Experimental and Simulation Investigation of Salinity Changes on Brine-Rock Interaction in Water Injection Process
Volume Title: 1
Authors
1Amirkabir University of Technologym, Research Institute of Petroleum Industry
2Department of petroleum engineering, Amirkabir University of Technology, Tehran, Iran
Abstract
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.
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