CORE FLOOD EXPERIMENTS: HALITE PRECIPITATION IN THE NEAR WELL-BORE REGION

Presently, large-scale geological storage of CO₂, originating from such sources as fossil-fired power plants and contaminated gas production, is seen as option for reducing anthropogenic emission of greenhouse gases. Deep saline aquifers and depleted oil and gas fields are considered as subsurface deposits for CO₂. The injected CO₂ interacts chemically with water bearing rock material and hence changes the mechanical properties of the rock and the fluid-flow field in the subsurface. Experimental results and numerical simulations of the simplest coupling between chemical reactions and fluid flow are presented: halite precipitation in brine-saturated Berea sandstone due to CO₂ injection. Core-flood experiments were performed by injecting super-critical CO₂ into brine-saturated sandstone samples (Berea). Density profiles were measured by micro-CT scanning during the injection process that allow separation of a CO₂-rich, an aqueous and a precipitated salt phase by CsCl doping of the brine for contrast enhancement. We will show the spatial and time evolution of halite precipitation in the rock sample under sequestration conditions. No permeability reduction was observed in the presented case. The results were complemented by environmental-SEM-EDS measurements to further investigate the precipitated salt phase. Numerical simulations using Tough2 and ToughReact give a qualitative understanding of the experimental results, show a dependency of the profile on the injection rate, and help to upscale the results.