Quantifying Fractal Dimension in Integrated Experimental Data of Tight Sandstones

Ren, Dazhong; Li, Rongxi; Liu, Dengke; Li, Yuhong; Liu, Na; Yang, Fangxing

doi:10.1155/2019/6463473

Cited by 4 publications

(10 citation statements)

References 55 publications

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“…Fractal theory expressed in terms of fractal dimensions provides an important method in the study of irregular forms with complex structures and self-similarity. Only within a certain scale can the pore throat structure have fractal characteristics for low permeability sandstone reservoirs [7,8,15]. Furthermore, the complex sedimentary, diagenetic, and tectonic superposition transformation of carbonate reservoirs creates complicated reservoir spaces and leads to the obvious heterogeneity in different kinds of reservoirs or various scales of pore throats.…”

Section: Methodsmentioning

confidence: 99%

Study on Heterogeneity of Pore Throats at Different Scales and Its Influence on Seepage Capacity in Different Types of Tight Carbonate Reservoirs

Qi¹,

Liu

Dong

et al. 2020

Geofluids

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The carbonate reservoirs in the middle Sichuan area have undergone complicated tectonics, resulting in various types of reservoir space, large secondary changes, and multiple complexities. Taking the tight carbonate gas reservoir of the Deng-4 member in this area as an example, based on casting thin sections, scanning electron microscopy, and high-pressure mercury injection experiments, the reservoir space and microstructural characteristics of the micropore throats were studied, and the influence of the microscale heterogeneity in different types of reservoirs on the seepage capacity was analyzed by applying fractal theory. The results showed that the reservoir space in the tight carbonate rock of the Deng-4 member in the study area could be divided into 3 types: pore-hole-fracture, pore-hole, and pore types. The distribution characteristics of the pore throat diameter were multimode wide type, double-mode high and low asymmetrical type, and single-mode concentrated type. The fractal dimension and seepage capability of the pore throat increased successively in sizes from less than 0.1 μm to 0.1~1.0 μm and greater than 1.0 μm. On the one hand, the development of karst caves and fractures controlled the percolation ability of tight carbonate reservoirs; on the other hand, it enhanced the heterogeneity of the micropore throat structure. However, the development degree of dissolved pores and microfractures has a weak contribution to the connectivity and seepage capacity of the reservoir space. Acidification, fracturing, and other measures can be adopted to enhance the connectivity between pores to improve the productivity of the gas reservoir. This study provides a scientific basis for the efficient exploration and development of tight carbonate reservoirs.

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Section: Methodsmentioning

confidence: 99%

Study on Heterogeneity of Pore Throats at Different Scales and Its Influence on Seepage Capacity in Different Types of Tight Carbonate Reservoirs

Qi¹,

Liu

Dong

et al. 2020

Geofluids

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“…In the fractal theory, the most important feature is self-similarity, which is a self-similar object that has similar structural features at different scales. Selfsimilar objects with fractal characteristics are represented by fractal dimension D f or D, which were greatly applied to quantitatively identify the heterogeneity and complexity of the pore-throat structure [19][20][21][22][23][34][35][36][37]. Generally, the value of fractal dimension ranges between 2 to 3, increasing with the heterogeneity and complexity of pore-throat structure [41][42][43][44][45][46].…”

Section: Fractal Theorymentioning

confidence: 99%

“…Accordingly, if the pore-throat structure has fractal characteristics, the amount of pore-throats which radiuses exceeded r can be calculated. Then, the relevant formula can be expressed as follows, and its instructions on parameters are detailed in relevant references [19][20][21][22][23]:…”

Section: Fractal Theorymentioning

confidence: 99%

“…Experimental methods are conducted to evaluate the pore-throat structure, such as image observation methods represented by scanning electron microscopy (SEM) and casting thin sections (CTS), photoelectromagnetic radiation methods by nuclear magnetic resonance (NMR) and CT scanning, and fluid injection method by N 2 gas adsorption measurements and high-pressure mercury injection (HPMI) as well as constant-rate mercury injection (CRMI) [9][10][11][12][13][14][15][16]. Considering the complex pore-throat characteristics and strong heterogeneity caused by complicated deposition and diagenesis processes, it is hard to identify the microporethroat structure of tight sandstone reservoirs by a single method [5,[17][18][19][20][21][22][23][24][25][26]. For instance, although the image observation methods (SEM and CTS) can directly observe the geometry and the size of the pore-throat within sight, its visual field is too narrow to represent the whole sample [27].…”

