Marine influence helps preserve the oil potential of coaly source rocks: Eocene Mangahewa Formation, Taranaki Basin, New Zealand

Sykes, Richard; Volk, Herbert; George, Simon C.; Ahmed, Manzur; Higgs, Karen E.; Johansen, Poul; Snowdon, Lloyd R.

doi:10.1016/j.orggeochem.2013.11.005

Cited by 48 publications

(41 citation statements)

References 37 publications

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“…They presented a simple graphical plot for adjusting the measured HI values to the effective HI values, which is near to the onset of oil expulsion. The Xihu coals are similar to Cretaceous-Cenozoic humic coals from New Zealand (see Sykes and Snowdon, 2002; Sykes et al., 2004, 2014) both in the coal petrology and bulk organic geochemistry, so it is suitable to gain effective HI values in this way. Firstly, we plotted the Rank (Sr) (see Suggate, 2002) and the measured HI of the coal samples in their diagram.…”

Section: Samples and Methodsmentioning

confidence: 99%

“…Coals can be one of the most important source rocks for oil and gas (Ayinla et al, 2017;Petersen et al, 2010;Snowdon, 1991). Coaly rocks as sources for oil and gas have been found in a number of oil basins worldwide, including the Jurassic of the Turpan-Hami Basin (Huang et al, 1991;Shao et al, 2003;Wu et al, 2016;Zhang et al, 1997), the Late Cretaceous to Eocene of the Gippsland Basin (Smith and Cook, 1984), and the Cretaceous-Cenozoic of the Taranaki Basins (Sykes et al, 2014). Coal macerals constitute the basic units of the coaly source rocks for hydrocarbon generation, and the liptinite macerals are regarded as the most important sources of liquid hydrocarbons in these oilprone coals (Sykes and Snowdon, 2002;Wilkins and George, 2002).…”

Section: Introductionmentioning

confidence: 99%

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Petrology and hydrocarbon significance of the coaly source rocks from the Pinghu Formation in the Xihu Sag, East China Sea Shelf Basin

Liu

Kang

Shen

et al. 2020

Energy Exploration & Exploitation

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The Xihu Sag in the East China Sea Shelf Basin contains abundant oil and gas reserves and is a focus for hydrocarbon exploration and development. Source rocks are mainly coals and coal-measures mudstones in the Paleogene Pinghu and Huagang formations. Samples from the Pinghu Formation in the Xihu Sag were collected for petrology, total organic carbon, and Rock-Eval analysis for the purpose of investigating macerals component and their contributions to hydrocarbon generation potential. The coaly source rocks from the Pinghu Formation are dominated by vitrinite (average 86.18%) but have an obviously elevated content of liptinite (average 12.59%) and a much lower amount of inertinite (average 1.23%). Liptinite of the samples is mainly composed of resinite, with a small amount of cutinite, sporinite and alginate in descending order. TOC values are 37.55%–65.58% (average 49.16%). Effective HI values are 167–281 mg HC/g TOC (average 223.5 mg HC/g TOC), suggesting the organic matter is type II kerogen. Relatively high HI values and macerals components suggest that the coaly source rocks can generate both oil and gas. Although the liptinite in the coaly source rocks has a content lower than vitrinite values, it makes a significant contribution to both total hydrocarbon and liquid hydrocarbon generation. The contributions of vitrinite, liptinite and inertinite to the total hydrocarbon generation approximately are 63.21%, 36.46% and 0.33%, respectively. The contributions of vitrinite and liptinite to the liquid hydrocarbon generation are approximately 40.95% and 59.05%, respectively. These results demonstrate that the coaly source rocks are dominated by vitrinite macerals with a relatively higher content of liptinite macerals, especially resinite, and these source rocks are more prone to both total hydrocarbon and liquid hydrocarbon generation. Paleogene coaly source rocks from other parts of the world should be considered for their oil-prone nature.

