Organic matter enrichment due to high primary productivity in the deep-water shelf: Insights from the lower Cambrian Qiongzhusi shales of the central Sichuan Basin, SW China

Li, Qiang; Liu, Guangdi; Song, Zezhang; Zhang, Benjian; Sun, Min; Tian, Xiaobo; Yang, Dedong; Wang, Yunlong; Zhu, Lei; Cao, Yushun

doi:10.1016/j.jseaes.2022.105417

Cited by 18 publications

(7 citation statements)

References 114 publications

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“…Partial data of bitumen were from Gao et al (2017); Ni et al (2018); Shi et al (2017); Zhang et al (2019); Zhu et al (2022). Source rocks data were from Chen, Simoneit, et al (2017); Gao et al (2017); Jin et al (2014); Li, Liu, Song, Zhang, Sun, et al (2022); Liu (2018); Ni et al (2018); Shi et al (2017); Wang, Li, et al (2019); Wang, Li, Tian, et al (2020); Wei et al (2015); Xiao et al (2020); Xiao et al (2021); Yang et al (2012); Zhu et al (2022).…”

Section: Resultsmentioning

confidence: 99%

Reconstruction of palaeo‐oil reservoirs in the ultra‐deep and over‐mature Sinian Dengying Formation of the Central Sichuan Basin: Insights from basin and petroleum system modelling

Li,

Liu,

Song

et al. 2024

Geological Journal

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Ultra‐deep Sinian carbonate rocks are rich in natural gas, and the Deng‐4 Member of the Central Sichuan Basin has been shown to have an extremely high degree of thermal evolution. They are characterized by dry gas produced due to the thermal cracking of palaeo‐oil reservoirs (PORs). The distribution of PORs as materials for the formation of cracked gas reservoirs remains unclear. The complex multistage evolution process and limited drilling data make it challenging to precisely and systematically recover a range of PORs. Based on basin and petroleum system modelling (BPSM), the bottom‐up migration and accumulation method was used to investigate the distribution of PORs. Research shows that the PORs in the Sinian Deng‐4 Member were mainly formed in the Early–Middle Triassic under the mixed contribution of Cambrian and Sinian source rocks, and the coupling of palaeostructural and trap settings controlled its accumulation. Generally, the distribution of PORs can be divided into two categories: one is located at the core of the uplift zone and is controlled by structural‐stratigraphic composite traps, whereas the other is controlled by a series of lithologic traps formed in the slope area. Sensitivity analysis showed that the distribution patterns of the PORs were mostly related to the facies conditions (physical characteristics) of the reservoirs. The widely distributed PORs provide necessary and sufficient material conditions for the formation of cracked Sinian gas reservoirs in the Central Sichuan Basin, and the North Slope area has great potential for natural gas exploration in the future.

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Section: Resultsmentioning

confidence: 99%

Reconstruction of palaeo‐oil reservoirs in the ultra‐deep and over‐mature Sinian Dengying Formation of the Central Sichuan Basin: Insights from basin and petroleum system modelling

Li,

Liu,

Song

et al. 2024

Geological Journal

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“…This may illustrate the environmental variation through whole piling-up process of the Є1q. In the duration of transgression immediately after the eogenetic karstification, subjecting to the karst landform, the deep-water shelf attained a greater quantity of organic-matter-bearing sediments than the shallow-water shelf; not only because of the larger depositional thickness, but also due to nutrients from hydrothermal upwelling, that made the primary productivity higher; and that the anoxic surroundings favoured preservation of these organic matters in deep-water shales (Li et al, 2022). All these come to that the hydrocarbon generation potential is higher in deep-water shelf than in the shallow-water shelf.…”

Section: Discussionmentioning

confidence: 99%

Karst paleotopography on top of the Dengying Formation and petroleum geological significance in the Central Sichuan Basin, China

Zhou

Wang

Yang

et al. 2022

Energy Exploration & Exploitation

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Reconstructing karst palaeogeomorphology is a useful approach to identifying target areas for oil and gas exploration. This study used the elevation method to reconstruct the karst palaeogeomorphology at the top of the 4th member (Z2dn4) of the Dengying Formation (Z2dn) in the Central Sichuan Basin based on 2D and 3D seismic and drilling data. The bottom of the Longwangmiao Formation and the top of the 2nd member (Z2dn2) of the Z2dn were optimized as the upper and lower base levels, respectively. The reconstructed palaeogeomorphology was divided into five types – slopes, erosional peneplains, monadnocks, domes and depressions – according to their morphology, scope and gradient, allowing inference of the palaeohydrological conditions. Slopes were subdivided into gentle (<1.2°) and steep (≥ 1.2°; maximum gradient around 16°). Reservoirs on steep slopes and monadnocks are the most developed, owing to their considerable hydraulic head differences, strong palaeohydrodynamics, and intense erosion and incision. Steep slopes with more developed karst porosities are banded and immediately adjoin a regional hydrocarbon generation centre. Hydrocarbons generated in this centre tend to migrate laterally and become entrapped in porous slopes and their vicinities. Consequently, hydrocarbons move upward along steep slopes and, preferentially, slopes and monadnocks. Thus, the steep slope zone and its vicinity (including some monadnocks, gentle slopes and peneplains) are the most favourable areas for exploration of hydrocarbon reservoirs and should be the primary targets.

