Pore structure and its fractal dimensions of transitional shale: A cross-section from east margin of the Ordos Basin, China

Li, Yong; Wang, Zhuangsen; Pan, Zhejun; Niu, Xinlei; Yu, Yun; Meng, Shangzhi

doi:10.1016/j.fuel.2018.12.066

Cited by 226 publications

(210 citation statements)

References 54 publications

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“…Fractal characteristics research based on FHH model and N 2 adsorption experiment data are commonly applied to quantitatively characterize the shale pore structure [12,39,43].…”

Section: Introductionmentioning

confidence: 99%

Full-Scale Pore Structure and Fractal Dimension of the Longmaxi Shale from the Southern Sichuan Basin: Investigations Using FE-SEM, Gas Adsorption and Mercury Intrusion Porosimetry

et al. 2019

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Pore structure determines the gas occurrence and storage properties of gas shale and is a vital element for reservoir evaluation and shale gas resources assessment. Field emission scanning electron microscopy (FE‐SEM), high‐pressure mercury intrusion porosimetry (HMIP), and low‐pressure N2/CO2 adsorption were used to qualitatively and quantitatively characterize full‐scale pore structure of Longmaxi (LM) shale from the southern Sichuan Basin. Fractal dimension and its controlling factors were also discussed in our study. Longmaxi shale mainly developed organic matter (OM) pores, interparticle pores, intraparticle pores, and microfracture, of which the OM pores dominated the pore system. The pore diameters are mainly distributed in the ranges of 0.4–0.7 nm, 2–20 nm and 40–200 μm. Micro‐, meso‐ and macropores contribute 24%, 57% and 19% of the total pore volume (PV), respectively, and 64.5%, 34.6%, and 0.9% of the total specific surface area (SSA). Organic matter and clay minerals have a positive contribution to pore development. While high brittle mineral content can inhibit shale pore development. The fractal dimensions D1 and D2 which represents the roughness of the shale surface and irregularity of the space structure, respectively, are calculated based on N2 desorption data. The value of D1 is in the range of 2.6480–2.7334 (average of 2.6857), D2 is in the range of 2.8924–2.9439 (average of 2.9229), which indicates that Longmaxi shales have a rather irregular pore morphology as well as complex pore structure. Both PV and SSA positively correlated with fractal dimensions D1 and D2. The fractal dimension D1 decreases with increasing average pore diameter, while D2 is on the contrary. These results suggest that the small pores have a higher roughness surface, while the larger pores have a more complex spatial structure. The fractal dimensions of shale are jointly controlled by OM, clays and brittle minerals. The TOC content is the key factor which has a positive correlation with the fractal dimension. Clay minerals have a negative influence on fractal dimension D1, and positive influence D2, while brittle minerals show an opposite effect compared with clay minerals.

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“…Fractal characteristics research based on FHH model and N 2 adsorption experiment data are commonly applied to quantitatively characterize the shale pore structure [12,39,43].…”

Section: Introductionmentioning

confidence: 99%

Full-Scale Pore Structure and Fractal Dimension of the Longmaxi Shale from the Southern Sichuan Basin: Investigations Using FE-SEM, Gas Adsorption and Mercury Intrusion Porosimetry

et al. 2019

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“…Finally, the clay mineral samples were dried in an oven with a temperature of less than 60°C. Quantitative analysis of 62 samples were conducted with a D/max-2500 FD335203 following the SY/T5163-1995 (Li et al, 2019). To reflect the carbonate content of sandstones more accurately, the selected samples reacted with dilute hydrochloric acid (at a concentration of 10%) after oil removal, crush, and drying.…”

Section: Samples and Methodsmentioning

confidence: 99%

Characteristics of Tight Sandstone Reservoirs and Controls of Reservoir Quality: A Case Study of He 8 Sandstones in the Linxing Area, Eastern Ordos Basin, China

Gao

Wang

et al. 2019

Acta Geologica Sinica (Eng)

