The geochemical and pore characteristics of a typical marine–continental​ transitional gas shale: A case study of the Permian Shanxi Formation on the eastern margin of the Ordos Basin

Qiu, Zhen; Song, Dongjun; Zhang, Leifu; Zhang, Qin; Zhao, Qun; Wang, Yuman; Liu, Hanlin; Liu, Dexun; Li, Shuxin; Li, Xingtao

doi:10.1016/j.egyr.2021.06.056

Cited by 31 publications

(27 citation statements)

References 37 publications

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“… 1 In addition, the difference may be caused by different hydrocarbon generation patterns between type III kerogen and type I/II kerogen developed in shales. 4 , 49 , 50 The development of inorganic nanopores in minerals cannot be ignored. Figure 1 F shows the intercrystalline pores of berry-shaped pyrite under high magnification.…”

Section: Resultsmentioning

confidence: 99%

Nanopore Structure and Origin of Lower Permian Transitional Shale, Eastern Ordos Basin, China

et al. 2022

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Nanopores in the shale play a vital role in methane adsorption, and their structural characteristics and origins are of great significance for revealing the mechanism of methane adsorption, desorption, and diffusion. In this paper, through low-temperature ashing and low-pressure gas adsorption experiments, the nanopore structure of original shales and ashed shales was quantitatively characterized, and the nanopore origins in the transitional shale of lower Permian in eastern Ordos Basin were analyzed. The results show that the pore volume (PV) and specific surface area (SSA) of nanopores in transitional shale reservoirs are 0.0217–0.0449 cm 3 /g and 13.91–51.20 m 2 /g, respectively. The average contribution rates of micropores (<2 nm), mesopores (2–50 nm), and macropores (50–100 nm) to PV are 18.78, 72.26, and 8.96%, respectively, and the average contribution rates to SSA are 66.19, 33.10, and 0.71%, respectively. In addition, it is found that the average contribution rates of inorganic minerals and organic matter to the SSA of micropores are 55.9 and 44.1%, respectively, and the average contribution rates to the SSA of mesopores are 92.3 and 7.7%, respectively. Combining the adsorption properties of the main clay minerals and kerogen in shale, it is concluded that organic pores control the adsorption of methane with an absolute advantage in transitional shales. It is of great significance to understand the mechanism of methane occurrence, desorption, and diffusion in shales by clarifying the origins of multiscale pores.

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Section: Resultsmentioning

confidence: 99%

Nanopore Structure and Origin of Lower Permian Transitional Shale, Eastern Ordos Basin, China

et al. 2022

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“…Sichuan Basin is a key target area for shale gas exploration and development in China. The marine shale of the Wufeng-Longmaxi Formation has the characteristics of a high TOC value, large thickness, high maturity, good brittleness, and high gas content and is the preferred horizon for shale gas exploration and development (Jin et al, 2018;Fan et al, 2020aFan et al, , 2020bMa et al, 2021;Qiu et al, 2021). Currently, three national shale gas demonstration areas, Fuling, Weiyuan-Changning, and Zhaotong, have been built for the shale gas of the Wufeng-Longmaxi Formation in the Sichuan Basin.…”

Section: Introductionmentioning

confidence: 99%

Pore structure and fractal characteristics of the marine shale of the longmaxi formation in the changning area, Southern Sichuan Basin, China

Jiling²,

Mou

et al. 2022

Front. Earth Sci.

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The pore structure is an important factor affecting reservoir capacity and shale gas production. The shale reservoir of the Longmaxi Formation in the Changning area, Southern Sichuan Basin, is highly heterogeneous and has a complex pore structure. To quantitatively characterize the shale’s pore structure and influencing factors, based on whole rock X-ray diffraction, argon ion polishing electron microscopy observations, and low-temperature nitrogen adsorption-desorption experiments, the characteristics of the shale pore structure are studied by using the Frenkel-Halsey-Hill (FHH) model. The research reveals the following: 1) The pores of the Longmaxi Formation shale mainly include organic pores, intergranular pores, dissolution pores and microfractures. The pore size is mainly micro-mesoporous. Both ink bottle-type pores and semiclosed slit-type pores with good openness exist, but mainly ink bottle-type pores are observed. 2) The pore structure of the Longmaxi Formation shale has self-similarity, conforms to the fractal law, and shows double fractal characteristics. Taking the relative pressure of 0.45 (P/P0 = 0.45) as the boundary, the surface fractal dimension Dsf and the structural fractal dimension Dst are defined. Dsf is between 2.3215 and 2.6117, and the structural fractal dimension Dst is between 2.8424 and 2.9016. The pore structure of micropores and mesopores is more complex. 3) The mineral components and organic matter have obvious control over the fractal dimension of shale, and samples from different wells show certain differences. The fractal dimension has a good positive correlation with the quartz content but an obvious negative correlation with clay minerals. The higher the total organic carbon content is, the higher the degree of thermal evolution, the more complex the pore structure of shale, and the larger the fractal dimension. The results have guiding significance for the characterization of pore structure of tight rocks.

