scholarly journals Rhenium-osmium geochronology and isotopic systematics in New Zealand source rocks and oils

2021 ◽  
Author(s):  
◽  
Enock Rotich
Keyword(s):  
Organic Matter ◽  
Marine Sediments ◽  
Black Shales ◽  
Source Rocks ◽  
Crude Oils ◽  
Sedimentation Rates ◽  
Isotopic Compositions ◽  
Potential Source ◽  
Oil Generation ◽  
Marine Influence

<p>The Re-Os radiogenic isotope system has over the past three decades been successfully applied to organic-rich sedimentary rocks and oils as a geochronometer and geochemical tracer. The Re-Os geochronometer has provided a direct way of constraining the depositional age of organic-rich sediments as well as the timing of oil generation events. Osmium isotopic compositions have further been utilised in understanding past climatic, oceanographic and geological events recorded in sediments, and in correlating oils to their source. Thus far, however, Re-Os studies of organic-rich sediments have mainly focused on marine black shales where Re and Os are primarily sourced from seawater. The work presented in this thesis seeks to investigate factors controlling Re-Os systematics and potential for geochronology in a range of fluvio-deltaic coaly rocks and terrestrial organic matter-dominated marine sediments, and associated oils from New Zealand’s Taranaki and East Coast basins. The Re-Os data presented here yield the first radiometric age for the late Paleocene Waipawa Formation (57.5 ± 3.5 Ma), a marine sedimentary unit that was formed by episodic input of large amounts of terrestrial woody plant matter resulting in high average sedimentation rates of up to ~10.6 cm/ky. This age is consistent with available biostratigraphic age determinations. The formation possesses Re (38.9 ± 17.6 ppb) and Os (526 ± 75.8 ppt) concentrations similar to those found in typical marine sediments containing amorphous organic matter deposited under much lower sedimentation rates. This indicates that organic matter type and sedimentation rate may not play a significant role in sequestration of these elements in organic-rich sediments. Unlike the Waipawa Formation, coals and coaly mudstones with varying degrees of marine influence (purely terrestrial to strongly marine-influenced) from the Rakopi, North Cape, Farewell and Mangahewa formations record low average Re (0.37 ± 0.25 ppb) and Os (24.5 ± 11.9 ppt) concentrations. These concentrations are up to two orders of magnitude lower than those of similarly marine-influenced coals from the Matewan coalbed, USA, suggesting that Re and Os enrichment in coals does not simply correlate with the level of marine influence; the timing and nature of the marine influence, as well as chelation ability of organic-rich sediments, are equally important. The initial 187Os/188Os (Osi) values for the Waipawa (~0.28) and underlying Whangai (~0.36) formations are broadly similar to those reported for coeval pelagic sediments from the central Pacific Ocean, further constraining the low-resolution marine 187Os/188Os record of the Paleocene. A broad correlation between this record and global temperature (δ18O and TEX86) and carbon isotope (δ13C) records is observed from the middle Paleocene to early Eocene, which is inferred to reflect climate-modulated changes in continental weathering patterns. Unlike the marine sediments, significant variations are noted in the Osi of the Taranaki Basin coaly rocks. These are linked to depositional and diagenetic conditions, degree of water connectivity with the open ocean, and sediment source. The large variations in Osi values combined with small ranges in 187Re/188Os ratios and relatively young ages are considered as factors that hindered development of Re-Os isochrons in these rocks. Crude oils sourced from the Taranaki coals and coaly mudstones also record low average Re (0.31 ± 0.09 ppb) and Os (14 ± 7.6 ppt) concentrations and have 187Re/188Os and 187Os/188Os ratios that do not correlate on an isochron diagram. The lack of an isochron fit for these oils is mainly attributed to a large variation in Osi values (0.47-1.14) resulting from the heterogeneous nature of their potential Rakopi and North Cape coaly source rocks and a lengthy (20 Myr) oil generation event. These Osi values, however, overlap with 187Os/188Os values for the potential source rocks at the time (ca.10 Ma) of oil generation (0.38-1.26), suggesting that Os isotopes may be utilised in tracing these oils. Crude oils that have potentially been sourced from the Waipawa and Whangai formations record much higher Re (2.86 ± 1.92 ppb) and Os (166 ± 142 ppt) concentrations than the coaly-sourced oils, and show Os isotopic compositions that either correlate with those of their potential source rocks (e.g., oil Osi = ~0.63 compared with Waipawa Formation 187Os/188Os = 0.48–0.68 at time of oil generation) or differ due to likely secondary alteration processes within the reservoir such as thermochemical sulfate reduction (TSR).</p>

scholarly journals Rhenium-osmium geochronology and isotopic systematics in New Zealand source rocks and oils

