Because of the substantial cost involved, subsea environments demand technologies which improve efficiency. This statement is particularly true in marginal developments. In such scenarios, multilateral completions have played an integral part in improving field economics through improved well performance and reducing both field and operating costs to a point where the field development is financially appealing. In the northwest shelf of Australia, there have been four major oil field developments to date which have been based either entirely or partially on multilateral completions. This paper describes the evolution of multilateral completions throughout the past 10 years in Australia for two such developments, outlining the efficiency and operational gains during that time period.
Sand face completion techniques in Australia's northwest shelf vary from conventional standalone screens (SAS) to more sophisticated sand control methods, such as gravel packing. For multilateral wells in this region, even though gravel packs have been installed in other regions, developments to date have been limited to oil producers with SAS with inflow control devices (ICDs) and swell packers for compartmentalization. Nonetheless, the process of constructing and completing a subsea multilateral completion can be complex, and often trip intensive. Early multilateral field developments borrowed technology from the Norwegian northwest shelf; however, as such, the completions were not optimized for the specific Australian operating environment. Following the first successful subsea multilateral field developments in Australia, customized technology began to be developed to address and improve completion efficiencies. Specifically, several global and regional first installations were implemented between 2014 and 2016 that reduced dedicated installation time by 42% and helped reduce or eliminate operational risks.
In addition to discrete technologies, well architectures have also been revisited to further the economic advantages of multilateral completions. Trilateral wells, where three laterals penetrate the reservoir, are now commonplace in subsea developments in Australia. The custom solutions developed throughout the past 10 years demonstrate not only industry maturity, but also region specific advancements in multilateral completion technology.
Australia's history of multilateral completions is a success story, highlighting an industry's adoption of new technology and appetite for improvement on a broader scale. In ten years, the step change in multilateral completion has been appreciable. The result of a decade worth of improvement and customization is a fit-for-purpose, reliable, robust and efficient completion practice.