Characteristics of Biogenic Silica and Its Effect on Reservoir in Wufeng-Longmaxi Shales, Sichuan Basin

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

doi:10.1111/1755-6724.12302_58

Cited by 7 publications

(8 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The contents of Al 2 O 3 , SiO 2 , and CaO in the main composition of O 3 w and S 1 l shale can be roughly corresponding to the contents of quartz- or SiO 2 -rich brittle minerals, clay minerals, and carbonate minerals . It has been reported that the O 3 w and S 1 l 1 shale has a high content of biogenic quartz, and biogenic quartz has a high positive correlation with TOC, while terrestrial input quartz has a negative correlation with TOC. , Therefore, it can be speculated that the strong biological activity during the sedimentary period of O 3 w and S 1 l 1 leads to the high content of biosilicon, and the remains form sedimentary organic matter after biological death. ,, In consequence, the quartz content and TOC in the shale of O 3 w and S 1 l 1 show a strong positive correlation. The content of quartz and carbonate minerals in the S 1 l 2+3 shales gradually decreased, and the clay minerals showed an upward trend.…”

Section: Resultsmentioning

confidence: 96%

Constraints of Sedimentary Environment on Shale Organic Matter Enrichment: Insights from Elemental Geochemistry and Multiple Factor Analysis

Shao,

Xu,

Jiang

et al. 2024

ACS Omega

View full text Add to dashboard Cite

The organic-rich shale of the Wufeng−Longmaxi formation is an important section for shale gas exploration. The traditional univariate or bivariate analysis causes researchers to have great controversy about its enrichment mechanism. This study explores the combination of multiple factor analysis (MFA) and element geochemistry to calculate the contribution rate of a paleoenvironment to organic matter enrichment and clarify the main controlling factors of organic matter enrichment. Research has shown that there is generally high productivity from the Wufeng (O 3 w)−Longmaxi formation (S 1 l) deposition. The degree of terrigenous clastic input and weathering during the period of the O 3 w is relatively low, and sedimentary water restriction is strong, mainly developing an anoxic−dysoxic sedimentary environment. During the deposition of S 1 l 1 , the input intensity and weathering of terrigenous debris were slightly enhanced, and the increase of the water column led to the development of an anoxic environment at the bottom of the water layer. During the S 1 l 2+3 period, the degree of terrigenous debris and weathering is the largest, and the high oxygen content of the water column is mainly a normal oxic environment. An MFA calculation shows that the paleoproductivity and paleoredox environment of the organic-rich shale section have the highest contribution rate of about 59.57% to the enrichment of organic matter, which is higher than that of paleoclimate conditions and terrigenous clastic input, indicating that the enrichment of organic matter is mainly controlled by paleoproductivity and the preservation environment. This study provides a basis for the application of MFA in element geochemistry and can serve as a model for other studies.

show abstract

Section: Resultsmentioning

confidence: 96%

Constraints of Sedimentary Environment on Shale Organic Matter Enrichment: Insights from Elemental Geochemistry and Multiple Factor Analysis

Shao,

Xu,

Jiang

et al. 2024

ACS Omega

View full text Add to dashboard Cite

show abstract

“…Microscopic observation showed that the Wulalike shale is enriched in siliceous microorganism fossils, i.e., radiolarians and sponge spicules, which is credible evidence for biogenic quartz (Figure 4A-E). [44] and reference [46], respectively.…”

Section: Origins Of Quartzmentioning

confidence: 99%

“…The type of quartz that commonly appears as siliceous cement can be observed under the microscope in the Wulalike shale (Figure 4H). The reaction formula is: [44] and reference [46], respectively.…”

Section: Origins Of Quartzmentioning

confidence: 99%

See 1 more Smart Citation

Quartz Origins and Paleoenvironmental Controls on Organic Matter Accumulation of Marine Shale in the Ordovician Wulalike Formation, Northwestern Ordos Basin, China: Significance for Shale Gas Exploration

Zhang

Xi³

et al. 2023

Energies

View full text Add to dashboard Cite

The Ordovician Wulalike marine siliceous shale is a notable hydrocarbon source rock in the Northwestern Ordos Basin. However, the causes of quartz and organic matter enrichment are still a mystery to experts. In this study, the organic geochemistry (maceral compositions, Rbitu, and TOC) and elemental geochemistry (major and trace elements) with mineralogy (XRD) and petrography were jointly acquired to systematically investigate the quartz origins and the paleoenvironment, and the main controlling factors for organic matter enrichment in the Wulalike shale. The results show that the organic matter is type I kerogen with low TOC concentrations (average 0.51%), and that the thermal evolution has reached mature and high mature stages (mean Requ is 1.08%). Three types of quartz are developed in Wulalike shale: biogenic quartz (average 63%) is the most dominant, followed by clastic quartz (average 31%) and microcrystalline quartz (average 6%). Babio and Ba/Al values indicate the low paleoproductivity, which is the primary cause for the low TOC found throughout the area. Redox indexes show the anoxic or dysoxic to oxic conditions from the bottom to the top of the section. Paleoclimate and paleowater depth proxies also changed from the bottom to the top. Various paleoenvironments and sedimentological evidence show that Wulalike shale went through the changing environments, and the early sedimentary environments were conducive to organic matter enrichment, leading to a relatively high TOC. The paleoproductivity and preservation conditions have an impact on organic matter enrichment. Based on the results of biogenic quartz distribution and sedimentary environments, it is considered that the bottom of the Wulalike Formation is the most favorable for shale gas exploration and development.

