Mineral types and organic matters of the Ordovician-Silurian Wufeng and Longmaxi Shale in the Sichuan Basin, China: Implications for pore systems, diagenetic pathways, and reservoir quality in fine-grained sedimentary rocks

Zhao, Jianhua; Jin, Zhijun; Jin, Zhenkui; Hu, Qinhong; Hu, Zhao; Du, Wei; Yan, Caina; Geng, Yuansheng

doi:10.1016/j.marpetgeo.2017.06.031

Cited by 118 publications

(67 citation statements)

References 90 publications

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“…According to previous studies, clay minerals usually have pores with diameter larger than OMs, ranging from mesopores and macropores (Chalmers and Bustin, 2008). In the Permian shales, the specific surface area shows a negative trend with clay content (Fig.15a), and the Hg-porosity has no relationship with clay content (Fig.15b), indicating that clay mineral is not conducive to shale porosity development and may inhibit the development of porosity in shales (Zhao et al, 2017b). Ye et al (2017) pointed that clay content has a relatively negative effect on pore structure in Niutitang Formation shales in the Southern Yangtze region, China, especially showing better negative correlation with micropores and mesopores than macropores, illustrating that clay is especially unfavorable to the development of micropores and fine mesopores.…”

Section: Effect Of Mineral Compositions On Pore Structurementioning

confidence: 69%

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Characteristics and controlling factors of pore structure of the Permian shale in southern Anhui province, East China

Cao

Deng

Song

et al. 2018

Journal of Natural Gas Science and Engineering

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The Permian shale reservoir in southern Anhui province, East China is regarded as a promising target for shale gas exploration. In order to investigate the characteristics of shale pore structures and their controlling factors, total organic carbon (TOC), Rock-eval, organic petrology, X-ray diffraction (XRD), scanning electron microscopy (SEM), field emission scanning electron microscopy (FE-SEM), nitrogen gas adsorption (N 2 GA), mercury intrusion porosimetry (MIP) and helium pycnometry were conducted on the Permian shales collected from two shale gas parameter wells. The results indicate that the BET surface areas determined by N 2 GA method vary between 1.05 and 49.25 m 2 /g. The porosities derived from MIP and helium pycnometry tests are in the range of 0.68%-8.9% and 1.15%-9.79%, respectively. FE-SEM reveals that organic matter (OM) pores and cracks are well developed in the Permian shales, though some OM grains contain few pores, which might be related to the maceral composition. At a high maturity stage, vitrinite do not develop secondary OM pores, and sapropelinite generally develop abundant OM (H. Luo).the shales of the Gufeng and Dalong Formations display a higher TOC content and a better physical property than the Longtan Formation shales and appear to be superior prospective shale gas exploration potential.

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Section: Effect Of Mineral Compositions On Pore Structurementioning

confidence: 69%

“…Lower Silurian shale in Middle Yangtze region and Sichuan Basin Zhao et al, 2017b). Therefore, the Permian shales have a good physical property compared with marine shale reservoirs in China.…”

Section: Comparison Of Physical Property Between Permian Intervalsmentioning

confidence: 99%

Characteristics and controlling factors of pore structure of the Permian shale in southern Anhui province, East China

Cao

Deng

Song

et al. 2018

Journal of Natural Gas Science and Engineering

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“…The lithology of the Longmaxi Formation is dominated by carbonaceous shale, siliceous shale, clay shale, and silty shale 31 . The shale is rich in graptolites, and a few radiolarians and spicules also appear 32 . The lower section of the Longmaxi Formation formed in a deep shelf with a slow deposition rate, anoxic environment, and high OM content 33 .…”

Section: Introductionmentioning

confidence: 99%

Characteristics, capability, and origin of shale gas desorption of the Longmaxi Formation in the southeastern Sichuan Basin, China

