PR244-21701-R01 Advancement of Through-tubing Inspection for Underground Gas Storage Wells

Maintaining the integrity of well casing in underground gas storage (UGS) wells is a significant challenge for operators, as undetected corrosion can lead to safety risks and operational failures. Existing inspection technologies, particularly through-tubing (TT) inspection tools, offer practical solutions for routine assessments, but they have known limitations with detecting and sizing certain types of corrosion. This research effort was initiated to address gaps in the understanding of the capability of TT inspection tools and to develop improved methods for using TT inspection tools in evaluating casing integrity.

This report provides a comprehensive overview of TT inspection technologies, including a review of current technologies, laboratory testing of commercial tools, development of a reliability-based assessment methodology, and field trials in operational wells. The research explores how TT inspection tools function, their strengths and weaknesses, and the factors that influence their performance. It also introduces a structured approach for interpreting inspection data and estimating the probability of casing failure, with the aim of supporting more informed maintenance and safety decisions.

This report is intended for UGS operators, regulators, and technical professionals responsible for well integrity management. The information presented can be used to guide the selection and deployment of inspection tools, improve maintenance planning, and support decision-making processes related to well safety. By adopting the recommendations and methodologies described, stakeholders can enhance their ability to manage corrosion risks and maintain the safe operation of UGS facilities.