One of the most giant offshore multi-reservoir oil fields in the world has been developed using vertical, deviated and short horizontal wells drilled off-shore from wellhead platform towers. Towards the concept of cost optimization, further redevelopment of the oil field was planned using extended-reach long horizontal wells with throws greater than 18,000 ft and measured depths greater than 25,000 ft with some wells exceeding 35,000 ft, from artificial built islands by reducing the number of wells required to drain the reservoir with improving recovery. In order to enable transition to such concept, new well design strategic concepts were required to come up with the robust well completion design (both upper and lower completions) that is expected to be fit-for-purpose for 30+ years – well life time. Lots of uncertainties and challenges are faced in order to get to the goal of understanding different reservoirs behaviors such as, for better reservoirs development relying on dynamic reservoir models combined with actual geological, petrophysical, seismic and production data. Each piece of information yielded a certain potential that led to a certain completion design based on available data and expectations.

This paper will discuss the upper and lower completion designs, execution and performance from production engineering perspective to maximize productivity for the whole life cycle of this long horizontal wells. The extended lateral length in these wells warrants innovative designs in upper and lower completions as traditional completion designs no longer valid in addressing the challenges in these wells. The key well design and planning process involves designing the upper completion – tubing, gas lift system, downhole gauge and lower completion liner – Pre-perforated liner (PPL), Limited-entry Liner (LEL) or Inflow Control Devices (ICD) with annular isolation with packers, efficient initial start-up and clean up strategy, regular monitoring well performance and surveillance (e.g. downhole pressure monitoring, PLTs, fluid sample analysis etc.). The paper will also address the challenges in long horizontal wells such as accessibility, production/injection conformance and effective stimulation of the laterals.

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