Arid climate disturbance and the development of salinized lacustrine oil shale in the Middle Jurassic Dameigou Formation, Qaidam Basin, northwestern China

Wang, Yuxuan; Xu, Shang; Hao, Fang; Poulton, Simon W.; Zhang, Yuanyin; Guo, Tonglou; Lu, Yangbo; Bai, Nan

doi:10.1016/j.palaeo.2021.110533

Cited by 18 publications

(8 citation statements)

References 110 publications

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“…Under arid climate conditions, the evaporation of lake water surpasses the replenishment of rainfall or river water, resulting in the gradual shrinkage of the lake basin, salinization, and the deposition of corresponding salt minerals (Du et al, 2020; Wang Yuxuan et al, 2021; Yuan, 2019). Deep brine, which is rich in salt substances, contributes to the increased concentration of salts in lake basin water.…”

Section: Sedimentary Characteristics Of the Saline Lacustrine Basinmentioning

confidence: 99%

Organic matter enrichment mechanism in saline lacustrine basins: A review

Wang

Bai³

et al. 2023

Geological Journal

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Organic‐rich shale in saline lacustrine basins holds significant importance as a source rock for conventional hydrocarbon exploration and has emerged as a prominent target for unconventional hydrocarbon exploration and development in recent years. Based on saline lacustrine basins, this paper provides a summary of the organic matter enrichment mechanisms in saline lacustrine basins, considering sedimentary characteristics, biological activities, factors for the organic matter enrichment and consumption, and hydrocarbon generation. The implications for these factors are discussed in relation to the distribution prediction of high‐quality lacustrine shale district settings and the exploration and development of shale oil. Saline lacustrine basins undergo distinct evolutionary stages, each corresponding to different sedimentary stages involving carbonate minerals, sulphate minerals, and alkaline minerals. Moreover, these basins exhibit diverse biological types and experience extensive biological activities. The prosperity of organisms and the accumulation of sedimentary organic matter are ensured by halophilic organisms. Organic matter enrichment in saline lacustrine basins is influenced by two main aspects: the primary productivity of organic matter, which is promoted by the proliferation of halophilic organisms, and the efficient preservation of organic matter facilitated by the strong reducing environment resulting from promoted water salinity stratification. The organic matter consumption in saline lacustrine basins involves bacterial sulphate reduction (BSR) in the early stages, thermochemical sulphate reduction (TSR) in the late stages, and dilution of salt minerals with higher depositional rates. of the presence of salt beds and saline minerals positively influences hydrocarbon generation and expulsion in organic‐rich shale within saline lacustrine deposition. Consequently, continental saline lacustrine basins in China offer favourable conditions for the formation of organic‐rich shale and present broad prospects for the exploration of shale oil and gas resources.

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Section: Sedimentary Characteristics Of the Saline Lacustrine Basinmentioning

confidence: 99%

Organic matter enrichment mechanism in saline lacustrine basins: A review

Wang

Bai³

et al. 2023

Geological Journal

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“…The Qaidam Basin is a prominent oil and gas exploration and production base of NW China’s Jurassic coal-bearing strata. − According to the source correlation studies of oil and gas, the hydrocarbons are derived mainly from the Lower-Middle Jurassic coal-bearing mudstone sequences. − Previous research related to the Lower-Middle Jurassic coal-bearing strata of the Qaidam Basin mainly focused on provenance, sedimentary environment, sequence stratigraphy, and palynoflora characteristics. − Although the organic geochemistry, source of organic matter, and hydrocarbon generation potential of the organic-rich shales of the Shimengou Formation (Callovian Stage) have been extensively studied in recent years, − the geochemical characteristics of the coal-bearing mudstones in the Middle Jurassic Dameigou and Shimengou formations from the Aalenian to Callovian stages in the Qaidam Basin are rarely reported. In addition, little is known about the paleoenvironmental conditions as well as their influences on the organic matter accumulation of the coal-bearing mudstones during the Middle Jurassic.…”

Section: Introductionmentioning

confidence: 99%

Geochemical Characteristics of the Middle Jurassic Coal-Bearing Mudstones in the Dameigou Area (Qaidam Basin, NW China): Implications for Paleoclimate, Paleoenvironment, and Organic Matter Accumulation

