Hydrocarbon generation characteristics and exploration prospects of Proterozoic source rocks in China

Geophysical Monograph Series

Ernst

Pei

et al. 2021

Recent results on ca. 1,380 Ma LIPs and black shales indicate a temporal link between LIPs and black shales and suggest a potential way for using coeval LIPs and black shales as natural markers for boundaries in the Mesoproterozoic timescale. In this chapter, we provide a brief review of LIPs and black shales during "the Boring Billion" in different cratons. The results show that in addition to the ca. 1,380 Ma LIP activity that is coeval with black shales, other major LIPs during this period can preliminarily be divided into several stages and are likely/possibly contemporaneous with black shales, especially the 1,650-1,620 Ma and ca. 1,100 Ma LIPs. Our results demonstrate that the global-scale LIPs and black shales in the Boring Billion can potentially be used as natural markers for subdivisions of the Proterozoic timescale. The results also suggest that, while the Boring Billion was characterized by suboxic or mildly oxygenated marine basins, it was interrupted by several OAEs that are partly caused by the environmental impact of LIPs. Preliminarily proposed correlation of LIPs and black shales provide a new way to explain the fluctuating evolution of atmosphere, life, and marine basins during the Boring Billion as identified by many recent studies.

Section: Ca 1650-1640 Masupporting

confidence: 75%

mentioning

confidence: 99%

Large Igneous Provinces (LIPs) and Anoxia Events in “The Boring Billion”

Geophysical Monograph Series

Ernst

Pei

et al. 2021

“…Regarding the factors affecting the oilbearing property of bedding fractures, apart from the temporal coupling of the formation of these fractures with mass hydrocarbon generation of the source rocks, their spatial coupling with the source rocks is also important [59,60]. That is, the development location of the bedding fractures in the formation matches and interacts with the location of the source rocks.…”

Section: Spatial Couplingmentioning

confidence: 99%

Research on the Oil-Bearing Difference of Bedding Fractures: A Case Study of Lucaogou Formation in Jimsar Sag

Zeng

et al. 2021

Geofluids

Lucaogou formation in Jimsar sag is host to large quantities of bedding fractures which are known to play a critical role in the enrichment, accumulation, and efficient development of tight oil. In this paper, we examine and finely characterize the development of the bedding fractures found in the upper and lower sweet spots of Lucaogou formation of tight oil reservoir through field outcrop and core observation, cast thin section analysis, and imaging log recognition and investigate the factors affecting their differentiated oil-bearing by means of inclusion temperature measurement, TOC testing, physical property testing, high-pressure mercury injection, and physical simulation experiment. By comparison with the linear density, bedding fractures are more developed in the lower sweet spot. These fractures occur in parallel to the formation boundary and have small aperture. Most of bedding fractures are unfilled fractures. Among the few types of fractures found there, bedding fractures have the best oil-bearing property, but the oil-bearing can differ from one bedding fracture to another. The factors affecting the differentiated oil-bearing of bedding fractures include the temporal coupling of the formation of these fractures with the hydrocarbon generation of the source rocks and the spatial coupling of the bedding fractures with the source rocks. In terms of temporal coupling, mass hydrocarbon generation in Jimsar sag began in Late Jurassic. Inclusion temperature measurement indicates that the bedding fractures there formed in or after Early Cretaceous. Hence, by matching the mass hydrocarbon generation period of the source rocks with the formation period of the bedding fractures, we discovered that the bedding fractures formed within the mass hydrocarbon generation period, which favored the oil-bearing of these fractures. The spatial coupling is manifested in TOC, porosity, permeability, and pore throat, with TOC being the main controlling factor. For TOC, the higher the formation TOC, the better the oil-bearing property of the bedding fractures. For porosity, subject to the TOC level, if the TOC is adequate, the larger the porosity, the larger the chloroform asphalt “A,” accordingly the higher the oil content of the formation, and the better the oil-bearing property of the bedding fractures developed therein. In this sense, in terms of spatial coupling, TOC constitutes the main controlling factor of the oil-bearing property of bedding fractures.

“…Thus, in contrast to the oxic ocean of the Phanerozoic, the surface ocean during the Mesoproterozoic was aerobic, although the majority of the deeper ocean was anoxic (Brocks and Schaeffer, 2008;Planavsky et al, 2011). Hence, heterotrophic microbes living in such anoxic seawater thrived in Mesoproterozoic (Jarrett et al, 2019;Zhao et al, 2019).…”

mentioning

confidence: 99%

“…Several sets of Mesoproterozoic organic-rich rocks with different thermal maturity are widely distributed in the North China Craton (Zhao et al, 2018(Zhao et al, , 2019. These can be used as suites of suitable organic-rich rock samples to study the characteristics of hydrocarbons generated at different thermal maturity.…”

mentioning

confidence: 99%

The Biomarkers in the Mesoproterozoic Organic‐rich Rocks of North China Craton: Implication for the Precursor and Preservation of Organism in the Prokaryotic Realm

Acta Geologica Sinica (Eng)

Jin

et al. 2022

Self Cite

have suggested that the atmospheric oxygen concentration during the Mesoproterozoic was higher than previously believed (Planavsky et al., 2014), may have reached 4-8% PAL (present atmospheric levels). The trace element concentrations, organic carbon content, and biomarker data of the 1400 Ma Xiamaling (XML) Formation in the North China Craton (Zhang et al., 2016(Zhang et al., , 2017 implied that that surface ocean was aerobic during the Mesoproterozoic. This promoted the flourish of phototrophic plankton during this period (Noffke et al., 2003;Zhao et al., 2020), which promoted the formation of the Mesoproterozoic organic-rich rock. However, there are some differences between the Mesoproterozoic and Phanerozoic organic-rich rocks in sedimentary environment, organic precursor and preservation pathway of organic matter.Although some fossil evidences of eukaryotic algae had