Study of fluid flow, transport and reaction in porous media with the Lattice Boltzmann method

摘要

In this study, we simulate the transport and reaction of fluids in porous media with the technique of lattice Boltzmann. To simulate such a system, it is necessary to account for the interaction of forced convection, molecular diffusion and surface reaction. The problem is further complicated by the evolution of the porous media geometry due to chemical reactions, which may significantly and continuously modify the hydrologic properties of the media. The particular application that motivates the present study is acid stimulation, a common technique used to increase production from petroleum reservoirs. This technique involves the injection of acid (e.g., hydrochloric acid HC1, acetic acid HAc) into the formation to dissolve minerals comprising the rock. As acid is injected, highly conductive channels or wormholes may be formed. The dissolution of two carbonate rocks is simulated with the lattice Boltzmann model developed in this study. The dependence of dissolution process as well as the geometry of the final wormhole pattern on the injection rate, the acid type, the acid concentration, and the diffusivity constant is studied. The results agree qualitatively with the experimental and theoretical analysis of others and substantiate the previous finding that there exists an optimal injection rate at which both the wormhole is formed and the number of pore volumes of the injected fluid to break through is minimized. This study confirms the experimentally observed phenomenon that the optimal injection rate decreases and the corresponding minimized number of pore volumes to break through increases as the acid is changed from HC1 to HAc. This study also shows that in wormhole formation, a low diffusion constant is more efficient than a high diffusion constant, and a low acid concentration results in a better economic utilization of acid.