scholarly journals Evaluation of Source Rock Quality in Chang-7 Member of Major Oil Fields in Ordos Basin

2022 ◽  
Vol 2152 (1) ◽  
pp. 012040
Author(s):  
Tianyi Li
Keyword(s):  
Source Rock ◽  
Sedimentary Environment ◽  
Ordos Basin ◽  
Oil Field ◽  
Oil Fields ◽  
Rock Quality ◽  
Multiple Dimensions ◽  
Kerogen Type ◽  
The Ordos Basin

Abstract Petroleum is an important natural resource for human. The demand for petroleum in the next several decades will continue to be high, which requires the exploitation of more petroleum sources. Chang-7 member of the Ordos basin is proven to be the richest among all members, and this research took a focus on making a comparison between the source rock quality of Chang-7 member in four major oil fields in the basin, to provide a simple view of priority oil fields for exploitation in the future. The research analyzed the source rock quality of four oil fields from the TOC, A%, rock type, R0, sedimentary environment, and kerogen type, and found a superiority of source rock quality of Maling and Zhidan oil field in multiple dimensions, mainly triggered by their sedimentary environment. The research concluded that the oil fields that was once in the central-southern region of the basin contains a slightly better source rock quality among the chosen fields, which is related to a more stable sedimentary environment in the early Triassic.

scholarly journals Triassic Low Temperature Hydrothermal Activities(LTHA) From the Ordos Basin of Northern China

2021 ◽  
Author(s):  
Jiyuan You ◽  
Yiqun Liu ◽  
Dingwu Zhou ◽  
Yiyao Yang
Keyword(s):  
Hydrothermal Vents ◽  
Sedimentary Environment ◽  
Ordos Basin ◽  
Sedimentary Rocks ◽  
Northern China ◽  
Source Rocks ◽  
Three Samples ◽  
The Ordos Basin ◽  
Hydrothermal Activities

Abstract Because few well-preserved hydrothermal channels have been found in terrestrial sedimentary rocks, research on LTHA in geological history is relatively sparse. In this study, we present our original discovery of “hydrothermal channels” from the Chang 7 source rocks of the Triassic Yanchang Formation in the Ordos Basin, China, and provide the best evidence for deciphering LTHA preserved in the geological record (i.e., sedimentary rocks). Three possible LTHA samples (i.e., samples 1551.6, 1551.6-2 and 1574.4) were collected for this study; they were interbedded with mudstones and oil shales, indicative of a deep-lake sedimentary environment. All three samples consist mainly of anhydrite, pyrite, and dolomite with the formation of mineral zoning across the walls of these structures, suggesting a sulfate-dominated stage and a carbonate-sulfide replacement stage. Moreover, their in situ geochemistry is characterized by high Eu, U, Th, Sr, Mn and U/Th ratios, which are typical indicators of hydrothermal vents. In addition, their S isotopes range from 7.89% to 10.88%, the magmatic sulfur accounted for approximately 94.3%, implying a possible magmatic trigger for these hydrothermal channels. All this evidence shows that the Triassic sedimentary rocks of the Ordos Basin probably contain LTHA. Comparing ancient LTHA to modern hydrothermal chimneys, we should note the important implications of LTHA; their formation mechanism may have been related to oil production, and they are possible indicators for future oil investigations. Further, they have great significance for studying the hydrothermal properties of primary dolomite.

GEOCHEMICAL CHARACTERISTICS AND SOURCE OF CHANG 8 CRUDE OIL IN THE EAST PART OF SHANBEI SLOPE, ORDOS BASIN, CHINA

2021 ◽  
pp. 1-31
Author(s):  
Zhenglu Xiao ◽  
Shijia Chen ◽  
Xiangdong Yin ◽  
Pan Wang ◽  
Jiang Zhu ◽  
...  
Keyword(s):  
Crude Oil ◽  
Source Rock ◽  
Higher Plants ◽  
Saturated Hydrocarbon ◽  
Vitrinite Reflectance ◽  
Sedimentary Environment ◽  
Ordos Basin ◽  
Aquatic Organisms ◽  
Source Rocks ◽  
East Part

There are three sets of potential source rocks in the Yanchang Formation in the east part of the Shanbei Slope in the Ordos Basin. Based on the experimental results of total organic carbon, vitrinite reflectance, rock organic matter extraction, and saturated hydrocarbon chromatography (GC-MS), we have analyzed the geochemical and biomarker characteristics of the Chang 7, Chang 8, and Chang 9 source rocks, and the Chang 8 reservoir extracts and find that the Chang 7, Chang 8, and Chang 9 source rocks were deposited in the sedimentary environment of weak oxidation and weak reduction. Higher plants contribute more in the parent materials of the Chang 7 and Chang 9 source rocks, whereas lower aquatic organisms contribute more to the Chang 8 source rock. However, the source of the Chang 8 crude oil in the east part of Shanbei Slope does not match the chemical fingerprint of the Chang 8 source rock. To address this problem, we examined samples taken from the Zhidan oilfield, where our results show that the Chang 7, Chang 8, and Chang 9 source rocks all have hydrocarbon-supplying capacity. The relative abundance of regular steranes (C27, C28, C29) and hopane (17α(H), 21β(H)-hopane, 17β(H)-rearranged hopane, 18α(H)-22,29,30-trinorhopane) provides a means to assign the crude oil components to a given. Further analysis of the biomarkers of the three source rocks and those of the Chang 8 crude oil indicate that crude oil in the Chang 8 reservoir was not generated in situ; rather, it was supplied by the underlying Chang 9 source rock.

