Multistage Completion Application's Best Practices, Experience, and Lessons Learned from Deep, Challenging Horizontal Wells in North Kuwait Jurassic Gas Unconventional Reservoirs

Abstract The North Kuwait Jurassic Gas asset holds strategic importance for Kuwait's production strategy as it includes the only non-associated gas-producing fields in the country. Multistage completion technology has been implemented since the early development stages in 2009, with expansion starting 2019 in deviated wells. This paper demonstrates the added value, experience, challenges and lessons learned from the recent application expansion in deep, challenging, long horizontal wells in Jurassic unconventional reservoirs. This approach enhances overall well production potential and intervention operation efficiency through selective stimulation, overcomes reservoir and intervention operations challenges, and ensures early production delivery. These factors are crucial for achieving the asset's strategic production target by 2026. The Jurassic gas asset primarily produces from deep, high-pressure, high-temperature, conventional and unconventional tight carbonate reservoirs. Recovery from these complex, heterogeneous reservoirs is extremely challenging if conventional development strategies are applied. Due to the high reservoir tightness, permeability contrast among different flow units, and dual permeability effect (matrix and natural fractures), well productivity potential significantly depends on the effectiveness of subsequent stimulation treatments to improve well productivity and connect the natural fractures. This is especially important in nano-Darcy Najmah carbonate reservoirs, where development is set for horizontal wells with selective multistage stimulation. Najma Limestone (NJ-LS) is a tight gas-condensate reservoir with typical porosity ranging from 2 to 9% and very low matrix permeability (~0.01mD), with primary production through natural fractures. To increase the chances of success in encountering fracture corridors, long drain-hole horizontal wells were deemed necessary. Multistage open-hole completion has been considered as the primary completion option in these NJ-LS horizontal wells. The asset team has implemented a step change in completion strategy by adopting open-hole HPHT multistage drop-ball completions using state-of-the-art MSC technology. This includes closable frac ports, a full 3.5in monobore post milling, and a debris sub to protect the MSC string during upper completion operations. This approach addresses reservoir complexity, eliminates wellbore cleaning and multiple perforation intervention challenges and risks, resolves cement quality uncertainties, improves overall cost, and accelerates well delivery to production. This significantly reduces operation time from approximately one month using the plug-and-perf technique to less than one week with continuous and fewer subsurface intervention operations, particularly in deep, long horizontal wells. An integrated asset team has developed a structured workflow for multistage design, planning, and running protocol, incorporating best practices and lessons learned. A total of nine (9) new multistage completions were successfully installed in Jurassic deep horizontal wells over the last two years in the unconventional Najmah reservoir, ranging from four to thirteen stages, including selective acid stimulation. The production results were mixed due to the uncertainty of reservoir natural fractures. Based on experience gained from highly deviated wells (47wells) and more recently in long horizontal wells (9 wells) as of July 2024, an integrated protocol for multi-stage candidate well selection, staging design and installation procedures has been developed by the integrated multidisciplinary team. This ensures a standardized process across fields and can be applied for other assets.