Effects of hydrous pyrolysis on biomarker thermal maturity parameters: Monterey Phosphatic and Siliceous members

The organic geochemistry of six oil samples from the offshore Block 17 (Lower Congo Basin, northwestern Angola) was studied by a combination of classical biomarker and extended diamondoid analyses to elucidate source rock facies, the extent of biodegradation, and thermal maturity. Based on molecular data, oils are interpreted as depicting a mixture of two pulses of hydrocarbon generation probably from the Bucomazi and Malembo formations. Geochemical results also gave evidence of mixing of a lacustrine siliciclastic-sourced oil charge and a second more terrestrially derived oil type in the samples analyzed. A single genetic oil family was identified through hierarchical cluster analysis; however, two groups of oils were identified on the basis of their biodegradation levels using the Peters/Moldowan scale. Lower and upper Malembo oils have a slight depletion and a notable absence of n-alkanes, suggesting PM levels of 1 and 2, respectively. Most molecular maturity parameters of the oil samples suggest a maturity level equivalent to the onset of the peak of the oil generative window.

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Novel Thermal Maturity Parameters Derived from Alkylbiphenyls and Alkyldiphenylmethanes

Energy & Fuels ◽

10.1021/acs.energyfuels.9b02084 ◽

2019 ◽

Vol 33 (9) ◽

pp. 8491-8502

Author(s):

Qianru Wang ◽

Haiping Huang ◽

Zheng Li ◽

Zongxing Li

Keyword(s):

Thermal Maturity ◽

Maturity Parameters

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Biomarker Molecular Indicators Predict Biodegraded Heavy Oil Physical Properties: A Case from Dongying Depression, Eastern China

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.524-527.2069 ◽

2012 ◽

Vol 524-527 ◽

pp. 2069-2073

Author(s):

Zhong Hong Chen

Keyword(s):

Physical Properties ◽

Eastern China ◽

Bohai Bay ◽

Thermal Maturity ◽

Dongying Depression ◽

Wide Range ◽

Biodegraded Oils ◽

Tricyclic Terpanes ◽

Molecular Indicators ◽

Maturity Parameters

To determine reliable molecular thermal maturity parameters for prediction of the physical properties of biodegraded oils, a suite of oils including 11 biodegraded oils from Caoqiao oilfield and 5 non-biodegraded oils from Wangjiagang oilfield in Dongying depression in Bohai-bay basin, eastern of China were analyzed. The oils were selected in a wide range of viscosity in order to investigate the relation between the parameters and oil properties. The data show the effects of biodegradation on some molecular thermal maturity parameters: C29 sterane parameters C2920S/(20S+20R) and C29ββ/(ββ+αα) increased apparently under heavy biodegradation (rank 6~7); parameters C3122S/(22S+22R), C3222S/(22S+22R), C293-methyl/C29 4-methyl, (C28+C29Tricyclics)/Ts and (C28+C29Tricyclics)/ (C28+C29Tricyclics +Ts) showed effects from heavy biodegradation (rank 6~7), and terpanes parameters Ts/(Ts+Tm), C29Ts/(C29Ts+C29Tm) and aromatic C20/(C28+C20), (C20+C21)/(C20+C21+C26+C27+C28) and D(3-6)/(D3-6+ C29 4-methylstigmastane 20R showed no effect from heavy biodegradation. Based on the comparison, the molecular maturity parameters C26 to C28 triaromatic parameters C26S/ (C26S+C28S), C27R/(C27R+C28R), C28/(C26+C27+C28) and tricyclic terpanes parameters C19/(C19+C23) were recommended to predict the physical properties of biodegraded oil for these parameters showed no effects from biodegradation(rank 6~7) and better relations with oil physical properties compared to other parameters. Some quantificational equations between these molecular thermal maturity parameters and the physical properties of biodegraded oils were inferred, which may assist in predicting the viscosity and API gravity of reservoired oils before production.

