Best Practices in Wells Workover Planning Using Four-In-One Well Integrity Suite Evaluation

Abstract Well integrity test plays an important segment in coal exploration as part of the preventive measures for any harmful substances entering the surrounding rock formations and aquifers. In compliance with local regulation and Code of Practice, the Coal Seam Gas (CSG) wells would need to be monitored in timely manner to ensure intact well integrity. A combination of four advanced diagnostic technologies, including magnetic flux leakage-, contact-type caliper-, ultrasonic cement impedance- and acoustic bond-based wireline logging tools had been deployed in a series of vertical, 5.5 to 7-inch CSG wells for accurate casing and cement inspection. The 4-in-1 method together with auxiliary measurements such as gamma ray and casing collar locator enables the acquisition of comprehensive sets of measurements in 3D view with just 2 logging runs, improving the operation efficiency and cost. The high-resolution flux leakage detection tool together with 40-arm caliper tool allowed detection of both internal and external defects or deformation. The ultrasonic cement impedance-based tool was utilized for cement quality check. Full spectrum of casing and cement inspection of logs has been successfully acquired for more than 400 CSG wells since 2020. Seven different case studies were demonstrated in this study, featuring some of the common type corrosions in some of the idle and injection wells, together with some of the industry's best remedial practices applied. Some of the cases had proven the successful integration of magnetic flux leakage-, caliper- and ultrasonic-based tools in the high-resolution circumferential analysis of internal and external defects in every single casing joint or even small 100% through hole. Time lapse corrosion logging has also proven an effective approach for monitoring the progression of highly penetrated external and internal defects and internal pitting in injection wells. Cement integrity was also evaluated simultaneously to pinpoint sections with poor cement coverage or potential channeling and its relation to the casing defects. In short, every single well counts in building a strong foundation for integrity management and it requires long-term commitment. Effective corrosion logging using a four-in-one well integrity suite helped users to define the strategy for workover better and ensure compliance with the local regulations.