Effects of pore topology on immiscible fluid displacement: Pore-scale lattice Boltzmann modelling and experiments using transparent 3D printed models

Abstract

Waterflooding technology has been widely applied to mobilise the residual oil in petroleum reservoirs. It is crucial to quantitatively characterise the topology of pore space and recognise its influence on the development of preferential fluid displacement paths for enhancing oil recovery. However, understanding the sensitivity of the preferential fluid displacement path to the topological characteristics of pore space is rather limited. To address this, this study constructs digital pore models with various pore topologies using information extracted from natural sandstones. The multicomponent lattice Boltzmann method is used to predict the pore-scale immiscible water-oil displacement in the constructed pore structures under different wetting conditions. Displacement experiments are performed in the transparent models fabricated using three-dimensional printing technology to examine the numerical predictions. The results reveal that the pore topological skeleton is one of the key factors controlling the immiscible fluid displacement in pore space and has a strong impact on the fluid invasion patterns and preferential fluid displacement path. The pore-scale immiscible displacement dynamics are associated with not only pore topology but also fluid wettability. As the wetting condition changes from drainage to imbibition, we observe a transition of the Euler characteristic effect on the pore structures with similar pore characteristics: the moving characteristics and invading fluid occupancy decrease under drainage and approximately increase under imbibition, when the Euler characteristic of the pore topology increases. This study provides insights on the effect of pore topology and its coupled effect with fluid wettability on the immiscible fluid displacement in porous rocks.