With most of the world's largest and easiest-to-exploit deepwater reservoirs already under development or producing, the industry is now facing new challenges. The tie-back of new smaller fields, often with complex fluids, to existing production facilities; or the transportation of multiphase production over long distances using large pipe diameters can appear as a viable route to unlocking reserves, which are often too small to be developed economically as a stand-alone facility.

If the use of subsea technologies and innovative field architectures is a step change in the industry for the development of such complex fields; operators have nevertheless to face inherent challenges. The most demanding are the flow assurance issues arising from the different operating regimes, deeper water, remote locations, harsher environment, etc. which may also be combined with more viscous fluids and/or reservoirs at low pressure and/or low temperature.

Flow assurance engineers use commercially available multiphase flow software for the design of field development facilities. Optimized design recommendations are heavily reliant on the accuracy of these multiphase flow simulators, but usually extensive sensitivity studies are needed to refine the concept in order to ensure compliance with operating constraints.

With increasing demand on flow assurance tools, development works are performed by the code suppliers to improve the simulation accuracy and operators have to undertake systematic internal validation tests and to apply a methodology before qualifying released versions.

This paper examines the accuracy of available commercial multiphase flow simulators against field data (oil dominated and gas dominated fields are considered) and laboratory tests. A methodology is also presented to address operational considerations such as degraded mode, turndown, pigging strategy and restart management as well as to handle uncertainty of multiphase flow simulation in the case of gas field development over long distance via a large diameter pipeline.

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