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Determining the process of densification and tectonic evolution of tight sandstone can help to understand the distribution of reservoirs and find relatively high‐permeability areas. Based on integrated approaches of thin section, scanning electron microscopy (SEM), cathode luminescence (CL), nuclear magnetic resonance (NMR), X‐ray diffraction (XRD), N2 porosity and permeability, micro‐resistivity imaging log (MIL) and three‐dimensional seismic data analysis, this work discussed the reservoir characteristics of the member 8 of the Permian Xiashihezi Formation (He 8 sandstones) in the Linxing area of eastern Ordos Basin, determined the factors affecting reservoir quality, and revealed the formation mechanism of relatively high‐permeability areas. The results show that the He 8 sandstones in the Linxing area are mainly composed of feldspathic litharenites, and are typical tight sandstones (with porosity <10% and permeability <1 mD accounting for 80.3% of the total samples). Rapid burial is the main reason for reservoir densification, which resulted in 61% loss of the primary porosity. In this process, quartz protected the original porosity by resisting compaction. The cementation (including carbonate, clay mineral and siliceous cementation) further densified the sandstone reservoirs, reducing the primary porosity with an average value of 28%. The calcite formed in the eodiagenesis occupied intergranular pores and affected the formation of the secondary pores by preventing the later fluid intrusion, and the Fe‐calcite formed in the mesodiagenetic stage densified the sandstones further by filling the residual intergranular pores. The clay minerals show negative effects on reservoir quality, however, the chlorite coatings protected the original porosity by preventing the overgrowth of quartz. The dissolution of feldspars provides extensive intergranular pores which constitute the main pore type, and improves the reservoir quality. The tectonic movements play an important role in improving the reservoir quality. The current tectonic traces of the study area are mainly controlled by the Himalayan movement, and the high‐permeability reservoirs are mainly distributed in the anticline areas. Additionally, the improvement degree (by tectonic movements) of reservoir quality is partly controlled by the original composition of the sandstones. Thus, the selection of potential tight gas well locations in the study area should be focused on the anticline areas with relatively good original reservoir quality. And the phenomena can be referenced for other fluvial tight sandstone basins worldwide.

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“…All of the coal samples were collected from the Linxing -Shenfu area, which is located in the north eastern Ordos Basin, and tectonic location of the Linxing-Shenfu area is on the Jinxi flexural fold belt of the eastern Ordos Basin (Fig. 1a, b) (Jiao et al, 2016;Tao et al, 2017;Gao et al, 2018;Li et al, 2019). The No.…”

Section: Sample Collection and Treatmentmentioning

confidence: 99%

Adsorption Mechanism and Kinetic Characterization of Bituminous Coal under High Temperatures and Pressures in the Linxing‐Shenfu Area

Tao

Wang

et al. 2020

Acta Geologica Sinica (Eng)

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The majority of coalbed methane (CBM) in coal reservoirs is in adsorption states in coal matrix pores. To reveal the adsorption behavior of bituminous coal under high‐temperature and high‐pressure conditions and to discuss the microscopic control mechanism affecting the adsorption characteristics, isothermal adsorption experiments under high‐temperature and high‐pressure conditions, low‐temperature liquid nitrogen adsorption‐desorption experiments and CO2 adsorption experiments were performed on coal samples. Results show that the adsorption capacity of coal is comprehensively controlled by the maximum vitrinite reflectance (Ro, max), as well as temperature and pressure conditions. As the vitrinite reflectance increases, the adsorption capacity of coal increases. At low pressures, the pressure has a significant effect on the positive effect of adsorption, but the effect of temperature is relatively weak. As the pressure increases, the effect of temperature on the negative effect of adsorption gradually becomes apparent, and the influence of pressure gradually decreases. Considering pore volumes of pores with diameters of 1.7–100 nm, the peak volume of pores with diameters 10–100 nm is higher than that from pores with diameters 1.7–10 nm, especially for pores with diameters of 40–60 nm, indicating that pores with diameters of 10–100 nm are the main contributors to the pore volume. The pore specific surface area shows multiple peaks, and the peak value appears for pore diameters of 2–3 nm, indicating that this pore diameter is the main contributor to the specific surface area. For pore diameters of 0.489–1.083 nm, the pore size distribution is bimodal, with peak values at 0.56–0.62 nm and 0.82–0.88 nm. The adsorption capability of the coal reservoir depends on the development degree of the supermicroporous specific surface area, because the supermicroporous pores are the main contributors to the specific pore area. Additionally, the adsorption space increases as the adsorption equilibrium pressure increases. Under the same pressure, as the maximum vitrinite reflectance increases, the adsorption space increases. In addition, the cumulative reduction in the surface free energy increases as the maximum vitrinite reflectance increases. Furthermore, as the pressure increases, the surface free energy of each pressure point gradually decreases, indicating that as the pressure increases, it is increasingly difficult to adsorb methane molecules.

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Pore structure and its fractal dimensions of transitional shale: A cross-section from east margin of the Ordos Basin, China

Cited by 226 publications

References 54 publications

Full-Scale Pore Structure and Fractal Dimension of the Longmaxi Shale from the Southern Sichuan Basin: Investigations Using FE-SEM, Gas Adsorption and Mercury Intrusion Porosimetry

Full-Scale Pore Structure and Fractal Dimension of the Longmaxi Shale from the Southern Sichuan Basin: Investigations Using FE-SEM, Gas Adsorption and Mercury Intrusion Porosimetry

Characteristics of Tight Sandstone Reservoirs and Controls of Reservoir Quality: A Case Study of He 8 Sandstones in the Linxing Area, Eastern Ordos Basin, China

Adsorption Mechanism and Kinetic Characterization of Bituminous Coal under High Temperatures and Pressures in the Linxing‐Shenfu Area

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