| The flow behavior in hilly terrain pipelines with low flow rates of gas and liquid is gravity dominated. For these conditions, steady or unsteady state flow can prevail, even for constant input gas and liquid mass flow rates. The transient behavior of the flow is due to pipeline geometry and the compressible nature of the gas phase. The result is the occurrence of terrain induced slugging which can cause operational problems.; Severe slugging in a pipeline-riser system can be considered as a special case of terrain slugging in hilly terrain pipelines. For this case, the system consists of with a downward inclined section followed by an upward inclined section. Therefore, in the first stage of this study, an improved quasi equilibrium model has been developed to simulate the transient flow behavior in pipeline-riser systems. The present model is tested against a broad range of experimental data showing a better performance than previously published models.; A new model is developed to simulate low velocity flow in hilly terrain pipelines by extending the improved severe slugging analysis. The model is based on fundamental principles and incorporates the physical phenomena. Flow instabilities can inherently be predicted by the model, and a separate stability analysis is not required.; Simulation results show that large amounts of liquid and gas can be produced in a short period of time due to the occurrence of terrain slugging. The model is also capable of predicting the flow behavior under a wide range of pipeline operation conditions. These include zero net liquid and gas flows, pipeline startup and shutoff practices, and the effects of pipeline rupture. |
