Flow Management: Steady-State and Transient Multiphase Pipeline Simulation

Abstract

Abstract Multiphase production systems are quite complex; however, a prioriprediction of their behavior is essential for successful design and operationof offshore facilities. Steady-state and transient simulators can be viewed ascomplementary rather than competitive, and there are specific situations whereeach would be greatly favored over the other. This paper will examine thestrengths and weaknesses of both steady-state and transient simulators, andrecommend best practices for when and how each should be applied, based uponvalidation against laboratory data and field experience. The ultimate objectiveis reliable flow management design and operation through the complementary useof both steady-state and transient multiphase simulations. Introduction Both steady-state and transient multiphase flow simulators have found wideuse in the design and operation of offshore facilities. However, informedapplication of these tools is made difficult both by the wide variety ofsteady-state correlations available, and by the complexities arising from fullytransient simulation. Also, there is little guidance as to when steady-statecorrelations will suffice, and when transient simulations will be required. This paper attempts to address itself to these issues, and provide reasonableguidelines for the use of both steady-state and transient models, based onvalidation against laboratory data and field experience. Benchmarking studiesof steady state and transient models was done against the SINTEF large-diameter(8"), high-pressure (20 to 90 bar) Tjiller flow loop database, used to develop OLGA. The focus of this paper is on horizontal and near-horizontalpipelines. At first glance, the decision whether to use steady-state or transient modelsmight seem a simple one. Clearly, there are many events that are inherentlytime-dependent, e.g., pipeline start-up and shutdown; obviously, in order toproperly capture these events, a transient model must be employed. Likewise, there are multiphase flows that are clearly steady-state, for example, steadyannular or bubble flow, for which a steady-state correlation would suffice.