Energy-efficient pressure regulation model and experiment of lift pump system in deepwater dual-gradient drilling

In order to improve the high-efficiency conversion between the pressure energy and the kinetic energy in the dual-gradient control of deepwater drilling, the energy-efficient pressure regulation model (EPRM) of the lift pump system (LPS) is established by energy efficiency prediction model of lift pump. Then the indoor and landwell similarity experimental platforms were designed. Indoor experiments show that when the deviation from the rated speed is more than 20%, the accuracy of the energy efficiency prediction model is improved by about 4%. The variable viscosity efficiency is more than 90% of the optimal from 40 m3/h to 75 m3/h, which shows that lift disc pump has good adaptability. Land-well experiments show that the average fluctuation error of inlet pressure is less than 5% with the flow change. During pressure regulation, the pressure fluctuation is less than 2.78%, and the minimum is 1.04%. In the pressure-increase and pressure-drop, the average pressure fluctuation is 1.445% and 2.02% respectively. For the pump with 2930 rpm, the regulation range should be controlled between 60% and 98% of the maximum speed, which can achieve more than 70% of the best efficiency. These make it possible to establish customizing targeted energy-efficient sections according to different actual drilling requirements.