THE ORGANIC GEOCHEMISTRY OF OIL AND GAS GENERATION AND ITS APPLICATION TO BASS STRAIT AND THE NORTHWEST SHELF

1978 ◽  
Vol 18 (1) ◽  
pp. 137 ◽  
Author(s):  
J. D Saxby
Keyword(s):  
Organic Matter ◽  
Chemical Reactions ◽  
Oil And Gas ◽  
Organic Geochemistry ◽  
General View ◽  
Geological Time ◽  
Gas Generation ◽  
Geological Time Scale ◽  
Specific Chemical ◽  
Gaseous Hydrocarbon

A study of the chemical reactions occurring within the geological environment can throw new light on the occurrence of petroleum and natural gas deposits. The principles of chemical kinetics enable extrapolations to be made so that the depths and temperatures of typical hydrocarbon-forming reactions can be deduced when intervals of geological time are available. In general, temperature is the crucial parameter with corrections being possible for shorter or longer heating times.Living organic matter available for incorporation in sediments is of four basic types: carbohydrates, proteins, lignin and lipids. Only the last two are significant precursors of organic matter (kerogen) in consolidated sediments. Lipid-derived material is the principal source of oil, while lignin-related kerogen gives methane as its main gaseous hydrocarbon product. Generation occurs in zones where the rate of cracking of the source material into volatile hydrocarbons due to increasing temperature becomes significant on the geological time-scale. During and after migration of oil from its source to reservoirs (usually at shallower depths and lower temperatures), other processes can alter the initial light oil. In particular, biodegradation by microorganisms can result in a heavier naphthenic or aromatic crude by the loss of normal alkanes.Application of organic geochemistry to specific basins involves the measurement on uncontaminated core samples of certain parameters (organic carbon, extractable hydrocarbons, normal alkane distributions, reflectance of vitrinite, H/C ratio of kerogen and spore coloration). These data, together with activation energies for specific chemical reactions, geothermal gradients, rates of subsidence and knowledge of the geological history of the basin enable a general view of generation, migration and preservation of oil and gas to be obtained. Such an overview is given for the Gippsland Basin, where generation of both oil and gas in the lower Latrobe Group is indicated, and for the Rankin Platform of the Northwest Shelf where a deep source at greater than 4000 m is suggested for the gas and condensate.

COAL AS A SOURCE OF OIL AND GAS: A CASE STUDY FROM THE BASS BASIN, AUSTRALIA

2003 ◽  
Vol 43 (1) ◽  
pp. 117 ◽  
Author(s):  
C.J. Boreham ◽  
J.E. Blevin ◽  
A.P. Radlinski ◽  
K.R. Trigg
Keyword(s):  
Organic Matter ◽  
Oil And Gas ◽  
Middle Eocene ◽  
Vitrinite Reflectance ◽  
Mineral Resources ◽  
Sedimentary Basins ◽  
Source Rocks ◽  
Gas Generation ◽  
Australian Context ◽  
Effective Source

Only a few published geochemical studies have demonstrated that coals have sourced significant volumes of oil, while none have clearly implicated coals in the Australian context. As part of a broader collaborative project with Mineral Resources Tasmania on the petroleum prospectivity of the Bass Basin, this geochemical study has yielded strong evidence that Paleocene–Eocene coals have sourced the oil and gas in the Yolla, Pelican and Cormorant accumulations in the Bass Basin.Potential oil-prone source rocks in the Bass Basin have Hydrogen Indices (HIs) greater than 300 mg HC/g TOC. The coals within the Early–Middle Eocene succession commonly have HIs up to 500 mg HC/g TOC, and are associated with disseminated organic matter in claystones that are more gas-prone with HIs generally less than 300 mg HC/g TOC. Maturity of the coals is sufficient for oil and gas generation, with vitrinite reflectance (VR) up to 1.8 % at the base of Pelican–5. Igneous intrusions, mainly within Paleocene, Oligocene and Miocene sediments, produced locally elevated maturity levels with VR up to 5%.The key events in the process of petroleum generation and migration from the effective coaly source rocks in the Bass Basin are:the onset of oil generation at a VR of 0.65% (e.g. 2,450 m in Pelican–5);the onset of oil expulsion (primary migration) at a VR of 0.75% (e.g. 2,700–3,200 m in the Bass Basin; 2,850 m in Pelican–5);the main oil window between VR of 0.75 and 0.95% (e.g. 2,850–3,300 m in Pelican–5); and;the main gas window at VR >1.2% (e.g. >3,650 m in Pelican–5).Oils in the Bass Basin form a single oil population, although biodegradation of the Cormorant oil has resulted in its statistical placement in a separate oil family from that of the Pelican and Yolla crudes. Oil-to-source correlations show that the Paleocene–Early Eocene coals are effective source rocks in the Bass Basin, in contrast to previous work, which favoured disseminated organic matter in claystone as the sole potential source kerogen. This result represents the first demonstrated case of significant oil from coal in the Australian context. Natural gases at White Ibis–1 and Yolla–2 are associated with the liquid hydrocarbons in their respective fields, although the former gas is generated from a more mature source rock.The application of the methodologies used in this study to other Australian sedimentary basins where commercial oil is thought to be sourced from coaly kerogens (e.g. Bowen, Cooper and Gippsland basins) may further implicate coal as an effective source rock for oil.

