Impact of fracture orientation on supercritical carbon dioxide -foam performance and optimization in sandstones

Abstract

Natural or induced fractures pose a significant challenge for subsurface energy extraction, carbon storage, and aquifer contaminant remediation. They provide high permeability channels that disrupt the natural state of the flow. Fractures prevent pressure buildup and induce early breakthrough of displacing fluid, leaving most of the target fluids behind. Foams can alleviate this problem by providing fluid diversion. The primary function of fluid diversion is to reduce the mobility inside the higher permeable regions by increasing the viscosity, resulting in high pressure buildup and allowing the displacing fluid to be diverted to the low permeable regions of the matrix. However, foam optimization must be performed prior to field application to ensure the foam's stability and compatibility with in-situ fluids. Moreover, the nature of the reservoir rock plays a vital role in maintaining the integrity of the foam system required for subsurface applications. This is particularly important in the case of fractured porous media as fracture properties, such as roughness and orientation, could significantly impact the in-situ foam generation/destruction processes. This study systematically investigates the effect of fractures and their orientations on scCO2 foam performance in a homogeneous sandstone. Furthermore, the foam system was optimized in both unfractured and fractured sandstone rocks at reservoir conditions relevant to a target field for dual-purpose CO2 storage-oil recovery. The surfactant solution used for foam generation was developed using the zwitterionic surfactant Lauramine Oxide where the optimum composition was found to be 0.6 wt% surfactant and 15 wt% total salts with an 80:20 ratio NaCl:CaCl2. Results also confirmed a shear thinning behavior which is typical of a zwitterionic-based foam. Moreover, the 10° fractured core exhibited a 50% higher apparent viscosity than the unfractured one which proves the foam's great ability in fluid diversion.