Advances in Geological CO2 Sequestration and Co-Sequestration with O2

摘要

The injection of CO2 for Enhanced Oil Recovery (EOR) and sequestration in brine-bearing formations for long term storage has been in practice or under investigation in many locations globally. This study focused on the assessment of cement wellbore seal integrity in CO2- and CO2-O2-saturated brine and supercritical CO2 environments. Brine chemistries (NaCl, MgCl2, CaCl2) at various saline concentrations were investigated at a pressure of 28.9 MPa (4200 psi) at both 50°C and 85°C. These parameters were selected to simulate downhole conditions at several potential CO2 injection sites in the United States. Class H portland cement is not thermodynamically stable under these conditions and the formation of carbonic acid degrades the cement. Dissociation occurs and leaches cations, forming a CaCO3 buffered zone, amorphous silica, and other secondary minerals. Increased temperature affected the structure of C-S-H and the hydration of the cement leading to higher degradation rates.