Chemical alteration of oil well cement with basalt additive during carbon storage application

Mokhtari Jadid, Kahila
Capturing and storing carbon dioxide (CO2) underground for thousands of years is one way to reduce atmospheric greenhouse gases, often associated with global warming. Leakage of CO2 through wells is one of the major concerns when storing CO2 in depleted oil and gas reservoirs. CO2-injection candidates could be new wells, or old wells that are active, closed or abandoned. To prevent the leakage, the possible leakage paths and the mechanisms triggering these paths must be examined and identified. It is known that the leakage paths can occur due to CO2-rock interaction and CO2-water-cement interaction. Interaction between well cement and carbon dioxide has attracted much renewed interest because of its implication in geological storage of carbon dioxide. The diffusion of CO2-water through well cement is a long-term phenomenon which can take many thousand years. Partial pressure, porosity, permeability, cement type, moisture content and temperature are the factors that affect the carbonation of well cement. The objective of this research is to investigate the chemical reactions of the dissolved CO2 in the synthetic formation water with the plugs of well cement. Cement specimens were left in contact with CO2 saturated brine at 1100 psi and 65 ˚C for three months. The 1100 psi pressure and 65 ˚C temperature are the points where CO2 is in the state of CO2 saturated brine. The four cement plugs studied differed in their basalt content from 0%, 6%, 9%, and 13% by whole mix weight. The effects of basalt content studied are change in porosity, permeability and compressive strength. The scanning electron microscope images were obtained to observe the depth of penetration of CO2-brine solution into cement plugs after three months of contact. The results indicate that presence of basalt increased the compressive strength of plugs and decreased porosity and permeability. As a conclusion the use of basalt as an additive to well cement can be beneficial in CO2 storage wells.
Citation Formats
K. Mokhtari Jadid, “Chemical alteration of oil well cement with basalt additive during carbon storage application,” M.S. - Master of Science, Middle East Technical University, 2011.