Sedimentary characteristics of the Lower Cambrian Niutitang shale in the southeast margin of Sichuan Basin, China

Liu, Jun; Yao, Yanbin; Elsworth, Derek; Pan, Zhejun; Sun, Xiaoxiao; Ao, Weihua

doi:10.1016/j.jngse.2016.03.085

Cited by 42 publications

(28 citation statements)

References 26 publications

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“…The sedimentary environment provided conditions for preservation of organic matter (Liu et al, ); what's more, the widespread black shale distributed in the stable environment. Based on a comprehensive evaluation of the factors discussed above, the south‐east part of the study area is most favourable for shale gas exploration.…”

Section: Discussionmentioning

confidence: 99%

Shale reservoir characterization and control factors on gas accumulation of the Lower Cambrian Niutitang shale, Sichuan Basin, South China

Liang

Jiang

et al. 2018

Geological Journal

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The Lower Cambrian Niutitang shale is reported to be the oldest strata for large‐scale shale gas reserves. Based on outcrop observations and laboratory analyses, this study used a comprehensive approach that integrated sedimentology, mineralogy, petrology, organic geochemistry, and reservoir geology to estimate the prospects for exploring for shale gas in the Lower Cambrian Niutitang Formation, southern China. Whole rock and clay mineral X‐ray diffraction, scanning electron microscope (SEM) observations, and petro‐physical property measurements indicate that the Niutitang shale is dominated by quartz and clay minerals with minor amounts of plagioclase, potassium feldspar, calcite, dolomite, and pyrite. The organic matter in the Niutitang shale is dominated by type‐1 kerogen, with TOC levels ranging from 1.35% to 14.3% (average 4.46%) and Ro values ranging from 1.86% to 4.18% (average 2.79%). The three primary types of pores in the shale are organic pores, microfractures, and micropores. The micropores are primarily found in the clay mineral crystals and pyrite, and the microfractures are found along the boundaries of quartz grains. Most of the pore diameters are less than 20 nm, mainly concentrate at about 10 nm, which is consistent with that the organic pores act as the main storage space. The pore volume and gas content are strongly controlled by the mineral composition and lithofacies, and TOC content. The factors favouring shale gas accumulation of the Niutitang shale in the study area include (1) an effective thickness and widespread distribution, (2) a high organic carbon content and appropriate organic matter maturity, and (3) a favourable depositional environment.

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Section: Discussionmentioning

confidence: 99%

Shale reservoir characterization and control factors on gas accumulation of the Lower Cambrian Niutitang shale, Sichuan Basin, South China

Liang

Jiang

et al. 2018

Geological Journal

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“…The Upper Yangtze changed into a deep muddy shelf system in the early Cambrian from a carbonate platform in late Neoproterozoic as a result of large-scale transgression, which could be divided, from west to east, into six sedimentary facies: (1) platform, (2) extension zone, (3) shallow shelf, (4) deep shelf, (5) slope, (6) deep basin (Zhu et al 2003;Liu et al 2013Liu et al , 2016aLiu et al , b, 2017a (Fig. 1a).…”

Section: Geological Settingmentioning

confidence: 99%

Controls on the organic carbon content of the lower Cambrian black shale in the southeastern margin of Upper Yangtze

Zhang

Jiang

et al. 2018

Pet. Sci.

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Control of various factors, including mineral components, primary productivity and redox level, on the total organic carbon (TOC) in the lower Cambrian black shale from southeastern margin of Upper Yangtze (Taozichong, Longbizui and Yanbei areas) is discussed in detail in this article. Mineral components in the study strata are dominated by quartz and clay minerals. Quartz in the Niutitang Formation is mainly of biogenic origin, and the content is in positive correlation with TOC, while the content of clay minerals is negatively correlated with TOC. Primary productivity, represented by the content of Mo bio (biogenic molybdenum), Ba bio (biogenic barium) and phosphorus, is positively correlated with TOC. The main alkanes in studied samples are nC 18-nC 25 , and odd-even priority values are closed to 1 (0.73-1.13), which suggest the organic matter source was marine plankton. Element content ratios of U/Th and Ni/Co and compound ratio Pr/Ph indicate dysoxic-anoxic bottom water, with weak positive relative with TOC. In total, three main points can be drawn to explain the relationship between data and the factors affecting organic accumulation: (1) quartz-rich and clay-mineral-poor deep shelf-slope-basin environment was favorable for living organisms; (2) high productivity provided the material foundation for organic generation; (3) the redox conditions impact slightly on the content of organic matter under high productivity and dysoxic-anoxic condition.

