The Role of Mineral Surface Processes During Burial and Hydrocarbon Burial/Storage  

Joniell Borges, Northwestern University, Department of Geological Sciences, Evanston, IL, USA, [email protected]

Projected hydrocarbon reserve estimates at current consumption rates have focused the petroleum industry towards enhanced recovery from conventional reservoirs and development of unconventional reserves. Although large (33% of total reserves), our understanding of unconventional hydrocarbon reserves is limited. This project seeks to improve our understanding of the origin/evolution of unconventional hydrocarbon plays. Economic unconventional plays are characterized by organic-rich sediments, thermal histories conductive to oil expulsion, gas generation, and some degree of natural fracture. Although many such reservoirs produce significant quantities of gas, especially upon fracture stimulation, we poorly understand where the gas resides and how it migrates out of low-porosity and permeability lithologies. Previously, work has focused on understanding fracture behavior, a critical parameter for play development. Less attention is given towards understanding the nature and relationship of lithologies to the contained organic matter (OM) which evolves hydrocarbon during thermal maturation. The key research questions include: (1) what is the relationship between mineral surfaces and OC content; (2) how does mineral surface area (MSA) change with variable diagenetic history; and (3) does MSA change and organic richness correspond to changes in the behavior of the reservoir across thermal gradients? Many researchers speculate that illitization of smectite during burial diagenesis and primary migration of hydrocarbon is related, as these processes occur at similar depths-temperature regimes. We attempt to test this idea in the Niobrara Formation by evaluating clay-surface and OM relationship, MSA changes and hydrocarbon generation/maturation, and finally comparing these results to the estimated generation history of the source rocks.