STUDY OF OIL-MINERAL INTERACTIONS BY ATOMIC FORCE SPECTROSCOPY

In many reservoirs, oil recovery is limited by the tendency of oil to adhere to surrounding mineral surfaces. Modern injection well techniques force fluids into the reservoir to enhance recovery by raising the hydrostatic pressure, but still leave behind a significant amount of the oil. Attractive intermolecular forces, especially van der Waals forces, are responsible for these inefficiencies; however, the relative strength of electrostatic repulsion in the solution also plays a role. This study seeks to maximize oil recovery by determining the factors that lead to adhesion at the nanoscale, thus allowing for optimized recovery techniques to be employed.

Atomic force spectroscopy provides direct and precise measurements of the oil-mineral interactions taking place in a simulated reservoir environment. This is a difficult system to test, due to the complexity of both the reservoir rock and the crude oil. Therefore, using materials from actual oil reservoirs rather than over-simplified model components keeps the experiment more analogous to the native conditions. In our experiments, an oil-functionalized probe is approached to the mineral surface and then promptly retracted. By working with crude oil and mineral grains in a liquid environment, the active forces can be assessed with piconewton resolution. Our results show that solution composition directly affects the interactions between oil and rock.