Structure Size Optimization and Internal Flow Field Analysis of a New Jet Pump Based on the Taguchi Method and Numerical Simulation

Interlayer contradiction (high-pressure oil that prevents low-pressure oil from being extracted) has always been the main factor affecting the oil-recovery efficiency of the many oil-bearing series in shale oil wells in Eastern Shandong, China. If steps to deal with interlayer contradiction are not taken, Shengli Oilfield's oil-recovery efficiency will be significantly reduced after a certain period of exploitation. Furthermore, as the drilling depth increases, the formation-fluid supply capacity of Shengli Oilfield becomes worse and further increases the difficulty of oil recovery as well as production costs. In order to improve the oil-recovery efficiency of shale oil wells in Eastern Shandong and realize cost reductions and efficiency increases, we designed a new jet pump in this study. The pump can be used for oil recovery according to the principle of Venturi jet propulsion, as the required power fluid is not a high-pressure fluid injected from the ground, but rather high-pressure oil that is present in the formation. Through the analysis of the overall structure of the new jet pump, it was found that the pump could not only transform the existing interlayer contradiction (co-mining of high and low oil layers by utilizing interlayer contradiction), but also had the characteristics of a simple structure and low production costs. Since the structural dimensions of the jet pump and the physical characteristic parameters of the fluid have significant impacts on pump efficiency, we first analyzed the internal flow field of the jet pump by using numerical simulations and found that the throat-nozzle distance, area ratio, throat length-diameter ratio, diffuser angle, and flow ratio had the most significant impacts on pump efficiency. After obtaining the specific numerical range of the abovementioned structural parameters when the pump efficiency was as its maximum, an orthogonal array designed according to the Taguchi method was used to conduct experiments. According to a range analysis and an analysis of variance, at an unchanged flow ratio (0.3156), the new jet pump achieved the highest efficiency (31.26%) when the throat-nozzle distance was 2.62 mm, the throat length was 46 mm, the throat diameter was 6.8 mm, and the diffuser angle was 7.5 degrees. In comparing its efficiency with that before optimization, we noticed that the efficiency was significantly improved by about 10%. These research results not only offer a new idea for the existing oil-recovery mode, but also introduce a new method for optimizing the structure of jet pumps.