A World-First: 3-Legged Lateral with Smart Completion, Smart Liners and Inflow-Tracers Across Low-Permeability Multi-Stacked Reservoirs

Abstract

In a giant, mature UAE offshore field, consisting of complex multi-stacked heterogeneous reservoirs, the western part has been less developed, due to contrasted reservoir properties and low-permeability layers. The development in that part of the field was re-visited, to account for reservoir challenges and surface limitations. The objective was to achieve production mandates, understand reservoir behavior, while minimizing well count and expenditures associated with interventions and surveillance activities. To evaluate this challenging area of the field, a unique multi-lateral well was designed, targeting three distinct reservoirs, and allowing to concurrently produce and understand them in a viable manner. The reservoirs have poor characteristics, with permeability lower than 10 mD, except for the deeper one, which has some high permeability streaks. Accounting for the tight formations, each horizontal leg had to be stimulated efficiently, despite being inaccessible with coiled-tubing. In addition, well production had to be reliably back-allocated to each drain, and meet pre-defined reservoir guidelines. Despite contrasting properties, all three drains had to be produced at reasonable rates, avoiding that one drain would dominate the other two. And finally, enhanced reservoir understanding was required within each drain, with qualitative indication of their flow profile and associated reservoir conformance. The 3-legged multi-lateral oil producer was drilled and completed successfully. In each of the three horizontal laterals, totaling more than 15,000 feet length, drop-off limited-entry ‘Smart Liners’ were installed, to allow bull-heading stimulation. This offered an effective high-volume matrix acidizing method, adapted to the contrasted properties and tight zones encountered along the laterals. The well was equipped with permanent downhole gauges and inflow control valves (ICV's) to dynamically monitor downhole contributions, modulate production from each drain, avoiding well delivery to be dominated by the highest potential reservoir and control unwanted water/gas production to the surface. To complete the picture, chemical in-flow tracers were installed, in the tubing and within each drain, to monitor the laterals’ flow profiles and performance, and measure the individual contribution from each reservoir. This aimed to determine the efficiency of the ‘Smart Liners’ design and proved a cost-effective option to quantify the contribution from the laterals, compared to running regular PLTs. The resulting pilot is the first well in the world to combine a smart completion with three limited entry ‘smart liners’ utilizing drop-off technique and chemical inflow tracers. The pilot well, which behavior is being evaluated over 2021, provides a groundbreaking approach to evaluate and unlock hydrocarbon resources in a poorly developed area of the field, allowing a significant optimization of well count and of associated capital and operating expenditures.