Low-salinity waterflooding (LSW) refers to improved oil recovery achieved by waterflooding a reservoir with brine of lower salinity than that of the field brine. This is a simple and promising oil recovery technique with large potential. Recent works confirm the possibility of LSW in carbonates. Many mechanisms were proposed in the literature that explain observed increase in oil recovery from carbonate cores and reservoirs. Here are some of them:

  • Rock Dissolution
  • Increase of pH
  • Diffuse Layer Expansion (DLE)
  • Multicomponent Ion Exchange (MIE)

No agreement exist on the reason for LSW in carbonates. Here we describe equilibrium behavior of the calcite/brine interface in carbonate reservoirs. We establish that equilibrium reaction with calcite rock alters brine composition in the reservoir and demonstrate the importance of aqueous speciation. These findings extended to field conditions negate many of the proposed mechanisms of LSW.  

Maxim Yutkin, John Lee, Himanshu Mishra, Tadeusz Patzek​​​ and Clayton Radke