Tang

Jiang

et al. 2019

Sci Rep

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Shale gas desorption and loss is a serious and common phenomenon in the Sichuan Basin. The characteristics, capability, and origin of shale gas desorption are significant for understanding the shale gas reservoir accumulation mechanism and guiding shale gas exploration. The shale gas of the Longmaxi Formation in the southeastern Sichuan Basin was studied based on a shale gas desorption simulation experiment, combined with mineral composition, total organic carbon, specific surface area, isothermal adsorption, and scanning electron microscope (SEM) data. Here, the shale gas desorption capability was quantitatively evaluated, and its controlling factors are discussed. The results show that the shale gas desorption process within the Longmaxi Formation varies significantly. The total time of the desorption process varies from 600 min to 4400 min, and it mainly occurs by the 98 °C desorption stage. The desorption capability of the lower Formation is markedly weaker than that of the upper Formation, and it is mainly determined by the shale properties. Organic matter (OM) is the most important controlling factor. As the OM content increases, the specific surface area, methane adsorption capacity, and OM pores increase, leading to a rapid decrease in shale gas desorption capability. In addition, feldspar exhibits a positive correlation with shale gas desorption capability due to its large pores but low specific surface area.

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“…The authigenic quartz moldic pores were the most common type of pores observed on the graptolite periderm in this study. In previous related studies, Wang et al (2014) and Zhao et al (2017) considered that the majority of the quartz in the WF-LMX Fm shale was biogenic in origin, and may have originated from biogenic silica dissolution and recrystallization. During the Lower Paleozoic period, the planktonic shells were usually siliceous, and the microcrystalline quartz in the shale may have evolved from various plankton debris during diagenesis processes.…”

Section: Contribution Of the Graptolites To The Shale Gas Reservoirsmentioning

confidence: 99%

Graptolite‐Derived Organic Matter and Pore Characteristics in the Wufeng‐Longmaxi Black Shale of the Sichuan Basin and its Periphery

Zhou

Sun

et al. 2019

Acta Geologica Sinica (Eng)

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A key target of shale gas exploration and production in China is the organic‐rich black shale of the Wufeng Formation‐Longmaxi Formation in the Sichuan Basin and its periphery. The set of black shale contains abundant graptolites, which are mainly preserved as flattened rhabdosomes with carbonized periderms, is an important organic component of the shale. However, few previous studies had focused on the organic matter (OM) which is derived from graptolite and its pore structure. In particular, the contributions of graptolites to gas generation, storage, and flow have not yet been examined. In this study, focused ion beam‐scanning electron microscope (FIB‐SEM) was used to investigate the characteristics of the graptolite‐derived OM and the micro‐nanopores of graptolite periderms. The results suggested that the proportion of OM in the graptolite was between 19.7% and 30.2%, and between 8.9% and 14.4% in the surrounding rock. The total organic carbon (TOC) content of the graptolite was found to be higher than that of the surrounding rock, which indicated that the graptolite played a significant role in the dispersed organic matter. Four types of pores were developed in the graptolite periderm, including organic gas pores, pyrite moulage pores, authigenic quartz moldic pores, and microfractures. These well‐developed micro‐nano pores and fractures had formed an interconnected system within the graptolites which provided storage spaces for shale gas. The stacked layers and large accumulation of graptolites resulted in lamellation fractures openning easily, and provided effective pathways for the gas flow. A few nanoscale gas pores were observed in the graptolite‐derived OM, with surface porosity lie in 1.5%–2.4%, and pore diameters of 5–20 nm. The sapropel detritus was determined to be rich in nanometer‐sized pores with surface porosity of 3.1%–6.2%, and pore diameters of 20–80 nm. Due to the small amount of hydrocarbon generation of the graptolite, supporting the overlying pressure was difficult, which caused the pores to become compacted or collapsed.

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Mineral types and organic matters of the Ordovician-Silurian Wufeng and Longmaxi Shale in the Sichuan Basin, China: Implications for pore systems, diagenetic pathways, and reservoir quality in fine-grained sedimentary rocks

Cited by 118 publications

References 90 publications

Characteristics and controlling factors of pore structure of the Permian shale in southern Anhui province, East China

Characteristics and controlling factors of pore structure of the Permian shale in southern Anhui province, East China

Characteristics, capability, and origin of shale gas desorption of the Longmaxi Formation in the southeastern Sichuan Basin, China

Graptolite‐Derived Organic Matter and Pore Characteristics in the Wufeng‐Longmaxi Black Shale of the Sichuan Basin and its Periphery

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