Section: Introductionmentioning

confidence: 99%

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Pore-Throat Structure and Fractal Characteristics of Tight Sandstones: A Case Study from the Chang 63 Sublayer, Southeast Ordos Basin

Han

Zhou

Wei³

et al. 2023

Geofluids

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The micropore-throat structure is a controlling factor on the capacity of storage and seepage for the tight sandstone reservoirs. Therefore, quantitatively analyzing the pore-throat structure is crucial for realizing the oil accumulated in the tight reservoirs. To study the micropore-throat, a battery of experiments such as casting thin sections, scanning electron microscopy, high-pressure mercury injection, and the petrophysical characteristics of reservoirs were conducted on ten samples gathered in the Late Triassic Chang 63 sublayer in the Southeast Ordos Basin, China. The main pore types of the samples are intergranular pores, feldspar dissolved pores, and intergranular dissolved pores. Meanwhile, the pore-throat structure of each sample was identified as large pores, medium pores, and small pores by combining the result of HPMI with fractal theory. The corresponding mean values of the fractal dimension D for large, medium, and small pores are 2.83, 2.69, and 2.31, respectively, indicating that the complex structure and strong heterogeneity were presented in the large pores according to the maximum fractal dimension. In addition, the fractal dimension of the medium pores ( D P − 2 ) has a negative correlation with porosity, permeability, median pore-throat radius, maximum mercury saturation, mercury withdrawal efficiency, displacement pressure, and content of quartz, while a positive correlation with feldspar content, sorting coefficient, and coefficient of variation. Thus, the reservoir space and seepage capacity of all samples in this study were determined by the size, complexity, and distribution of the medium pores. Furthermore, the content of quartz contributes to the storage of the reservoir and the homogeneity of the pore-throat structure, thereby the storage capacity improves with the increase of quartz content. Feldspar dissolution pores are developed widely in the study area, leading to various pores with diverse types, sizes, complex structures, and large fractal dimensions. Although the storage capacity of tight sandstone reservoirs was enhanced with increasing feldspar content, the pore-throat structure complexity was also stronger, resulting in the reduction seepage capacity of fluid.

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“…Pressure-controlled mercury intrusion and rate-controlled mercury intrusion (PCMI/RCMI) are the standard techniques to quantify the pore size distributions [15,16]. Combining PCMI and RCMI can give us information about the whole pore size distributions of more than 3.6 nm [17].…”

Section: Introductionmentioning

confidence: 99%

Microscale Mineral and Pore Structure Characterization of the Low‐Permeability Sandstone in the Ordos Basin, China

Gao¹,

Sun

Liu

et al. 2021

Advances in Civil Engineering

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Given the insufficient understanding of the characteristics and controlling factors of the low-permeability sandstone reservoir in the Heshui area, the Ordos Basin, the present study examined the microscale mineral and pore structure of Chang 2 reservoir. It analyzed its major controlling factors using a series of methods, including imaging and indirect methods. The results show that the rocks of Chang 2 reservoir in the study area are dominated by lithic arkose and feldspathic detritus quartz sandstone. The reservoir space develops intragranular pores, feldspar dissolved pores, lithic dissolved pores, and intercrystallite pores. Microcracks can occasionally be found. The average porosity is 10.5%, and the average permeability is 2.2 mD, featuring a low-porosity-ultralow-permeability reservoir. During the reservoir development, traps formed by small-scale nose-shaped uplifts resulting from the tectonic effects provide opportunities for good reservoir space. Sedimentation and diagenetic processes control the degree of development and direction of the evolution of reservoir porosity to a certain degree. Multisegment capillary pressure curve and long missing zone were corresponding to relatively good pore-throat structures. Illite was the predominant diagenetic clay minerals that determine the reservoir quality. These three effects all contribute to the overall development of the reservoir.

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Quantifying Fractal Dimension in Integrated Experimental Data of Tight Sandstones

Cited by 4 publications

References 55 publications

Study on Heterogeneity of Pore Throats at Different Scales and Its Influence on Seepage Capacity in Different Types of Tight Carbonate Reservoirs

Study on Heterogeneity of Pore Throats at Different Scales and Its Influence on Seepage Capacity in Different Types of Tight Carbonate Reservoirs

Pore-Throat Structure and Fractal Characteristics of Tight Sandstones: A Case Study from the Chang 63 Sublayer, Southeast Ordos Basin

Microscale Mineral and Pore Structure Characterization of the Low‐Permeability Sandstone in the Ordos Basin, China

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