Geological characteristics and development potential of transitional shale gas in the east margin of the Ordos Basin, NW China

Kuang, Lichun; Dong, Dazhong; He, Wen; Wen, Shengjun; Sun, Shasha; Li, Shuxin; Qiu, Zhen; Li, Xinwei; Li, Yong; Wu, Jin; Zhang, Leifu; Shi, Zhensheng; Wen, Guo Chun; Zhang, Surong

doi:10.1016/s1876-3804(20)60066-0

Cited by 91 publications

(87 citation statements)

References 25 publications

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“…Obvious capillary condensation on the adsorption branch occurs at a pressure nearby 0.8 with no adsorption saturation, indicating that there are parallel plate pores with four edges open. Yet sudden evaporation takes place on the desorption branch at the relative pressure of 0.5, implying that there are thin bottleneck pores or ink bottle pores [35].…”

Section: 2mentioning

confidence: 99%

“…Compared with marine shale, less attention has been paid to marine-continental transitional shale, which is mostly found in delta facies where rapid microfacies changes have caused the marine-continental transitional shale to be thinner and less continuous, making it more difficult to be developed [33,34]. However, the transitional shale gas resources are large, about 19:8 × 10 12 m 3 [35], and marine-continental transitional shale will be the future research highlight for shale gas exploration and development in China. The establishment of a complete set of the marine-continental transitional shale gas theory will fill the gap of the unconventional oil and gas theory.…”

Section: Introductionmentioning

confidence: 99%

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A Comparative Study of the Micropore Structure between the Transitional and Marine Shales in China

Jiao

Zhou

et al. 2021

Geofluids

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To compare the micropore structure of marine-continental transitional shale with marine shale, organic geochemical, field emission scanning electron microscopy, and low-temperature nitrogen adsorption experiments were conducted on shale samples from the Shanxi Formation in the eastern Ordos Basin and the Longmaxi Formation in the southern Sichuan Basin. The results show that Shanxi Formation shale has a smaller specific surface area and pore volume than Longmaxi Formation shale; therefore, the transitional shales fail to provide sufficient pore spaces for the effective storage and preservation of natural gas. Both the transitional and marine shales are in an overmature stage with high total organic carbon content, but they differ considerably in pore types and development degrees. Inorganic pores and fractures are dominantly developed in transitional shales, such as intragranular pores and clay mineral interlayer fractures, while organic nanopores are rarely developed. In contrast, organic pores are the dominant pore type in the marine shales and inorganic pores are rarely observed. The fractal analysis also shows that pore structure complexity and heterogeneity are quite different. These differences were related to different organic types, i.e., type I of marine shale and type III of transitional shale. Marine Longmaxi shale has experienced liquid hydrocarbon cracking, gas generation, and pore-forming processes, providing good conditions for natural gas to be preserved. However, during the evolution of transitional Shanxi shale, gas cannot be effectively preserved due to the lack of the above evolution processes, leading to the poor gas-bearing property. The detailed comparison of the micropore structure between the transitional and marine shales is of great importance for the future exploitation of marine-continental transitional shale gas in China.

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Section: 2mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A Comparative Study of the Micropore Structure between the Transitional and Marine Shales in China

Jiao

Zhou

et al. 2021

Geofluids

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“…In the current investigation, the above-mentioned data were combined, and it was determined that the minimum TOC value of the Shanxi Formation and Taiyuan Formation was 0.17%; maximum TOC value was 10.62%; and the majority ranged between 1.0 and 2.5%. In addition, it was observed that when compared with the Ordos Basin, the study area of the Shanxi Formation was found to have better potential than the Ordos Basin, and the organic matter development of Taiyuan Formation was like that of the Ordos Basin (Xue et al, 2019;Kuang et al, 2020;Zhai et al, 2020). On the plains, the Yutai Sag and the first line of the Shanxian coalfield displayed a distribution trend of "high in the middle and low on both sides," as detailed in Figure 5B.…”

Section: Organic Carbon Contentmentioning

confidence: 99%

“…The Brittleness Index Ⅱ represented the fracturing ability of the shale (Zhang et al, 2015; Brittleness Index Ⅱ (quartz + feldspar + calcite + dolomite)/(quartz + feldspar + calcite + dolomite + clay minerals) × 100%). It was found that the Taiyuan Formation was rich in brittle minerals with a higher fraction of brittleness index (Brittleness Index Ⅱ was 14.22-81.73, with an average of 51.61), which was slightly better than that of the Ordos Basin (Xue et al, 2019;Kuang et al, 2020;Zhai et al, 2020). Therefore, it was considered to have conditions which would be suitable for future industrial development.…”

Section: Characteristics Of Shale Gas Reservoirs Petrology Characteristics and Mineral Content Levelsmentioning

confidence: 99%

“…The single well of the Shanxi Formation has attained stable gas production, highly controlled reserves, and good formation recoverability and fracturing ability. It is expected that a breakthrough will soon be made in the eastern margin of the basin and large-scaled production will be achieved (Kuang et al, 2020). According to the national shale gas survey and evaluation carried out by the Ministry of Land and Resources in 2012, it is believed that massive thick shale gas reservoirs have developed in the Carboniferous Permian of the southern section of northern China and other North China regions (2012).…”

Section: Introductionmentioning

confidence: 99%

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Shale Gas Exploration Potential in Southwestern Shandong Province of Eastern China

Huang

Shao

et al. 2021

Front. Earth Sci.

