Investigation of Wellbore Integrity Factors in Historical Oil and gas Wells for CO2 Geosequestration in the Midwestern U.S

A systematic investigation was completed to evaluate wellbore integrity factors for oil and gas wells in the Midwestern U.S. in relation to CO2 geosequestration. In this region, over one million oil and gas wells have been drilled, and there is a perception that many areas are not suitable for geosequestration. The project focused on Michigan and Ohio as study areas. Records were obtained for over 280,000 wells. Plugging and abandonment reports were tabulated for 1,730 wells, and 278 cement bond logs were analyzed with a systematic method to grade the cement present in the well. Sustained casing pressure was monitored and analyzed for cement defect factor on thirteen wells in various configurations. The data was summarized with maps and graphs. The test site assessments provide examples of the steps and costs necessary to address wells in the region. Results indicate that a variety of well construction and plugging approaches were used over time, but many of the geologic formations being considered for CO2 storage are not penetrated by many wells. The project provided practical tools for CO2 storage applications including: database of well parameters, systematic cement bond log evaluation tool, and sustained casing pressure analysis method for cement defect factor.