Factors controlling the petroleum generation characteristics of Palaeogene source rocks in the Austrian Molasse Basin as revealed by principal component analysis biplots

Abstract

After Rock-Eval & TOC screening and heterogeneity evaluation on 91 Palaeogene source rock samples from a well drilled in the Austrian Molasse Basin, ten shale samples were selected for detailed investigations by means of pyrolysis-gas chromatography, bulk kinetics and biomarker identification and quantification. Afterwards, 2-D biplots based on principal component analysis were applied to unravel the palaeo-environmental control on the development of petroleum source rocks. All samples are immature source rocks with good petroleum generation potentials. The redox environment during deposition was generally reducing, and palaeosalinity is suggested to be the main factor causing the differences in organic carbon contents among the samples. The hydrogen index values, the gas generation preferences and the aromaticity of the products are controlled by both depositional environment and precursors, and the product of a salinity indicator (MTTC) and the oleanane index is introduced as predictive proxy to evaluate these features. The maturity indicator (Tmax) is revealed as dominated by the stability of the kerogen structure which is controlled by the proportion of organic sulphur compounds in the kerogen. The global Eocene-Oligocene climate change from a greenhouse to an icehouse world is suggested to play an important role in changing the palaeoenvironment and further in influencing the development of petroleum source rocks by triggering upwelling, increasing the palaeo-sea water salinity and decreasing the deposition of carbonate-minerals. The chemometric method suggested here acts as a powerful tool in identifying the controlling factors for the petroleum generation potential among many variables, and can be applied more widely in petroleum geology when multi-parameters are involved to get quick and meaningful correlations.

Preliminary results based on geochemical sedimentary constraints on the hydrocarbon potential and depositional environment of a Messinian sub-salt mixed siliciclastic-carbonate succession onshore Crete (Plouti section, eastern Mediterranean)

“…However, even in some of the sandy limestones, terrestrial organic particles could be identified, leading to elevated concentrations of TOC in these intervals. Generally, productivity (Totman Parrish and Curtis 1982;Pedersen andCalvert 1990), preservation (Demaison andMoore 1980;Demaison 1991;Vasiliev et al 2019), sedimentation rate (Ibach 1982;Creaney and Passey 1993), and salinity influence (Horsfield et al 1994;Yang and Schulz 2019) are typically considered as the most important factors controlling the organic matter and TOC enrichment in petroleum source rocks (Littke et al 1997). In Plouti section, organic matter is more abundant in the more siliciclastic parts of the section and less common in the more calcareous intervals.…”

Application of biomarkers in characterization of organic matter source, maturity and palaeoredox condition of black shales from the upper Permian Dalong Formation in Southern Anhui Province, South China

“…TOC is widely used to analyse the organic matter richness in source rocks (Dang et al, 2016; Hou & Feng, 2011; Nie et al, 2019; Peters & Cassa, 1994; Yang & Schulz, 2019). Table 1 shows TOC values for the 20 target samples from Dalong Formation exhibiting variable richnesses that ranged from 1.18% to 4.35% with an average of 2.53%.…”

Organic Geochemical Characteristics and Organic Matter Enrichment of the Upper Permian Longtan Formation Black Shale in Southern Anhui Province, South China

“…With TOC values ranging from 0.96% to 9.54% for the ten target samples (Table 1), most of the samples can be classified as "Very Good Source Rock (2.0% < TOC < 4.0%)" to "Excellent Source Rock (TOC > 4.0%)" based on their organic matter richness. 32,33 Notably, TOC contents vary among different sedimentary systems. Specifically, the target samples collected from the Daoshanchong section, which were deposited in a tidal flat-lagoon system, exhibited high TOC contents ranging from 7.32% to 9.54% (average 8.42%; Table 1).…”