2021 ◽  
Author(s):  
◽  
Enock Rotich
Keyword(s):  
Organic Matter ◽  
Marine Sediments ◽  
Black Shales ◽  
Source Rocks ◽  
Crude Oils ◽  
Sedimentation Rates ◽  
Isotopic Compositions ◽  
Potential Source ◽  
Oil Generation ◽  
Marine Influence

<p>The Re-Os radiogenic isotope system has over the past three decades been successfully applied to organic-rich sedimentary rocks and oils as a geochronometer and geochemical tracer. The Re-Os geochronometer has provided a direct way of constraining the depositional age of organic-rich sediments as well as the timing of oil generation events. Osmium isotopic compositions have further been utilised in understanding past climatic, oceanographic and geological events recorded in sediments, and in correlating oils to their source. Thus far, however, Re-Os studies of organic-rich sediments have mainly focused on marine black shales where Re and Os are primarily sourced from seawater. The work presented in this thesis seeks to investigate factors controlling Re-Os systematics and potential for geochronology in a range of fluvio-deltaic coaly rocks and terrestrial organic matter-dominated marine sediments, and associated oils from New Zealand’s Taranaki and East Coast basins. The Re-Os data presented here yield the first radiometric age for the late Paleocene Waipawa Formation (57.5 ± 3.5 Ma), a marine sedimentary unit that was formed by episodic input of large amounts of terrestrial woody plant matter resulting in high average sedimentation rates of up to ~10.6 cm/ky. This age is consistent with available biostratigraphic age determinations. The formation possesses Re (38.9 ± 17.6 ppb) and Os (526 ± 75.8 ppt) concentrations similar to those found in typical marine sediments containing amorphous organic matter deposited under much lower sedimentation rates. This indicates that organic matter type and sedimentation rate may not play a significant role in sequestration of these elements in organic-rich sediments. Unlike the Waipawa Formation, coals and coaly mudstones with varying degrees of marine influence (purely terrestrial to strongly marine-influenced) from the Rakopi, North Cape, Farewell and Mangahewa formations record low average Re (0.37 ± 0.25 ppb) and Os (24.5 ± 11.9 ppt) concentrations. These concentrations are up to two orders of magnitude lower than those of similarly marine-influenced coals from the Matewan coalbed, USA, suggesting that Re and Os enrichment in coals does not simply correlate with the level of marine influence; the timing and nature of the marine influence, as well as chelation ability of organic-rich sediments, are equally important. The initial 187Os/188Os (Osi) values for the Waipawa (~0.28) and underlying Whangai (~0.36) formations are broadly similar to those reported for coeval pelagic sediments from the central Pacific Ocean, further constraining the low-resolution marine 187Os/188Os record of the Paleocene. A broad correlation between this record and global temperature (δ18O and TEX86) and carbon isotope (δ13C) records is observed from the middle Paleocene to early Eocene, which is inferred to reflect climate-modulated changes in continental weathering patterns. Unlike the marine sediments, significant variations are noted in the Osi of the Taranaki Basin coaly rocks. These are linked to depositional and diagenetic conditions, degree of water connectivity with the open ocean, and sediment source. The large variations in Osi values combined with small ranges in 187Re/188Os ratios and relatively young ages are considered as factors that hindered development of Re-Os isochrons in these rocks. Crude oils sourced from the Taranaki coals and coaly mudstones also record low average Re (0.31 ± 0.09 ppb) and Os (14 ± 7.6 ppt) concentrations and have 187Re/188Os and 187Os/188Os ratios that do not correlate on an isochron diagram. The lack of an isochron fit for these oils is mainly attributed to a large variation in Osi values (0.47-1.14) resulting from the heterogeneous nature of their potential Rakopi and North Cape coaly source rocks and a lengthy (20 Myr) oil generation event. These Osi values, however, overlap with 187Os/188Os values for the potential source rocks at the time (ca.10 Ma) of oil generation (0.38-1.26), suggesting that Os isotopes may be utilised in tracing these oils. Crude oils that have potentially been sourced from the Waipawa and Whangai formations record much higher Re (2.86 ± 1.92 ppb) and Os (166 ± 142 ppt) concentrations than the coaly-sourced oils, and show Os isotopic compositions that either correlate with those of their potential source rocks (e.g., oil Osi = ~0.63 compared with Waipawa Formation 187Os/188Os = 0.48–0.68 at time of oil generation) or differ due to likely secondary alteration processes within the reservoir such as thermochemical sulfate reduction (TSR).</p>

