Khurais field has seen, on an average, a 35% increase in reservoir pressure during the past three years due to water injection for production maintenance. A workover campaign started two years ago to reenter and workover some of the power water injection (PWI) wells. The campaign saw a dramatic increase in non-productive time (NPT) due to differential sticking and loss of circulation as well as difficulty in working over these wells conventionally.

Subsequently, Saudi Aramco started a campaign in late 2012 to workover these wells utilizing managed pressure drilling (MPD). MPD has enabled personnel to workover these wells at a 20% reduced mud weight, preventing stuck pipe and fishing related NPT.

This paper summarizes Saudi Aramco's experience gained during the working over of a well where drilling two formations together enabled the target hole size to be maintained as well as eliminating running the expandable liner for pressure isolation between these two zones. It further highlights the operational complexity and the challenges faced during the implementation of this technology while drilling the two formations with varying pore pressures. It also elaborates on the interdisciplinary team that was instrumental behind the safe and successful implementation of managed pressure drilling.

The paper also elaborates on the lessons learned and how they were implemented continuously with regard to health, safety and environment (HSE) during the workover operations. The long-term goal was to evaluate whether the application of MPD can be extended to other asset teams/areas effectively to reap its potential benefit.

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