Applying sedimentary geochemical proxies for paleoenvironment interpretation of organic-rich shale deposition in the Sichuan Basin, China

Zhao, Jianhua; Jin, Zhijun; Jin, Zhenkui; Geng, Yuansheng; Wen, Xiangming; Yan, Caina

doi:10.1016/j.coal.2016.06.015

Cited by 158 publications

(90 citation statements)

References 87 publications

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“…Additionally, the Ba bio content of LLA in both the Jiaoshiba and Zhaotong areas was significantly smaller than that of LLB (Table 1). This result is consistent with recent studies on the Longmaxi Formation in the Sichuan Basin (Yan et al, 2015;Li et al, 2015;Zhao et al, 2016). Since it is possible for barite to dissolve in sulfatereducing conditions, leading to Ba loss (van Os et al, 1991;Torres et al, 1996;van Santvoort et al, 1996), the Ba bio content might not completely reflect the paleoproductivity of the Longmaxi Formation shale.…”

Section: Implications For the Paleoenvironment 511 Primary Productisupporting

confidence: 86%

“…JY2, YS12, and W201 are all key exploration wells in the Sichuan Basin and could respectively reflect the geological characteristics of the Longmaxi Formation shale in these areas. The data for JS2 and W201 were provided by Wang et al (2015 and Zhao et al (2016), respectively. The data for YS12 were provided by the current study's experimental analyses and well logs.…”

Section: Samples and Methodsmentioning

confidence: 99%

“…Although the Longmaxi Formation shale is generally considered to have been deposited in an oxygendeprived deep-sea environment, the abundance of organic matter in the Longmaxi Formation shale shows strong vertical and lateral heterogeneity (Zhang et al, 2012;Guo, 2013;Guo and Zhang, 2014;Li et al, 2016). Therefore, numerous studies have been conducted on the mechanism of the organic-matter enrichment in the Longmaxi Formation shale in the Sichuan Basin and its peripheral areas Wang et al, 2015;Yan et al, 2015;Zhao et al, 2016;Wu et al, 2017;Zhang et al, 2018). These studies have generally suggested that the lower part of the shale, characterized by high organic-matter abundance, was deposited in an anoxic or dysoxic environment, while the upper shale, characterized by low organic-matter content, was deposited in an oxic environment.…”

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confidence: 99%

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Geochemistry, Paleoenvironment and Mechanism of Organic‐Matter Enrichment in the Lower Silurian Longmaxi Formation Shale in the Sichuan Basin, China

Chen

Cui

Ren

et al. 2019

Acta Geologica Sinica (Eng)

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To investigate the mechanism of the organic‐matter enrichment in the Lower Longmaxi Formation shale, the geochemistry and total organic carbon (TOC) of the Longmaxi Formation black shales in the Jiaoshiba, Zhaotong, and Weiyuan areas of the Sichuan Basin were analyzed. Paleoproductivity proxy parameters (Babio, Siex, and Ni/Al), clastic influx proxies (TiO2 and Ti/Al), redox indices (V/Cr, Ni/Co, V/(V+Ni), and U/Th), and hydrothermal indicators (Fe, Mn, and Y concentrations; Fe/Ti ratio and a Ni‐Zn‐Co diagram) were employed to decipher the paleoenvironment of the Lower Longmaxi Formation shales. TiO2 and Ti/Al indicated low terrigenous detrital influx in all three areas. However, Babio, Siex, and Ni/Al indicated high productivity in the Jiaoshiba area. V/Cr, Ni/Co, and U/Th indicated higher oxygen content with larger fluctuations in the Zhaotong and Weiyuan areas. Fe, Mn, and Y concentrations and the Fe/Ti ratio implied greater active hydrothermal activity in the Weiyuan area. These heterogeneities were considered to be closely related to the paleoenvironment and paleogeography, and the large basement faults that developed during the Chuanzhong paleo‐uplift could have provided vents for deep‐hydrothermal‐fluid upwelling. The redox indices (V/Cr, Ni/Co, and U/Th) and a paleoproductivity proxy (Ni/Al) displayed a significant correlation with the TOC, suggesting that both excellent preservation conditions and high paleoproductivity were the controlling factors for the enrichment of organic matter in the Longmaxi Formation shale. There was no obvious correlation between the clastic influx proxy (Ti/Al) and the TOC due to the extremely low supply of terrigenous debris. The hydrothermal indicator (Fe/Ti) was negatively correlated with the TOC in the Weiyuan area, indicating that hydrothermal activity may have played a negative role in the accumulation of organic matter. This study suggests that the enrichment of organic matter in the Longmaxi Formation marine shale varied according to the paleogeography and sedimentary environment.

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Section: Implications For the Paleoenvironment 511 Primary Productisupporting

confidence: 86%

Section: Samples and Methodsmentioning

confidence: 99%

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confidence: 99%

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Geochemistry, Paleoenvironment and Mechanism of Organic‐Matter Enrichment in the Lower Silurian Longmaxi Formation Shale in the Sichuan Basin, China

Chen

Cui

Ren

et al. 2019

Acta Geologica Sinica (Eng)

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“…The LSL formation originated from typical marine sediments and is the most successful stratum for commercial shale gas production in China so far. 31,32 Moreover, nine continental shale samples were collected from a freshly exposed outcrop of the Middle Jurassic Dameigou (MJD) formation at Yueyashan profile of southern Altun Mountains, in western Qaidam basin of northwest China. The MJD formation in the sampling location, deposited in a lacustrine environment, is a pretty promising stratum for shale gas exploration because of its huge gas resources potential.…”

