Assessment of Well Integrity at Nagaoka CO2 Injection Site Using Ultrasonic Logging and Cement Bond Log Data

This paper reports logging results for well integrity conducted at the CO2 injection site in Japan. Well integrity is one of the essential issues for safety in geological CO2 storage. Wells in the Nagaoka site have been used for monitoring logging of CO2 behavior for more than ten years, and have experience of large earthquakes near the site. Time-lapse ultrasonic and cement bond logging have been employed to investigate the well integrity of the observation wells. Results of the ultrasonic logging showed that there was no sever damage or deformation in the casing at the reservoir depth. No clear change in cement can be seen in either logging results, even at the depth where the cement was exposed to the CO2. These results showed that there was no clear evidence of CO2 leakage at Nagaoka.