CO2-resistant cement system enables injection of CO2 into well drilled in 1960

At an onshore well in Hungary drilled in 1960 and previously considered unsuitable for CO₂ injection, the EverCRETE™ CO₂‑resistant cement system was used to successfully eliminate the sustained casing pressure in the 6⅝‑in by 9⅝‑in annulus, allowing CO₂ to be injected into the well.

An operator in Hungary planned to inject CO₂ into a well drilled in 1960, which had experienced sustained casing pressure in the 6⅝-in by 9⅝-in annulus. A sonic bond log showed poor bonding, suggesting the well might not be suitable for CO₂ injection. To overcome this challenge, the operator chose the EverCRETE system, which is specifically designed to act as a durable barrier in CO₂ storage wells and high-CO₂ formations.

The operator milled open a window in the 6⅝‑in casing between 2,250 and 2,280 m, then underreamed the section to 9½ in. A 4½-in tieback casing was installed, and both the openhole and tieback casing were cemented in two stages: Stage 1 used the EverCRETE system, and Stage 2 employed a bentonite filler slurry. This process eliminated the sustained casing pressure that had developed in the 6⅝‑in by 9⅝‑in annulus, enabling continued CO₂ injection into the well. Four years later, no sustained casing pressure was detected in either cemented annulus. The use of this reduced portland cement system minimizes leaching, degradation, and carbon footprint.