Effect of shutdown pressure on restart-up behaviors of gelled crude oil pipeline

When a pipeline is shut down, it is inevitably under pressure due to topographic relief, which affects its restartup behaviors. In this paper, gelled-crude-oil loop experiments were performed by employing three pressurization ways to investigate the effect of different shutdown pressures on the restart-up behaviors of gelled crude oil pipeline. First, after transient pressure is applied on the inlet, the pipeline is sealed and kept still at constant temperature. Second, different constant pressures are applied on the inlet continuously while the pipeline rests at constant temperature. And third, the pipeline is sealed and kept still at constant temperature after the inlet is pressurized continuously for a stipulated period. Then, pipeline restart-up pressure was tested and the corresponding yield stress was calculated. It is indicated that the restart-up yield stress increases with the increasing of pressure, when the pressure is applied transiently; the yield stress increases and then decreases as the pressure increases, when the pressure is applied continuously. Moreover, the yield stress is, in a way, affected by the pressurization time. The research result provides the technical support for the safe and efficient operation of oil pipelines.