Geochemical characteristics of He and CO 2 from the Ordos (cratonic) and Bohaibay (rift) basins in China

Dai, Jianhua; Ni, Yunyan; Qin, Shanshan; Huang, Shipeng; Gong, Daoyi; Liú, Dan; Feng, Ziqi; Peng, Weilong; Han, Wenxue; Fang, Chenchen

doi:10.1016/j.chemgeo.2017.02.011

Cited by 47 publications

(43 citation statements)

References 39 publications

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“…Therefore, the inorganic mantle gases could not migrate to reservoirs and mix with the organic gases. Dai et al (2017) have also confirmed that the Ordos Basin has no inorganic mantle gas injection. The possibility of the mixture with inorganic mantle gases is excluded.…”

mentioning

confidence: 53%

Geochemical characteristics and reasons for the carbon isotopic reversal of natural gas in the southern Jingbian gas field, Ordos Basin, China

Han

Chang

et al. 2019

Geol. Mag.

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The carbon isotope value of ethane in the southern part of the Jingbian gas field is lower than that in the northern part, indicating a carbon isotopic reversal in the southern Jingbian gas field (δ13Cmethane > δ13Cethane). Through comparing the geochemical characteristics of gases in the southern and northern parts of the gas field, the reasons for the carbon isotopic reversal in the southern Jingbian gas field were determined to be high thermal maturity and mixing action. When thermal maturity reaches a critical value, the carbon isotope value of ethane becomes relatively more depleted with thermal maturity. Although the carbon isotope value of methane increases with thermal maturity, the extent is relatively smaller. Finally, the rare phenomenon of δ13Cmethane > δ13Cethane occurs. High thermal maturity leads to the secondary thermal cracking of gases. Mixing of the cracked gases and primary gases also leads to carbon isotopic reversal. Both of the above mechanisms share a common premise, which is high thermal maturity.

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mentioning

confidence: 53%

Geochemical characteristics and reasons for the carbon isotopic reversal of natural gas in the southern Jingbian gas field, Ordos Basin, China

Han

Chang

et al. 2019

Geol. Mag.

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“…The Ordos Basin is in central-northern China and is associated with the inner-craton depression basin. The typical inland basin represents one of the most tectonically stable areas in China and has an area of over 250,000 m 2 [26]. The basin falls above and below the Archean granite and lower Proterozoic greenschist in the North China block, respectively.…”

Section: Geological Settingsmentioning

confidence: 99%

“…By analyzing the P-wave velocity and time-averaged fault slip rate, they concluded that mantle volatiles are generated in the upwelling asthenosphere, following which they rise through faults and fractures in which permeabilities are controlled by slip rates. In a study comparing the geochemical characteristics of helium and CO 2 in the cratonic and rift basins in China, Dai et al [26] determined that gas samples collected from the cratonic basins have lower levels of CO 2 and R/Ra ratios than those from the rift basins. Gas samples in the rift basin have been shown to have a larger range of variation in δ 13 C CO2 , implying the presence of stronger tectonic activities.…”

Section: Introductionmentioning

confidence: 99%

Fluid Geochemistry within the North China Craton: Spatial Variation and Genesis

Zhi

et al. 2021

Geofluids

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The North China Craton (NCC) is a typical representative of the ancient destruction craton. Numerous studies have shown that extensive destruction of the NCC occurred in the east, whereas the western part was only partially modified. The Bohai Bay Basin is in the center of the destruction area in the eastern NCC. Chemical analyses were conducted on 122 hot spring samples taken from the eastern NCC and the Ordos Basin. The δ 2 H and δ 18 O in water, δ 13 C in CO2, and 3He/4He and 4He/20Ne ratios in gases were analyzed in combination with chemical analyses of water in the central and eastern NCC. The results showed an obvious spatial variation in chemical and isotopic compositions of the geofluids in the NCC. The average temperature of spring water in the Trans-North China Block (TNCB) and the Bohai Bay Basin was 80.74°C, far exceeding that of the Ordos Basin of 38.43°C. The average δ D in the Eastern Block (EB) and the TNCB were −79.22‰ and −84.13‰, respectively. The He isotope values in the eastern region (TNCB and EB) ranged from 0.01 to 2.52, and the rate of contribution of the mantle to He ranged from 0 to 31.38%. δ 13 C ranged from −20.7 to −6.4‰ which indicated an organic origin. The chemical compositions of the gases in the EB showed that N2 originated mainly from the atmosphere. The EB showed characteristics of a typical gas subduction zone, whereas the TNCB was found to have relatively small mantle sources. The reservoir temperatures in the Ordos Basin and the eastern NCC (EB and TNCB) calculated by the K-Mg temperature scale were 38.43°C and 80.74°C, respectively. This study demonstrated clear spatial variation in the chemical and isotopic compositions of the geofluids in the NCC, suggesting the presence of geofluids from the magmatic reservoir in the middle-lower crust and that active faults played an important role in the transport of mantle-derived components from the mantle upwards.

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“…(3) 二次裂解 [72] ; (4) 过渡金属和水介质在 250~300℃环境中发生氧化还原作用, 导致乙烷和丙烷瑞利分馏 [73] . Dai等人 [40] 把由正碳同位素系列次生 [81] , 一般<0.05 [82] , 地幔氦Ra通常大于5 [83] , 上地幔氦为8.8±2.5, 下地幔(deep mantle)氦为5~50 [84] , Ra值在壳源气和幔源气之间为壳幔混合氦, 常出现在裂谷型盆地, 如渤海湾盆地, 壳源氦常出现在克拉通盆地, 如鄂尔多斯盆地和四川盆地, 前者93个气样…”

Section: 但由于某种地质因素影响腐殖煤壳质组比例unclassified

“…的 Ra 平均值为 0.033 [83] , 后者 78 个 Ra 值为 0.002~0.050 [85] . 四川盆地五峰-龙马溪组页岩气具有次生型负碳同位素系列的Ra值为0.01~0.04 [62,63] .…”

Section: 但由于某种地质因素影响腐殖煤壳质组比例unclassified

Coal-derived gas theory and its discrimination

Dai¹

2018

Chin. Sci. Bull.

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Geochemical characteristics of He and CO 2 from the Ordos (cratonic) and Bohaibay (rift) basins in China

Cited by 47 publications

References 39 publications

Geochemical characteristics and reasons for the carbon isotopic reversal of natural gas in the southern Jingbian gas field, Ordos Basin, China

Geochemical characteristics and reasons for the carbon isotopic reversal of natural gas in the southern Jingbian gas field, Ordos Basin, China

Fluid Geochemistry within the North China Craton: Spatial Variation and Genesis

Coal-derived gas theory and its discrimination

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