Fractal-based NMR permeability estimation in tight sandstone: A case study of the Jurassic rocks in the Sichuan Basin, China

Wu, Feng; Li, Yang; Burnham, Brian; Zhang, Zeyu; Yao, Cong; Yuan, Lijun; Zhang, Fengsheng; Deng, Haoyang; Xi, Yanping; He, Jiang

doi:10.1016/j.petrol.2022.110940

Cited by 12 publications

(5 citation statements)

References 57 publications

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“…Many studies indicate that the pore structure of porous rock materials presents typical fractal characteristics, which can be quantitatively described by fractal dimension 49–51 . According to the fractal geometry principle 52–56 . The relationship between cumulative pore volume fraction S v and T 2 can be expressed as

S_{v} goodbreak= {(\frac{T_{2}}{T_{2, \max}})}^{3 - D_{f}}

where T 2,max represents maximum transverse relaxation time and D f represents the fractal dimension of pores.…”

Section: Resultsmentioning

confidence: 99%

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Evolution of mechanical properties and microstructure in thermally treated granite subjected to cyclic loading

Fan,

Wang,

Qiu

et al. 2024

Fatigue Fract Eng Mat Struct

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In high‐temperature geological engineering applications, cyclic loads induced by various factors (e.g., earthquakes, excavation, and blasting) can exacerbate the thermal damage of engineered rock formations. Therefore, this study investigates the mechanical properties and microstructure evolution of thermally treated granite subjected to cyclic loading. First, the mechanical property variations of thermally treated granite under cyclic loading were studied through cyclic loading experiments. Subsequently, nuclear magnetic resonance (NMR) was employed to examine the microstructure evolution of thermally treated granite under cyclic loading. Lastly, the effects of cyclic loading on maximum strain, Young's modulus, pore size distribution, and porosity of thermally treated granite were discussed. Results indicate that at the same number of cycles, maximum strain increases with increasing temperature, while Young's modulus decreases. For granite subjected to the same thermal treatment, the maximum strain increases as the cyclic number increases, while Young's modulus decreases. Concurrently, porosity and fractal dimension initially decrease and then increase with a rising number of cycles.

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S_{v} goodbreak= {(\frac{T_{2}}{T_{2, \max}})}^{3 - D_{f}}

where T 2,max represents maximum transverse relaxation time and D f represents the fractal dimension of pores.…”

Section: Resultsmentioning

confidence: 99%

“…[49][50][51] According to the fractal geometry principle. [52][53][54][55][56] The relationship between cumulative pore volume fraction S v and T 2 can be expressed as…”

Section: Effects Of Cyclic Number On Porosity and Fractal Dimensionmentioning

confidence: 99%

Evolution of mechanical properties and microstructure in thermally treated granite subjected to cyclic loading

Fan,

Wang,

Qiu

et al. 2024

Fatigue Fract Eng Mat Struct

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“…where T 2 is the relaxation time of the hydrogen-containing fluid in the pore; T 2b is the bulk relaxation time; T 2s is the surface relaxation time; T 2d is the diffusion relaxation time [78]. T 2b is higher for distilled water, so that the term 1/T 2b can be neglected, and diffusion relaxation can be reduced when a low and uniform magnetic field and shorter pulse intervals are used.…”

Section: Methodsmentioning

confidence: 99%

“…In the fractal model, the number of pores N(r) with dimensions greater than r is ca culated from the total fractal equation above. In NMR measurements, the cumulative po rosity 𝑉𝑉 𝑝𝑝 can be expressed by Equation (32) [19,78,79,[129][130][131][132][133][134].…”

Section: Fractal Dimension (Df) Of Nuclear Magnetic Resonancementioning

confidence: 99%

Microscopic Characterization and Fractal Analysis of Pore Systems for Unconventional Reservoirs

