Experimental and simulation study of low salinity brine interactions with carbonate rocks

Injection of low salinity water is one of the demanding enhanced oil recovery (EOR) methods that gained considerable attentions in the recent years. Among many mechanisms proposed for success of low salinity water injection (LSWI), brine/rock interactions are important with a critical role in carbonate formations that leads to dissolution, precipitation and ion exchange at the rock surface. This study presents experimental and simulation study of brine/rock interactions for thin sections of calcite and dolomite samples with four different brines. Mass difference, pH, and Scanning Electron Microscopy (SEM) were applied to monitor brine/rock interactions. A geochemical package (PHREEQC) was used to simulate geochemical reactions and sensitivity analysis. Good agreement between experimental and simulation results was achieved. SEM images confirmed the interactions at the calcite rock surface for different diluted brines. Among negative species at surface, is less sensitive to salinity changes, thus would not be the reason of surface charge alteration.