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“…The shale gas exploration in China started relatively late, but significant achievements had been made, such as the daily production of marine shales of Wufeng–Longmaxi in the Sichuan Basin can reach 3000 × 10 4 m 3 . However, for meeting energy demand, petroleum explorers are seeking the possibility of industrial exploration for non–marine shale petroleum resources. , …”

Section: Introductionmentioning

confidence: 99%

“…10 However, for meeting energy demand, petroleum explorers are seeking the possibility of industrial exploration for non−marine shale petroleum resources. 11,12 Marine−continental transitional shales are mainly deposited in shallow water, such as shallow lake, epicontinental sea, delta, tidal flat, and lagoon environments. 13,14 Marine−continental transitional shales are widely distributed in the world, such as the Triassic Mungaroo shale in the Northern Carnarvon Basin of Australia; Cretaceous Gongila shale of in the Chad Basin of Nigeria; Permian Shanxi to Taiyuan shale in Ordos Basin of China; and the Permian Longtan shale in the Sichuan Basin of China.…”

Section: Introductionmentioning

confidence: 99%

Depositional Environment Variation and Organic Matter Accumulation Mechanism of Marine–Continental Transitional Shale in the Upper Permian Longtan Formation, Sichuan Basin, SW China

Wang

Guo

et al. 2022

ACS Earth Space Chem.

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Marine−continental transitional shale gas exploration is one of the hottest topics in the academic and industrial community. Frequent sedimentary environment changes lead to substantial heterogeneity and complex organic matter enrichment mechanisms, and it is of great practical significance to clarify the paleoenvironment of marine−continental transitional shale and reveal the enrichment mechanism of organic matter for subsequent shale gas exploration. However, strong heterogeneity creates divergence for our understanding of organic matter enrichment mechanisms and resource potential. This paper selected the marine−continental transitional shale of the Permian Longtan Formation in the southeastern Sichuan Basin as an example. Through TOC analysis, XRD measurements, and major and trace element analyses, we identify the depositional cycle and lithofacies, characterize the paleosedimentary environments of different lithofacies, establish depositional models, and clarify the organic matter enrichment mechanism. Four lithofacies can be identified in the Longtan Formation in the study area: organic−lean carbonate shale (LC), organic−lean mixed shale (LM), organic−lean argillaceous shale (LCM), and organic−rich argillaceous shale (RCM). The terrestrial detrital influx of the LCM and RCM shales is obviously strong, while the RCM shale was deposited in a relatively dysoxic and humid environment. For the Longtan shale, the terrestrial detrital influx and redox environment determine the enrichment of organic matter. In the lagoon sediment system, due to the high terrestrial detrital influx, the argillaceous shale in the transitional shale gas system should be given more attention in future exploration. For different kinds of shale gas systems (marine, marine− continental transitional, and lacustrine), the effect of the terrestrial detrital influx is the main difference. In marine−continental and lacustrine shale gas systems, shales with high TOC values can still exist in the context of oxic sedimentary environments. The research results of this paper can provide a theoretical basis for future marine−continental transitional shale gas sweet spot prediction and exploration from geochemical perspectives.

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The geochemical and pore characteristics of a typical marine–continental transitional gas shale: A case study of the Permian Shanxi Formation on the eastern margin of the Ordos Basin

Cited by 31 publications

References 37 publications

Nanopore Structure and Origin of Lower Permian Transitional Shale, Eastern Ordos Basin, China

Nanopore Structure and Origin of Lower Permian Transitional Shale, Eastern Ordos Basin, China

Pore structure and fractal characteristics of the marine shale of the longmaxi formation in the changning area, Southern Sichuan Basin, China

Depositional Environment Variation and Organic Matter Accumulation Mechanism of Marine–Continental Transitional Shale in the Upper Permian Longtan Formation, Sichuan Basin, SW China

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The geochemical and pore characteristics of a typical marine–continental​ transitional gas shale: A case study of the Permian Shanxi Formation on the eastern margin of the Ordos Basin

Cited by 31 publications

References 37 publications

Nanopore Structure and Origin of Lower Permian Transitional Shale, Eastern Ordos Basin, China

Nanopore Structure and Origin of Lower Permian Transitional Shale, Eastern Ordos Basin, China

Pore structure and fractal characteristics of the marine shale of the longmaxi formation in the changning area, Southern Sichuan Basin, China

Depositional Environment Variation and Organic Matter Accumulation Mechanism of Marine–Continental Transitional Shale in the Upper Permian Longtan Formation, Sichuan Basin, SW China

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The geochemical and pore characteristics of a typical marine–continental transitional gas shale: A case study of the Permian Shanxi Formation on the eastern margin of the Ordos Basin