THE EVOLUTION OF PETROLEUM SYSTEMS AND FLUID FLOW IN THE ILLINOIS BASIN (Invited Presentation)

The Illinois Basin is dominantly a foreseep, intracratonic basin that formed during the evolution of Appalachian tectonics approximately 530 to 280 Ma. The Illinois Basin has long been a productive petroleum system yielding oil, natural gas from shale (e.g., New Albany Shale), and natural gas from coalbed methane reservoirs (e.g., Seelyville, Springfield). Nonetheless, there are still many unknowns concerning the genetic source, hydrocarbon and groundwater residence time, the age of microbial methane generation, migration histories of natural gas accumulations, and the timing of episodic recharge of glacial meltwaters. Our recent work demonstrates that the integration of traditional hydrocarbon molecular and stable isotope geochemistry with noble gas data one can provide greater certainty in resolving the genetic source of natural gases. Here, we review published data and present new noble gas isotope data that provides estimates of the timing of of groundwater recharge during interglacial periods, the age of microbial methane generation, and the timing of thermogenic hydrocarbon generation from various formations in the Illinois Basin.