Fiber Optics Application in Annulus Pressure Management and Well Integrity

Field A is a carbonate field in Sarawak, Malaysia which was completed through a number of overburden sands (F, SB3.4 and H sands). Most of the wells experienced sustained annulus pressure from the start of production. A comprehensive surveillance plan has been put in place to establish the risk of operating these wells and monitor for potential escalation of the leak and its sources.

A periodic DAS and DTS data acquisition on fibers has been chosen as one of the surveillance methodologies. This is complemented with annular investigation and gas isotopes analysis for further validation.

We see repeatability between the conventional noise logging to the fiber optics DAS data within the 10–20Hz frequency window, where indications of leaks are observed from ∼2000 ft upwards (F sands). However, at the deeper sands, some signs of fluid movements were only detected on DAS data.

This surveillance strategy, in combination with the safeguards in place are key in safely operating the wells with sustained annulus pressure since 2019. Distributed acoustic and temperature sensing on fiber optics has been successful in characterizing the source of the leak path, despite the low rates (low frequency) nature of the leak.