Rheology and start up pressure of waxy crude oil

Waxy crude oils present challenging transportation problems especially when sudden decrease in temperature arises to the oil gelling, effectively crystallizing the paraffin and heavy hydrocarbons molecules. A study on Libyan waxy crude oils is carried out to establish the rheology of these crude oils under various conditions and to determine the start-up of these oils when the temperature decreases below the gel point. The rheological data cover a range of temperature and cooling histories representative of conditions under pipeline operations. A new laboratory pipeline rig developed for conditioning the oil and measuring the corresponding start-up pressures after a range of stoppage time is put forward. The data obtained shows good agreement with the measured yield stresses in the rheological tests and the start-up pressure tests but only when the conditioning of the oil in the pipeline rig is duplicated in the rheological tests. Practical guidelines on the minimum pressures required after certain time of pipeline stoppage are elucidated. This is an abstract of a paper presented at the 18th International Congress of Chemical and Process Engineering (Prague, Czech Republic 8/24-28/2008).