Well delivery in Pre-Cambrian salt with high-pressure floaters in the South of Oman provides several challenges, including Well Control Events, losses, supercharging, salt creeping, casing collapse and a negative drilling windows if section TD is picked incorrectly. The well design does not allow for an additional casing string with redundancy to case of troublesome zones.
To overcome this, PDO initiated a barefoot completion as an extra hole section instead of well abandonment. As a wells recovery plan in 2017, PDO initiated different potential options to complete Ara salt wells and one of visible alternative options was to complete wells as open hole "Barefoot" completion. A design solution developed across technical functions on the suitability of barefoot completion in the carbonate reservoirs. The method to drill and complete with 3.615" hole as "Barefoot" was then expedited through detailed design as per the well delivery process. Key factors, which were considered included inflow performance and hole stability, the review of BHA design, drilling hydraulics, fluids selection and barrier considerations for barefoot completion. The operational challenges were reviewed and optimized with each implementation to drive further value.
To date three wells recovered successfully with the new barefoot completion method. The wells completed with solids free drilling mud placed across the reservoir section and a suspension plug installed in the upper completion to facilitate rig release. During well testing operations; the suspension plug is removed, the openhole section is clean-up with coil tubing to remove filter cake with Enzyme treatment and finally the carbonate reservoir stimulated with gelled acid. During production tests all wells showed excellent production results and reservoir flowing coverage confirmed by spectrum noise logs (SNL), high precision temperature (HPT) and production logs (PLT). Based on three wells results; it is concluded that openhole completion can offer a valuable completion option for well recovery & may be used for optimization for current designs. The cost of the barefoot completion delivery has reduced by 20%. The production output from the wells is higher than expected; Productivity Index of those wells is relatively much better than the nearby wells.
The Newly proposed design provide continuity to develope Ara Salt wells and recovery plan to overcome challenges and avoiding well abandonments. This completion option was reviewed and accepted as base case completion for some deep fields in South of Oman, where oil is encapsulated in high-pressure carbonate floaters and there no risk of water or gas breakthrough. One more additional well was planned to be completed as openhole "Barefoot" completion and cost saving of ~15% over the total well cost was achieved. This recovery option will benefit all the upcoming future wells in the area.