Research On The Ground Control Hydraulic-driven Oil Lift System

The hydraulic production system can convert the hydraulic energy of the power fluid into the mechanical energy of the hydraulic actuator. Ground pump station provides high pressure power fluid to the ground control hydraulic-driven oil lift system. High pressure power fluid is output by switch valve to the tubing, through which it is transmitted to the downhole hydraulic actuator and drive the pump. After adaptability analysis for two types of power fluid pressuring systems, ground pump set and beam pumping unit, the paper optimized the pumping set feed system. The paper analyzes the structural characteristic and operating principle of hydraulic production system and gives parameters designing for this system, including the choice for ground equipment, downhole hydraulically operated set, pump and pipe strings combination pattern. The paper also deduces the calculation formula for the associated equipment parameters of accumulator, downhole hydraulic actuator and oil pump. Based on the mechanical analysis for hydraulic actuator and pump set, the paper establishes power fluid pressure calculation model. In this model, the effects such as the compressibility of power fluid, expansibility effect of tubing, the viscous friction of liquid and the leakage of power fluid are considered comprehensively. Meanwhile, the method develops the calculating method for critical pressure of the power fluid during upward-stroke and down-stroke process. In view of the long-distance transmission for power fluid in hydraulic production system, the conventional hydraulic pressure theory is not suitable, so that pressure wave model is proposed and used to calculate the pressure during long-distance transmission in this paper. Time delay method during hydraulic fluid transmission in the long-distance pipejacking is also deduced. Combining with kinetic analysis of hydraulic actuator and pump set, the method of determining ground switching time is given. The process and calculation on swabbing parameter and system efficiency of the production system are derived too. Finally, through laboratory well experiments and 2 wells production data test in oilfield, the theory and partial calculation methods are verified.