Sedimentology and geochemistry of Carboniferous-Permian marine-continental transitional shales in the eastern Ordos Basin, North China

Zhang, Leifu; Dong, Dazhong; Qiu, Zhen; Wu, Chenjun; Zhang, Qin; Wang, Yuman; Liu, Dexun; Deng, Ze; Zhou, Shangwen; Pan, Songqi

doi:10.1016/j.palaeo.2021.110389

Cited by 49 publications

(59 citation statements)

References 61 publications

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“…The whole-rock mineral composition has been identified by using XRD analysis. -4) in the study area (modified after [46]). 2 Geofluids…”

Section: Methodsmentioning

confidence: 99%

“…Samples of the Shanxi Formation and Taiyuan Formation from the Ordos Basin were analyzed for whole-rock mineral and whole-rock clay fraction composition using the PANa-lytical X'Pert Pro X-ray Diffractometer equipped with a copper X-ray source (Co-Kα radiation, 40 kV, 40 mA). Each sample weighing 5 g was dried for two days in an oven, then [46]). ground to powder form having <200 mesh size with agate mortar and pestle.…”

Section: Methodsmentioning

confidence: 99%

“…A thick sequence of carbonate rocks was deposited in the marine settings from Proterozoic-Lower Paleozoic time [25,43]. The Carboniferous to Permian system is a distinctive marinecontinental transitional system that results in the deposition of interbedded shale, sandstones, coal, and carbonate rocks in the Upper Carboniferous Benxi Formation, the Lower Permian Taiyuan Formation, and the Shanxi Formation in the Ordos Basin [44][45][46] (Figure 2). The well DJ3-4 is located in the southeast part of the Ordos Basin.…”

Section: Geological Backgroundmentioning

confidence: 99%

“…Figure 1: Location map of the study area in the Ordos Basin. The star shows the position of a well (DJ3-4) in the study area (modified after[46]). …”

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confidence: 99%

“…Figure 2: Stratigraphic chart of the study area. The Lower Permian Shanxi and Taiyuan formations are investigated in this study (modified from[46]). …”

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Reservoir Characteristics of the Lower Permian Marine-Continental Transitional Shales: Example from the Shanxi Formation and Taiyuan Formation in the Ordos Basin

et al. 2021

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The pore types and pore structure parameters of the heterogenetic shale will affect the percolation and reservoir properties of shale; therefore, the research on these parameters is very important for shale reservoir evaluation. We used X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), low-pressure CO2 adsorption analysis, mercury injection capillary pressure (MICP), and high-pressure methane adsorption analysis to analyze the characteristics of different pore types and their parameters of the Lower Permian Shanxi Formation and Taiyuan Formation in the Ordos Basin. The influence of different mineral contents on the porosity and pore size is also investigated. The Shanxi Formation (SF) is composed of quartz (average of 38.4%), plagioclase, siderite, Fe-dolomite, calcite, pyrite, and clay minerals (average of 50.1%), while the Taiyuan Formation (TF) is composed of calcite (average of 37%), siderite, Fe-dolomite, quartz, pyrite, and clay minerals (average of 32.3%). The most common types of pores observed in this formation are interparticle pores (InterP pores), intraparticle pores (IntraP pores), interclay pores, intercrystalline pores (InterC pores), organic matter pores (OM pores), and microfractures. CO2 adsorption analysis demonstrates the type I physisorption isotherms, showing microporous solids having comparatively small external surfaces. The similar types of isothermal shapes of the Shanxi Formation (SF) and Taiyuan Formation (TF) suggest that both types have similar pore size distribution (PSD) within the measured pore range by the low-pressure CO2 adsorption experiment. The micropore pore size of the TF is larger than that of the SF. MICP shows the larger pores (>50 nm), and most of the volume was adsorbed by macropores. Methane gas sorption capacity increases with increasing pressure. Clay minerals and quartz played an important role in providing adsorption sites for methane gas. The overall analysis of both formations shows that TF has good reservoir properties than SF.

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“…The whole-rock mineral composition has been identified by using XRD analysis. -4) in the study area (modified after [46]). 2 Geofluids…”

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Geological Backgroundmentioning

confidence: 99%

“…Figure 1: Location map of the study area in the Ordos Basin. The star shows the position of a well (DJ3-4) in the study area (modified after[46]). …”

mentioning

confidence: 99%

“…Figure 2: Stratigraphic chart of the study area. The Lower Permian Shanxi and Taiyuan formations are investigated in this study (modified from[46]). …”

mentioning

confidence: 99%

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