Experimental investigation on the restart characterization of shale oil-water flow in a horizontal pipe

With the dwindling conventional oil resources and increasing energy demand, shale oil development has gradually become a hot spot in the global energy industry. Moreover, the shale oil pipeline also inevitably experiences abnormal operations, such as shutdown and restart during regular maintenance or emergency accident repairs. However, previous restart research primarily focused on conventional crude oil pipelines, and there is still a research gap on shale oil-water flow. Therefore, this work conducted the shale oil-water restart flow experiment in the multi-test section pipe flow loop, considering the temperature (20-50 degrees C), starting frequency (15-25 hz), and water content (0-80%). Based on the restart pressure and volume flow rate change, the response characteristics of start pressure are studied. Moreover, the changing rules of restart pressure are explored with starting frequency, temperature, and water content. Eventually, the variation trend of the restart pressure absolute errors between the calculated value and the experimental data with the starting frequency is analyzed. The results show that the restart pressure reaches the maximum around 10 s after the pump starts, and the maximum restart pressure is approximately 1.5 times the stabilized restart pressure. Moreover, the restart pressure increases linearly with the starting frequency and decays exponentially with the temperature and water content (after the inversion point). With the starting frequency reduced from 45 hz to 15 hz, the restart pressure reduces from 24.6 kPa to 10.0 kPa at 20 degrees C. Furthermore, the empirical formulas can predict the starting pressure at low frequencies. This research lays a theoretical foundation for the safe restart of shale oil-water flow.