Synergetic effects of matrix components and diagenetic processes on pore properties in the Lower Cambrian shale in Sichuan Basin, South China

Li, Xin; Jiang, Zhenxue; Jiang, Shu; Wang, Shuai; Miao, Yanying; Wu, Fan; Cao, Xiangni

doi:10.1016/j.jngse.2021.104072

Cited by 16 publications

(14 citation statements)

References 25 publications

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“…Sichuan Basin is a multistage superimposed basin located at the southwest margin of the Upper Yangtze Platform in South China. It is a diamond-shaped basin composed of five tectonic zones, including the northwest district, the central district, the eastern district, the southwest district, and the southern district, with a total area of approximately 18 × 10 4 km 2 , and surrounded by Longmen Mountain, Mixing Mountain, Daba Mountain, and Daliang Mountain, 17 as illustrated in Figure 1a. The study area is situated in the southwest district and the southern district of Sichuan Basin.…”

Section: Geological Settingmentioning

confidence: 99%

“…15,16 Furthermore, the information of various pores and microfractures among lithofacies can be extracted and counted via high-resolution field-emission scanning electron microscopy (FE-SEM) image stitching technology. 17 The 3D images reconstructed by micro/nano-CT and FIB-SEM are an effective method to characterize shale nanopore systems. 17−19 The quantitative characterization methods, including gas adsorption, mercury intrusion capillary pressure, and low-field nuclear magnetic resonance, can reveal the pore size distribution and SSA characteristics ranging from nanometers to millimeters.…”

Section: Introductionmentioning

confidence: 99%

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Study on the Pore Structure and Fractal Characteristics of Different Lithofacies of Wufeng–Longmaxi Formation Shale in Southern Sichuan Basin, China

Qian

Shen

et al. 2022

ACS Omega

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Gas content and flow characteristics are closely related to shale lithofacies, and significant differences exist in the pore structure and fractal characteristics among lithofacies. In this study, X-ray diffractometer (XRD), field-emission scanning electron microscopy (FE-SEM), gas adsorption (N 2 and CO 2 ), and fractal theory were employed to systematically characterize the pore attributes of the marine Wufeng−Longmaxi formation shales. The information of various pores and microfractures among lithofacies was extracted and quantified via high-resolution FE-SEM image stitching technology. Shales were classified into four types based on mineral compositions, and siliceous shales possess the largest SEM-based surface porosity (2.84%) and the largest pore volume (PV) (average 0.0243 cm 3 /g) as well as specific surface area (SSA) (average 28.06 m 2 / g). The effect of lithofacies variation on the PV of shale is minor. In contrast, the lithofacies variation has a significant impact on the SSA, and the SSA of siliceous shale is 39.11% higher than that of argillaceous shale. PV and SSA show strong positive correlation with the total organic carbon (TOC) content but negative correlation with clay minerals. Siliceous shales have the greatest fractal dimension D1 (pore surface roughness) (average 2.6821), which is contributed by abundant organic matter pores with more complicated boundaries. The largest fractal dimension D2 (pore structure complexity) (average 2.8263) is found in mixed shales, which is attributed to well-developed intraparticle (intraP) pores associated with carbonate mineral dissolution. This indicates that siliceous shales have the highest methane adsorption capacity and that shale gas desorption, diffusion, and seepage are more difficult in mixed shales.

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Section: Geological Settingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Study on the Pore Structure and Fractal Characteristics of Different Lithofacies of Wufeng–Longmaxi Formation Shale in Southern Sichuan Basin, China

Qian

Shen

et al. 2022

ACS Omega

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“…According to previous research (Li et al, 1995;Li et al, 2002;Wang and Li, 2003;Zhang et al, 2017;Li et al, 2021), southern China has two plates of primary continental crust, i.e., the Yangtze Plate and Cathaysian Plate in the early Mesoproterozoic, which are in a state of tension during the Lower Cambrian when massive transgression took place.…”

