Novel Approach to Cementing Production Liners in Deep HPHT Gas Wells with Narrow Subsurface Pressure Windows

Abstract

Abstract Cementing the production liners in the deep gas field in the Kingdom Saudi Arabia (KSA) has been incredibly challenging due to narrow pore-frac pressure windows resulting in higher well control risks. Hydraulic isolation becomes even more critical as the reservoir pressure is on the high spectrum. To mitigate these risks, reliable hydraulics simulations and flexible cementing fluids designs are needed to accurately manage the circulating pressures during cement placement. When pore pressure is revised upward during drilling, mud weight cannot be further increased due to fracture pressure limitation and circulating pressures must be managed to maintain well control. Accordingly, the cement and spacer densities must be adjusted to fit the new drilling window. Wet addition of a special weighting agent featuring controlled fine particle size enables last minute slurry design adjustment without the need to switch blends. An Engineered Lost Circulation (ELC) spacer was designed to mitigate losses. A collaborative workflow between the surface auto-choke system and a field proven hydraulics simulator allowed pressure management during cement placement. This innovative design and execution approach contributed to increasing the success rate of cementing some of the most critical production intervals in KSA. The added design flexibility helped save rig time by avoiding the need to proceed with a complete rework and prevented unnecessary blend disposals by allowing slurry adjustments thru wet addition of a special weighting agent instead of building a new blend. The ELC spacer solution was highly effective, giving confidence to proceed with the cement job without having to consume drilling fluids and rig time trying to cure losses upfront. More importantly, the successful pressure management methodology promoted well integrity assurance. The proven success track record encouraged other drilling departments in KSA to adopt the same approach when encountering similar challenges in their wells. To the authors’ knowledge, the combination of these techniques has yet to be explored, particularly in the context of deep high-pressure high-temperature (HPHT) gas reservoirs. Notably, the existing body of literature lacks illustrations of such unique multi-disciplinary approaches.