Advanced Cement Evaluation in Complex Wellbore Completions Using Radioactive Method

Abstract Assessing cement integrity behind multiple casing strings is challenging due to substantial cost and technological complexity. Ensuring a cost-effective approach on cement evaluation is critical to the success of Plug and Abandonment (P&A). Traditional methods relying on acoustic measurements struggle in complex well completions especially involving multiple strings of tubing and casing which introduce barriers between the logging tool and cement. Factors such as varying tubing positions and different fluids in annular spaces contribute to inconclusive results. To address these limitations, alternative cement evaluation techniques based on different physical principles are needed. This paper explores the use of radioactive methods including neutron-neutron, neutron-gamma, and gamma-gamma techniques as a robust alternative to traditional acoustic methods. These radioactive techniques provide high quality cement evaluation data and comprehensive evaluation of cement integrity in complex wellbore scenarios, where traditional methods often fall short. By integrating these methods, we are able to acquire high-quality data that can be critical to the development of reliable P&A strategies. The study was based on a highly deviated, single oil producer, well with 3-1/2-inch tubing, and 9-5/8-inch production casing. Evaluating cement quality behind 9-5/8-inch casing while logging inside 3-1/2-inch tubing requires special handling, especially with high inclination and fluid inside the well. The results obtained, using radioactive methods in complex wellbore completions, are compared to industry standard acoustic cement evaluation techniques conducted earlier in the well’s lifecycle, before the completion had reached its current complexity. The initial acoustic evaluation was performed when the well’s geometry was simpler, before multiple casing strings and tubulars were introduced. Despite the increased wellbore complexity in the later stages, the radioactive methods provided cement integrity results that were comparable to the earlier acoustic evaluations. However, radioactive methods showed particular strength in maintaining data reliability despite the presence of high inclination and fluid interference, areas where the acoustic methods tend to suffer from degraded performance. The findings demonstrate that radioactive methods not only provide reliable cement integrity assessments in these challenging environments, but also offer a more-cost effective solution when compared to acoustic techniques. This approach not only provides reliable data but will also offer a cost-effective solution for cement evaluation, especially in complex wellbore scenarios, thereby facilitating the development of successful and optimized P&A strategies.