The study of heterogeneous two-phase flow around small-scale heterogeneity in porous sandstone by measured elastic wave velocities and lattice Boltzmann method simulation

Two-phase fluid flow is strongly controlled by small-scale (subcore-scale) heterogeneity of porous sandstone. We monitor the heterogeneous/anisotropic two-phase flow (CO₂ and water) in porous sandstone and conduct multichannel VP and VP anisotropy measurements under super critical CO₂ conditions during CO₂ injection (drainage) and water reinjection (imbibition) processes. In drainage, VP shows large reduction (~10%) in all sections of the core sample and changes from the bottominlet side to upper outlet side. It is considered that VP reduction reflects the CO₂ movement in the specimen. The VP anisotropy of the upper two planes indicates clear increase. The results of this experiment indicate the heterogeneous CO₂ flow around laminae in porous sandstone and characteristic behavior of these laminae as a barrier for CO₂. On the other hand, flow of water is not affected by this barrier. This characteristic CO₂ water flow around laminae is observed in the numerical simulation results. This simulation study also indicates that the capillary number is not directly affected on two-phase fluid flow around small-scale heterogeneity in porous sandstone. These results suggest that the small-scale heterogeneity behaves as a CO₂ gate and strongly controls CO₂ behavior in porous sandstone.