Section: Tectonic Characteristicsmentioning

confidence: 99%

Research on the Occurrence State of Methane Molecules in Postmature Marine shales—A Case Analysis of the Lower Silurian Longmaxi Formation Shales of the Upper Yangtze Region in Southern China

et al. 2022

Self Cite

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The Yangtze region in southern China is endowed with abundant marine shale gas. Methane molecules exist in either adsorption state or free state in postmature marine shales, depending on the components of shales. In this study, the core samples of the selected well in the Lower Silurian Longmaxi Fm. shales from the Sichuan Basin, upper Yangtze region, southern China, were taken as study objects. We carried out TOC content, organic matter maturity, mineral component, and core gas content analyses and isothermal adsorption, FIB-SEM, and FIB-HIM experiments to analyze the occurrence state of methane molecules in postmature marine shales. The conclusions are as follows: most methane molecules exist in the organic matter pores of the postmature marine shales, and only a small amount of them exist in clay mineral pores. The organic matter pores in organic-rich shales are large in number with excellent roundness and are well connected, with large pores covering small ones. Thus, abundant free gas can be stored in the organic matter pores and pore throats, making it possible to densely and continuously adsorb methane molecules with a relatively large adsorption space. The flake-shaped clay minerals have a small number of pores with low roundness. Among the three clay minerals in postmature marine shales of the Longmaxi Fm., the I/S mixed layer offers certain reservoir spaces for adsorbed and free gases and chlorite stores a little adsorbed gas and little free gas, while illite hardly stores the adsorbed gas but contains a little free gas.

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“…The broad valleys between the arc-shaped mountains are Jurassic trapped syncline. The high-angle fault fold belt is ejective from both tectonic and geomorphic aspects (Wang et al, 2018;Wang et al, 2021a;Li et al, 2021b;Wang et al, 2021b).…”

Section: Tectonic Characteristicsmentioning

confidence: 99%

Study on characteristics of oil and gas occurrence and reservoir space of medium-high maturity continental shale—A case study of middle jurassic lianggaoshan formation in fuling block, southeast of sichuan basin, south China

et al. 2022

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Possessed of easy access to development and fair economic benefits, medium-high maturity continental shale oil and gas have become the focus of shale oil and gas study in the future. Shale oil and gas mainly occur in pores, but studies on the pore characteristics of shale oil and gas occurrence are by no means sufficient. Focused on shale from the Middle Jurassic Lianggaoshan Formation in Well TYX, Fuling block, southeast of Sichuan Basin where a breakthrough in shale oil and gas exploration was recently achieved, this study selects core samples and conducts a series of analyses, including vitrinite reflectance analysis, kerogen microscopic examination experiment, total organic carbon (TOC) content analysis, mineral composition analysis, gas content measurement, isothermal adsorption experiment, S1 content analysis, and others. The analyses are to identify the pore characteristics of the continental medium and high maturity shale oil and gas by virtue of scanning electron microscope (SEM) with Ar-ion milling and the image processing software ImageJ. The conclusions are drawn as follows: in terms of lithofacies, medium-high maturity continental shale oil and gas mainly occur in organic-rich clay shale and organic-rich mixed shale; with regard to material composition, shale oil and gas mainly occur in organic matter, illite-smectite mixed layers and illite. Shale adsorbed gas content accounts for at most 40% of the total shale gas content and shale free gas content takes up at least 60% of the total shale gas content. Pores of solid bitumen, solid bitumen-clay mineral complex mass, clay minerals, structured vitrinite, and funginite are mostly developed in shale. Among them, the first three types of pores are the main reservoir space in shale considering their large number, good roundness, medium pore diameter, fairly good roundness of pore edges, and the complex shapes which altogether contribute to the large surface porosity.

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Synergetic effects of matrix components and diagenetic processes on pore properties in the Lower Cambrian shale in Sichuan Basin, South China

Cited by 16 publications

References 25 publications

Study on the Pore Structure and Fractal Characteristics of Different Lithofacies of Wufeng–Longmaxi Formation Shale in Southern Sichuan Basin, China

Study on the Pore Structure and Fractal Characteristics of Different Lithofacies of Wufeng–Longmaxi Formation Shale in Southern Sichuan Basin, China

Research on the Occurrence State of Methane Molecules in Postmature Marine shales—A Case Analysis of the Lower Silurian Longmaxi Formation Shales of the Upper Yangtze Region in Southern China

Study on characteristics of oil and gas occurrence and reservoir space of medium-high maturity continental shale—A case study of middle jurassic lianggaoshan formation in fuling block, southeast of sichuan basin, south China

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