A new calculation method of start-up yield stress for gelled crude oil pipe flow

To accurately predict the start-up yield stress for gelled crude oil is the key to realize safe and economic transportation of waxy crude oilpipeline and avoid its condensation accident. Based on pipe flow test data, impact of pipeline axial compression time difference on themeasured result of gelled crude oil start-up yield stress is analyzed. The results indicate that in the pipe flow device, the measured value of start-up yield stress decreases with the increase of the length of measured pipe section. Combined with three-parameter hyperbolic model thixotropic equation, a data-processing method based on nonlinear least squares fitting principle is proposed, which can calculate the startup yield stress of gelled crude oil when the measured pipe tends to be unlimitedly short and unify evaluation standards of gelled oil structural strength under specific condition.