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Chemical-based wettability modification has become important for the worldwide abundance of fractured carbonates with the potential to enhance water imbibition to expel more oil from a matrix to the fractures. A systematic experimental and modeling approach on the combined benefit of wettability alteration for enhanced water imbibition and interfacial tension reduction is presented. Brine, alkali, and alkali–surfactant solutions are injected sequentially to improve oil recovery from a fractured mixed-wet carbonate core. The experiment was successfully modeled with a 3D chemical flooding reservoir simulator with wettability alteration capability. Part I discussed the laboratory results and presented the modeling approach and the waterflood history match results. The history match procedure and results for wettability modification using an alkali agent and interfacial tension (IFT) reduction with surfactant are discussed in this article. Sensitivity simulations to some key parameters are also presented. [ABSTRACT FROM AUTHOR]

Reservoir souring is an after-production phenomenon in reservoirs that are subjected to seawater injection. Souring can damage the reservoir rocks, production facilities, and the environment. In order to predict the onset of reservoir souring, several models have been developed. Study of the published models for the reservoir souring prediction shows that there are many inconsistencies between the simulated results and field data. These differences are due to the capability of the models to consider the effective parameters in the porous media. In this study, we introduce a new model that has more features than previous models in simulation of generation and transportation of H2S in reservoir for the purpose of field applications. [ABSTRACT FROM AUTHOR]

Reservoir souring is a process in which a previously sweet oil field starts to produce fluids (oil, gas, or water) that contain H2S. It is costly and difficult to address these problems after a field development plan is already in place. In this article, a new reservoir souring model developed and implemented in a chemical flooding simulator is used to evaluate the capabilities of the previous models on reservoir souring. This study reveals the limitations of the published models in prediction of reservoir souring in oil fields and advantages of the developed model and simulator. [ABSTRACT FROM AUTHOR]