Unlocking the Potential of Fiber-Optic Distributed Temperature Sensing in Resolving Well Integrity Issues

Multiple leaks in production tubing of deep wells can be efficiently identified using fiber-optic distributed temperature measurement and thereby mitigating the health, safety and environment (HSE) risk associated with a potential well barrier failure. Further, a production log can be used to gain more insight and finalize a way ahead to resolve the issues of the well integrity. An innovative solution-driven approach was identified with fiber-optic distributed measurement playing a key role. Multiple leaks were suspected in the production system and a fiber-optic cable was run to identify possible areas of leak path. In these deep wells, after the fiber-optic data acquisition, a production log was recorded across selective depths to provide more insights on leak paths. Post identification of leak depths, a definitive decision between tubular patching and production system overhaul was decided based on combined outputs of fiber-optic, production log and tubular patch technology. Results are presented for a two-well operation. Taking an example of Well A, leaks were successfully identified at three depths using the novel operational approach. Further, operation time was reduced from three days (conventional production log measurement performed during daylight operation) to one day (combination of fiber-optic distributed temperature sensing and production log in a single run). Diagnosis of production system issues were completed in one flowing and one shut-in survey condition, thereby reducing the risk of HSE exposure with multiple flowing conditions (conventional production log measurement). Additional insight and confirmation on leaks were observed from production log data which helped identify the presence of a leak across the tubing body. This observation was substantial in deciding whether to proceed with tubing patch or replace the entire production tubing. Tubing patch technology was not satisfactorily recognized to provide well integrity across leak depths. Hence, the decision was made to replace the entire production tubing. The novel operational approach affirms the versatility of fiber-optic distributed temperature measurement in solving critical issues of operation time and reducing HSE exposure while delivering decisive information on production system issues. The paper serves as a staging area for other applications of similar nature to unlock even wider horizons for distributed temperature sensing.