A major Abu Dhabi oil and gas producer targeted an increase in production from their major offshore oilfields. Better optimization of the reservoir through advanced well architecture was considered an option. One way to achieve this objective was through accessibility and hydraulic control of all horizontal drains. Multilateral technology is commonly used to increase the production per well and reduce drilling time while optimizing production facilities. The project targeted multiple reservoirs with two separate laterals to meet reservoir requirements. The application required individual through tubing access for intervention into each lateral. Multilateral technology has been traditionally limited to commingled production with limited or no access to the laterals. To help address and overcome these challenges, the operator planned and installed their first Level 5 multilateral tieback system (MLTBS).

ADNOC Group of Companies are embarking on drilling many of development wells in the upcoming years to achieve the forecasted production mandates. Therefore, the wells completion should be designed to cater for the following reservoir requirements as per as per company expectations: ▪Full accessibility (to TD) for production logging and stimulation.▪Flexibility for conformance control.▪Defined production allocation.▪Fit for purpose completion that can absorb the change in reservoir dynamics throughout well life. The current practice of completing the horizontal wells as open hole "bare-foot" completion and geosteering practice might save some short-term cost, but it may impact the hole accessibility and cost more in the long term. Horizontal well application is one of the key development strategies that will improve the sweeping efficiency and recovery to minimize field development cost by reducing well counts. Longer horizontal require lower completion liners to meet the objectives of the well. Full multi- disciplinary input are needed to properly install an effective lower completion, but robust design often brings strong performance. This paper describes the outcomes of accessibility, geo-steering practices evaluation, fundamental criteria and workflow for selecting the most suitable lower completion design for new and sidetracked wells to achieve ADNOC's production mandates while complying with completion requirements and adhering to reservoir management guidelines. The objective is to optimize the procedures as per ADNOC guidelines in designin, planning and deploying horizontal wells including the Well Post Rig Operation & Monitoring Process, Lessons Learned and assuring full accessibility while meeting integrity and quality of the development wells for future prognosis. The main drivers and objectives for running lower completion are listed below: ▪Enabled to maximize reservoir contact aiming for cost and production optimizations▪Full Accessibility to allow PLTs, Stimulation and re-stimulations.▪Compartmentalized lower completion for remedial actions▪Achieve uniform flow conformance utilizing ICVs & ICDs▪Mitigate and manage water production