scholarly journals The Silurian shales of central and western North Greenland: evaluation of hydrocarbon source rock potential

1989 ◽  
Vol 143 ◽  
pp. 47-71
Author(s):  
F.G Christiansen ◽  
H Nøhr-Hansen
Keyword(s):  
Organic Matter ◽  
Source Rock ◽  
Black Shales ◽  
Drainage Area ◽  
Source Rocks ◽  
Thermal Maturity ◽  
Hydrocarbon Source Rock ◽  
Potential Source ◽  
Drastic Increase ◽  
North Greenland

The Silurian shales of central and western North Greenland form a more than 400 m thick succession which contains some potential hydrocarbon source rock intervals. Deposition of these organic-rich units was restricted in both time and space and potential source rocks only formed when and where black shales covered wide areas of sballow-water carbonates. Such deposition started in the middle Llandovery in Washington Land and continued tboughout the region in the late Llandovery. Neither the Wenlock nor the Ludlow shales contain sufficient organic matter to be considered as potential source rocks. The potential source rocks are dominated by oil-prone organic matter (large amorphous kerogen particles, mainly type Il) and typically show TOC values between 2% and 6%. The generative potential of immature to early mature samples is high with values up to 30 mg Hag rock. A drastic increase in thermal maturity of surface rocks is observed from south to north and most of the potential drainage area is thermally mature to postmature. This leaves only few chances of finding trapped hydrocarbons sourced by Silurian shales in North Greenland.

scholarly journals Effective source rock selection and oil–source correlation in the Western Slope of the northern Songliao Basin, China

2021 ◽  
Vol 18 (2) ◽  
pp. 398-415
Author(s):  
He Bi ◽  
Peng Li ◽  
Yun Jiang ◽  
Jing-Jing Fan ◽  
Xiao-Yue Chen
Keyword(s):  
Organic Matter ◽  
Source Rock ◽  
Thermal Evolution ◽  
Songliao Basin ◽  
Source Rocks ◽  
Crude Oils ◽  
Western Slope ◽  
Geochemical Parameters ◽  
Group I ◽  
Oil Source

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.

OIL GEOCHEMISTRY AND POTENTIAL SOURCE ROCKS OF THE OFFICER BASIN, SOUTH AUSTRALIA

1980 ◽  
Vol 20 (1) ◽  
pp. 68 ◽  
Author(s):  
D.M. McKirdy ◽  
A.J. Kantsler
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Carbonate Rocks ◽  
Depositional Environment ◽  
South Australia ◽  
Source Rocks ◽  
Potential Source ◽  
Playa Lake ◽  
Oil Source ◽  
Extractable Organic Matter

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%.

A GEOCHEMICAL INVESTIGATION OF OILS AND SOURCE ROCKS FROM THE SURAT BASIN

1986 ◽  
Vol 26 (1) ◽  
pp. 172 ◽  
Author(s):  
R. P. Philp ◽  
T. D. Gilbert
Keyword(s):  
Land Plant ◽  
Source Material ◽  
Source Rocks ◽  
Potential Source ◽  
Oil Generation ◽  
Formation History ◽  
Tentative Evidence ◽  
Geochemical Analyses ◽  
Geochemical Investigation ◽  
Migration Parameter

