Research on working condition diagnosis method of downhole oil-water separation system with sucker-rod pump

Compared with the rod-pumping oil production system of the conventional pumping unit, the structure of the down-hole oil-water separation system from the rod pump is more complicated, and the down-hole working conditions are worse. Existing technology no longer meets the needs of its downhole condition diagnosis. It seriously affected the production output and economic benefits of the oil field. Because of this, a fault pre-diagnosis method for the downhole oil-water separation system from the rod pump was proposed. Through the theoretical calculation of oil well production and pump efficiency. After field investigation and collection of many suspension point indicators diagrammed for comparison and analysis, the injection pump's failure probability was 90% above. At this time, the extraction pumps work normally. Therefore, a reverse calculation method is proposed: establish and solve the static/dynamic load model of the production pump, and obtain the load-displacement function of the production pump. The load-displacement function of the suspension point derived from the suspension point indicator diagram is subtracted from the calculated load-displacement function of the production pump to obtain the load-displacement function of the injection pump so that the working condition diagnosis can be performed according to the injection pump work diagram. In the application of 18 wells within the field, the judgment result of injection pump failure and the result of pump inspection coincided with 91.3%, which verified the correctness of the calculation model. This method provides necessary theoretical guidance for the field application and working condition diagnosis of rod pump downhole oil-water separation system and is of great significance for improving the comprehensive benefit of oilfield production.