Source rock maturation owing to igneous intrusion in rifted margin petroleum systems

Intrusive and extrusive volcanism is a common feature associated with many sedimentary basins formed along rifted margins. As a result, igneous intrusions are often found in potential hydrocarbon-producing source rock horizons. Although direct thermal effects on source rocks have been studied in detail, few studies have dealt with understanding the thermal effects on source rocks across a range of different thermal histories prior to intrusion. The metamorphic aureoles of three intrusions have been characterized for source rock maturation using organic geochemistry and Raman spectroscopy. Results show that a unique combination of organic geochemical and Raman spectroscopic techniques adds further insight to intrusion and host rock interactions, with an effective oil window and extended gas window located in the aureole of an immature and mature source rock respectively. Such varied and potentially beneficial geochemical responses further the need to re-evaluate source rock intervals in rifted margin basins.