Fluid-Mineral Interactions in Shale
March 5 “Fluid-Mineral Interactions in Shale”, Presented by John Kaszuba, University of Wyoming.
In addition to its fundamental significance as the most common sedimentary rock in the continental crust, shale is an important economic and industrial resource. Interest in shale has grown with the advent of new techniques to extract hydrocarbons from ‘unconventional’ shale reservoirs. Chemical imbalance between shale and injected fluids potentially drives geochemical reactions and mineral dissolution/precipitation that may alter properties of the rock. Hydrothermal experiments are being conducted at the University of Wyoming to elucidate the dynamics of these processes. Experiments yield geochemical data (both aqueous and mineralogic) that define real-time reaction pathways and constrain fluid-shale interactions that may take place at reservoir conditions. The lithology of the shale and the chemistry of the formation fluid as well as stimulation fluids determine the specifics of a particular dissolution/precipitation cycle. Carbonate and silicate minerals are also potential sources for metals; precipitation of secondary clays, oxides, and sulfides provide sinks for these metals. Redox state and pH of the formation water and stimulation fluids control mechanisms of release and subsequent scavenging. Soluble metals potentially serve as in-situ tracers to identify fluid sources and document fluid mobility within a reservoir and along potential leakage pathways.