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Evaluating Molecular Evolution of Kerogen by Raman Spectroscopy: Correlation with Optical Microscopy and Rock-Eval Pyrolysis

Energies ◽

10.3390/en11061406 ◽

2018 ◽

Vol 11 (6) ◽

pp. 1406 ◽

Cited By ~ 12

Author(s):

Seyedalireza Khatibi ◽

Mehdi Ostadhassan ◽

David Tuschel ◽

Thomas Gentzis ◽

Humberto Carvajal-Ortiz

Keyword(s):

Raman Spectroscopy ◽

Organic Matter ◽

Structural Information ◽

Vitrinite Reflectance ◽

Nondestructive Method ◽

Thermal Maturity ◽

Shale Formations ◽

Reflectance Analysis ◽

Rock Eval ◽

Maturity Parameters

Vitrinite maturity and programmed pyrolysis are conventional methods to evaluate organic matter (OM) regarding its thermal maturity. Moreover, vitrinite reflectance analysis can be difficult if prepared samples have no primary vitrinite or dispersed widely. Raman spectroscopy is a nondestructive method that has been used in the last decade for maturity evaluation of organic matter by detecting structural transformations, however, it might suffer from fluorescence background in low mature samples. In this study, four samples of different maturities from both shale formations of Bakken (the upper and lower members) Formation were collected and analyzed with Rock-Eval (RE) and Raman spectroscopy. In the next step, portions of the same samples were then used for the isolation of kerogen and analyzed by Raman spectroscopy. Results showed that Raman spectroscopy, by detecting structural information of OM, could reflect thermal maturity parameters that were derived from programmed pyrolysis. Moreover, isolating kerogen will reduce the background noise (fluorescence) in the samples dramatically and yield a better spectrum. The study showed that thermal properties of OM could be precisely reflected in Raman signals.

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Testing the preservation of biomarkers during experimental maturation of an immature kerogen

International Journal of Astrobiology ◽

10.1017/s1473550416000069 ◽

2016 ◽

Vol 15 (3) ◽

pp. 165-175 ◽

Cited By ~ 16

Author(s):

H. Mißbach ◽

J.-P. Duda ◽

N.K. Lünsdorf ◽

B.C. Schmidt ◽

V. Thiel

Keyword(s):

Vitrinite Reflectance ◽

Lipid Biomarkers ◽

Sampling Point ◽

Thermal Maturity ◽

Short Term ◽

Degradation Behaviour ◽

Green River ◽

Hydrous Pyrolysis ◽

Life On Earth ◽

Reflectance Data

AbstractLipid biomarkers have been extensively applied for tracing organisms and evolutionary processes through Earth's history. They have become especially important for the reconstruction of early life on Earth and, potentially, for the detection of life in the extraterrestrial realm. However, it is not always clear how exactly biomarkers reflect a paleoecosystem as their preservation may be influenced by increasing temperatures (T) and pressures (P) during burial. While a number of biomarker indices reflecting thermal maturity have been established, it is often less well constrained to which extent biomarker ratios used for paleoreconstruction are compromised by T and P processes. In this study we conducted hydrous pyrolysis of Green River Shale (GRS) kerogen in gold capsules for 2–2400 h at 300°C to assess the maturation behaviour of several compounds used as life tracers and for the reconstruction of paleoenvironments (n-alkanes, pristane, phytane, gammacerane, steranes, hopanes and cheilanthanes). Lignite samples were maturated in parallel with the GRS kerogen to obtain exact vitrinite reflectance data at every sampling point. Our experiment confirms the applicability of biomarker-based indices and ratios as maturity indicators (e.g. total cheilanthanes/hopanes ratio; sterane and hopane isomerization indices). However, several biomarker ratios that are commonly used for paleoreconstructions (e.g. pristane/phytane, pristane/n-C17, phytane/n-C18 and total steranes/hopanes) were considerably affected by differences in the thermal degradation behaviour of the respective compounds. Short-term experiments (48 h) performed at 400°C also revealed that biomarkers >C15 (especially steranes and hopanes) and ‘biological’ chain length preferences for n-alkanes are vanished at a vitrinite reflectance between 1.38 and 1.83% RO. Our data highlight that ‘thermal taphonomy’ effects have to be carefully considered in the interpretation of biomarkers in ancient rocks and, potentially, extraterrestrial materials.

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