Summary: Basing on the results of industrial experiments, carried out on the real pipeline, the patterns of flowrate changes during unsteady processes, caused by a changing the number of working units at oil pumping stations, were established. The method of determining mean oil flowrate against time and length was developed, which allows to specify the flow capacity of the oil pipeline during unsteady processes in operation.

Keywords: unsteady hydrodynamic process, oil flowrate, flow capacity, pumping units start.