scholarly journals Elements of regional organic geochemistry and separate prediction of oil and gas content of regions

Georesursy ◽  
2021 ◽  
Vol 23 (2) ◽  
pp. 35-43
Author(s):  
Tatiana K. Bazhenova
Keyword(s):  
Organic Matter ◽  
Oil And Gas ◽  
Organic Geochemistry ◽  
Gas Content ◽  
Quantitative Prediction ◽  
Genetic Types ◽  
Regional Aspect ◽  
Hydrocarbon Emission ◽  
Gaseous Hydrocarbons

The article considers the elements of organic geochemistry in the regional aspect, which aims to separate quantitative prediction of oil and gas content of regions. The principles and results of balance calculations of generation and emission of liquid and gaseous hydrocarbons for different facies-genetic types of organic matter and methods for calculating the scale of hydrocarbon emission are considered. Finally, a list of the main regularities of organic geochemistry is given.

scholarly journals An unconventional Neoproterozoic – Early Cambrian source rock interval in southern Oman: Implications for oil and gas generation

GeoArabia ◽  
2009 ◽  
Vol 14 (4) ◽  
pp. 53-86
Author(s):  
Isabelle Kowalewski ◽  
Bernard Carpentier ◽  
Alain-Yves Huc ◽  
Pierre Adam ◽  
Sylvie Hanin ◽  
...  
Keyword(s):  
Organic Matter ◽  
Kinetic Parameters ◽  
Source Rock ◽  
Oil And Gas ◽  
Bulk Composition ◽  
Early Cambrian ◽  
Type Ii ◽  
Gas Generation ◽  
Standard Type ◽  
Geochemical Parameters

