Source analysis of siliceous minerals and uranium in Early Cambrian shales, South China: Significance for shale gas exploration

Jiang, Tao; Jin, Zhijun; Liu, Guangxiang; Liu, Quanyou; Gao, Bo; Liu, Zhongbao; Nie, Haikuan; Zhao, Jianhua; Wang, Ruyue; Zhu, Tong; Yang, Tao

doi:10.1016/j.marpetgeo.2018.11.002

Cited by 17 publications

(8 citation statements)

References 61 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Paleoproductivity refers to the total amount of organic matter fixed per unit area per unit time (Algeo et al, 2011;Pan et al, 2020). Generally speaking, high organic productivity is one of the key factors for the formation of hydrocarbon source rocks (Talbot, 1988;Nelson et al, 1995;Mansour et al, 2020a;Mansour et al, 2020b;Yang et al, 2016;Zhao et al, 2021), and a large number of studies have shown that siliceous plankton in marine source rocks is the main provider of marine primary productivity (De Wever and Baudin, 1996;Chou et al, 2012;Xiang et al, 2013;Shaldybin et al, 2017;Jiang et al, 2019;Zhang et al, 2019), whose content is closely related to the biological reproduction in surface water, and its temporal and spatial distribution can be used to reflect the changing process of paleoproductivity. In recent years, many studies have shown that radiolarians enriched in marine hydrocarbon source rocks can gather together and absorb a lot of symbiotic algae in their bodies by using a large number of pseudopodia, forming a good symbiotic relationship with them (Lyle et al, 1988;Erbacher and Thurow, 1997;Xiang et al, 2013;Khan et al, 2019).…”

Section: Relationship Between Biogenic Silica and Organic Mattermentioning

confidence: 99%

The Origin of Silica of Marine Shale in the Upper Ordovician Wulalike Formation, Northwestern Ordos Basin, North China

Zhang

Huang

et al. 2021

Front. Earth Sci.

View full text Add to dashboard Cite

The shale of the Wulalike Formation developed in the northwestern Ordos Basin is considered to be an effective marine hydrocarbon source rock. One of the key factors for successful shale gas exploration in the Wufeng–Longmaxi Formation in the Sichuan Basin is the high content of biogenic silica. However, few people have studied the siliceous origin of the Wulalike shale. In this study, we used petrographic observation and element geochemistry to analyze the origin of silica in the Wulalike shale. The results show that the siliceous minerals are not affected by hydrothermal silica and mainly consist of biogenic and detrital silica. A large number of siliceous organisms, such as sponge spicules, radiolarians, and algae, are found under the microscope. It has been demonstrated that total organic carbon has a positive correlation with biogenic silica and a negative correlation with detrital silica, and biogenic silica is one of the effective indicators of paleoproductivity. Therefore, the enrichment of organic matter may be related to paleoproductivity. Through the calculation of element logging data in well A, it is found that biogenic silica is mainly distributed in the bottom of the Wulalike Formation, and the content of biogenic silica decreases, while the content of detrital silica increases upward of the Wulalike Formation. Biogenic silica mainly exists in the form of microcrystalline quartz, which can form an interconnected rigid framework to improve the hardness and brittleness of shale. Meanwhile, biogenic microcrystalline quartz can protect organic pores from mechanical compaction. Therefore, it may be easier to fracture the shale gas at the bottom of the Wulalike Formation in well A.

show abstract

Section: Relationship Between Biogenic Silica and Organic Mattermentioning

confidence: 99%

The Origin of Silica of Marine Shale in the Upper Ordovician Wulalike Formation, Northwestern Ordos Basin, North China

Zhang

Huang

et al. 2021

Front. Earth Sci.

View full text Add to dashboard Cite

show abstract

“…The uranium content of the Qiongzhusi shale is clearly higher than those of the Wufeng-Longmaxi shale (Cai et al, 2017;Zhao et al, 2016), which further indicates that the occurrence of the thucholite may be closely related to the distribution of the radioactive elements. Furthermore, the enrichment of uranium was derived from hydrothermal fluids (Jiang et al, 2019). As a result, the reflectance of thucholites was not measured due to its anisotropy.…”