A series of twelve oils and five source rocks and potential source rocks from the Surat Basin have been subjected to detailed geochemical analyses. Particular attention has been given to determining the distribution of various classes of biomarkers such as the steranes and triterpanes. The results from this study have shown that the Cabawin oil is derived from the Permian Back Creek Formation and has a high content of marine organic source material. The Triassic/Jurassic oils have a different source from the Cabawin oil and are dominated by land plant source material. Within the Triassic/Jurassic oils there are subtle variations in biomarker distributions suggesting that some oils may have small but additional amounts of different source materials. A number of Cretaceous and Jurassic potential source rocks (i.e. Walloon) have biomarker parameters clearly indicating levels of maturity at which oil generation is impossible.A number of the oils in this basin are extensively biodegraded. In particular biodegradation has been very heavy in the Riverslea/Yapunyah area. With the exception of Conloi oil, all the oils appear to have been exposed to similar levels of maturity. A biomarker migration parameter has provided some tentative evidence to suggest that, in general, oils in the southern part of the basin have migrated further than those in the northern part.In summary, the biomarker data from oils and source rocks of the Surat Basin have been used to provide a new insight into the origin of the Surat Basin oils and their post-formation history.

scholarly journals Microbial bioavailability regulates organic matter preservation in marine sediments

2013 ◽  
Vol 10 (2) ◽  
pp. 1131-1141 ◽  
Author(s):  
K. A. Koho ◽  
K. G. J. Nierop ◽  
L. Moodley ◽  
J. J. Middelburg ◽  
L. Pozzato ◽  
...  
Keyword(s):  
Organic Matter ◽  
Marine Sediments ◽  
Source Rocks ◽  
Low Oxygen ◽  
Carbon Burial ◽  
Organic Carbon Burial ◽  
Oxygen Conditions ◽  
The Indian Ocean ◽  
Biochemical Quality ◽  
Oil Source

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.

scholarly journals Petroleum Geochemistry Regional Study of Murzuq Basin: Insights from Biomarkers Characteristic, Stable Carbon Isotope and Environmental Characterization

2020 ◽  
Vol 4 (1) ◽  
pp. 1-14
Author(s):  
Aboglila S
Keyword(s):  
Carbon Isotope ◽  
Vitrinite Reflectance ◽  
Stable Carbon Isotope ◽  
Source Rocks ◽  
Crude Oils ◽  
Type I ◽  
Stable Carbon ◽  
Potential Source ◽  
Geochemical Parameters ◽  
Rock Eval

This search aims to apply developed geochemical methods to a number of oils and source rock extracts to better establish the features of ancient environments that occurred in the Murzuq basin. Geochemical and geophysical approaches were used to confirm further a source contribution from other Paleozoic formations to hydrocarbon accumulations in the basin. One hundred and forty rock units were collected from B1-NC151, D1-NC174, A1-NC 76, D1-NC 151, F1-NC58, A1-NC 186, P1-NC 101, D1-NC 58, H1-NC58 and A1-NC58 wells. Seven crude oils were collocated A1-NC186, B1-NC186, E2-NC101, F3-NC174, A10-NC115, B10-NC115 and H10-NC115 wells. A geochemical assessment of the studied rocks and oils was done by means of geochemical parameters of total organic carbon (TOC), Rock-Eval analysis, detailed-various biomarkers and stable carbon isotope. The TOC values from B1-NC151 range 0.40% to 8.5%, A1-NC186 0.3% and 1.45, A1-NC76 0.39% to 0.74%, D1-NC151 0.40% to 2.00% to F1-NC58 0.40% to 1.12%. D1_NC174 0.30% to 10 %, P1-NC101 0.80% to 1.35%, D1-NC58 0.5% to 1.10%, H1-NC58 0.20% to 3.50%, A1-NC58 0.40% to 1.60%. The categories of organic matter from rock-eval pyrolysis statistics point to that type II kerogen is the main type, in association with type III, and no of type I kerogen recognized. Vitrinite reflectance (%Ro), Tmax and Spore colour index (SCI) as thermal maturity parameters reflect that the measured rock units are have different maturation levels, ranging from immature to mature sources. acritarchs distribution for most samples could be recognized and Palynomorphs are uncommon. Pristane to phytane ratios (> 1) revealed marine shale to lacustrine of environmental deposition. The Stable carbon isotope ( δ 13 C) values of seven rock-extract samples are -30.98‰ and -29.14‰ of saturates and -29.86‰ to -28.37‰ aromatic fractions. The oil saturate hydrocarbon fractions range between -29.36‰ to -28.67‰ and aromatic are among -29.98 ‰ to -29.55 ‰. The δ 13 C data in both rock extractions and crude oils are closer to each other, typical in sign of Paleozoic age. It is clear that the base of Tanezzuft Formation (Hot shale) is considered the main source rocks. The Devonian Awaynat Wanin Formation as well locally holds sufficient oil prone kerogen to consider as potential source rocks. Ordovician Mamuniyat Formation shales may poorly contain oil prone kerogen to be addressed in future studies. An assessment of the correlations between the oils and potential source rocks and between the oils themselves indicated that most of the rocks extracts were broadly similar to most of the oils and supported by carbon stable isotope analysis results.