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“…V/Sc ratios are considered to be more sensitive and reliable than V/Cr ratios, because Sc and V are insoluble elements, and V abundance can be normalized by Sc (Kimura and Watanabe, 2001;Powell, 2009;Li et al, 2022) (Fig. 13d).…”

Section: Redox Conditionsmentioning

confidence: 99%

“…This study on U and Mo uses ‗enrichment factors' (EF), where X EF = [(X sample /Al sample )/(X PAAS /Al PAAS )], and X and Al stand for the weight concentrations of elements X and Al, respectively (Algeo and Tribovillard, 2009;Liang et al, 2020), and additionally, uses PAAS for normalization (Taylor and McLennan, 1985). Furthermore, the patterns of U-Mo covariation were established to identify the reducing degree of bottom water and determine the redox conditions (Tribovillard et al, 2012;Liang et al, 2020;Li et al, 2022). However, this method was first proposed in the reconstruction of marine systems, and the U-Mo covariation of lacustrine systems has not yet been proven; several studies suggested that the aqueous concentrations of U and Mo in lakes are lower than those in marine systems (Chappaz et al, 2010;Smedley and Kinniburgh, 2017).…”

Section: Redox Conditionsmentioning

confidence: 99%

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Paleoenvironmental Characteristics of Paleogene Lacustrine Source Rocks in the Western Bozhong Sag, Bohai Bay Basin, China: Evidence from Biomarkers, Major and Trace Elements

WANG,

LIU,

SONG

et al. 2024

Acta Geologica Sinica (Eng)

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The organic matter (OM) enrichment mechanisms and depositional environment characteristics of lacustrine source rocks in western Bozhong Sag, Bohai Bay Basin (BBB) remain controversial. To address these issues, based on Rock‐Eval pyrolysis, kerogen macerals, H/C and O/C ratios, GC‐MS, major and trace elements, the Dongying Mbr 3 (E3d3), the Shahejie Mbrs 1 and 2 (E2s1+2), and the Shahejie Mbr 3 (E2s3) source rocks in the western Bozhong Sag were studied. The above methods were used to reveal their geochemical properties, OM origins and depositional environments. The results indicate that the E2s1+2 and E2s3 are excellent source rocks, and the E3d3 of the second good quality. E3d3 source rocks were formed under a warm and humid climate, mainly belong to fluvial/delta facies, the E3d3 sediments have formed under weakly oxidizing and freshwater conditions. Comparatively, the depositional environments of E2s1+2 source rocks were arid and cold climate, representing saline or freshwater lacustrine facies, and the sediments of E2s1+2 belong to anoxic or suboxic settings with large evaporation and salinity. During the period of E2s3, the climate became warm and humid, indicating the freshwater lacustrine facies, and E2s3 was characterized by freshwater and abundant algae. Moreover, compared with other intervals, the OM origin of E3d3 source rocks has noticeable terrestrial input. The OM origin of the E2s1+2 and E2s3 are mainly plankton and bacteria. Tectonic subsidence and climate change have affected the changes of the depositional environment in the western Bozhong Sag, thus controlling the source rocks distribution, the geochemical characteristics in the three intervals of lacustrine source rocks have distinct differences. Overall, it is effective to evaluate the paleoenvironmental characteristics of source rocks by biomarkers, major and trace elements. The established models may have positive implications for research of lacustrine source rocks in offshore areas with few drillings.

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Organic matter enrichment due to high primary productivity in the deep-water shelf: Insights from the lower Cambrian Qiongzhusi shales of the central Sichuan Basin, SW China

Cited by 18 publications

References 114 publications

Reconstruction of palaeo‐oil reservoirs in the ultra‐deep and over‐mature Sinian Dengying Formation of the Central Sichuan Basin: Insights from basin and petroleum system modelling

Reconstruction of palaeo‐oil reservoirs in the ultra‐deep and over‐mature Sinian Dengying Formation of the Central Sichuan Basin: Insights from basin and petroleum system modelling

Karst paleotopography on top of the Dengying Formation and petroleum geological significance in the Central Sichuan Basin, China

Paleoenvironmental Characteristics of Paleogene Lacustrine Source Rocks in the Western Bozhong Sag, Bohai Bay Basin, China: Evidence from Biomarkers, Major and Trace Elements

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