experimental and simulation investigation of salinity changes on brine-rock interaction in water injection process

Water flooding as a common enhanced oil recovery method, has been proven to be economically efficient technique# from experimental studies has been observed that changing injection water composition in carbonates can enhance the oil recovery, most likely by alteration of rock surface properties during brine-rock interaction# in this research, a set of bulk experiments is performed to study brine-rock reactions# dissolution and deposition are examined for anhydrite, calcite and dolomite# dissolution of one of minerals will result in deposition of the other one and as the calcite reaction constant is larger than that of the dolomite; most of the calcite is dissolved# anhydrite is formed due to the bonding of low-salinity water sulfate ion with carbonate rock# sem and edax results also revealed that the dissolution was dominant mechanism compared to deposition# the surface tendency to absorb divalent cations is compared to monovalent cations increases# as a result, the lower the salinity, the more ca2+ and mg2+ ions bond with the rock surface# in general, at the temperatures below 100 ° c, the ca2+ ions are more active than mg2+ and account for a higher percentage of bonds with the rock surface# in contrast, increasing the mg2+ concentration indicates an increase in its activity# low-salinity water changes the surface charge and reduces it# this negative charge is mainly due to the presence of caso4- ions# # in general, since the dissolution mechanism dominates the sediment, the ph is increased in the presence of low-salinity water#