Abstract
The Troll Phase 3 (TP3) wells were designed to enable high gas rates and sand free production for an expected lifetime of 40 years with a minimum pressure drop. By taking reservoir and production properties into account, open-hole gravel pack (GP) sand screens in the lower completion and big bore tubing in the upper completion were selected. To further reduce the pressure loss in the well, reduce rig time and cost, and reduce deployment risks, eliminating the intermediate completion was proposed. Traditionally, an intermediate completion is required to serve as a gas-tight barrier for running of the upper completion, mainly due to historical limitations of the GP extension (GP sleeve) not being a barrier qualified to API 19AC Validation grade V0 (referred to as V0 hereafter) after pumping sand slurry through it (post-erosion). An extensive qualification program was completed to qualify the GP system to API 11D1 and API 19AC V0 for use as a gas-tight barrier post-erosion. This allows the GP system to serve as a primary barrier while installing the upper completion and temporarily abandoning the well. The GP packer was qualified to API 11D1 V0 with the additional requirement to perform entire qualification in as-rolled casing and including a plug-in-tailpipe load case. The GP sleeve provided the most technically challenging requirements: a full-scale erosion test, immediate closure of the sleeve after pumping operation, followed by API 19AC Annex A V0 validation. Challenges were encountered trying to meet the rigorous V0 (zero bubble) acceptance criteria post-erosion. A significantly different approach was developed to achieve gas-tight performance in debris-laden environments. The new design successfully passed the post-erosion API 19AC V0 qualification to the full rating of the GP sleeve. The GP system development and qualification enabled the industry-first V0 post-erosion GP system for Equinor, which eliminates the need for an intermediate completion. This state-of-the-art gravel pack system enabled the simplified high gas rate, big-bore well design, not previously possible given well barrier considerations. The reduced pressure drop across the lower completion is expected to yield a higher gas production rate for the 40 years expected well life, contributing significant value to the TP3 project.