Revolutionizing Leak Identification in Mature Fields: Coiled Tubing Telemetry and Distributed Temperature Sensing (DTS) Unveiled in a Paradigm-Shifting, Cost-Effective Intervention Approach—A Case Study from North Kuwait Border Field
Authors: Slama Mohamed Hedi , Badrawy Kareem , Ayyad Hazim , Al-Matar Mohammed , Al-Sabee Ali Q. , Sunagatov Rustem , Sebaih Mohannad Adel , Fajardo Sergio Rondon , Pochetnyy Valentin , Al-Oumi Abdul-latif Waleed 
Published: September 2024

Abstract
Maintaining well integrity is paramount in the oil and gas industry, necessitating vigilant monitoring throughout the well's life cycle, particularly in mature fields. Casing leaks pose a significant threat, potentially leading to production losses, reserved resources due to formation damage, personnel injuries, and environmental harm. Early detection of casing leaks is crucial to prevent these issues and the associated high costs of workover operations and potential well suspension or abandonment. Identifying leaks in well completions is essential for averting uncontrolled hydrocarbon releases and minimizing risks to personnel and the environment.
Over the past decade, Distributed Temperature Sensing (DTS) has been widely applied in wellbore completions with preinstalled fiber optic lines to detect leaks by capturing and interpreting temperature surveys along the installation's length. A new method, on the other hand, calls for using an instrumented optical fiber-enabled Coiled Tubing (CT) to measure temperature through DTS surveys in a well with a basic completion configuration. The incorporation of fiber optics within a CT pipe allows real-time downhole measurements, including bottomhole and annulus pressures, casing collar locator (CCL) for depth control and precise correlation of well parameters, and most importantly, a real-time capture of temperature anomalies, detecting any deviation from the baseline gradient. As a result, the temperature profile was sensitive to not only the borehole condition but also the formation type and the casing-formation annulus temperature shift related to the detected leak.
In North Kuwait, a deviated oil-producing well faced a casing leak that couldn't be pinpointed during profiling with production logging tools. A comprehensive well hydraulics analysis preceded the use of DTS to identify the leak. CT equipped with fiber optics was deployed, and a series of DTS surveys were conducted, correlating with different operational stages. The leak location was conclusively identified after analyzing the DTS data. During the real-time analysis, an innovative method was used: nitrogen was pumped into the annulus between the casing and tubing to make the leak point appear. This helped to find the likely leaky spot at the junction of the liner and casing. This paradigm-shifting approach made its global debut within the unique context of the subject. This innovative protocol entails a deliberate effort to induce flow at the suspected leak point (expected at 5,000 psi), encouraging the migration of fluids into the wellbore.
This case study enhances industry insight into the application of DTS in CT interventions for wells with completion leaks. This refined procedure marks its inaugural implementation in this particular case, where a nitrogen injection was strategically employed through the annulus of the kill string. The synergy of these techniques enhances the confirmation of the leak's location, complementing the initial findings derived from the preliminary DTS protocol. The intuitions and methodologies from this case study now serve as a benchmark for interventions for well integrity protocols across the Middle East.