High microbial gas potential of Pleistocene lacustrine deposits in the central Qaidam Basin, China: An organic geochemical and petrographic assessment

Qiao, Jinqi; Grohmann, Sebastian; Baniasad, Alireza; Zhang, Chen; Jiang, Zhenxue; Littke, Ralf

doi:10.1016/j.coal.2021.103818

Cited by 11 publications

(5 citation statements)

References 118 publications

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“…However, Cheng et al suggest that the abnormally low regular sterane isomerization (0.03–0.41, 0.16 on average) in source rocks deposited in the high-salinity environment is an objective phenomenon related to the sedimentary environment (Figure f) . The data sets provided by Zhu et al and Qiao et al also contain many source rocks with abnormally low isomerization ratios (Figure f and Table S3). More importantly, as reported by Pan et al, C 29 -20S/(20S+20R) of six saline lacustrine source rocks with a depth range of 2830–3055 m collected from well YH-103 in the Qaidam Basin, China, also show two reversals at shallow and deep depths similar to our experiments, which only varied between 0.11 and 0.25 (Figure g).…”

Section: Discussionmentioning

confidence: 99%

Multistage Hydrocarbon Generation of Saline Lacustrine Source Rocks in Hydrous Pyrolysis: Insights from Clay Mineral–Organic Matter Interactions

Cai

et al. 2023

ACS Omega

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The organic matter (OM) in shale is closely associated with clay minerals, and its maturation is usually accompanied by the diagenesis of these minerals, especially smectite illitization. However, the effect of mineral transformation and its accompanying change of mineral–OM interactions in shale on hydrocarbon generation is still unclear. To investigate this question, smectite-rich immature shale was selected to carry out hydrous pyrolysis. Organic geochemistry and mineralogy of pyrolysates at different temperatures show that the maturation of OM is accompanied by the transformation of bulk and clay minerals. Based on the change in hydrocarbon yield, Rock-Eval parameters, and mineral composition, hydrocarbon generation in this study is divided into three stages: 25–300, 300–400, and 400–500 °C, which are the result of the synergistic evolution of clay minerals and OM. Multistage hydrocarbon generation can be attributed to the mineral transformation-induced desorption of mineral-bound soluble OM (SOM), decarboxylation and hydrocracking of kerogen promoted by solid acids, and cross-linking and cracking reactions of free SOM and residual kerogen under high temperatures. Although different from the classical hydrocarbon generation model of kerogen, this multistage hydrocarbon generation is consistent with the characteristics of the saline lacustrine source rocks in nature. The mineral transformation-induced desorption of SOM is a new pathway for petroleum formation, which can well explain the formation of low-mature oils in nature. In addition, the release of mineral-bound and kerogen-bound biomarkers results in two reversals of isomerization ratios. Considering mineral transformation and mineral–OM interactions can help us better understand and refine the hydrocarbon generation theory of OM.

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Section: Discussionmentioning

confidence: 99%

Multistage Hydrocarbon Generation of Saline Lacustrine Source Rocks in Hydrous Pyrolysis: Insights from Clay Mineral–Organic Matter Interactions

Cai

et al. 2023

ACS Omega

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“…1a). It has developed into a tectonic pattern characterized by high elevations in the west and low elevations in the east with the uplift of the Tibetan Plateau, and the Sanhu Depression is in the east Su et al, 2006;Qiao et al, 2021) (Fig. 1b).…”

Section: Tectonic Characteristicsmentioning

confidence: 99%

Evaluation of organic matter abundance of source rocks of biogenic gas: a case from the Quaternary Qigequan Formation Shale, Sanhu Depression, Qaidam Basin