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Section: Samples and Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Petrology and hydrocarbon significance of the coaly source rocks from the Pinghu Formation in the Xihu Sag, East China Sea Shelf Basin

Liu

Kang

Shen

et al. 2020

Energy Exploration & Exploitation

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“…Excess sulfur from marine water enhances the preservation of hydrogen-rich plant and bacterial lipids through sulfurization (Marshall et al, 2015). Sykes et al (2014) found that the HI value of marine affected coals is positively correlated with the total S content, which is an indicator of degrees of marine influence (Zieger and Littke, 2019). Anyhow, the coals and coaly mudstones are generally within the band of humic coals (Petersen, 2006) (Figure 9b).…”

Section: Hydrocarbon Potentialmentioning

confidence: 94%

Organic matter provenance and depositional environment of marine-to-continental mudstones and coals in eastern Ordos Basin, China—Evidence from molecular geochemistry and petrology

Tan

et al. 2020

International Journal of Coal Geology

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“…9 Organic-rich sediments and coal samples of the Parvadeh coalfield plotted in the DBT/Phen against Pr/Ph diagram of Hughes et al (1995) showing the depositional setting indicative for marine influence on the coal forming peat, as seawater is enriched in sulfate and interactions of seawater and organic matter leads to the formation of abundant pyrite due to the activities of sulfate reducing bacteria (Casagrande et al 1977;Given and Miller 1985). The amount of sulfur in coals not affected by marine waters is around 0.5%, and increases to 0.5%-1.5% and [ 1.5% in coals which became subject to slight or strong marine influence, respectively (Sykes et al 2014;Stock et al 2016). The interpretive TOC/TS plot developed by Jasper et al (2010) reveals that the Triassic coals plot in the field of topogenic to transitional mires, but not in the field of ombrogenous mires.…”

Section: Depositional Environmentmentioning

confidence: 99%

Organic petrology and geochemistry of Triassic and Jurassic coals of the Tabas Basin, Northeastern/Central Iran

Nazanin

Rajabzadeh

Littke

et al. 2019

Int J Coal Sci Technol

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Jurassic and Triassic coals and organic matter-rich shales of the Tabas Basin, Iran, were investigated with respect to their thermal maturation and petrographic composition. The Triassic coals of the Parvadeh coal field range in vitrinite reflectance between 1.17% and 1.37% and the Jurassic coals of the Mazino coal field between 2.08% and 2.29% VR r . Maceral analysis revealed a predominance of vitrinite in all samples, with slightly higher percentages of inertinite in the Jurassic samples. Rock-Eval analyses confirm the presence of type III kerogen in the Triassic coals, while the Jurassic coals contain strongly carbonized residual kerogen. The range of sulfur contents for coals from the Parvadeh coal field (0.37% to 4.64%) and Mazino coal field (0.45% to 2.92%) is related to the effect of marine water in peat. The studied samples are characterized by the predominance of short-over long-chained n-alkanes. The relatively high Pr/Ph ratios indicate predominance of terrestrial organic matter whereas Pr/n-C 17 and Ph/n-C 18 ratios prove oxic conditions during deposition. In addition, the DBT/Phen ratio shows that these coals formed in fluvial/deltaic environments. Molecular geochemical parameters such as carbon preference index (CPI, 0.99-1.04), methyl phenanthrene index (MPI, 1.20-1.60), methyl naphthalene ratio (MNR, 1.61-3.45), and ethyl naphthalene ratio (ENR, 4-6.78) confirm the high maturity of the samples. Burial and thermal history reconstruction indicates necessity of an erosional thickness of about 4000 m in the Parvadeh area. Towards the Mazino area, a higher basal heat flow up to 80 mW m -2 is assumed for the Paleogene leading to higher maturities.

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Marine influence helps preserve the oil potential of coaly source rocks: Eocene Mangahewa Formation, Taranaki Basin, New Zealand

Cited by 48 publications

References 37 publications

Petrology and hydrocarbon significance of the coaly source rocks from the Pinghu Formation in the Xihu Sag, East China Sea Shelf Basin

Petrology and hydrocarbon significance of the coaly source rocks from the Pinghu Formation in the Xihu Sag, East China Sea Shelf Basin

Organic matter provenance and depositional environment of marine-to-continental mudstones and coals in eastern Ordos Basin, China—Evidence from molecular geochemistry and petrology

Organic petrology and geochemistry of Triassic and Jurassic coals of the Tabas Basin, Northeastern/Central Iran

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