Investigation of Performance and Compatibility of Smart Waters Containing Scale Inhibitor in Carbonate Reservoirs

Low oil recovery provides a great need to apply the enhanced oil recovery techniques in carbonate reservoirs. Moreover, positive effects on smart water injection have been reported, and it has been known as one of the most cost-effective methods to enhance oil recovery in carbonate reservoirs by improving the wettability of carbonate rocks to more water-wetness state and positively affect the capillary pressure and relative permeability. One of the problems in water injection is the formation of mineral scales due to incompatibility of injection water and formation water which causes serious problems in the reservoir and wells. The most effective method for dealing with this problem is the use of suitable scale inhibitors (SIs) to prevent or delay scale formation. In this study, both in the absence and presence of various SIs, different smart waters were mixed with formation water to measure the amount of solid scale which may precipitate out of the mixed solution. Also, OLI Scale Chem simulator is used to investigate the incompatibility between blank smart waters without SIs and formation water. The amount and type of scales, the effect of water composition on the formation of these scales and the efficiency of used scale inhibitors are discussed. Also, by using the contact angle measurement method, the wettability alteration of the carbonate thin section over a specified time period and the benefits of smart water containing scale inhibitor in comparison with blank smart water without scale inhibitor are investigated. Finally, results show that smart waters, with optimized ionic composition, containing proper scale inhibition chemicals, not only reduce the risk of scale formation in mixing incompatible waters, but also have positive impact on oil recovery by changing the wettability of oil-wet carbonate rocks to water-wet state.