High abundance of carotanes in the brackish-saline lacustrine sediments: A possible cyanobacteria source?

Ding, Wenjing; Hou, Dujie; Jiang, Lian; Jiang, Yuhan; Wu, Piao

doi:10.1016/j.coal.2019.103373

Cited by 45 publications

(30 citation statements)

References 91 publications

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“…The relevant parameters in the study area fall within the above range, reflecting the low maturity of crude oil and the overall heavy oil quality. The reasons are as follows: (1) in the strong reducing environment where the water body is salty, the organic matter such as algae is relatively rich, and the content of isoparaffins and naphthenes in the produced crude oil is relatively high; 35 (2) the source rocks of Lucaogou Fm have a good organic matter type and early hydrocarbon generation, forming large-scale low mature shale oil, with a high content of gum and asphaltene (nonhydrocarbon + asphaltene distributed between 15.39 and 72.77%, with an average value of 34.65%) ( Table 6 ). During the short-distance migration, the above components were not adsorbed by the formation but remained in the crude oil.…”

Section: Resultsmentioning

confidence: 99%

Evaluation of the Shale Oil Reservoir and the Oil Enrichment Model for the First Member of the Lucaogou Formation, Western Jimusaer Depression, Junggar Basin, NW China

et al. 2021

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The Lucaogou Formation (Fm) in the Jimusaer depression is the first large-scale development of a terrigenous clastic sedimentary shale oil reservoir in China. Nearly one billion tons of shale oil resources have been discovered. However, the current exploration and development is concentrated in the eastern part of the sag. The limited geological understanding in the western area has restricted the prediction and development of “sweet spots” for shale oil. To help rectify this, we have studied the petrology, geochemistry, oil content, and pore properties of the second part of the first member (Mbr) of the Lucaogou Fm (P 2 l 1 2 ) in a typical well (Ji-X) in the western part of the sag. The results show that P 2 l 1 2 in the Jimusaer sag is a mixed fine-grained sedimentary system composed of sandstone, mudstone, and carbonate, which can be divided into seven types: dolomitic mudstone, calcareous mudstone, mudstone, mixed fine-grained rock, argillaceous limestone, sandstone, and argillaceous dolomite. The organic matter type of P 2 l 1 2 in well Ji-X is dominated by types I and II, and this is the best source rock in the whole exploration area of the Jimusaer sag. The overall oil saturation is relatively high, but the maturity of crude oil is low, and the overall oil quality is heavy, which is mainly controlled by the sedimentary environment and maturity of source rocks. Lithology and reservoir physical properties are the key to control oil content. The high-quality light oil reservoir lithology is argillaceous dolomite and sandstone. The higher the content of macropores and mesopores, the weaker the heterogeneity of the pore structure, and the better the oil content in the reservoir. There are four light oil sweet spots in the upper part (burial depth less than 4366 m), and there are excellent source rocks with high HI and high organic matter content near each sweet spot. This discovery of shale oil enrichment regularity will effectively guide the development of shale oil in continental lacustrine basins in other parts of the world.

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Section: Resultsmentioning

confidence: 99%

Evaluation of the Shale Oil Reservoir and the Oil Enrichment Model for the First Member of the Lucaogou Formation, Western Jimusaer Depression, Junggar Basin, NW China

et al. 2021

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“…The Permian Lucaogou Formation is the main source rock in the Jimsar Sag and the main stratum for shale oil exploration. The 100-300 m thick Lucaogou Formation was deposited in a semi-deep to deep lake environment with an arid climate and a high salinity (Cao et al, 2016;Ding et al, 2020). The Lucaogou Formation has a complex lithology and strong heterogeneity.…”

Section: Geologic Settingmentioning

confidence: 99%

Total Scanning Fluorescence Characteristics and Implications of Shale Oil in the Lucaogou Formation, Jimsar Sag, Junggar Basin, NW China

Zhao

Hou

et al. 2021

Front. Earth Sci.

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The Lucaogou Formation in the Jimsar Sag is a typical lacustrine shale oil development area where the first large-scale shale oil field in China was discovered, and a large number of studies have been conducted on the genesis and distribution of the shale oil in this formation. However, few detailed studies have been conducted on the comparison between the characteristics of the hydrocarbons in the shale and the adjacent tight reservoirs in the same shale sequence package. In this study, the total scanning fluorescence (TSF) quantitative fluorescence technique, which has been rarely applied to and studied in the Lucaogou Formation in the Jimsar Sag, was used to conduct systematic quantitative fluorescence analysis of the shale, tight reservoirs, and crude oils in the Lucaogou Formation. The geochemical analysis was also carried out for all samples. The results revealed that the shale, tight reservoirs, and oils have similar single-peak TSF spectrograms, and different values of the TSF parameters in the Lucaogou Formation. The TSF parameters R1 and R2 values of the blocky shale, fractured shale, tight reservoirs, and produced oils are decreased successively. The TSF parameters can be used as indicators of hydrocarbon composition, physical properties, thermal maturity, migration, and oil-producing layers. The values of TSF parameters R1 and R2 are generally smaller in the upper section of the Lucaogou Formation (P2l2) than in the lower section (P2l1), indicating that the hydrocarbons in the upper section have better physical properties and higher thermal maturity. The distribution of TSF parameters R1 and R2 in the upper section of the Lucaogou Formation is relatively scattered, indicating that the hydrocarbons have undergone obvious lateral migration. Based on the TSF parameter comparison of core and oil samples, it was preliminarily determined that the shale oil in the upper and lower sections of the Lucaogou Formation was mainly produced from the tight reservoirs in the shale sequence. The results of this study provide new data and ideas for fine studies of the shale oil in the Lucaogou Formation in the Jimsar Sag.

