Massive electric charges will be generated due to the contact of oils flowing in the non⁃metallic pipeline with the inner wall of the pipeline. Excessive charge gathering discharge will cause spark discharge, which will lead to perforation of the pipe wall and fire, and seriously affect the normal production. Through analysis on the cause of static electricity and influencing factors, it is easy to find that the electrification rate is influenced by the oil flow rate, temperature, water content, pipe material and roughness. The results show that there is a positive correlation between the electrification rate and the oil flow rate, between the electrification rate and the pipe roughness; the rise of oil temperature adversely affects the accumulation of oil static; the electrification rate grows with the moisture content in a certain content range, and decreases with the increase of water content beyond the range; in combination with the existing experiment data, an oil flow⁃induced static model is built.

Non⁃metallic pipeline has become the new direction of oil and gas pipeline technology because of its excellent performance. However, the electrostatic problem during the oil transportation process threatens the safe operation of pipeline. Based on diffuse double layer theory, the electrostatic electrification mechanism of metal and nonmetallic pipes is analyzed and compared. The effects of flow regime, pipe properties and oil properties on the oil flow electrification are systematically elucidated. The main forms and hazards of electrostatic discharge of oil pipeline are analyzed in detail. Moreover, a series of electrostatic control and hazard protection measures are put forward from the perspectives of avoiding electrostatic generation and neutralizing static electricity.

The optimal dehydration rate of two cylindrical cyclone separators were compared under the water cut of 95%, 90%, 80% and 70% at the inlet, by changing oil-water mixing flow rate and split ratio. The experimental results show that when the inlet water cut is 95%, 90% and 80%, the optimal dehydration rate of the cylindrical cyclone with orifice vortex finder is 12%~22% higher than the cylindrical cyclone without orifice vortex finder. And the pressure drop between the inlet and the overflow increases 3~52 kPa. When the inlet water cut is 70%, the optimal dehydration rate of the former has little difference with the latter, but the maximum pressure drop between the former and the latter is 68 kPa. Under different experimental conditions, the pressure drop between the inlet and the underflow is not obvious, and the former is slightly higher than the latter. At the same time, when the inlet water cut is constant, the relationship between the optimal split ratio and oil-water mixing flow rate is consistent with the dehydration rate.