Modeling of injection of modified seawater into oil-wet Carbonate at Ekofisk field

Spontaneous imbibition (SI) is the main recovery mechanism in low matrix permeability, naturally fractured reservoirs. However, for imbibition to occur, the reservoir rock should be preferentially water-wet. Several studies have indicated that smart water may increase the water-wetness of an oil-wet carbonate reservoirs. Published experimental data suggest that sulfate ion in the injected fluid can alter wetting state of the carbonate from preferentially oil-wet to water-wet.Numerical and analytical models have been developed to describe SI process in carbonate reservoirs. The suggested models attempt to capture the complex interactions among different phases and species during SI process. In this study, using the already existing surfactant model of ECLIPSE 100 simulator, dynamic effect of adsorption of sulfate on wettability alteration in core scale is modelled. Wettability change option of the surfactant model is employed to capture change in wettability due to adsorption of sulfate ion. Using the procedure of weight factor, wettability of the core shifts dynamically from oil-wet to water-wet conditions proportional to the adsorbed amount of sulfate. Laboratory experiments have been matched with the established procedure.The result showed that the wettability change option under surfactant model in ECLIPSE 100 is capable of modelling the change in wettability due to adsorption of sulfate ion. The model is able to predict experimental data using the procedure of weight factor. Moreover, a correlation between weight factor and Amott wettability index is established. The basic model that could be used for further investigations or upscaling to field scale is established.

Keywords:

Wettability , Sulfate ion , Smart water , EOR , Carbonate , Spontaneous imbibition (SI)