Comparison Of Multiphase Flow Simulators OLGA And LedaFlow

With the oil-gas resource exploration extending rapidly to off-shore fields,the rational design and operation of multiphase flow pipelines have become important issues,which also require accurate predictions of multiphase flow phenomena.In this context,different companies and research institutes have developed a large number of multiphase flow simulators.In this paper we use a new simulator called LedaFlow and a widely used simulator called OLGA to test different field cases,including both steady-state and transient phenomena,especially slug flows.The objective of this paper is to present comparisons of the results obtained by both tools and to illustrate their advantages and shortcomings in predicting different working conditions.In the steady-state conditions,both LedaFlow and OLGA can give quite accurate predictions of the inlet pressure and the outlet temperature,and their calculation results are slightly higher or lower than the field data at the same time.However the two codes fail to predict the total liquid content correctly,they perform equally well in certain conditions and equally poorly in other conditions.So it is hard to tell which one is better here.As for transient conditions such as pipeline shutdown and startup,flow rate increase,valve opening and closing,the two codes show the same variation rules against time apart from minor differences in the values.Particularly,the prediction performances of LedaFlow and OLGA on terrain slugs,severe slugs and hydrodynamic slugs are compared.It is found that when using Unit Cell Model to predict terrain slugs,LedaFlow can obtain transient results,but OLGA can only obtain steady state results.As a result,applying Slug tracking model with OLGA and Slug capturing model with LedaFlow would be better to predict terrain slugs,and necessary to predict hydrodynamic slugs.By tuning the delay constant in OLGA and the mesh lengths in LedaFlow,the two models may get similar simulation results.However the delay constant is just a purely empirical fitting parameter,with no physical significance,but LedaFlow can simulate based on underlying physical laws.In this term,LedaFlow is better than OLGA in handling slugs.In terms of time-consuming,OLGA is better than LedaFlow.In conclusion,the major differences between OLGA and LedaFlow lie in their predictions for slugs,and there is no significant difference in the predictions of steady state and ordinary transient conditions.