The present work is an attempt to formulate the today’s understanding of the EOR mechanisms of “Smart” waterflooding as a closed system of equations, aiming to adapt it to numerical modelling applications. Within a two-phase water-oil framework, the model describes how the dissolved ions Ca2+, SO42−, Na+ and Cl− interact within the rock-fluid system. Complex phenomena, involving thinning out of the electrical double layer by lowering the overall water salinity and changes in water chemical composition, are represented by an adsorption/desorption scheme. Since Ca2+ ions at the rock surface react with polar oil components, causing detachment of oil (wettability change), special bi-parametric adsorption isotherms are introduced for Ca2+ ions, together with mono-parametric adsorption isotherms for SO42− ions. This is the key-component affecting the behavior of Ca2+ by mitigating the positive surface potential at the carbonate surface. The model also accounts for the non-equilibrium kinetics.

The main target on the development of this technique is describing the processes that occur inside the matrix block when “Smart” waterflooding is used to increment the oil recovery in fractured-porous systems. Special emphasis is put on the molecular diffusion mechanisms that are responsible for establishing the water compositional equilibrium between fracture and matrix structures.


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