show abstract

“…Previous studies have shown that major shale formations are generally associated with volcanic ash layers (Liu et al, 2021), such as the Upper Devonian-Lower Carboniferous Bakken Formation in the Williston Basin (Dennison and Textoris, 1970), the Middle Devonian Marcellus Formation in the Appalachian Basin (Hayward, 2012), the Upper Cretaceous Eagle Ford Formation in Gulf Coast Basin (Robison, 1997;Duggen et al, 2007;Lee et al, 2018), the Devonian-Carboniferous Bazhenov Formation in Western Siberia, Russia (Shaldybin et al, 2019;Liang et al, 2020), the Jurassic Vaca Muerta Formation in Neuquen Basin, Argentina (Kietzmann et al, 2014), etc. In the Mesozoic and Cenozoic terrigenous petroliferous basins in China, organic-rich shale is also generally accompanied by volcanic activity (Zhao and Liu, 2016), such as the Qingshankou Formation (Gao et al, 2008;Lee et al, 2018) and Yingcheng Formation (Shan et al, 2013) in the Songliao Basin, Shahejie Formation in the Bohai Bay Basin (Du et al, 2014), Yanchang Formation in the Ordos Basin (Qiu et al, 2009;Zhang et al, 2009), Hargau (Li et al, 2010) and Lucaogou (Wu et al, 2012) formations in the Santanghu Basin, and Longmaxi Formation in the Sichuan Basin (Zhao et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

Organic-rich formation and hydrocarbon enrichment of lacustrine shale strata: A case study of Chang 7 Member

Liu

Peng

Jin

et al. 2021

Sci. China Earth Sci.

Self Cite

View full text Add to dashboard Cite

Lacustrine shale is an important target for the exploration of unconventional oil and gas in China beyond marine shale gas. However, the formation environment of lacustrine shale differs from that of marine shale, resulting in a different reservoir composition, organic matter, oil and gas content, and hydrocarbon mobility. In this study, the Chang 7 shale of the Yanchang Formation in the Ordos Basin was used to analyze the effect of volcanic activity on the paleoproductivity and preservation conditions during the formation of lacustrine shale. The results show that algae and bacteria were developed before the eruption. After the eruption, the number of bacteria declined, but the increased prosperity of algae reflects that the volcanic activity enhanced ancient productivity. The sulfate generated by volcanic activity promotes bacterial sulfate reduction, and the produced H 2 S leads to a strong reducing environment in the waterbody, which is conducive to the preservation of organic matter. Organic geochemical analysis shows that the black shale in the shale strata has a high total organic carbon (TOC) content and strong hydrocarbon generation potential, whereas the tuff has a low TOC content and can scarcely generate hydrocarbons, indicating that the tuff deposited by volcanic activity cannot be considered as effective source rock. In terms of storage space, shale is mainly laminar and dispersed, and it includes organic and inorganic pores. The development of organic pores is affected by thermal maturity, whereas inorganic pores mainly occur between detrital particles and crystals. Tuff is mainly supported by heterogeneous matrix and associated with alteration. Its pores include inter-and intragranular mineral pores. The development of tight sandstone pores is affected by compaction, cementation, and dissolution, which mainly consist of intra-and intergranular pores. The Chang 7 lacustrine shale generally contains oil, but different lithologies have different oil drainage efficiencies. Sandstone and shale exhibit the best and worst oil drainage efficiency, respectively. It is mainly affected by the pore size distribution, fluid properties, and rock wettability. Therefore, the development of shale oil should mainly focus on lacustrine shale formations with interbeds. The mutual dissolution of organic matter and hydrocarbons in the shale section leads to the poor mobility and difficult development of hydrocarbons.

show abstract

Characteristics of Biogenic Silica and Its Effect on Reservoir in Wufeng-Longmaxi Shales, Sichuan Basin

Cited by 7 publications

References 0 publications

Constraints of Sedimentary Environment on Shale Organic Matter Enrichment: Insights from Elemental Geochemistry and Multiple Factor Analysis

Constraints of Sedimentary Environment on Shale Organic Matter Enrichment: Insights from Elemental Geochemistry and Multiple Factor Analysis

Quartz Origins and Paleoenvironmental Controls on Organic Matter Accumulation of Marine Shale in the Ordovician Wulalike Formation, Northwestern Ordos Basin, China: Significance for Shale Gas Exploration

Organic-rich formation and hydrocarbon enrichment of lacustrine shale strata: A case study of Chang 7 Member

Contact Info

Product

Resources

About