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“…The quantity of organic matter is mainly controlled by the abundance of organic matter and, to some extent, is affected by the thermal maturity. The quality of organic matter depends on the type of organic matter and its precursors (Erik et al, 2005;Hakimi and Abdullah, 2013;Tissot and Welte, 1984). In this study, we use PG values and the ratio of chloroform bitumen to TOC to assess the hydrocarbon generation capacity.…”

Section: Source Rock Geochemistrymentioning

confidence: 99%

“…A high b-carotane index reflects a reducing and high-salinity environment because saltresistant photosynthetic organisms (e.g. Dunaliella) can accumulate b-carotane to >14% of their dry cell weight, and adapt to a high-salinity environment (Ding et al, 2020;Francavilla et al, 2010;Tao et al, 2019). Unlike the Fengcheng Formation, in which the b-carotane index is >1.0 (Figure 10(a); Xia et al, 2020a), the b-carotane index values of most Carboniferous, Jiamuhe Formation, and Lower-Wuerhe Formation samples are <1.0.…”

Section: Sedimentary Environment Indicated By Biomarkersmentioning

confidence: 99%

Organic petrology, geochemistry, and hydrocarbon generation capacity of Permo–Carboniferous source rocks in the Mahu Sag, northwestern Junggar Basin, China

Qin

Zhi

2021

Energy Exploration & Exploitation

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The Mahu Sag in the Junggar Basin, China, is a hydrocarbon-rich sag. Abundant hydrocarbon source rocks were developed in the late Paleozoic there across the Carboniferous–Permian boundary. However, studies of the source rocks have focused mainly on the lower Permian Fengcheng Formation. Here we compare the Fengcheng Formation with other Carboniferous rocks and those of the lower Permian Jiamuhe and middle Permian Lower-Wuerhe formations. Based on organic petrological and geochemical data, the organic matter precursors, sedimentary facies, and resource potential of these source rocks were investigated. The bio-precursors of Carboniferous, Jiamuhe, and Lower-Wuerhe Formations were dominantly estuarine higher plants, Nematothallus -higher plants, and spores, respectively. The bio-precursors of Fengcheng Formation were mainly bacteria and algae, and the organic matter is abundant, with a high hydrocarbon-generating capacity and significant shale oil potential. In contrast, the other three formations contain poor-quality source rocks, although the Lower-Wuerhe Formation has a higher organic matter abundance than the Jiamuhe Formation. The Carboniferous organic matter contains mainly type II kerogen, whereas the Jiamuhe and Lower-Wuerhe formations contain type III kerogen. The thermal maturities determined from Tmax values is larger than those indicated by biomarkers. The biomarkers show that the three studied formations contain a mixture of terrestrial higher plants and bacteria–algae, with the contribution of green algae being higher than that of bacteria in most samples. However, the ratio of algae to bacteria is lower than that of the Fengcheng Formation. The Fengcheng Formation was deposited in a strongly reducing, high-salinity, and water-stratified sedimentary environment. The other three formations were deposited in an oxidizing–reducing, low-salinity, and water-unstratified environment. They are characterized by the predominance of mudstone over carbonate rocks and the descending distribution type of tricyclic terpenes. Our results provide a basis for research on upper Paleozoic source rocks in western China, and useful information for oil and gas exploration in the Mahu Sag.

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High abundance of carotanes in the brackish-saline lacustrine sediments: A possible cyanobacteria source?

Cited by 45 publications

References 91 publications

Evaluation of the Shale Oil Reservoir and the Oil Enrichment Model for the First Member of the Lucaogou Formation, Western Jimusaer Depression, Junggar Basin, NW China

Evaluation of the Shale Oil Reservoir and the Oil Enrichment Model for the First Member of the Lucaogou Formation, Western Jimusaer Depression, Junggar Basin, NW China

Total Scanning Fluorescence Characteristics and Implications of Shale Oil in the Lucaogou Formation, Jimsar Sag, Junggar Basin, NW China

Organic petrology, geochemistry, and hydrocarbon generation capacity of Permo–Carboniferous source rocks in the Mahu Sag, northwestern Junggar Basin, China

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