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The shale layers of the Permian Shanxi Formation and Taiyuan Formation in the southwestern part of Shandong Province are marine-continental transitional sedimentary facies. When compared with the Ordos Basin, which was a typical breakthrough in marine-continental transitional shale gas exploration, the geological characteristics, exploration, and development prospects of marine-continental transitional shale gas in the southwestern section of Shandong Province are more defined. The shale gas deposits of the Shanxi and Taiyuan Formations in southwestern Shandong Province have the following geological characteristics. The sedimentary environments of Shanxi and Taiyuan Formations are considered to be stable and characterized with widely distributed organic-rich shale, which can be used as composite evaluation layers. The total thickness of the shale range is between 140 and 350 m, with an average of 230 m. The main types of organic matter in the Shanxi Formation are Type Ⅲ and Type Ⅱ2 kerogen, while the main types of organic matter in the Taiyuan Formation are rock types. The abundance and maturity of the organic matter are high, and the gas generating capacity is strong. The reservoir rock mineral composition is complex in the region. The clay mineral content is relatively high and the brittle mineral content is rich. Also, the shale fracturing ability is good. The region has the characteristics of a low porosity and low permeability reservoir, with relatively good reservoir capacity. Three primary points of interest have stably been developed within the region, which are located in the upper high water level system, near the initial flood surface, and the majority of flood surface, including a transgressive system tract and high level system tract. The total gas content is estimated to range between 0.03 and 4.47 m3/t, with an average of 0.30 m3/t. The shale gas resources are rich, including one favorable Class I location with an area of 819.06 km2 and a resource amount of 985.84 × 108 m3; four favorable Class Ⅱ locations with an area of 1,979.68 km2 and a resource amount of 2,278.14 × 108 m3; and five prospective locations with an area of 8,385.52 km2 and a resource amount of 7,299.48 × 108 m3. Therefore, the region was considered to have major exploration potential.

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Pore structure and fractal characteristics of transitional shales with different lithofacies from the eastern margin of the Ordos Basin

Wang,

Deng,

et al. 2023

Energy Science & Engineering

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To better characterize the heterogeneity of transitional shale pore structure and understand its impact on shale gas enrichment, fine characterization of the pore structure of different shale lithofacies was performed by field‐emission scanning electron microscopy, high‐pressure mercury injection, low‐temperature N2 adsorption, and low‐pressure CO2 adsorption. Fractal theory was used to obtain the fractal dimension of the shale pores at different scales and reveal the relationships among the pore structural characteristics, mineral composition, total organic carbon content, and fractal dimension of the shale and their geological significance. The results showed that organic pores, intergranular pores, intragranular pores, and microcracks were generally developed in the transitional shale samples from the study area; elliptic or irregular organic pores were mainly developed in the argillaceous shale lithofacies and siliceous shale lithofacies, and wedge‐shaped or irregular intragranular pores were mainly developed in the calcareous shale lithofacies. The pore size distribution showed a multipeak pattern, and mesopores were the main contributors to the total pore volume (PV), while micropores and macropores contributed little to the total PV. The PV and specific surface area of the siliceous shale were lower than those of the argillaceous shale but higher than those of the calcareous shale, indicating that the change in lithofacies had a significant effect on the shale pores. The common influence of clay minerals, quartz content, and total organic carbon content results in strong heterogeneity and complex pore structure characteristics of shale reservoirs. The pores in the transitional shale from the study area had obvious multiscale fractal characteristics, and the fractal dimension characteristics of different lithofacies and pores at different scales were different, which reflected that the pore structure of the shale had strong heterogeneity. The heterogeneity of the shale pores mainly originated from the macropores and mesopores, while the heterogeneity of micropores was relatively low. The heterogeneity of the pore development and structure at different scales was controlled by the mineral composition matter and organic matter abundance to varying degrees.

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Geological characteristics and development potential of transitional shale gas in the east margin of the Ordos Basin, NW China

Cited by 91 publications

References 25 publications

A Comparative Study of the Micropore Structure between the Transitional and Marine Shales in China

A Comparative Study of the Micropore Structure between the Transitional and Marine Shales in China

Shale Gas Exploration Potential in Southwestern Shandong Province of Eastern China

Pore structure and fractal characteristics of transitional shales with different lithofacies from the eastern margin of the Ordos Basin

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