Research On Gas-liquid Separation Device And Control System Of Subsea Separator

With the rapid development of the oil and gas industry,the developed countries in the world have gradually turned their attention to marine resources and gradually developed from shallow water to deep-sea areas.Subsea separator system mainly includes subsea separator and subsea control module,which is the key equipment in subsea oil and gas production system.It can accomplish gas-liquid two-phase separation or oil-water-gas three-phase separation even in deepwater environment.In this paper,the key structure and control system of the underwater separator are analyzed and studied.The underwater separator and the control system prototype are successfully developed.The joint experiments are carried out to test the key performance of the system.Based on the analysis of the development status of subsea separators and control modules both at home and abroad,the overall scheme of subsea separators and control modules are proposed and a three-dimensional model is carried out.The scheme of the gas-liquid separation module,the oil-water separation module and the sled body of the subsea separator are confirmed,and the overall scheme of the mechanical structure,the hydraulic system and the electronic control system of the subsea separator control module are determined.According to the working conditions and production requirements of subsea separator,the gas-liquid separation module of gravity subsea separator is studied.The structure and parameters of the inlet pipe of the gas-liquid separation module are determined.,and the best downward Angle is determined through analyzing and simulating the influence of different entrance pipe dip angles on the velocity field,pressure field and pressure loss in the gas-liquid separation module.Considering the high and low gas-liquid ratio conditions,the diameter range of the riser is preliminarily determined,and the optimum diameter of the riser is optimized by simulating the influence of different diameters on the volume fraction of liquid phase,pressure drop and separation efficiency at the overflow.Based on columnar swirl separation theory,the height of the inlet and outlet of the riser was determined,and the best height of drip zone is selected by analyzing and simulating the effects of different height of drop zone on the volume fraction of liquid phase,pressure drop,separation efficiency at the overflow.According to the control requirements of the subsea separator,the development of square subsea control module is completed.The layout of hydraulic and electrical connector is completed,the upper and lower docking plate structural is designed.It is determined to adopt a two-stage guidance method,in which the fine guidance adopts the “one-sided two-pin” positioning method in which the cylindrical pin and the diamond-shaped pin are matched,and the positioning error is analyzed.A simple and reliable locking mechanism is designed,and the appropriate safety pin material is selected by analyzing the force.According to the working principle of the hydraulic system,the hydraulic valve block and its internal oil circuit are arranged,then the internal oil circuit of the hydraulic valve block is designed and checked.The redundant control scheme using two subsea electronic modules with redundant signals is determined and the hardware and software design of the subsea electronic modules are completed.The docking experiment,safety pin shearing experiment and hydraulic system experiment were performed on the control system to verify that the performance meets the design requirements.The joint experiment is carried out to verify that the subsea control module can collect the information of the transmitter on the subsea separator and control the actuator of the subsea liquid-controlled ball valve in real time,and also can stably control the oil-liquid surface,the oil-water interface and the separator pressure.