Probing the Role of Water Chemistry on the Behavior of Clays in Process and Natural Environments Using Solution Calorimetry

摘要

Clays, due to their specific surface area and electrical charge density, are among the most active minerals in aquifers, oil and gas reservoirs, and tailings ponds. Important problems, such as limited yield of oil recovery during petroleum exploration, involve the interaction of process fluids with minerals which constitute reservoir pore walls. During mine tailings treatment and management, water chemistry impacts the aggregation and settling of clays. Solution calorimetry is a sensitive probe for species transfer to and from clay surfaces, and for the measurement of the effects of water chemistry (temperature, pH, salinity) on clay particle surfaces, in this case, kaolinite, illite, and montmorillonite. In this work, we show that interactions between clays and surrounding water are temperature-independent for all three clay types and that water chemistry has no measurable effect on the surface properties of illite. For kaolinite, water pH does impact surface properties and has a synergistic impact with salinity at high pH. The surface properties of montmorillonite are sensitive to water pH and salinity. These data and observations extend a solution enthalpy modeling framework for clays and contaminated clays in water and liquid hydrocarbons. In the next phases of this work, entropic effects will be addressed so that a quantitative Gibbs free energy modeling framework for the enthalpy of solution of clays can be constructed and linked to clay settlement kinetics.