Spectrometric analysis reveals altered dibenzothiophene biomarker ratios across secondary altered condensates, highlighting constraints on maturity and source evaluations.
Key Points
To investigate the impacts and mechanisms of thermochemical sulfate reduction, thermal cracking, gas invasion, and migration fractionation on dibenzothiophene biomarker distributions in petroleum condensates.
Analyzed condensate samples from the Tarim Basin affected by thermochemical sulfate reduction and thermal cracking, alongside condensates from the Baiyun Sag altered by gas invasion and migration fractionation.
Characterized molecular distributions and sulfur compounds using gas chromatography–mass spectrometry (GC–MS) and high-resolution Orbitrap mass spectrometry.
Thermochemical sulfate reduction markedly increased DBT/P ratios and S1 species while decreasing 4-/1-MDBT ratios, rendering both ratios unreliable for environmental and maturity assessments.
Thermal cracking decreased 4-/1-MDBT ratios and sulfur species due to macromolecular cracking, compromising 4-/1-MDBT for maturity assessment while leaving DBT/P ratios viable for depositional interpretation.
Gas-invaded condensates exhibited lower 4-/1-MDBT ratios from differential gas displacement entrapment, whereas migration-fractionated condensates displayed higher 4-/1-MDBT ratios.