Guan,

Cai,

et al. 2024

JMSE

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The complex pore structure of unconventional oil and gas reservoirs is one of the reasons for the difficulties in resource evaluation and development. Therefore, it is crucial to comprehensively characterize the pore structure, understand reservoir heterogeneity from multiple perspectives, and gain an in-depth understanding of fluid migration and accumulation mechanisms. This review outlines the methods and basic principles for characterizing microporous systems in unconventional reservoirs, summarizes the fractal analysis corresponding to the different methods, sorts out the relationship between the fractals and reservoir macroscopic physical properties (porosity, permeability, etc.) with the reservoir microscopic pore structures (pore structure parameters, pore connectivity, etc.). The research focuses on cutting-edge applications of characterization techniques, such as improved characterization accuracy, calibration of PSD ranges, and identification of different hydrogen compositions in pore systems for dynamic assessment of unconventional reservoirs. Fractal dimension analysis can effectively identify the quality level of the reservoir; complex pore-throat structures reduce permeability and destroy free fluid storage space, and the saturation of removable fluids is negatively correlated with Df. As for the mineral composition, the fractal dimension is positively correlated with quartz, negatively correlated with feldspar, and weakly correlated with clay mineral content. In future qualitative characterization studies, the application and combination of contrast agents, molecular dynamics simulations, artificial intelligence techniques, and 4D imaging techniques can effectively improve the spatial resolution of the images and explore the adsorption/desorption of gases within the pores, and also help to reduce the computational cost of these processes; these could also attempt to link reservoir characterization to research on supercritical carbon dioxide-enhanced integrated shale gas recovery, carbon geological sequestration, and advanced underground hydrogen storage.

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“…At present, various methods have been selected to study the pore structure of fine-grained sandstone, and three of them are most frequently used . The first one is to manifest the morphological characteristics of pores based on observation and analysis of the microscopic images. − The second one is to calculate the numerical value of gas adsorption and fluid injection, such as a high-pressure mercury injection (HPMI) experiment , and nuclear magnetic resonance (NMR) experiment. − The third one is three-dimensional numerical reconstruction and simulation using ray detection, such as CT scanning, and small angle scattering experiments …”

Section: Introductionmentioning

confidence: 99%

Mechanism Affecting the Pore Differentiation Characteristics of Fine-Grained Tight Sandstones: A Case Study of Permian Shanxi Formation in Ordos Basin

Guo

Wang

et al. 2023

ACS Omega

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In this study, the pore-throat structure and lithological and fractal characteristics of fine-grained sandstone reservoirs of Permian Shanxi Formation in Ordos Basin are investigated using various experiments, including casting thin section, scanning electron microscopy (SEM), high-pressure mercury injection (HPMI), and nuclear magnetic resonance (NMR). The relation between rock type difference and pore structure difference is explored, and the controlling effect of porethroat structure on physical properties of fine-grained sandstone reservoir is studied. The results show that the sandstone sample can be categorized into quartz arenites, sublitharenite, and lithic sandstone. The average porosity and permeability are, respectively, 4.46% and 0.129 mD. The pores are mainly of intergranular and intercrystalline types, and the throats are lamellar and tubular types. Furthermore, the fine-grained sandstone is typically characterized by a binary pore structure. Micropore-throat, as the main reservoir space, is the dominant factor of the reservoir physical property difference. In addition, the correlation between fractal dimension and rock composition is studied with pore-throat morphology being comprehensively analyzed. The results indicate that the quartz arenite is dominated by quartz intergranular lamellar throats, and there are numerous intergranular pores and tubular throats connecting them in litharenite and sublitharenite. Moreover, the content of pores and throats play major roles in the change of fractal dimension. The characteristics, causes, and main controlling factors of micropore and throat types should be emphatically analyzed to predict the physical properties of fine-grained sandstone.

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Fractal-based NMR permeability estimation in tight sandstone: A case study of the Jurassic rocks in the Sichuan Basin, China

Cited by 12 publications

References 57 publications

Evolution of mechanical properties and microstructure in thermally treated granite subjected to cyclic loading

Evolution of mechanical properties and microstructure in thermally treated granite subjected to cyclic loading

Microscopic Characterization and Fractal Analysis of Pore Systems for Unconventional Reservoirs

Mechanism Affecting the Pore Differentiation Characteristics of Fine-Grained Tight Sandstones: A Case Study of Permian Shanxi Formation in Ordos Basin

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