Openhole gravel pack is the preferred completion method of sand control in unconsolidated deepwater formations with sanding tendencies. The design phase of an openhole gravel pack treatment spans drilling of the reservoir section, wellbore preparation, sand screen installation, gravel placement, and well flowback. This paper discusses several ultra-deepwater wells of India, where openhole gravel packs were performed by integrating drilling, wellbore cleanout, wellbore displacement and gravel pack methodologies to achieve a holistic approach towards openhole gravel pack completions.
The reservoir sections were drilled with streaks of shale and dolomite sections, the liner shoe often landing in shale, exposing a shaly rat hole. Next, the wells were displaced to dedicated production screen testing (PST) mud prior to running in screens. Screens were then placed across the openhole with memory gauges to capture downhole events during the gravel pack. The displacement pills train was engineered to displace the open hole with water-based fluid prior to starting the gravel-pack treatment. Extensive lab testing and displacement simulations for efficient spotting of pills and optimal sweeping effect were performed. The gravel-pack treatment was executed using Alternate Path technology and a high-temperature viscoelastic surfactant (VES) carrier fluid system.
11 ultra-deepwater wells off the east coast of India were completed. Displacement of open hole from drilling fluid to water-based system was done with direct displacement and reverse displacement methods. Due to the narrow fracturing window of 200-300 psi in all the wells, bottomhole pressures were managed by deploying multiple techniques such as using a lighter VES-based brine, optimizing the rheology of the fluid and taking returns through the riser. Roping behavior of the pre-pad and slurry have also been studied, and results presented to correlate with design. All open-hole gravel packs were executed without losses and achieved complete packs. Finally, flowback and well test data were analyzed by the operator and found to be as expected with no sand ingression. A holistic approach toward open-hole gravel-pack treatments has been developed, analyzing all the interlinked elements and the efficacy of the design process verified against surface and downhole data gathered for each well.
This paper discusses the approach, simulations, lab testing, and evaluation, analyzing captured data from drilling phase of the open hole to completing the well by placing gravel across the screens and flowing back. The design approach, integration strategies, and lessons learned in these wells offshore India can be applied to improve success rates of sand control completion wells around the world.