ABSTRACT The Neoproterozoic – Early Cambrian Ara intra-salt petroleum system in Oman has been the subject of several studies since the early 1990s, not least because of the exploration success that has accompanied the emergence of the play. As one of the oldest known commercial hydrocarbon systems, the properties of the source organic matter have been of particular interest. The Ara intra-salt hydrocarbon system consists of the Al Shomou Silicilyte, a rock which is composed of pure microcristalline silica, and carbonate colloquially known as “stringers”. Both occur as slabs encased in the Ara salt. In the case of the Silicilyte, the slabs can be shown to act both as source rock and reservoir. However, in the case of the carbonate stringers, the association is more ambiguous. A set of rock and oil samples have been selected from different wells penetrating the silicilyte and carbonate stringer plays to better characterize and understand these systems. As far as the sedimentary organic matter is concerned, the Al Shomou Silicilyte domain has an average Total Organic Carbon (TOC) of approximately 4 wt.%. The carbonate-prone domains exhibit rare organic-rich lithofacies (TOC of approximately 2 wt.%) and additional intra-salt shales (TOC of approximately 4 wt.%). The organic matter present in both the Silicilyte and carbonate plays is associated with a hypersaline and anoxic depositional environment, rich in sulfur, and showing very similar chemical signatures (bulk composition, elemental analysis, biomarker content, δ13C). The organic matter associated with these sequences is characterized by an unusual “asphaltenic” nature. Compared to classical fossil organic matter taken at an equivalent maturity level, the organic matter found in the intra-salt silicilyte, shales or carbonates releases a large amount of solvent soluble material, which is very rich in Nitrogen-Sulfur-Oxygen (NSO) compounds, implying a standard Type II-S kerogen. However, the organic matter differs from this classic characterization of kerogen (solvent insoluble) in that a large proportion appears to be a sulfur-rich “soluble” kerogen, which has not been previously described. Independent geochemical parameters (Rock-Eval analysis, kinetic parameters) seem to be consistent with this hypothesis. The thermal maturity of the whole set of samples examined places them in the oil window. Moreover, Thermochemical Sulfate Reduction (TSR) did not occur in these samples. As far as the soluble part is concerned, differences in the molecular (significant molecular variations for norhopanes, secobenzohopanes, carotane, X compounds, thianes, thiolanes) and sulfur isotopic composition were demonstrated, and are assumed to reflect subtle variations in depositional settings between Silicilyte and carbonate stringers. The specific properties of this unconventional organic matter has to be accounted for in the thermal modeling of oil and gas generation. Although the kinetic distribution for kerogen cracking is close to that of a Type II-S kerogen, it is slightly more mono-energetic. A compositional 2-D basin modeling (Temis 2D) was performed on a cross-section through the South Oman Salt Basin, using specific kinetic parameters measured on this unconventional Neoproterozoic – Early Cambrian kerogen (based on a linear grouping of insoluble kerogen and NSO like “soluble kerogen” kinetic parameters). The gas-to-oil ratio GOR prediction was improved within the silicilyte, when compared to the use of classical parameters assigned to Type II-S kerogen. Finally, the microcrystalline silica mineral matrix of the silicilyte plays is proposed to play a major role in the composition of the fluid, which is expelled and produced by imposing a strong geochromatographic effect on fluids and the retention of polar compounds. The preferential release of aliphatics would lead to the production of oils exhibiting a strong condensate character. This effect has to be considered when modeling the actual composition of the movable fluid in the silicilyte. The significance of the geochromatographic effect is yet to be quantified, but according to available observations, we suggest that this geochromatographic effect could explain the observed API gravity difference between oils produced from silicilyte and carbonate plays.

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.

Seismic reservoir characterization of Duvernay shale with quantitative interpretation and induced seismicity considerations — A case study

2017 ◽  
Vol 5 (2) ◽  
pp. T185-T197 ◽  
Author(s):  
Satinder Chopra ◽  
Ritesh Kumar Sharma ◽  
Amit Kumar Ray ◽  
Hossein Nemati ◽  
Ray Morin ◽  
...  
Keyword(s):  
Media Coverage ◽  
Induced Seismicity ◽  
Oil And Gas ◽  
Reservoir Characterization ◽  
Learning Experience ◽  
Rock Physics ◽  
Quantitative Interpretation ◽  
Gas Generation ◽  
Gaseous Hydrocarbon

The Devonian Duvernay Formation in northwest central Alberta, Canada, has become a hot play in the past few years due to its richness in liquid and gaseous hydrocarbon resources. The oil and gas generation in this shale formation made it the source rock for many oil and gas fields in its vicinity. We attempt to showcase the characterization of Duvernay Formation using 3D multicomponent seismic data and integrating it with the available well log and other relevant data. This has been done by deriving rock-physics parameters (Young’s modulus and Poisson’s ratio) through deterministic simultaneous and joint impedance inversion, with appropriate quantitative interpretation. In particular, we determine the brittleness of the Duvernay interval, which helps us determine the sweet spots therein. The scope of this characterization exercise was extended to explore the induced seismicity observed in the area (i.e., earthquakes of magnitude [Formula: see text]) that is perceived to be associated with hydraulic fracture stimulation of the Duvernay. This has been a cause of media coverage lately. We attempt to integrate our results with the induced seismicity data available in the public domain and elaborate on our learning experience gained so far.

scholarly journals Origins of hydrocarbons in the Geneva Basin: insights from oil, gas and source rock organic geochemistry

2021 ◽  
Vol 114 (1) ◽  
Author(s):  
Damien Do Couto ◽  
Sylvain Garel ◽  
Andrea Moscariello ◽  
Samer Bou Daher ◽  
Ralf Littke ◽  
...  
Keyword(s):  
Organic Matter ◽  
Source Rock ◽  
Oil And Gas ◽  
Organic Geochemistry ◽  
Source Rocks ◽  
Type Ii ◽  
Dominant Type ◽  
Type Iii ◽  
North Alpine Foreland Basin ◽  
Migration Pathways

