Applications of Polycyclic Aromatic Hydrocarbons to Assess the Source and Thermal Maturity of the Crude Oils from the Lower Indus Basin, Pakistan

Abstract

A suite of six crude oils from Lower Indus Basin, Pakistan, were analyzed for geochemical characterization of source organic matter (OM) and thermal maturity. Distribution of polycyclic aromatic hydrocarbons (PAHs), alkylnaphthalenes, alkylphenanthrenes, alkyldibenzothiophenes, and aromatic biomarkers were reported from aromatic fractions of the crude oils. The aromatic hydrocarbons parameters revealed a higher thermal maturity of OM of source rock-generated Lower Indus Basin oils. Calculated vitrinite reflectance values from the methylphenanthrenes index 1 (MPI-1) and methyldibenzothiophene ratio (MDR) indicate that most of the oils reached a late oil generation window of thermal maturity. PAH distributions revealed the oils of two different origins are present in the Lower Indus Basin; two oil samples indicate aquatic source of OM and the aromatic biomarker distributions of retene, 1-MP, and 1,7-DMP indicate a significant contribution of land plant OM in the other four oils. This is the first study to report the distribution of aromatic hydrocarbons from Lower Indus Basin crude oils.

Applying biomarkers as paleoenvironmental indicators to reveal the organic matter enrichment of shale during deep energy exploration: a review

“…170,202,209,225 DBFs appear to predominate in freshwater source rocks, terrestrial oils, and coals, 170,209,[225][226][227] whereas their sulfur-heterocyclic counterparts dibenzothiophenes (DBTs) appear to predominate in marine shales and carbonates. 212,227,228 Radke et al (2000), Asif (2010), and Kruge (2000) indicated that the relative abundance of alkyldibenzothiophene (ADBT) compared to alkyldibenzofuran (ADBF) may be used to identify depositional settings (Fig. 16).…”

“…16). 202,205,229 Variations in the relative abundances of uorenes, dibenzofurans, and dibenzothiophenes have been reported to be a reliable indicator of source rock sedimentary settings. 203,230 The concentrations of the dibenzothiophene series were high in marine carbonate source rocks, while those of uorenes and dibenzofurans series were high in freshwater source rocks.…”

Physico-chemical and Geochemical Correlation Study of Aliphatic Hydrocarbons for Sindh Basin (Pakistan) Condensate Samples

“…Such information can be provided, for instance, by the n-alkane distribution curve or by the gas chromatography record of the saturated hydrocarbon fraction on a capillary column 4 . A study for source assessment based on the geochemical characterization of organic matter and maturity of the crude oil samples obtained from Lower Indus Basin, Pakistan has indicated two different origins; one contains majorly aquatic source of organic matter and the other has significant share of land plant organic matter 5 . The Goru formation is dominantly shale or mudstone, frequently calcareous.…”

“…The sample and internal standard (IS) were mixed in the ratio 80:20 and 1 µL was injected into the GC column in a splitless mode. The GC operating conditions were: 60(1)@4 ºC/min-280 (5). Injector and detector (FID) temperatures were 250 and 280 ºC respectively.…”

Petroleum geochemistry of Lower Indus Basin, Pakistan: I. Geochemical interpretation and origin of crude oils

“…Previous studies report that the crude oils from Lower Indus Basin are light to highly condensates (Asif et al, 2011;Nazir and Fazeelat, 2011). The crude oils from Lower Indus Basin are characterized by high API gravities, low sulfur contents, waxy and highly paraffinic in nature.…”