Variation in Critical Porosity from Different Pore Fluid Compositions Evaluated Through Nuclear Magnetic Resonance

Abstract In repurposing of wells in depleted oil reservoirs for carbon storage it is importance to ensure lasting sealing of the well annuli, which exist where the mechanical rebound of the cap rock formation was insufficient in closing the gap to the well casing. Due to the reactivity of fine (primarily clay) particles to pore water composition, well sealing through chemically induced swelling could be a viable option. To quantify this potential, the pore space of 39 soil samples from the cap rock was investigated using Nuclear Magnetic Resonance to measure both the pore volume and pore size distribution. The samples varied only in the pore water based on: Na 2 SO 4 , LiCl, NaCl, CaCl 2 , NaI, MgCl 2 , KCl, NaClO 4 , HCl, Na 2 SiO 3 and NaOH at different concentrations. Na 2 SiO 3 and NaOH were found to induce the most significant swelling for this soil, which was very reactive despite its relatively low content of constituents that are classically considered to be part of swelling soil.