Startup flow of gelled waxy crude oils in pipelines: The role of volume shrinkage

Predicting an accurate startup pressure for gelled waxy crude oils in pipelines is an old challenge yet to be overcome. It is known that the conventional force balance grossly overestimates the minimum axial pressure gradient required. Some researchers suggest that the occurrence of volume shrinkage due to gelation affects the gelled oil morphology and consequently the startup pressure. In this paper, the volume shrinkage of gelled crudes in rheometric and tube flows is investigated. We also study the relationship between the rheological properties and the minimum pressure gradient required for the onset of flow in the presence of volume shrinkage. Two different waxy crudes were used in the investigation, here called Petroleum #1 and Petroleum #2. A method to predict the minimum startup pressure by accounting for shrinkage as a correction to the conventional force balance is outlined.