Section: Qiongzhusi Shalementioning

confidence: 99%

Maturity and thermal evolution differences between two sets of Lower Palaeozoic shales and its significance for shale gas formation in south‐western Sichuan Basin, China

et al. 2021

View full text Add to dashboard Cite

The Lower Cambrian Qiongzhusi shale and the Upper Ordovician-Lower Silurian Wufeng-Longmaxi shale are major source rocks and important shale gas exploration targets in the Sichuan Basin. Cutting and core samples from two shale gas wells in south-western Sichuan Basin have been selected for organic matter (OM) reflectance measurement and Raman spectra analysis with the aim to determine maturity. The results were incorporated for basin modelling to construct the thermal evolution of this area. Graptolite fragments and pyrobitumens are the dominant form of OM in

show abstract

“…GR of shale originates almost entirely from potassium (K)-40 and elements in the uranium (U) and thorium (Th) decay chains, in which K and Th are preferentially related to clay minerals, , while the occurrence of U is controversial. Due to the anoxic conditions required for their deposition and preservation, U and OM are intimately linked; most studies support that U preferentially bonds to OM. − In contrast, by the means of a sequential chemical extraction procedure, some studies propose that U and Th preferentially bond to clay minerals, phosphate, and other inorganic mineral compositions. − …”

Section: Introductionmentioning

confidence: 99%

Factors Controlling the Lower Radioactivity and Its Relation with Higher Organic Matter Content for Middle Jurassic Oil Shale in Yuqia Depression, Northern Qaidam Basin, China: Evidence from Organic and Inorganic Geochemistry

Guo

Chen

et al. 2021

ACS Omega

View full text Add to dashboard Cite

Organic-rich oil shale with unusual lower radioactivity (expressed by GR) was found in Member 7 of Dameigou Formation, middle Jurassic (J 2 d 7 ) in Yuqia depression of northern Qaidam Basin, China. In order to systematically and contrastively investigate the factors controlling the lower GR and its relation with higher organic matter (OM) content (expressed by total organic carbon, abbr. TOC), organic and inorganic geochemical analyses were performed on samples consisting of oil shale and the underlying conformable contact dark shale from Well YQ-1Y. Our study shows that GR of J 2 d 7 oil shale is mainly derived from uranium and thorium. Compared with dark shale, oil shale is characterized by higher OY and TOC, lower GR, and clay mineral content. During oil shale deposition, the paleoclimate was relatively arid, indicated by a decreased C value and siderite content as well as an increased carbonate content and Classopollis. Under such paleoclimate conditions, sedimentary water became more anoxic, suggested by higher V/(V + Ni), pyrite content and lower pristane/phytane (Pr/Ph). From oil shale to dark shale deposition, according to analyses of Al 2 O 3 /TiO 2 , TiO 2 versus Zr, La/Sc versus Th/Co, La/Th versus Hf, and La−Th−Sc, the felsic igneous rock could always be deduced as the parent rock of provenance; however, the increasing arid paleoclimate resulted in weakened chemical weathering of provenance, inferred by relatively low chemical index of alteration, chemical index of weathering, and plagioclase index of alteration corresponding to the input degree of radioactive materials and other terrigenous detrital materials (TDMs), evidenced by Ti and Al contents and terrigenous (%). Meanwhile, the relatively high P/Ti and Ba/Al both indicated increased primary paleoproductivity. Together with the maximum flooding stage of oil shale deposition, the relatively low radioactivity tends to be associated with the inhibited input of clay minerals and radioactive materials, largely caused by increasing arid paleoclimate. The accompanying decreased TDM benefited primary paleoproductivity and anoxic conditions; their combined influence could induce sapropelic OM accumulation.

show abstract

Source analysis of siliceous minerals and uranium in Early Cambrian shales, South China: Significance for shale gas exploration

Cited by 17 publications

References 61 publications

The Origin of Silica of Marine Shale in the Upper Ordovician Wulalike Formation, Northwestern Ordos Basin, North China

The Origin of Silica of Marine Shale in the Upper Ordovician Wulalike Formation, Northwestern Ordos Basin, North China

Maturity and thermal evolution differences between two sets of Lower Palaeozoic shales and its significance for shale gas formation in south‐western Sichuan Basin, China

Factors Controlling the Lower Radioactivity and Its Relation with Higher Organic Matter Content for Middle Jurassic Oil Shale in Yuqia Depression, Northern Qaidam Basin, China: Evidence from Organic and Inorganic Geochemistry

Contact Info

Product

Resources

About