Pore structure and fractal analysis of Lower Carboniferous carbonate reservoirs in the Marsel area, Chu-Sarysu basin

Zhang, Kun; Pang, Xiongqi; Zhao, Zhengfu; Shao, Xinhe; Xue, Zhang; Li, Wei; Wang, Ke

doi:10.1016/j.marpetgeo.2018.03.027

Cited by 43 publications

(34 citation statements)

References 91 publications

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“…Figure 12(a) shows that the pore throat structure of type I has multifractal characteristics with three different slopes. This correlates with the many studies that have pointed out that pore structure has multifractal characteristics and thus indicates that there are great differences among macropores, mesopores, and micropores [30,69]. In this paper, type I has been shown to have a variety of pore types, including macropores (intergrain pores, etc.…”

Section: Classification Validity Analysis and Structural Featuresupporting

confidence: 72%

“…Analysis. The fractal dimension (D) deduced from fractal theory can quantitatively evaluate pore surface roughness and structural irregularity [30,[69][70][71][72]. Many researchers have shown that D can be used to evaluate pore structure and analyze the influence factors of various reservoirs [69,70].…”

Section: Classification Validity Analysis and Structural Featurementioning

confidence: 99%

“…NMR tests are used to evaluate the pore structure of rock through the transverse relaxation time (T 2 ) spectrum and thus to obtain the movable fluid saturation (S wm ). S wm is usually calculated by the T 2 cut-off value (T 2cut-off ) [29]; however, continuous studies show that when there is a diffusion of fluid molecules between the large and small pores, the effectiveness of the method will be loosed [30][31][32]. The new methods that have been proposed to overcome these problems still need to be verified [33][34][35][36].…”

Section: Introductionmentioning

confidence: 99%

“…In addition, the fractal dimension has proven to be able to characterize the reservoir's pore structure characteristics [30]; therefore, fractal dimensions were used to verify the effectiveness of pore structure classification.…”

mentioning

confidence: 99%

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Pore Structure Characteristics and Permeability Prediction Model in a Cretaceous Carbonate Reservoir, North Persian Gulf Basin

Tang

Wang

et al. 2021

Geofluids

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Due to the diversity of pore types, it is challenging to characterize the Middle East’s Cretaceous carbonate reservoir or accurately predict its petrophysical properties. In this paper, pore structure in the reservoir is first classified using a comprehensive method. Then, based on the identified pore structure types, a new permeability model with high prediction precision is established. The reservoir is dominated by 6 pore types, such as intergrain pores and moldic pores, and 6 rock types. Grainstone, algal packstone, algal wackestone, and foraminifera wackestone are porous rock types, and echinoderm wackestone and mudstone are nonporous rock types. The types of pore structure in the study area can be divided into four types. Type I has midhigh porosity and medium-high permeability due to its large throat, while type II has a fine throat type with midhigh porosity and midpermeability. Due to their isolated pores, the permeability is low in types III and IV, and out of these two, type III has better storage capacity. Movable fluid saturation calculated by the spectral coefficient method and r apex can characterize the boundary between the connected pores and unconnected pores very well in the research area. It is not accurate enough to simply classify the pore structure by permeability and porosity. The combination of porosity, permeability, r apex , flow zone indicator, and the reservoir quality index can effectively distinguish and classify pore structure types in noncoring wells. The characteristics of each pore structure type are consistent with those of the fractal dimension, which thereby proves the effectiveness of the pore structure classification. New permeability prediction models are proposed for different pore structure types, and good prediction results have been obtained. This study is of great significance for enhancing oil recovery.

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Section: Classification Validity Analysis and Structural Featuresupporting

confidence: 72%

Section: Classification Validity Analysis and Structural Featurementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Pore Structure Characteristics and Permeability Prediction Model in a Cretaceous Carbonate Reservoir, North Persian Gulf Basin

Tang

Wang

et al. 2021

Geofluids

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“…Obviously, the values of fractal dimension obtained with this method are quite different from the actual results, and cannot truly reflect the pore-throat distribution of carbonate cap rock . Therefore, when calculating the fractal dimension, we carried out a piece regression according to the distribution of data points and the range of pore sizes (Zhang et al, 2018). In this way we not only ensure the data integrity, but also truly reflect the pore distribution.…”

Section: Fractal Dimension Calculationmentioning

confidence: 99%

Impact of pore structure and fractal characteristics on the sealing capacity of Ordovician carbonate cap rock in the Tarim Basin, China

