An Investigation Of The Characteristics Of The Gelled Crude Oil On Constant Pressure Startup

The experimental study on shutdown and restart characteristics of the gelled crude oil in pipelines is done on the model loop-line test apparatus. Based on the constant pressure tests, the restart time, restart progress, and the regular pattern of the flowing after restart and the thixotropic progress of the gelled crude oil are analyzed, and the pressure transmission of the restart progress, and the pressure transmission and compressibility coefficient of the hot crude oil are researched.The restart time is intently concerned with the restart pressure and temperature, when the pipelines of gelled crude oil are restarted on constant pressure; The Su Dan (SD) and Xiang Fan (XF) crude oil have the same restart time variation with the restart pressure changing; There have the transition restart pressure that means the restart time sharp increase under the pressure and the minimal restart pressure that is in the critical situation on different restart temperature.After seriously analyzed the restart progress, the restart progress could be divided into three parts: the compressive deformation progress, the creeping progress, the thixotropic progress. The instantaneous pressure could cause certain compressive deformation of the gelled crude oil, because of the lasting pressure, the gelled crude oil creep up, and the pipeline restarts successfully, and the structure of the gelled crude oil is destroyed, until the structure is in the balanced state under the pressure.The flowing after restart of the SD and XF crude oil has the same regular pattern, and is fitted as the exponential form; The restart yield stress increases linearly with the restart pressure boosting; Under the common contribution of the gelled structural strength of the gelled crude oil, the creep after the force of the pressure, and the compressive deformation, the restart yield stress of the pipeline is the integral reflection of the restart characteristics of the gelled pipeline.After the analyzing thixotropic progress of the SD and XF crude oil, the regular pattern is different at the different location of the pipeline; The thixotropic progresses of the SD crude oil are identical; The thixotropic progresses of the XF crude oil are different, the rate of the structure cracking is increasing with the pipeline distance extend; When the thixotropy of the gelled crude oil is in equilibrium position, the required time is changing with the restart pressure and temperature.The pressure transmitting speed in the gelled crude oil isn't the constant value, and decreases with the distance extend; The restart celerity is apparently less than the pressure transmitting speed; The pressure transmitting speed and the restart celerity are increasing with the restart pressure and temperature increasing; The compressibility coefficient of the hot crude oil is increasing with the temperature increasing and is coincided with the theoretical value. The pressure transmitting speed in the hot crude oil is the constant value and very close to the theoretical value, and decreases with the temperature of the crude oil increasing.