Section: Samplesmentioning

confidence: 99%

Comparison of Pore Fractal Characteristics Between Marine and Continental Shales

Yao

Liu

et al. 2018

Fractals

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Fractal characterization offers a quantitative evaluation on the heterogeneity of pore structure which greatly affects gas adsorption and transportation in shales. To compare the fractal characteristics between marine and continental shales, nine samples from the Lower Silurian Longmaxi formation in the Sichuan basin and nine from the Middle Jurassic Dameigou formation in the Qaidam basin were collected. Reservoir properties and fractal dimensions were characterized for all the collected samples. In this study, fractal dimensions were originated ¶ Corresponding author. This is an Open Access article published by World Scientific Publishing Company. It is distributed under the terms of the Creative Commons Attribution 4.0 (CC-BY) License. Further distribution of this work is permitted, provided the original work is properly cited. 1840016-1Fractals 2018.26. Downloaded from www.worldscientific.com by 13.66.222.141 on 06/19/19. Re-use and distribution is strictly not permitted, except for Open Access articles. J. Liu et al.from the Frenkel-Halsey-Hill (FHH) model with N 2 adsorption data. Compared to continental shale, marine shale has greater values of quartz content, porosity, specific surface area and total pore volume but lower level of clay minerals content, permeability, average pore diameter and methane adsorption capacity. The quartz in marine shale is mostly associated with biogenic origin, while that in continental shale is mainly due to terrigenous debris. The N 2 adsorption-desorption isotherms exhibit that marine shale has fewer inkbottle-shaped pores but more plate-like and slit-shaped pores than continental shale. Two fractal dimensions (D 1 and D 2 ) were obtained at P/P o of 0-0.5 and 0.5-1. The dimension D 2 is commonly greater than D 1 , suggesting that larger pores (diameter >∼ 4 nm) have more complex structures than small pores (diameter <∼ 4 nm). The fractal dimensions (both D 1 and D 2 ) positively correlate to clay minerals content, specific surface area and methane adsorption capacity, but have negative relationships with porosity, permeability and average pore diameter. The fractal dimensions increase proportionally with the increasing quartz content in marine shale but have no obvious correlation with that in continental shale. The dimension D 1 is correlative to the TOC content and permeability of marine shale at a similar degree with dimension D 2 , while the dimension D 1 is more sensitive to those of continental shale than dimension D 2 . Compared with dimension D 2 , for two shales, dimension D 1 is better associated with the content of clay minerals but has worse correlations with the specific surface area and average pore diameter.

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“…The fact that the organic matter is richer in the shale and mudstone samples than in the sandstone samples is closely associated with their distinct genesis. According to Rimmer et al [54] and Zhao et al [55], both the influx of terrigenous clastic and the redox environment play important roles in the enrichment of organic matter during diagenesis process. Because of the abundant clastic influx and the partial oxidation environment, the content of organic matter in sandstone is normally lower than in the mudrocks.…”

Section: Toc and Mineralogical Compositionsmentioning

confidence: 99%

Nanoscale Pore Structure Characterization and Permeability of Mudrocks and Fine-Grained Sandstones in Coal Reservoirs by Scanning Electron Microscopy, Mercury Intrusion Porosimetry, and Low-Field Nuclear Magnetic Resonance

et al. 2018

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Porosity and permeability of two typical sedimentary rocks in coal bearing strata of underground coal mines in China, i.e., mudrocks and fine-grained sandstones, were comprehensively investigated by multiple experimental methods. Measured porosity averages of the helium gas porosity ( ), MIP porosity ( MIP ), water porosity ( ), and NMR porosity ( NMR ) of the twelve investigated rock samples range from 1.78 to 16.50% and the measured gas permeabilities ( ) range from 0.0003 to 2.4133 mD. Meanwhile, pore types, pore morphologies, and pore size distributions (PSD) were determined by focused ion beam scanning electron microscopy (FIB-SEM), mercury intrusion porosimetry (MIP), and low-field nuclear magnetic resonance (NMR). FIB-SEM image analyses showed that the mineral matrix pores including interparticle (interP) and intraparticle (intraP) pores with varied morphologies are the dominant pore types of the investigated rock samples while very few organic matter (OM) pores were observed. Results of the MIP and the full water-saturated NMR measurements showed that the PSD curves of the mudrock samples mostly present a unimodal pattern and nanopores with pore diameter less than 0.1 m are their predominant pore type, while the PSD curves of the fine-grained sandstone samples are featured by a bimodal distribution. Furthermore, comparison of the full water-saturated and irreducible-water-saturated NMR measurements indicated that pores in the mudrocks are solely adsorption pores (normally pore size < 0.1 m) whereas apart from a fraction of adsorption pores, a large part of the pores in the sandstone sample with relatively high porosity are seepage pores (normally pore size > 0.1 m). Moreover, the PSD curves of NMR quantitatively converted from the NMR 2 spectra by 2 and weighted arithmetic mean (WAM) methods are in good agreement with the PSD curves of MIP. Finally, the applicability of three classic permeability estimation models based on MIP and NMR data to the investigated rock samples was evaluated.

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Applying sedimentary geochemical proxies for paleoenvironment interpretation of organic-rich shale deposition in the Sichuan Basin, China

Cited by 158 publications

References 87 publications

Geochemistry, Paleoenvironment and Mechanism of Organic‐Matter Enrichment in the Lower Silurian Longmaxi Formation Shale in the Sichuan Basin, China

Geochemistry, Paleoenvironment and Mechanism of Organic‐Matter Enrichment in the Lower Silurian Longmaxi Formation Shale in the Sichuan Basin, China

Comparison of Pore Fractal Characteristics Between Marine and Continental Shales

Nanoscale Pore Structure Characterization and Permeability of Mudrocks and Fine-Grained Sandstones in Coal Reservoirs by Scanning Electron Microscopy, Mercury Intrusion Porosimetry, and Low-Field Nuclear Magnetic Resonance

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