractal analysis

Guo

Zhang

et al. 2019

Energy Science & Engineering

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Nuclear magnetic resonance (NMR) T2 cutoff value is an important parameter for pore structure evaluation. It is complicated and uneconomical to obtain T2 cutoff value by an experimental method; therefore, it is necessary to explore a prediction method of T2 cutoff value. In this paper, 10 samples of tight gas reservoirs in the eastern Ordos Basin were selected, and then saturation and centrifugal experiments of nuclear magnetic resonance were carried out. On this basis, multifractal theory was introduced to calculate the multifractal characteristics of the NMR T2 spectrum of each sample, and the relationship between multifractal parameters and T2 value was analyzed. The influencing factors of the T2 cutoff value were clarified, and the prediction model of the T2 cutoff value was constructed accordingly. The results show that the T2 spectra of sandstones in the study area can be divided into three types: single steeple peak, double steeple peak, and irregular double peak. The pore diameter of the three types is 1 nm ~ 3×104 nm, 1 nm ~ 104 nm and 1 nm ~ 4×103 nm, respectively. The T2 cutoff value ranges from 9.72 to 35.16 ms. The correlation analysis suggests that the symmetrical fractal dimension difference and symmetrical multifractal dimension ratio (Dmin−Dmax, Dmin/Dmax) shows a positive linear correlation with the T2 cutoff value. The value of T2 cutoff gradually decreases with the increase of the flow zone indicator (FZI). Therefore, three parameters, including symmetrical fractal dimension difference, symmetrical multifractal number ratio, and FZI are optimized, and the prediction model for the NMR T2 cutoff value of sandstone samples in the study area is proposed. The introduction of porosity‐related parameters compensates for the shortcomings of previous T2 cutoff value prediction models. At the same time, the prediction model is proven to be accurate and reliable by testing the measured data of the samples near the study area. The results of this paper can be used for further study of the NMR T2 cutoff value prediction of tight sandstone reservoirs in different areas.

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“…However, the water relative permeability (k rw ) cannot be obtained by the proposed model. 22 Recently, Zhao et al 23 investigated the pore structure of Lucaogou tight oil formation by NMR measurements. And the heterogeneity of pore structure was studied by multifractal analysis.…”

Section: Introductionmentioning

confidence: 99%

A Fractal Model for Water Flow Through Unsaturated Porous Rocks

et al. 2018

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In this work, considering the effect of porosity, pore size, saturation of water and tortuosity fractal dimension, an analytical model for the capillary pressure and water relative permeability is derived in unsaturated porous rocks. Besides, the formulas of calculating the capillary pressure and water relative permeability are given by taking into account the fractal distribution of pore size and tortuosity of capillaries. It can be seen that the capillary pressure for water phase decreases with the increase of saturation in unsaturated porous rocks. It is found that the capillary pressure for water phase decreases as the tortuosity fractal dimension decreases. It is further seen that the capillary pressure for water phase increases with the decrease of porosity, and at low porosity, the capillary pressure increases sharply with the decrease of porosity. Besides, it can be observed that the water relative permeability increases with the increase of saturation in unsaturated porous rocks. This predicted the capillary pressure and water relative permeability of unsaturated porous rocks based on the proposed models which are in good agreement with the experimental data and model predictions reported in the literature. § Corresponding author. This is an Open Access article published by World Scientific Publishing Company. It is distributed under the terms of the Creative Commons Attribution 4.0 (CC-BY) License. Further distribution of this work is permitted, provided the original work is properly cited. 1840015-1 B. Xiao et al.The proposed model improved the understanding of the physical mechanisms of water flow through unsaturated porous rocks.

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Investigation on the pore structure and multifractal characteristics of tight oil reservoirs using NMR measurements: Permian Lucaogou Formation in Jimusaer Sag, Junggar Basin

Cited by 218 publications

References 47 publications

Pore-Throat Structure and Fractal Characteristics of Shihezi Formation Tight Gas Sandstone in the Ordos Basin, China

Pore-Throat Structure and Fractal Characteristics of Shihezi Formation Tight Gas Sandstone in the Ordos Basin, China

A method to determine nuclear magnetic resonance T₂ cutoff value of tight sandstone reservoir based on multifractal analysis

A Fractal Model for Water Flow Through Unsaturated Porous Rocks

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Investigation on the pore structure and multifractal characteristics of tight oil reservoirs using NMR measurements: Permian Lucaogou Formation in Jimusaer Sag, Junggar Basin

Cited by 218 publications

References 47 publications

Pore-Throat Structure and Fractal Characteristics of Shihezi Formation Tight Gas Sandstone in the Ordos Basin, China

Pore-Throat Structure and Fractal Characteristics of Shihezi Formation Tight Gas Sandstone in the Ordos Basin, China

A method to determine nuclear magnetic resonance T2 cutoff value of tight sandstone reservoir based on multifractal analysis

A Fractal Model for Water Flow Through Unsaturated Porous Rocks

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A method to determine nuclear magnetic resonance T₂ cutoff value of tight sandstone reservoir based on multifractal analysis