Catagenesis of organic matter of oil source rocks in Upper Paleozoic coal formation of the Bohai Gulf basin (eastern China)

2007 ◽  
Vol 48 (5) ◽  
pp. 415-421 ◽  
Author(s):  
Li Rongxi ◽  
Li Youzhu ◽  
Gao Yunwen
2021 ◽  
Vol 18 (2) ◽  
pp. 398-415
Author(s):  
He Bi ◽  
Peng Li ◽  
Yun Jiang ◽  
Jing-Jing Fan ◽  
Xiao-Yue Chen

AbstractThis study considers the Upper Cretaceous Qingshankou Formation, Yaojia Formation, and the first member of the Nenjiang Formation in the Western Slope of the northern Songliao Basin. Dark mudstone with high abundances of organic matter of Gulong and Qijia sags are considered to be significant source rocks in the study area. To evaluate their development characteristics, differences and effectiveness, geochemical parameters are analyzed. One-dimensional basin modeling and hydrocarbon evolution are also applied to discuss the effectiveness of source rocks. Through the biomarker characteristics, the source–source, oil–oil, and oil–source correlations are assessed and the sources of crude oils in different rock units are determined. Based on the results, Gulong and Qijia source rocks have different organic matter primarily detrived from mixed sources and plankton, respectively. Gulong source rock has higher thermal evolution degree than Qijia source rock. The biomarker parameters of the source rocks are compared with 31 crude oil samples. The studied crude oils can be divided into two groups. The oil–source correlations show that group I oils from Qing II–III, Yao I, and Yao II–III members were probably derived from Gulong source rock and that only group II oils from Nen I member were derived from Qijia source rock.


1980 ◽  
Vol 20 (1) ◽  
pp. 68 ◽  
Author(s):  
D.M. McKirdy ◽  
A.J. Kantsler

Oil shows observed in Cambrian Observatory Hill Beds, intersected during recent stratigraphic drilling of SADME Byilkaoora-1 in the Officer Basin, indicate that oil has been generated within the basin. Shows vary in character from "light" oils exuding from fractures through to heavy viscous bitumen in vugs in carbonate rocks of a playa-lake sequence.The oils are immature and belong to two primary genetic families with some oils severely biodegraded. The less altered oils are rich in the C13 - C25 and C30 acyclic isoprenoid alkanes. Source beds within the evaporitic sequence contain 0.5 - 1.0% total organic carbon and yield up to 1900 ppm solvent-extractable organic matter. Oil-source rock correlations indicate that the oils originated within those facies drilled; this represents the first reported examples of non-marine Cambrian petroleum. The main precursor organisms were benthonic algae and various bacteria.Studies of organic matter in Cambrian strata from five other stratigraphic wells in the basin reveal regional variations in hydrocarbon source potential that relate to differences in precursor microbiota and/or depositional environment and regional maturation. Micritic carbonates of marine sabkha origin, located along the southeast margin of the basin, are rated as marginally mature to mature and good to prolific sources of oil. Further north and adjacent to the Musgrave Block, Cambrian siltstones and shales have low organic carbon values and hydrocarbon yields, and at best are only marginally mature. Varieties of organic matter recognised during petrographic studies of carbonates in the Officer Basin include lamellar alginite (alginite B) and "balls" of bitumen with reflectance in the range 0.2 to 1.4%.


2020 ◽  
Vol 21 (1) ◽  
pp. geochem2019-060
Author(s):  
Yu Guo ◽  
Wenzhe Gang ◽  
Gang Gao ◽  
Shangru Yang ◽  
Chong Jiang ◽  
...  

