Abstract
Design of acidizing job involves application of reactive flow modeling. Most of the existing research and commercial codes for reactive transport modeling are based on Darcy-scale continuum representation of porous media. Such kind of simulations requires application of tuning coefficients, which, if not chosen properly, lead to inappropriate design of acidizing job. To overcome this issue, we have proposed direct reactive flow modeling approach at a pore scale using exact pore geometry.
The approach developed in this work is based on the combination of principles of chemical kinetics/thermodynamics and density functional theory applied for hydrodynamics (DFH). Chemical reactions are introduced to hydrodynamic simulation within the framework of partial local equilibrium assumption.
In the current study, it is demonstrated that developed approach adequately describes dissolution of porous dolomite rock by solution of hydrochloric acid. Simulations have been performed using 2D model of dolomite granule, 2D model of porous structure and 3D model of Silurian dolomite microstructure. Upon acid injection, the geometry of a rock is gradually changing in the area of acid penetration. As a result of modeling of dissolution of dolomite non-porous granule by solution of hydrochloric acid it is shown that the rate of dolomite dissolution depends on the rate of fluid injection. The average rate of dissolution is increased from 0.07 to 0.23 kmol/(m3·s) with the increase of Péclet number from 0.28 to 46. Similar correlations for porous rock with exact geometry can be utilized for corrections of the reaction rate constants which are used in Darcy scale simulations. Developed approach allows to perform modeling of dissolution reactions at pore scale and paves the way for increasing the consistency between the models used in reactive flow modeling and pore structure features of real rocks which will lead to improvements in acidizing job design.
