Fracture healing and transport properties of wellbore cement in the presence of supercritical CO₂
2011
Liteanu, E. | Spiers, C.J.
This paper investigates the process and rate of carbonation reaction of Class A wellbore cement exposed to CO₂-saturated solution at confined conditions similar to those employed in geological storage of CO₂. The main goal was to investigate whether reaction improves or degrades the sealing/healing capacity of fractured Type A cement plugs. Batch reaction experiments were performed for up to three months, on both intact and fractured Class A Portland cement cylinders, at a constant confining pressure of 30MPa, a temperature of 80°C and a CO₂ pressure of 10MPa. The experiments were carried out on water-saturated samples, exposing them to the supercritical CO₂ at one end. All samples were jacketed in sleeves to seal them from the high pressure confining medium. The results indicate that cement carbonation front advanced in time, leading to a densification of the material. Extrapolation of the reaction rates to 1-year period indicates a carbonation depth of about 1.38mm, and about 7.56mm after 30years of exposure to CO₂-saturated solution. Thermogravimetric analyses, Scanning Electron Microscopy observations and permeability measurements indicate that carbonation of wellbore cement leads to a decrease of the porosity of the material on the reaction front and moreover, has the potential for healing pre-existent fractures and for improving the sealing properties of good-quality cement samples in time, at reservoir conditions.
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