Characteristics of low-temperature gathering of crude oil with high pour point and high viscosity in high water-cut period

As most of the oilfields in China enter the high water-cut period, the flow characteristics of crude oil change greatly, and the flow lines with the traditional two-pipe mixing hot water process have high energy consumption. In this case, it is urgent to study the flow characteristics of gathering at low temperature, so as to reduce the energy consumption and optimize the flow process of gathering. For this reason, a visual test pipeline was built in a block of Huabei Oilfield, and a test of low-temperature gathering was carried out in long time. In this way, the change law of wellhead pressure and the variation of flow pattern in the pipelines of crude oil at high water cut during low-temperature gathering were studied continuously. The results show that the wellhead pressure of wells where low-temperature gathering is impracticable rises rapidly to the safety threshold, while the wellhead pressure of the wells where low-temperature oil gathering is feasible changes in four stages. By long-term monitoring, it is found that the wellhead pressure fluctuates regularly, and the low-temperature gathering characteristics are comprehensively affected by the factors, including oil properties, liquid production, water cut and ambient temperature. In addition, stratified oil-water flow is observed in the starting section of the pipeline in the test, while the flow pattern in the end section changes from the stratified flow without gel deposition to the wavy stratified flow with gel deposition as the oil gathering temperature decreases. Conclusively, the study results could provide guidance to the in-depth study on the field safety of production and the characteristics of low-temperature gathering.