PETROLEUM SOURCE ROCKS IN THE ROPER GROUP OF THE MCARTHUR BASIN: SOURCE CHARACTERISATION AND MATURITY DETERMINATIONS USING PHYSICAL AND CHEMICAL METHODS

1994 ◽  
Vol 34 (1) ◽  
pp. 279 ◽  
Author(s):  
Dennis Taylor ◽  
Aleksai E. Kontorovich ◽  
Andrei I. Larichev ◽  
Miryam Glikson
Keyword(s):  
Organic Matter ◽  
Chemical Evolution ◽  
Oil And Gas ◽  
Source Rocks ◽  
Type I ◽  
Peak Oil ◽  
Gas Generation ◽  
Oil Generation ◽  
Physical And Chemical ◽  
Extractable Organic Matter

Organic rich shale units ranging up to 350 m in thickness with total organic carbon (TOC) values generally between one and ten per cent are present at several stratigraphic levels in the upper part of the Carpentarian Roper Group. Considerable variation in depositional environment is suggested by large differences in carbon:sulphur ratios and trace metal contents at different stratigraphic levels, but all of the preserved organic matter appears to be algal-sourced and hydrogen-rich. Conventional Rock-Eval pyrolysis indicates that a type I-II kerogen is present throughout.The elemental chemistry of this kerogen, shows a unique chemical evolution pathway on the ternary C:H:ONS diagram which differs from standard pathways followed by younger kerogens, suggesting that the maturation histories of Proterozoic basins may differ significantly from those of younger oil and gas producing basins. Extractable organic matter (EOM) from Roper Group source rocks shows a chemical evolution from polar rich to saturate rich with increasing maturity. Alginite reflectance increases in stepwise fashion through the zone of oil and gas generation, and then increases rapidly at higher levels of maturation. The increase in alginite reflectance with depth or proximity to sill contacts is lognormal.The area explored by Pacific Oil and Gas includes a northern area where the Velkerri Formation is within the zone of peak oil generation and the Kyalla Member is immature, and a southern area, the Beetaloo sub-basin, where the zone of peak oil generation is within the Kyalla Member. Most oil generation within the basin followed significant folding and faulting of the Roper Group.

Use of infrared spectrophotoscope examination of bituminous components for determination of the oilgeneration zones in the mesozoic and Cenozoic deposits of the Azov-Kuban petroleum basin

2018 ◽  
pp. 92-99
Author(s):  
T. B. Mikerina ◽  
N. P. Fadeeva
Keyword(s):  
Organic Matter ◽  
Source Rocks ◽  
Infrared Spectrometry ◽  
Spectrometry Method ◽  
Genetic Types ◽  
Oil Generation ◽  
Petroleum Basin

Use of infrared spectrometry method for examination of bituminous components of dispersed organic matter in Mesozoic and Cenozoic deposits of the Azov-Kuban petroleum basin gave very important information about conditions of formation of source rocks containing organic matter and the degree of its diagenetic or catagenetic transformation level. Character of infrared spectrums represented by 15 genetic types of chloroform bitumen allows to subdivide the zones with the source beds absence, zones of oil generation and zones where this processes have come to the end.

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