Operating Condition Diagnosis Research On Water Injection System With Hydraulic Driving Single Screw Pump

Separate layer water injection technology can maintain pressure,improve the overall recovery efficiency,and has become one of the most important measures of oilfield to increase and stabilize oil production.Now a new separate layer water injection technology is under investigation,by which the hydraulic driving single screw pump is put between two layers,and a portion of water is injected into the high pressure layer after being pressurized by screw pump while the other is injected into the low pressure layer after being depressurized by screw motor.By using this new scheme,pressure loss of flow nipple in common water injection pipelines can be avoided.Besides,it has a compact structure and can pressurize and depressurize the water simultaneously.Owing to the complicated structure,the problem of how to diagnose water injection effectiveness and operation condition of the hydraulic driving single screw pump is still under investigation.Thus,based on building mathematical model of working condition diagnosis,a condition diagnosis method is studied by theoretical analysis and a software using this method is developed.On the basis of analyzing the structure of separate layer water injection system with hydraulic driving single screw pump,the whole system can be divided into four subsystems: wellhead subsystem,wellhole and pipeline subsystem,hydraulic driving single screw pump subsystem and water layer subsystem.Analyze these four subsystems and build a mathematical model for each of them.By using nodal systems analysis method,the pressure and flow rate relationships between each two nodes are established.On account of mathematical models of each subsystem,pressure and flow rate relationships and pressure and flow rate parameters monitored from water injection well,a working condition diagnosis method for hydraulic driving single screw pump which is utilized in separate layer water injection system is proposed.According to this working condition diagnosis model,a software employing Visual Basic 6.0 and MATLAB packages is developed.When using this software to diagnose the working condition of the single screw pump,parameters such as overall efficiency,effective output,pressurization value and depressurization value can be calculated,then estimate the reasonability of the working condition of the single screw pump by comparing the position relation between the actual operating point and high efficiency zone of the pump.Suggestions and recommendations are proposed if the actual operating point is out of high efficiency zone.