Liu,

Jiang,

Tang

et al. 2024

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A correct understanding of organic matter abundance is key to understanding the conditions necessary for generating biogenic gas, seeking favorable exploration intervals and fields and evaluating resources correctly. The Qigequan Formation shale of the Quaternary in the Sanhu Depression of the Qaidam Basin is taken as the research object. The abundance of dissolved organic matter was determined through total carbon, pyrolysis and other experiments. The evaluation criteria were established and applied. The resource quality is calculated. The results are as follows. (1) Dissolved organic matter is the basis for biogenic gas generation and should be emphasized in the evaluation. (2) The shale has a relatively high dissolved organic carbon (DOC) content, with an average of 2.48 times that of insoluble organic carbon. (3) The DOC of the good source rock is more than 0.60%, that of the medium is 0.25~0.60%, and that of the poor is less than 0.25%. (4) The distribution of good source rocks is influenced by the position and depth of the water column and the paleoclimate. Favorable intervals are mainly in the upper sections of K10, K9 and K8 and the middle section of K7. The favorable areas are mainly the Tainan, Sebei and Sedong areas.

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“…For example, ratios of 22S/(22S + 22R) hopanes and ββ/(ββ + αα) steranes show a higher maturity stage in immature extracts from hypersaline rocks (ten Haven et al, 1986;Rullkötter et al, 1994). This discrepancy can be observed in the Pleistocene hypersaline sediments in the Qaidam Basin, i.e., the obviously too high hopane and steranes maturity-dependent ratios in the definitely immature sediments (Qiao et al, 2021b). Moreover, sterane isomerization ratios are also affected by biodegradation and weathering (Peters et al, 2005).…”

Section: Thermal Maturity Of Om and Hydrocarbon Potentialmentioning

confidence: 99%

Formation conditions and enrichment mechanisms of the Jurassic lacustrine organic-rich shale in the East Fukang Sag, Junggar Basin, NW China: A reassessment based on organic geochemistry

et al. 2023

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Chemical composition of sediments is often used to evaluate paleoclimate condition, provenance, tectonic setting, depositional condition, and paleoproductivity. However, the validity of these proxies has long been questioned. The comprehensive use of organic and inorganic multi-indicators in combination when interpreting issues related to terrestrial shales should be advocated. The paleodepositional environment, origin of organic matter (OM) and factor controlling OM accumulation in the Early Jurassic Badaowan (J1b) and Sangonghe (J1s) as well as Middle Jurassic Xishanyao (J2x) lacustrine shales in the East Fukang Sag are reassessed by using organic geochemical characteristics of the OM. Some previous knowledge is updated, and some knowledge is further supported by more evidence. The typical clay-rich shale developed under a lacustrine sedimental environment, and the thermal maturity of these organic-rich shales has entered the oil window and formed economic hydrocarbon potential for the tight-oil and shale-oil reservoirs. The paleoclimate conditions of the study area were warm and humid from the Early to Middle Jurassic periods but were colder and drier after the Middle Jurassic period. The salinity of the water column ranged from freshwater to brackish conditions. The J2x Formation was deposited under oxic conditions, while J1b and J1s formations developed under suboxic and reducing environmental conditions. The J2x Formation OM mainly derived from higher plants was deposited in a terrestrial environment,while the OM of J1b and J1s formations was a mixed OM derived from higher plants and bacteria with little algae deposited under bay/estuary environments alternated with terrestrial environments. It is effective to reflect the paleoclimate by element index and judge the salinity by the updated element thresholds, but it is not effective to evaluate the paleoredox conditions by common elemental ratios and to evaluate the paleoproductivity by Ba in the study area.

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High microbial gas potential of Pleistocene lacustrine deposits in the central Qaidam Basin, China: An organic geochemical and petrographic assessment

Cited by 11 publications

References 118 publications

Multistage Hydrocarbon Generation of Saline Lacustrine Source Rocks in Hydrous Pyrolysis: Insights from Clay Mineral–Organic Matter Interactions

Multistage Hydrocarbon Generation of Saline Lacustrine Source Rocks in Hydrous Pyrolysis: Insights from Clay Mineral–Organic Matter Interactions

Evaluation of organic matter abundance of source rocks of biogenic gas: a case from the Quaternary Qigequan Formation Shale, Sanhu Depression, Qaidam Basin

Formation conditions and enrichment mechanisms of the Jurassic lacustrine organic-rich shale in the East Fukang Sag, Junggar Basin, NW China: A reassessment based on organic geochemistry

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