Start-up of gelled crude oil pipelines

Abstract

A simple method is presented for predicting the time necessary to start up and clear out a pipeline full of gelled crude oil after an operational or emergency shut-down. The numerical procedure for calculating the clearing time is based on the rheological properties of the gelled oil as described by Houska's model of thixotropy. Input data for the equations representing the clearing process are the rheological parameters of the gel, the dynamic viscosity of the Newtonian clearing liquid, the pipeline length and inside diameter and the maximum pressure head of the pump. Results of the numerical procedure are given in terms of relations between the flow rate and time. Sensitivity of the clearing time to the value of the yield stress and to the viscosity of the incoming clearing liquid is discussed. In comparing the results of the present theoretical approach with experimental data obtained on a full-scale pipeline, good agreement has been found. 5 figs., 12 refs.