Uncertainty in multiphase flow estimates for a field development case
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Commercial multiphase flow simulators typically give one value for each output parameter simulated in a pipeline. Field development project managers want to know the uncertainty in these predictions in order to assess the risk. A study on two field cases, one gravity dominated case and one friction dominated, from the Troll P10 pipeline was conducted using the multiphase flow simulator OLGA and the functions in the embedded RMO (Risk Management and Optimization) module. A sensitivity analysis was performed to investigate the linear effects of the input- and model parameters on the output, and the most influential parameters were found. To see simultaneous effects, an uncertainty analysis was executed, drawing input- and model parameter values using Latin Hypercube sampling according to a probability distribution, and calculating the output values. Thus, uncertainty ranges were found for the output parameters. The results were then compared to measurements from the Troll field, to see how well OLGA simulated the pipeline. A tuning session was performed to see if the calculations were closer to the measurements when altering some of the model parameters. This proved challenging, as the pipeline has low liquid loading and a high pipe inclination towards land.As a methodology for uncertainty estimation of multiphase simulation results, the RMO module has potential to be a useful and practical tool. However, it currently has too much erratic behavior which causes loss of data and time. Generally, this sort of uncertainty estimation methodology was very useful to visualize flow assurance risk in connection with a field development project, and represents a significant step forward in this regard.