Paleogene sediments, especially the third member of the Dongying Formation (Ed3) and the first and third members of the Shahejie Formation (Es1 and Es3), have been regarded as the most important source rocks in the Nanpu Sag. Organic and inorganic analyses, including Rock-Eval pyrolysis, gas chromatography-mass spectrometry, and element geochemistry, in 91 mudstone samples, were used to reconstruct the palaeoenvironmental conditions, such as palaeoclimate, palaeo-salinity and palaeo-redox conditions, and to recognize the origin of organic matter. The results show that Es3 has a higher TOC content than Es1 and Ed3. Hydrocarbon genetic potential (S1 + S2) of the samples indicate fair to good hydrocarbon potential. The kerogen type of Ed3 and Es1 source rocks are Type II1–II2, while Es3 source rocks are dominated by Type II2–III kerogens. Biomarkers and inorganic geochemical indicatives of source rocks, such as Pr/Ph, V/(V + Ni) and Cu/Zn, indicate a lacustrine environment with fresh to brackish water under suboxic to anoxic conditions during deposition. Ed3 source rocks are characterized by low G/C30H (gamacerane/C30hopane) (<0.1), TT/C30H (tricyclic terpane/C30hopane) and S/H (serane/hopane), high Pr/Ph (pristane/phytane) and C24TeT/C23TT (C24tetracyclic terpane/C23tricyclic terpane), indicating mixed input of both algae and terrestrial higher plants, dominated by terrestrial higher plants. Es1 source rocks display medium G/C30H, TT/C30H, S/H, Pr/Ph and C24TeT/C23TT, indicative of a mixed input of both algae and terrestrial higher plants. Es3 source rocks are characterized by high G/C30H (>0.1), TT/C30H and S/H, low Pr/Ph and C24TeT/C23TT, typical of a mixed input of algae and terrestrial higher plants, with algal dominance. Ed3, Es1 and Es3 source rocks were mostly deposited in semi-arid to humid-warm climate conditions, with an average temperature higher than 15°C. This study suggests that suitable temperatures, a fresh to brackish lacustrine environment and suboxic to anoxic conditions could result in a high organic matter concentration and preservation, thus providing prerequisites for the formation of high-quality source rocks.Supplementary material: Tables S1–S3 are available at https://doi.org/10.6084/m9.figshare.c.5227684


2013 ◽  
Vol 10 (2) ◽  
pp. 1131-1141 ◽  
Author(s):  
K. A. Koho ◽  
K. G. J. Nierop ◽  
L. Moodley ◽  
J. J. Middelburg ◽  
L. Pozzato ◽  
...  

Abstract. Burial of organic matter (OM) plays an important role in marine sediments, linking the short-term, biological carbon cycle with the long-term, geological subsurface cycle. It is well established that low-oxygen conditions promote organic carbon burial in marine sediments. However, the mechanism remains enigmatic. Here we report biochemical quality, microbial degradability, OM preservation and accumulation along an oxygen gradient in the Indian Ocean. Our results show that more OM, with biochemically higher quality, accumulates under low oxygen conditions. Nevertheless, microbial degradability does not correlate with the biochemical quality of OM. This decoupling of OM biochemical quality and microbial degradability, or bioavailability, violates the ruling paradigm that higher quality implies higher microbial processing. The inhibition of bacterial OM remineralisation may play an important role in the burial of organic matter in marine sediments and formation of oil source rocks.


2002 ◽  
Vol 42 (1) ◽  
pp. 387 ◽  
Author(s):  
S.C. George ◽  
H. Volk ◽  
T.E. Ruble ◽  
M.P. Brincat

Geochemical evidence is presented for a previously unrecognised oil generative source rock in the Nancar Trough area. This source rock supplements the middle to late Jurassic source rocks, which have previously been shown to have generated most of the oils in the northern Bonaparte Basin and the Vulcan Sub-basin. Fluids with a strong contribution from this new source rock, defined here as the Nancar oil family, have an unusually high abundance of mid-chain substituted monomethylalkanes. In comparison, oils from the Vulcan Sub-basin contain mostly terminally substituted monomethylalkanes and the overall abundance is much lower. Oils from the Laminaria High and some from the northern Vulcan Sub-Basin show intermediate characteristics and may be co-sourced. Evidence from the analysis of fluid inclusion oils was important in establishing the presence of the new oil family because interference from drilling mud contaminants could be excluded. The detailed geochemistry of Ludmilla–1 fluid inclusion oil suggests the source rock for the Nancar oil family was deposited in a marine environment under sub-oxic conditions with limited sulphur content, a low contribution of terrestrial organic matter and a high contribution of organic matter from bacterial activity. Since monomethylalkanes are typical biomarkers of cyanobacteria, the source rock that gave rise to the new oil family may be rich in cyanobacterial organic matter. Further studies on sediment extracts are needed to establish an explicit oil-source rock correlation and to identify the stratigraphic location/palaeo-environment of the source rock. Such information will be valuable in determining the prospectivity of the large and relatively unexplored province draining the Nancar Trough kitchen.


