关键词: 含蜡原油输送管道,   ,  停输再启动,   ,  流变性,   ,  屈服行为,   ,  黏弹性,    , 触变性

Abstract: Via heating pipelining method, Changqing waxy crude oils with few resins and asphaltenes are transported in Jiangsan-Jinger pipelines, which makes great demands on the safe, economic and efficient pipelining technology. Based on crude oil rheology, physical chemistry and gel chemistry theory, the control stress rheometer was first used to test the complex rheological behaviors of the crude oil, such as viscosity-temperature, yielding, viscoelastic and thixotropic properties. The rheological equation and thixotropic model were then created to fit the Changqing waxy crude oil. Finally, based on the rheological properties, pipeline flow and heat transfer properties, thermal and hydraulic coupling characteristics of the Jingsan-Jinger pipelines, the restart characteristics were forecasted. Results showed that the shear dilution properties became more obvious with the decreasing temperatures below abnormal point; above the pour point, the gelled crude oil showed ductility properties, while below the pour point, it showed a strong brittleness nature, and with the decrease of temperature, yielding stress value increased exponentially; under the constant shear rate, the destruction and reformation of the gel structure occurred in the early 10 min. The prediction of the pipeline restart properties showed that after being shut down for 32 h, pipeline crude oil temperature at the end would drop to the abnormal point; after being shut down for 48 h, pipeline crude oil temperature at the end would drop to the pour point. Considering the safety of pipeline operation, the maximal shutdown time was 32 h, corresponding to the restart pressure of 1.51 MPa.

Key words:  Waxy crude oil pipelines,    , Shutdown and startup,    , Rheological property,    , Yield behavior,    , Viscoelasticity,    , Thixotrop