Tang

Gomez‐Rivas

et al. 2019

Marine and Petroleum Geology

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：Evaluating the heterogeneity and sealing capacity of carbonate cap rocks is of great significance for hydrocarbon production. However, the main controls on pore size distribution in carbonate cap rocks are not well constrained. In this contribution we analyze drill core samples of carbonate cap rocks from the Ordovician Yingshan Formation (Tarim Basin) to study their pore properties and investigate the controls of pore-throat structure and fractal dimension on the sealing capacity of the cap rock. Results from petrography and a combination of mercury injection capillary pressure and nitrogen gas adsorption tests reveal that there are four lithological cap rock types, with micrite being the most prevalent one, followed by calcarenite. Six types of pore-throat structures and fractal dimensions (from D 1 to D 6 ) are classified based on the pore size distributions, including macropore-I, macropore-II, mesopore-I, mesopore-II, transitional pore-I and transitional pore-II. The fractal dimensions show that there is a decreasing trend from D 1 to D 6 with decreasing pore-size diameter, suggesting that the macropore and mesopore types present more complex pore-throat structures than the transitional type. The total fractal dimension (D total ) indicates that the pore throat structures are complex and heterogeneous. The sealing heights of the gas column have a positive correlation with cement content in calcarenite and a negative correlation with microfracture density. Mesopore-II and transitional pore types make a significant contribution to enhancing the breakthrough pressure. The fractal variations mainly result from macropores and mesopores, while transitional pores and micropores weaken the impact of the whole pore system on the D total value. The heterogeneity and anisotropy of macropores is the main control on the sealing capacity of the cap rock. The increasing of D 1 considerably contributes to the pore shape heterogeneity and enhances the capillary resistance force to hydrocarbon migration. Therefore, the fractal dimension is an effective approach for investigating the pore throat structure and sealing capacity of carbonate cap rocks.

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Pore structure of tight sandstones with differing permeability: The He 8 Member of the Middle Permian Lower Shihezi Formation, Gaoqiao area, Ordos Basin

Chen,

Zhu,

Wang

et al. 2023

Energy Science & Engineering

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Tight sandstone has strong pore heterogeneity and complex pore structure, and the pore structure of tight sandstone varies with different permeability. To study the differences in the pore structure of tight sandstone with different permeability, this study investigated the tight sandstone of the He 8 Member in the Gaoqiao area of the Ordos Basin. Factors influencing pore formation are analyzed through experiments utilizing methods, such as distinguishing casting thin sections, scanning electron microscopy, high‐pressure mercury intrusion, and low‐temperature nitrogen adsorption. The results indicate that in this area, the pores of the tight sandstone are primarily dissolution and intercrystalline pores, with occasional intergranular pores and microcracks. Type Ⅱ samples (permeability > 0.2 × 10−3 μm2) are primarily composed of dissolution and intercrystalline pores, with a few visible intergranular and microcracks. In contrast, Type Ⅰ samples (permeability < 0.2 × 10−3 μm2) mainly consist of micropores and intercrystalline pores, where microcracks are observed locally. Pore size research demonstrates that Type Ⅰ samples have pore size under 1000 nm, with peaks primarily at 4–5 nm. There are also peaks between 10–1000 nm, but without a consistent pattern. For Type Ⅱ samples with sizes smaller than 1000 nm, pore distribution is evident. Peak values when the pore size exceeds 1000 nm. Type Ⅰ samples have fewer micron‐level pores, while Type Ⅱ samples are primarily dissolution pores. The nanopores of Type Ⅰ samples consist of flat pores with good connectivity, whereas those of Type Ⅱ samples are mainly blind pores with poor connectivity. Type Ⅰ samples have larger pore fractal dimensions, more intricate pore morphology, and rougher and irregular pore throat surfaces compared to Type II samples. Hence, the sedimentary environment, diagenesis, and mineral composition affect the pore distribution in tight sandstone. The research findings highlight the variations in the pore structure of tight sandstone with varying permeability, providing crucial guidance for classifying and assessing pore structure in tight sandstone reservoirs.

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Pore structure and fractal analysis of Lower Carboniferous carbonate reservoirs in the Marsel area, Chu-Sarysu basin

Cited by 43 publications

References 91 publications

Pore Structure Characteristics and Permeability Prediction Model in a Cretaceous Carbonate Reservoir, North Persian Gulf Basin

Pore Structure Characteristics and Permeability Prediction Model in a Cretaceous Carbonate Reservoir, North Persian Gulf Basin

Impact of pore structure and fractal characteristics on the sealing capacity of Ordovician carbonate cap rock in the Tarim Basin, China

Pore structure of tight sandstones with differing permeability: The He 8 Member of the Middle Permian Lower Shihezi Formation, Gaoqiao area, Ordos Basin

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