Zhou,

Sun,

Yang

et al. 2023

ACS Omega

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The Qaidam Basin is a prominent oil and gas exploration and production base of NW China’s Jurassic coal-bearing strata. Coal-bearing mudstones are important source rocks for unconventional reservoirs and can record valuable paleoenvironment and paleoclimate information. Here, geochemical analysis including total organic carbon (TOC), total sulfur, organic carbon isotopic composition, rock pyrolysis, X-ray diffraction, and major and trace elements were carried out on mudstone samples from the Middle Jurassic coal-bearing strata of the Dameigou section in the Qaidam Basin to reveal the paleoclimatic and paleoenvironmental conditions during the deposition of the strata and their controls on organic matter accumulation. Results show that the Middle Jurassic Dameigou and Shimengou formations include three significant stages based on their average TOC values of (3.32%, Stage I; 0.87%, Stage II; and 4.42%, Stage III) from the bottom to the top. The organic matter in mudstones in Stages I and II are mainly derived from terrestrial higher plants, while the organic matter has mixed sources of higher plant debris and lower aquatic organisms in Stage III. Paleoclimate parameters indicate that the mudstones in Stage I were deposited under humid and warm conditions, while the climate in Stage II changed to semiarid and warm conditions before turning dry and hot in Stage III. The varying paleoenvironmental characteristics under different paleoclimatic conditions have also been reconstructed. Our results suggest that the accumulation of organic matter in Stages I and II was primarily controlled by redox conditions, while paleoproductivity is the major controlling factor for organic matter accumulation in Stage III.

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“…Oil shale is typically defined by a minimum oil yield of 3.5 wt.% and a maximum ash yield of 40% and can be subdivided according to the oil yield into three groups: low-quality oil shale (oil yield of 3.5-5.0%), medium-quality oil shale (5.0-10.0%), and high-quality oil shale (10.0% and above) [11,[19][20][21][22]. Large amounts of oil shales have been found in the Middle Jurassic Mudstone Member of the Shimengou Formation in the northern Qaidam Basin, where they are widely distributed with a large thickness but of different qualities [23][24][25][26]. Their average oil yield is 6.2 wt.%, with a maximum value of 11.5 wt.%.…”

Section: Introductionmentioning

confidence: 99%

A Comparative Study of Different Quality Oil Shales Developed in the Middle Jurassic Shimengou Formation, Yuqia Area, Northern Qaidam Basin, China

et al. 2022

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Oil shales are developed in the Shale Member of the Middle Jurassic Shimengou Formation in the Qaidam Basin, China. The oil shales can be classified into three quality groups (low-, medium-, and high-quality oil shales) through a comprehensive analysis protocol that includes Rock-Eval pyrolysis, total organic carbon (TOC) content, proximate analysis, gas chromatography-mass spectrometry (GC-MS), X-ray diffraction (XRD), major and trace element analyses, and maceral analysis. The low-quality oil shales mainly contain type II1 kerogen, the medium-quality oil shales mainly contain type I-II1 kerogen, and the high-quality oil shales mainly contain type I kerogen. All are immature to early thermally mature. The oil yield of the oil shales is directly related to their quality and are positively correlated with TOC content and calorific value. All studied samples were deposited under anaerobic conditions but in different paleoenvironments. The low-quality oil shales were mainly deposited in fresh-water environments, whereas the high-quality oil shales were usually developed in highly saline and reducing environments. Salinity stratification and evidence of algal blooms that are conducive to organic matter enrichment were identified in both medium- and high-quality oil shales, the latter having the highest paleoproductivity and the best preservation conditions. In summary, shale quality is controlled by a combination of factors, including algal abundance, preservation conditions, the existence of algal blooms and salinity stratification, and paleoproductivity. This study reveals how these different factors affect the quality of oil shales, which might provide an in-depth explanation for the formation process of lacustrine oil shales.

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Arid climate disturbance and the development of salinized lacustrine oil shale in the Middle Jurassic Dameigou Formation, Qaidam Basin, northwestern China

Cited by 18 publications

References 110 publications

Organic matter enrichment mechanism in saline lacustrine basins: A review

Organic matter enrichment mechanism in saline lacustrine basins: A review

Geochemical Characteristics of the Middle Jurassic Coal-Bearing Mudstones in the Dameigou Area (Qaidam Basin, NW China): Implications for Paleoclimate, Paleoenvironment, and Organic Matter Accumulation

A Comparative Study of Different Quality Oil Shales Developed in the Middle Jurassic Shimengou Formation, Yuqia Area, Northern Qaidam Basin, China

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