Organic geochemistry of oil and source rock strata of the Ordos Basin, north-central China

AAPG Bulletin ◽  
2007 ◽  
Vol 91 (9) ◽  
pp. 1273-1293 ◽  
Author(s):  
Andrew D. Hanson ◽  
Bradley D. Ritts ◽  
J. Michael Moldowan
Keyword(s):  
Source Rock ◽  
Organic Geochemistry ◽  
Ordos Basin ◽  
Central China ◽  
North Central ◽  
The Ordos Basin ◽  
Rock Strata

scholarly journals Carbon and Hydrogen Isotopic Reversals in Highly Mature Coal-Derived Gases: A Case Study of Paleozoic Gases in the Southern Ordos Basin, China

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-23
Author(s):  
Dan Liu
Keyword(s):  
Source Rock ◽  
Vitrinite Reflectance ◽  
Ordos Basin ◽  
Isotopic Fractionation ◽  
Carbon Isotopic ◽  
Wet Gas ◽  
The Ordos Basin ◽  
Almost All ◽  
Mixing Of Gases

The compositional carbon isotopic seriesδ13C-CH4<δ13C-C2H6<δ13C-C3H8<δ13C-C4H10is common in thermogenic gases. With the exploration of deeper strata, however, isotopic reversals (δ13C-CH4>δ13C-C2H6>δ13C-C3H8) in overmature unconventional shale gases and conventional (coal-derived) gases have been identified. Paleozoic gases in the southern Ordos Basin, China, with partial or complete isotopic reversals, were studied as examples of isotopic fractionation in overmature coal-derived gases. Isotopic compositions of gases of different maturities from the Ordos Basin and shale gases from around the world were compared. Results indicate that carbon isotopic series are related to maturity. Complete isotopic reversal occurs mostly in regions with vitrinite reflectanceRo>2.4%. Where2.4%>Ro>2.0%, almost all gases display partial isotopic reversal, withδ13C-CH4>δ13C-C2H6orδ13C-C2H6>δ13C-C3H8. Carbon isotopic reversal in coal-derived gases is not caused by abiotic origin, the mixing of gases from different types of source rock, abiotic polymerization, wet gas cracking, and other mechanisms that contribute to reversal in shale gases. Based on the unique structure of coaly source rock and the geology of the Ordos Basin, closed-system aromatization-polycondensation reactions are considered the most likely cause of carbon isotopic reversal. During the reactions, isotopically light gases are generated by recombination of previously formed hydrocarbons and residual kerogen-coal. Hydrogen isotopic reversal in the southern Ordos Basin might also be caused by aromatization-polycondensation reactions.

Stable carbon isotope compositions and source rock geochemistry of the giant gas accumulations in the Ordos Basin, China

2005 ◽  
Vol 36 (12) ◽  
pp. 1617-1635 ◽  
Author(s):  
Jinxing Dai ◽  
Jian Li ◽  
Xia Luo ◽  
Wenzheng Zhang ◽  
Guoyi Hu ◽  
...  
Keyword(s):  
Carbon Isotope ◽  
Source Rock ◽  
Ordos Basin ◽  
Stable Carbon Isotope ◽  
Stable Carbon ◽  
The Ordos Basin

Geochemical characteristics and resource potential analysis of Chang 7 organic-rich black shale in the Ordos Basin

2018 ◽  
Vol 156 (07) ◽  
pp. 1131-1140 ◽  
Author(s):  
JIANGMIN DU ◽  
YANDE ZHAO ◽  
QINGCHUN WANG ◽  
YANQIU YU ◽  
HUI XIAO ◽  
...  
Keyword(s):  
Trace Elements ◽  
Large Scale ◽  
Sedimentary Environment ◽  
Ordos Basin ◽  
Biological Marker ◽  
Geochemical Characteristics ◽  
Gas Chromatography Mass Spectrometry ◽  
Hydrocarbon Generation ◽  
Resource Potential ◽  
The Ordos Basin

AbstractThe Ordos Basin is the largest and most important intracontinental sedimentary depression in China, and a significant amount of crude oil resources has developed within this Mesozoic formation. High-grade organic-rich shale is prevalent in the large-scale areas of the Chang 7 sedimentary stage and provides essential hydrocarbon resources for abundant oil enrichment in the Mesozoic. This research investigated the geochemical characteristics of Chang 7 shale using core samples and well logs and via laboratory tests. In addition, the microscopic components of the shale organic matter (OM), biological marker compounds, carbon isotopes, enrichment grade of trace elements, and elemental ratio were analysed systematically. Moreover, the aspects related to the shale OM source, sedimentary environment and resource potential were evaluated. Our results revealed that spherical alginate and calcium spherical alginate were predominant in the micropetrological components of the shale. Many biomarkers, including n-alkanes, steranes and terpanes, were detected in the gas chromatography – mass spectrometry spectra. An analysis of n-alkanes, regular sterane shapes (C21−/C22− and C26+C27/C28+C29), odd–even predominance index (OEP) and carbon preference index (CPI) values and carbon isotope distributions showed that OM was produced from aquatic organisms. The indicators of trace elements, such as Sr/Ba and V/V+Ni, combined with the biomarker compound in Pr/Ph and the gammacerane index showed the presence of a semi-deep – deep lake environment containing fresh–brackish water. In addition, the hydrocarbon conversion rate index and shale rock pyrolysis parameters revealed that Chang 7 has a high hydrocarbon generation ability and hydrocarbon expulsion efficiency.

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