Modeling of CO2- WAG Injection with Geochemical and Geomechanical Effects in Carbonate Reservoirs Summary

Injection of water and CO2 as an alternating scheme (WAG) is one of the most successful EOR methods. Implementing the fractional flow theory, Walsh and Lake (1987, 1989, and 1991) presented a graphical method to determine the optimum WAG ratio under simplifying assumptions such as (1) the porous medium is homogeneous with respect to permeability (2) First Contact Miscible (FCM) displacement.

As the first part, the contribution in this work is to verify the results of that method once those assumptions are not satisfied. The results will be compared with numerical simulator outcomes.

The second part of this research would be studying the effect of rock-fluid reactions occur in simultaneous CO2 and water flooding in the carbonate rocks. Both kinetic of reactions and reactive surfaces will be considered as two wings of geochemistry effect in WAG injection.

The effective reactive surface in the case of multiphase flow will be decreasing and this is the key point for the rest of this work. The reactive surface will be divided into two parts (1) surface covered by stagnant aqueous phase (2) surface covered by flowing aqueous phase. These two types of aqueous phase go differently in reaction with CaCO3 so they should be distinguished; but none of the current simulators model that in this way. The new method of geochemical modeling for WAG injection will be implemented in this research.

The third part of this work devoted to variation in rock geomechanical properties, compaction, due to dissolution. Finding a correlation between carbonate dissolution and subsequent variation in rock geomechanical properties is one of the objectives.