As the number of aging wells grows in the oil and gas industry, there is a recurrent need for monitoring the health of these wells over their productive life and providing assurance of the integrity of the well barriers that isolate them from uncontrolled formation pressure and fluids. Tubing and casing condition evaluation is a crucial aspect of this evaluation. The industry utilizes a number of conventional technologies for evaluation of tubing and casing integrity, such as internal mechanical calipers, electromagnetic and ultrasonic thickness (UT) tools, which are generally quite satisfactory for the evaluation of the inner casing but are often affected by internal tubular diameters in terms of their application. Most conventional tubular evaluation tools are unable to evaluate multiple concentric barriers. When combined with the low diameter production tubing completions the options for evaluating the production and outer casings become very limited, necessitating the need to pull the inner casing by performing a workover at a considerable expense and inspect the outer casing with conventional technology. A new electromagnetic casing corrosion evaluation technology was applied in a group of critical wells completed with small diameter tubing. The technology utilizes electromagnetic pulsed transient eddy currents to simultaneously inspect tubing and the casing behind it and provide quantifiably segregated measurements of thickness in the tubing and the first concentric casing as well as qualitatively characterized by a third casing string. This slim tool with a diameter of 1-11/16" allows measurements through slim production tubing. The objective of the study was to assess the integrity of a group of mature wells completed with small diameter restrictions, near populated areas and associated with high H 2 S environment. This study includes the candidate generation, field application, results evaluation and general recommendations for the well integrity program. The results exhibited that the data obtained from the tool is reliable. A quantifiable assessment of the metal loss of casing behind the tubing could be made, which made a mitigation strategy possible to prevent casing leaks, which in these wells are critical due to their population sensitive location.

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Locating downhole casing leaks in producer and injector wells is not a complex undertaking when using rig-operated straddle packers with pressure testing. However, this established technique has limited effectiveness because it does not necessarily address the overall comprehensive integrity of the entire completion, which might include additional intervals of serious corrosion leading to leaks in the near future.We examined the results of low-frequency electromagnetic (EM) remote frequency eddy current (RFEC) wireline logs from over 80 wells in one mature Middle Eastern offshore field, profiling the severity of measured metal loss (ML) from concentric casings against proven rig-discovered leaks and rigless measurements of subsurface ML. Casing leaks that otherwise would have been detected only by conventional zonal pressure testing from a workover rig can now be located and forecasted with a high degree of probability when using this evaluation tool.The importance of maintaining oilfield casing integrity for safety, environmental, and flow assurance objectives, combined with the high costs of drilling new wells, creates a necessity for this integrated well integrity appraisal approach. Application of this EM logging technology to identify intervals of external ML has great significance in being able to anticipate casing intervals with high likelihood of failure due to invasive corrosion.

An evaluation process was conducted in assessing various solutions towards remedial action to a 7" liner with an identified leak in a water injector well. The leak to the 7" liner was identified through pressure testing of the well. A comprehensive investigation and analysis was performed to identify the liner condition, exact leak location and the extent of the leak. It was accomplished by analyzing all previous activities performed during the life of the well and through running special pressure testing as well as logging the well with ultrasonic and physical logs.The problem identification and proposed solutions were focused on curing the leak and bringing the well back on injection with the least operational risk and highest possibility of success. Corrosion and cement bond logs were ran and showed a better picture in regards to the extent of the corroded section and the quality of cement behind it. A caliber log was also run in the open hole which showed a washed out area near the 7" liner shoe.Several solutions that could repair the 7" liner leak were assessed including: i) cement squeeze in the leak zone, ii) setting an off bottom 4.5" liner and iii) using a 5.5" expandable liner. The evaluation process included each solution's impact on the future injectivity of the well, the effectiveness of each option, operational challenges and associated risks. Moreover, nodal analysis was performed to evaluate possible reduction of the injection rate associated with each solution.The final decision to repair the leak was to run an expandable liner and it was based on its advantages and deployment challenges. Lessons learned from this operation included the methods used to identify and assess the damage of the casing leak. Proper preparation and cleanout of the corroded section and the operation procedures performed to expand the liner are summarized in this paper.