2012 ◽  
Vol 9 (9) ◽  
pp. 13187-13210
Author(s):  
K. A. Koho ◽  
K. G. J. Nierop ◽  
L. Moodley ◽  
J. J. Middelburg ◽  
L. Pozzato ◽  
...  

Abstract. Burial of organic matter (OM) plays an important role in marine sediments, linking the short-term, biological carbon cycle with the long-term, geological subsurface cycle. It is well established that low-oxygen conditions promote organic carbon burial in marine sediments. However, the mechanism remains enigmatic. Here we report biochemical quality, microbial degradability, OM preservation and accumulation along an oxygen gradient in the Indian Ocean. Our results show that more OM, and of biochemically higher quality, accumulates under low oxygen conditions. Nevertheless, microbial degradability does not correlate with the biochemical quality of OM. This decoupling of OM biochemical quality and microbial degradability, or bioavailability, violates the ruling paradigm that higher quality implies higher microbial processing. The inhibition of bacterial OM remineralisation may play an important role in the burial of organic matter in marine sediments and formation of oil source rocks.


2004 ◽  
Vol 44 (1) ◽  
pp. 223 ◽  
Author(s):  
H. Volk ◽  
S.C. George ◽  
C.J. Boreham ◽  
R.H. Kempton

The molecular composition of fluid inclusion (FI) oils from Leander Reef–1, Houtman–1 and Gage Roads–2 provide evidence of the origin of palaeo-oil accumulations in the offshore Perth Basin. These data are complemented by compound specific isotope (CSI) profiles of n-alkanes for the Leander Reef–1 and Houtman–1 samples, which were acquired on purified n-alkane fractions gained by micro-fractionation of lean FI oil samples, showing the technical feasibility of this technique. The Leander Reef–1 FI oil from the top Carynginia Formation shares many biomarker similarities with oils from the Dongara and Yardarino oilfields, which have been correlated with the Early Triassic Kockatea Shale. The heavier isotopic values for the C15-C25 n-alkanes in the Leander Reef–1 FI oil indicate, however, that it is a mixture, and suggest that the main part of this oil (~90%) was sourced from the more terrestrial and isotopically heavier Early Permian Carynginia Formation or Irwin River Coal Measures. This insight would have been precluded when looking at molecular evidence alone. The Houtman–1 FI oil from the top Cattamarra Coal Measures (Middle Jurassic) was sourced from a clay-rich, low sulphur source rock with a significant input of terrestrial organic matter, deposited under oxic to sub-oxic conditions. Biomarkers suggest sourcing from a more prokaryotic-dominated facies than for the other FI oils, possibly a saline lagoon. The Houtman–1 FI oil δ13C CSI n-alkane data are similar to those acquired on the Walyering–2 oil. Possible lacustrine sources may exist in the Early Jurassic Eneabba Formation and are present in the Late Jurassic Yarragadee Formation. The low maturity Gage Roads–2 FI oil from the Carnac Formation (Early Cretaceous) was derived from a strongly terrestrial, non-marine source rock containing a high proportion of Araucariacean-type conifer organic matter. It has some geochemical differences to the presently reservoired oil in Gage Roads–1, and was probably sourced from the Early Cretaceous Parmelia Formation.


2018 ◽  
Vol 53 (5) ◽  
pp. 2334-2351 ◽  
Author(s):  
Zhongnan Wang ◽  
Guangdi Liu ◽  
Ping Gao ◽  
Wan Chen ◽  
Yuran Yang ◽  
...  

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