are broadly similar but differ in terms of source-rock depositional paleoenvironment, organic matter precursors, thermal maturation and microbial degradation. Age and maturity biomarker fingerprints show that these hydrocarbons were generated from at least two active pods of Upper Cretaceous and Oligocene or younger source rocks, as confirmed by high oleananes, bicadinanes, and high C 24-norcholestane indices. 26 Gas chemical and isotopic compositions of propane, ethane, and methane reveal a mixed microbial and thermogenic origin, where the relative proportion of biogenic component reaches up to ~70%. The thermogenic gas was generated from mixed Type-II/III or Type-II kerogen with a wide range of maturity between 1.0% and 1.5% R from primary kerogen cracking to the late stage of gas cracking. Heavier C hydrocarbon isotope o 2+ signatures and bulk compositions indicate that the shallower gas accumulations are severely biodegraded, unlike that in the deep hydrocarbon reservoirs. The co-occurrence of unaltered gas with biodegraded condensates may indicate different microbial communities involved in these processes, or more likely, the gas arrived in the reservoir as a second charge after biodegradation of the original condensate.

Elkahky, S., Lagat, C., Sarmadivaleh, M., Barifcani, A., 2019. A comparative study of density estimation of asphaltene structures using group contribution methods and molecular dynamic simulations for an Australian oil field. Journal of Petroleum Exploration and Production Technology 9, 2699-2708.

https://doi.org/10.1007/s13202-019-0641-x One of the major challenges faced by oil extraction industry is the unstable behavior of asphaltene formation, yet not fully understood. The prediction of asphaltene formation depends on the small changes in chemical characteristics and composition of the crude oil. Consequently, the study of molecular structure and molecular properties such as density is of a great practical interest. Other properties become very complex to assess when the asphaltene fraction contains 105 different molecules. Average molecular parameters are used to obtain information about asphaltenes. The density of the asphaltenes can easily be calculated and, thus, can be used to evaluate predictive capacities of the average structure. This present work of molecular dynamic simulations was carried out to evaluate the asphaltene densities of an Australian oil field. Simulations of molecular dynamics are used to assess the average structure densities representing different asphaltenes in a specific oil field. These simulations assist in predicting the formation of asphaltene structural model. Comparatively, the experimental densities are higher than the calculated ones. However, the calculated values demonstrate the appropriate trend. The chemical structure shows essential accuracy, as evidenced by average structures, which can be used to estimate the densities qualitatively. Hence, systematic study was carried out on the basis of the effects of various structures on the calculated densities of asphaltene. The main characteristics of the molecules which yielded highest densities are those found with low hydrogen - carbon ratio and big condensed aromatic rings. Moreover, better and improved density values were produced by a recently developed group contribution method than simulations of molecular dynamics, which is still being lower than that of experimental values.

Elkasabi, Y., Wyatt, V., Jones, K., Strahan, G.D., Mullen, C.A., Boateng, A.A., 2020. Hydrocarbons extracted from advanced pyrolysis bio-oils: Characterization and refining. Energy &Fuels 34, 483-490.

https://doi.org/10.1021/acs.energyfuels.9b03189 Catalytic fast pyrolysis (CFP) and tail-gas reactive pyrolysis (TGRP) of biomass produce partially deoxygenated bio-oils (10 - 20 wt %O) which allow for subsequent separation into phenolic and hydrocarbon fractions. The hydrocarbon fraction, while low in oxygen (<2 wt %), still requires further upgrading to become a finished fuel blendstock. In particular, the hydrogen deficiency, molecular weight distribution, and benzene content require further treatment. Specific biomass feedstocks like guayule carry over significant amounts of ∼ sulfur ( 500 ppm) even after catalytic hydrodeoxygenation. Our strategy was to fractionate the hydrocarbon fraction using distillation and then upgrade each fraction according to its needed product changes, including desulfurization. For each hydrocarbon fraction, sulfur levels ranged from 80 - 700 ppm, increasing with respect to decreasing volatility. Light fractions contained primarily one-ring aromatics, with heavy fractions increasing to two-ring aromatics. The lightest fraction (<143 °C) contained 6 wt %benzene, and fraction 2 (143 - 163 °C) required minimal treatment, as it consisted of nearly 100% BTEX (benzene, toluene, ethylbenzene, and xylenes). Sponge nickel catalysis in one step (<80 °C) eliminated sulfur in all fractions down to below 10 ppm