Monitoring well integrity at the Cranfield field phase III CO2 storage project

Two purpose-built monitoring wells monitoring wells at the Cranfield Field Phase III CO2 Storage Project were studied in detail using time-lapse well integrity logging, cased-hole sidewall core sampling, and point pressure testing to study the effect of CO2 on the materials used to construct wells for carbon capture, utilization, and storage (CCUS) projects. The wells were constructed using conventional steel casing, fiberglass casing, and conventional well cements. Both wells were heavily outfitted with monitoring equipment in the annulus between the formation and casing. The time-lapse comparison of the well integrity logs showed a general degradation of signal in many places along the well. Laboratory analyses of the sidewall cores showed that CO2 affected the cement in the well at every point that was cored, with significant alteration occurring adjacent to one of the monitoring control lines collected as part of a core. Additionally, the time-lapse logs and sidewall cores showed the fiberglass casing was strongly affected in the CO2 reservoir, causing the inside diameter of the casing to decrease. This study provides insight into how decisions regarding well materials and monitoring technology can impact well integrity over a period as short as 6 years.