Distribution and carbon isotope composition of pregnane in carbonate-evaporitic rocks from the Bonan Sag, Bohai Bay Basin, Eastern China: Insights into sources and associated lake environments

The faulted lacustrine Bohai Basin in eastern China contains abundant hydrocarbon resources. In these reservoirs, understanding the sandstone diagenesis and the resulting formation water provides a means to unravel the evolution processes in the basin. In most cases, the lack of isotopic and trace element analysis tests in this type of basin limits the research on the origin and evolution of formation water in this area. We have used multivariate statistical methods to classify the geochemical characteristics of the formation water for the Cenozoic Formation of Bonan Sag in the Bohai Bay Basin. Analysis of correlations among the evolution processes of different ions in different types of formation water provides an understanding of the primary factors influencing the ion content. We also evaluate the water-rock interactions of different types of formation water to evaluate their geologic significance, and we find three types. Type I formation water includes a mixture of river water, lake water, and atmospheric precipitation and exhibits weak water-rock interactions. Type II formation water contains primitive freshwater and brackish lake water that has undergone an evolution process similar to that of type I formation water, but that was followed by evaporation and concentration, the dissolution and precipitation of calcite and iron calcite, and feldspar dissolution. Type III formation water, which is a product of rock reconstruction, originates from saline lake sediment water. After undergoing evolution processes similar to those of types I and II, type III formation water is also affected by dissolution of evaporite, albite, dolomite, and iron dolomite. Thus, type III formation water is the product of water-rock interactions such as precipitation, SO42− reduction, and pyrite precipitation in which the water-rock reaction controls the development mechanism and characteristics of the reservoir space.

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Predictive distribution of high-quality tight reservoirs of coarse clastic rocks by linking diagenesis to sedimentary facies: Evidence from the upper Sha 4 Member in the northern Bonan Sag, Bohai Bay Basin, eastern China

Interpretation ◽

10.1190/int-2017-0139.1 ◽

2018 ◽

Vol 6 (2) ◽

pp. T413-T429 ◽

Cited By ~ 5

Author(s):

Dong Wu ◽

Xiantai Liu ◽

Yushan Du ◽

Long Jiang ◽

Ziyan Cheng

Keyword(s):

Eastern China ◽

Sedimentary Facies ◽

Middle Part ◽

Bohai Bay ◽

Bohai Bay Basin ◽

High Quality ◽

Clastic Rocks ◽

Bonan Sag ◽

Tight Reservoirs ◽

Channel Deposits

Coarse clastic rocks of the upper Sha 4 Member in the northern Bonan Sag of the Bohai Bay Basin in eastern China are important hydrocarbon reservoirs. The deposits are tight reservoirs owing to the low porosity (less than 10%) and low permeability (less than 1 mD). Because of the strong heterogeneity, although the reserve in the northern Bonan Sag is remarkable, only 4.9% of the reserves are recovered. We have studied these tight reservoirs by linking diagenesis to sedimentary facies to help predict the distribution of high-quality tight reservoirs. Petrographic analysis is undertaken based on cores, thin sections, X-ray diffraction and scanning electron microscope, helpful to understand the impacts on tight reservoirs of sedimentary factors and diagenesis factors. Sedimentary microfacies, lithologic characteristics, reservoir property, diagenesis, and diagenetic minerals are studied. Coarse clastic rocks are deposited mainly in nearshore subaqueous fans and fan deltas. The multistage sandstones are the valid reservoirs of coarse clastic rocks and dominated by feldspathic litharenite, lithic arkose, and arkose. The reservoir property is poor principally owing to the strong compaction and cementation. Pores are composed of secondary pores and primary pores. The secondary pore, generated in the dissolution of detrital minerals and/or cements, is the major type of pores and important to porosity improvement. By linking diagenesis to sedimentary facies, it can be concluded that high-quality tight reservoirs of coarse clastic rocks of the upper Sha 4 Member in the northern Bonan Sag of Bohai Bay Basin in eastern China are associated with medium to coarse-grain sandstones, found in the middle part of underwater distributary channel deposits in fan deltas and in the middle part of underwater channel deposits in nearshore subaqueous fans, with abundant secondary porosity but low cement contents, vertically at depths ranging from 3500 to 4100 m.

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Comparison of the carbon isotope composition of total organic carbon and long-chain n-alkanes from surface soils in eastern China and their significance

Science Bulletin ◽

10.1007/s11434-008-0296-3 ◽

2008 ◽

Vol 53 (24) ◽

pp. 3921-3927 ◽

Cited By ~ 11

Author(s):

ZhiGuo Rao ◽

GuoDong Jia ◽

ZhaoYu Zhu ◽

Yi Wu ◽

JiaWu Zhang

Keyword(s):

Organic Carbon ◽

Total Organic Carbon ◽

Carbon Isotope ◽

Isotope Composition ◽

Eastern China ◽

Carbon Isotope Composition ◽

Surface Soils ◽

Long Chain

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Geochemical characteristics and source of natural gases in the northern Jizhong Subbasin, Bohai Bay Basin, eastern China

10.5194/egusphere-egu2020-3789 ◽

2020 ◽

Author(s):

Nian Liu ◽

Nansheng Qiu

Keyword(s):

