The Restarting Pressure Research of a Hot Waxy Crude Pipeline

Laboratory tests on an indoor circular pipeline have been conducted to simulate the actual process of restarting a highly waxy crude pipeline after shut-down. The following questions have been solved on the basis of tests and analyses: first the tests verified that this restarting process consisted of three stages: analyzing initial yield with an elastic deformation theory, describing fractured yield with the time-dependent rheological equations and depicting residual yield with the time-independent rheological equations; second the results confirmed that the pressure transmitting mechanism in the gelled crude is different from that of sound wave transmitting process. The pore structure of the gelled oil is a critical factor affecting the pressure transmitting velocity. The damping effect from the pores in the gelled crude and the bagging effect due to the gelled crude yielding in radial direction are two important factors. A new model of pressure transmitting speed for a gelled crude restarting operation has been developed. The new mathematical model of restarting pressure has been established with the association of thermodynamic and hydraulic analyses, its calculating results correspond with the experimental data. The two pressure peaks and the distribution of flowing radius for a gelled crude restarting operation have been forecast on the basis of calculation.