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“…The thickness of the UOW varies from 3 m to 10 m [22]. The LCN, located at the bottom of the Cambrian strata, possesses a maximum burial depth of 5500 m and a thickness of approximately 20-120 m [10]. The sedimentary center of the LSL and UOW is located in the northern study region, while that of the LCN lies in the south of the study area [9,10].…”

Section: Geological Settingmentioning

confidence: 99%

“…The LCN, located at the bottom of the Cambrian strata, possesses a maximum burial depth of 5500 m and a thickness of approximately 20-120 m [10]. The sedimentary center of the LSL and UOW is located in the northern study region, while that of the LCN lies in the south of the study area [9,10]. Therefore, the LSL and UOW are thicker in the central and northern study region than in the southern study region, whereas the LCN is thicker in the southern study region (Figure 1).…”

Section: Geological Settingmentioning

confidence: 99%

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Comparison of Three Key Marine Shale Reservoirs in the Southeastern Margin of the Sichuan Basin, SW China

et al. 2017

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This study performs a comprehensive comparison of three key marine shale reservoirs in the southeastern margin of the Sichuan Basin, and explains why commercial gas production was only achieved in the Lower Silurian Longmaxi (LSL) and Upper Ordovician Wufeng (UOW) formations, but not in the Lower Cambrian Niutitang (LCN) formation. The experimental methods included in situ gas content and gas composition tests, methane adsorption analysis, low-pressure N 2 adsorption, field emission scanning electron microscopy (FE-SEM), and total organic carbon (TOC) and vitrinite reflectance (R o ) analyses to evaluate the lithology, mineralogy, physical properties of the reservoir, organic geochemistry, in situ gas content and methane adsorption capacity characteristics of the three shales. The LCN shale has lower quartz and clay mineral contents and a low brittleness index, but higher contents of feldspar, pyrite and carbonate minerals than the LSL and UOW shales. The porosity and permeability of the LSL and UOW shales are higher than those of the LCN shale. The primary contributions to the high permeability in the LSL shale are its well-developed fractures and organic matter pores. In contrast, the over-mature LCN shale is unfavorable for the development of organic pores and fractures. Although the LCN shale has a higher methane sorption capacity than the LSL and UOW shales, the gas content and methane saturation of the LCN shale are distinctly lower than those of the LSL and UOW shales. This is primarily due to gas migration from the LCN shale, resulting from the activities of tectonic uplift and the unconformable contact between the LCN shale and the Dengying formation. When compared with gas shale in North America, the LSL shale is the most favorable shale reservoir out of the three Sichuan shales, while the combination of the LSL and UOW shales is also potentially productive. However, the individual single layer production of the UOW or LCN shales is still limited due to poor resource potential and/or reservoir physical characteristics in the study area.

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Sedimentary characteristics of the Lower Cambrian Niutitang shale in the southeast margin of Sichuan Basin, China

Cited by 42 publications

References 26 publications

Shale reservoir characterization and control factors on gas accumulation of the Lower Cambrian Niutitang shale, Sichuan Basin, South China

Shale reservoir characterization and control factors on gas accumulation of the Lower Cambrian Niutitang shale, Sichuan Basin, South China

Controls on the organic carbon content of the lower Cambrian black shale in the southeastern margin of Upper Yangtze

Comparison of Three Key Marine Shale Reservoirs in the Southeastern Margin of the Sichuan Basin, SW China

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