Effect of individual ions on rock-brine-oil interactions: A microcalorimetric approach

Understanding the mechanisms behind the additional oil recovery by low salinity water flooding (LSWF) in carbonates has been difficult because of the complexity of the crude oil + brine + rock system. This study is an attempt to isolate fluid–fluid and rock-fluid interactions through Isothermal Titration Calorimetry (ITC) to get a deeper understanding of the oil recovery process. The results from the fluid–fluid interactions pointed out that the observed endothermic response is determined by the formation of micro-dispersions, in which Mg²⁺ is more active than Ca²⁺. The incorporation of Ca²⁺, Mg²⁺, SO₄^2- and HCO₃^- onto the chalk lattice effectively does not need energy from the surroundings to proceed. On the other hand, the incorporation of Mg²⁺ or Ca²⁺ into the calcite structure in the presence of SO₄^2- is less energetically favorable due to pair creation.