AbstractAn extensive subsurface investigation evaluating the geothermal energy resources and underground thermal energy storage potential is being carried out in the southwestern part of the Swiss Molasse Basin around the Geneva Canton. Among this process, the evaluation of the petroleum source-rock type and potential is an important step to understand the petroleum system responsible of some oil and gas shows at surface and subsurface. This study provides a first appraisal of the risk to encounter possible undesired occurrence of hydrocarbons in the subsurface of the Geneva Basin. Upon the numerous source-rocks mentioned in the petroleum systems of the North Alpine Foreland Basin, the marine Type II Toarcian shales (Lias) and the terrigenous Type III Carboniferous coals and shales have been sampled from wells and characterized with Rock–Eval pyrolysis and GC–MS analysis. The Toarcian shales (known as the Posidonia shales) are showing a dominant Type II organic matter composition with a Type III component in the Jura region and the south of the basin. Its thermal maturity (~ 0.7 VRr%) shows that this source-rock currently generates hydrocarbons at depth. The Carboniferous coals and shales show a dominant Type III organic matter with slight marine to lacustrine component, in the wet gas window below the Geneva Basin. Two bitumen samples retrieved at surface (Roulave stream) and in a shallow borehole (Satigny) are heavily biodegraded. Relative abundance of regular steranes of the Roulave bitumen indicates an origin from a marine Type II organic matter. The source of the Satigny bitumen is supposedly the same even though a deeper source-rock, such as the lacustrine Permian shales expelling oil in the Jura region, can’t be discarded. The oil-prone Toarcian shales in the oil window are the most likely source of this bitumen. A gas pocket encountered in the shallow well of Satigny (Geneva Canton), was investigated for molecular and stable isotopic gas composition. The analyses indicated that the gas is made of a mixture of microbial (very low δ13C1) and thermogenic gas. The isotopic composition of ethane and propane suggests a thermogenic origin from an overmature Type II source-rock (> 1.6 VRr%) or from a terrigenous Type III source at a maturity of ~ 1.2 VRr%. The Carboniferous seems to be the only source-rock satisfying these constraints at depth. The petroleum potential of the marine Toarcian shales below the Geneva Basin remains nevertheless limited given the limited thickness of the source-rock across the area and does not pose a high risk for geothermal exploration. A higher risk is assigned to Permian and Carboniferous source-rocks at depth where they reached gas window maturity and generated large amount of gas below sealing Triassic evaporites. The large amount of faults and fractures cross-cutting the entire stratigraphic succession in the basin certainly serve as preferential migration pathways for gas, explaining its presence in shallow stratigraphic levels such as at Satigny.

Characteristics of the Overpressure Resulted from Hydrocarbon Generation

2013 ◽  
Vol 295-298 ◽  
pp. 2707-2710
Author(s):  
Hai Yan Hu ◽  
Hui Wang
Keyword(s):  
Organic Matter ◽  
Oil And Gas ◽  
Vitrinite Reflectance ◽  
Junggar Basin ◽  
Hydrocarbon Generation ◽  
Sonic Velocity ◽  
Gas Generation

Overpressure is often encountered in the Jurassic tight sandstones in the central Junggar Basin. In this studt, a new mechanism of overpressure formation related to gas generation is proposed. Organic-rich mudstones have sonic velocity well-line reserves but their densities continue to increase in the over-compacted mudstone system resulting in the overpressure development during the conversion of the organic matter to oil and gas. The top of the overpressure zone correlates with the depth required for a large quantity of gas generation in which the vitrinite reflectance (Ro) is about 0.7%, showing that the overpressure in organic-rich mudstones is closely associated with gas generation.

scholarly journals Elements of regional organic geochemistry and separate prediction of oil and gas content of regions

Georesursy ◽  
2021 ◽  
Vol 23 (2) ◽  
pp. 35-43
Author(s):  
Tatiana K. Bazhenova
Keyword(s):  
Organic Matter ◽  
Oil And Gas ◽  
Organic Geochemistry ◽  
Gas Content ◽  
Quantitative Prediction ◽  
Genetic Types ◽  
Regional Aspect ◽  
Hydrocarbon Emission ◽  
Gaseous Hydrocarbons

The article considers the elements of organic geochemistry in the regional aspect, which aims to separate quantitative prediction of oil and gas content of regions. The principles and results of balance calculations of generation and emission of liquid and gaseous hydrocarbons for different facies-genetic types of organic matter and methods for calculating the scale of hydrocarbon emission are considered. Finally, a list of the main regularities of organic geochemistry is given.

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