(42h) New High Temperature/Pressure Surface Forces Apparatus (TP-SFA) to Study Mineral Dissolution and Restructuring Under Sub-Surface Geological Conditions

Injecting diluted brine into carbonate (e.g., calcite) oil reservoirs has been shown to enhance the oil recovery; yet the mechanisms behind this ‘dilution effect’ remains elusive. We have found a number of crucial effects on dilution — the two most important of which are rapid (ion-specific) surface chemical dissolution and restructuring — that previously were not anticipated or suspected as being important, but which can have equally large or even larger effects as the changes in the physical/colloidal (electric double-layer, van der Waals, and hydration) forces on the water contact angles, wettability, and hence on oil-recovery. The effects of dilution on both the physical and chemical reactions are also ion-specific and temperature-dependent, and, especially at higher temperatures, gives rise to both very rapid (minutes) local and long-term, rock morphology-dependent, surface pitting, dissolution and re-precipitation, leading to roughening and restructuring of calcite and carbonate surfaces. We have observed dissolution/restructuring in Surface Forces Apparatus (SFA) (and AFM) experiments, whose rate increases with increasing temperature up to 70°C. Therefore, to mimic reservoir conditions it is essential to increase our measuring temperature even further, to 150°C. We will here describe our new design for an SFA that can operate at temperatures up to 150°C and pressures up to 150 atm, where we will be able to measure both dynamic advancing and receding contact angles, SFA electrochemical interactions, and surface (FECO) imaging of dissolution and restructuring, all in real time.