Chemically-tuned Waterflooding

In the proposed research, coreflood experiments will be conducted to study the effect of three of the main contributors to variations in the performance of CTWF, namely: injected water ion composition, salinity, and temperature (RezaeiDoust et al. 2009). As reported by Fathi, S. J. et al. (2012), there are three main PDIs whose concentration in injected water significantly affects SWF performance: Sulfate (SO42-), Magnesium (Mg2+), and Calcium (Ca2+). In an attempt to verify whether wettability alteration is the primary reason for improved recovery by CTWF, selected core scale experiments will be performed on smaller scale core plugs. X-ray micro-CT imaging will be used to scan the micro-corefloods to directly measure contact angles in 3D to get a contact angle distribution for each micro-coreflood performed. Monitoring changes in contact angle, and tying the result to the changes in recovery observed in the corresponding macro-scale coreflood experiments will help verify whether wettability alteration is the primary mechanism, or if there are other mechanisms involved. The objectives of the proposed research are: (1) Macro-scale investigation of the effect of salinity, ion composition, and temperature on oil recovery from oil-wet carbonate rocks, using coreflood experiments. (2) Pore-scale, direct quantification of wettability alteration under different salinities, ion compositions and temperatures. This will be achieved by replicating some of the coreflood experiments performed in stage-1 on mini-core plugs, and developing an algorithm for automated 3D in-situ contact angle calculations from micro-CT images to generate a contact angle distribution for each micro-coreflood experiment. (3) Results from 1 and 2 are integrated to further the development of a relative permeability equation of state.