Laboratory study on carbonate rocks characterization and porosity changes due to co2 injection

Abstract

Enhanced oil recovery methods must be improved continuously to provide higher recovery factors for the new fields under development in a globally competing market. CO2 injection processes in carbonate rocks involve reactions between acid brine and the rock. These interactions promote petrophysical changes in the rock structure due to calcite dissolution or precipitation. Lab experiments in saturated coquina samples were carried out to better understand the effects on porosity by CO2 injection. X-ray Photoelectron Spectrometer (XPS) was used to analyze the surface chemistry of the rock sample for elemental composition measurement. X-Ray Micro-CT and Mercury Injection Capillary Pressure (MICP) were carried out to calculate mean porosity in the rock sample. X-Ray scans were run for each pore volume injected. The results show that dissolution should be considered when supercritical CO2 is injected in the reservoir. This process has relevance for project design, risk analysis, economic evaluation and reservoir behavior forecast