Characterizing Reactive Transport and Permeability Reduction in Etched 3D Printed Cores using Core Flooding Experiments
A core flooding experiment is a laboratory method used to explore reactive flow in natural and artificial geological materials, particularly focusing on flow and transport properties with geochemical reactions. These phenomena are crucial for understanding societally relevant processes such as contaminant transport and carbon sequestration. To replicate subsurface heterogeneity, cores with etched channels are used to produce samples with highly variable permeability distributions. The influence of flow rate on reactive transport in highly heterogeneous media is largely unexplored at laboratory scales due to limitations in sample replication. This study utilizes 3D-printed core samples with “etched” channels as a proxy for fractured rocks and explores how precipitation patterns and mixing dynamics change as the etched channel fills with precipitate. Experiments were conducted using dual injections of 6 mM sodium carbonate (Na2CO3) and 6 mM calcium chloride (CaCl2) to promote calcium carbonate (CaCO3) mixing and precipitation in 3D printed cores. Two experimental runs investigated clogging's impact on precipitation patterns: one using over-pressuring, where injection pressure was allowed to increase until a 200 psi pressure limit triggered an automatic shut-off, and another ending after a set duration. Results displayed precipitation patterns with spatial densities predominately localized in the etched conduits, with slight anisotropic permeability observed within the geometry, indicating a higher fluid flux to a specific preferential flow path. Additional comparative analysis between experiment types revealed varying interactions with the fracture plane, with the time-dependence run promoting increased precipitate formation on the fracture plane compared to the over-pressuring run.