Carbon Dioxide ◽

Carbon Isotope ◽

Eastern China ◽

Geochemical Characteristics ◽

Bohai Bay ◽

Bohai Bay Basin ◽

Organic Matters ◽

Natural Gases ◽

Isotopic Compositions ◽

Shallow Strata

The geochemical characteristics and source of natural gases in the northern Subbasin, Bohai Bay Basin, eastern China are investigated systematically by the chemical components, stable isotopic compositions, noble gases isotopic compositions, and geochemical characteristics of associated oils. The results show that several genetic gases are identified in the study area, including thermogenic gas (sapropelic and humic gas), biogenetic gas (primary and secondary microbial gas) and mixed gas. Gases in the shallow strata (Ed, Es1, Es2, Es3 and some Es4 samples) are mainly oil-associated gases, whereas the gases in the deep strata (some Es4 samples, C-P and O) are mainly coal-derived gases and mixed-source gases. Some microbial gases including primary and secondary microbial gases can be identified in shallow Es1 and Es3 reservoirs. The carbon dioxide reduction under anaerobic conditions may be responsible for the anomalously heavy carbon isotope in carbon dioxide and light carbon isotope in methane in the biodegradation gases from the shallow strata (<1900 m), whereas carbon dioxide with heavy isotope compositions in the deeply buried Ordovician reservoirs may be the production of strong acids react with carbonate rocks during acidification and fracturing. The oil-associated gases in shallow strata are derived primarily from the Paleogene Es3 and Es4+Ek bearing sapropelic organic matters, whereas the coal-derived gases in the relatively deep reservoirs are mainly derived from the Paleozoic C-P coal-bearing source rocks and mixed organic matters in Es4+Ek. In addition, the dry gas (secondary cracking gas) in deep to ultra-deep carbonate reservoir may be the potential and favorable exploration field.

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Lacustrine shale oil resource potential of Es 3 L Sub-Member of Bonan Sag, Bohai Bay Basin, Eastern China

Journal of Earth Science ◽

10.1007/s12583-016-0945-4 ◽

2017 ◽

Vol 28 (6) ◽

pp. 996-1005 ◽

Cited By ~ 4

Author(s):

Shuangfang Lu ◽

Wei Liu ◽

Min Wang ◽

Linye Zhang ◽

Zhentao Wang ◽

...

Keyword(s):

Eastern China ◽

Bohai Bay ◽

Shale Oil ◽

Bohai Bay Basin ◽

Resource Potential ◽

Bonan Sag ◽

Lacustrine Shale

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High time-resolved measurement of stable carbon isotope composition in water-soluble organic aerosols: method optimization and a case study during winter haze in eastern China

Atmospheric Chemistry and Physics ◽

10.5194/acp-19-11071-2019 ◽

2019 ◽

Vol 19 (17) ◽

pp. 11071-11087 ◽

Cited By ~ 4

Author(s):

Wenqi Zhang ◽

Yan-Lin Zhang ◽

Fang Cao ◽

Yankun Xiang ◽

Yuanyuan Zhang ◽

...

Keyword(s):

Carbon Isotope ◽

Isotope Composition ◽

Eastern China ◽

Stable Carbon Isotope ◽

Organic Aerosols ◽

Carbon Isotope Composition ◽

Water Soluble ◽

Total Carbon ◽

Stable Carbon ◽

Air Mass

Abstract. Water-soluble organic carbon (WSOC) is a significant fraction of organic carbon (OC) in atmospheric aerosols. WSOC is of great interest due to its significant effects on atmospheric chemistry, the Earth's climate and human health. The stable carbon isotope (δ13C) can be used to track the potential sources and investigate atmospheric processes of organic aerosols. However, the previous methods measuring the δ13C values of WSOC in ambient aerosols require a large amount of carbon content, are time-consuming and require labor-intensive preprocessing. In this study, a method of simultaneously measuring the mass concentration and the δ13C values of WSOC from aerosol samples is established by coupling the GasBench II preparation device with isotopic ratio mass spectrometry. The precision and accuracy of isotope determination is better than 0.17 ‰ and 0.5 ‰, respectively, for samples containing WSOC amounts larger than 5 µg. This method is then applied for the aerosol samples collected every 3 h during a severe wintertime haze period in Nanjing, eastern China. The WSOC values vary between 3 and 32 µg m−3, whereas δ13C−WSOC ranges from −26.24 ‰ to −23.35 ‰. Three different episodes (Episode 1, Episode 2 and Episode 3) are identified in the sampling period, showing a different tendency of δ13C−WSOC with the accumulation process of WSOC aerosols. The increases in both the WSOC mass concentrations and the δ13C−WSOC values in Episode 1 indicate that WSOC is subject to a substantial photochemical aging during the air mass transport. In Episode 2, the decline of the δ13C−WSOC is accompanied by the increase in the WSOC mass concentrations, which is associated with regional-transported biomass burning emissions. In Episode 3, heavier isotope (13C) is exclusively enriched in total carbon (TC) in comparison to WSOC aerosols. This suggests that the non-WSOC fraction in total carbon may contain 13C-enriched components such as dust carbonate, which is supported by the enhanced Ca2+ concentrations and air mass trajectory analysis. The present study provides a novel method to determine the stable carbon isotope composition of WSOC, and it offers a great potential to better understand the source emission, the atmospheric aging and the secondary production of water-soluble organic aerosols.

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