Research On Dynamics And Reliability Of Pressure-Reducing First Constant Flux Blanking Plug Used In Oil-Field Water Injection System

The separated layer water injection is the most popular EOR (Enhanced Oil Recovery) technology in China now, and it is of far reaching importance for the increasement and stabilization of the petroleum production. The flow control of each layer is a key matter of this technique. With the enhancement of the voidage-injection imbalance and the exploitation of the complicated heterogeneous fault-block oil field, the confliction among wells or layers is becoming more and more serious. This leads to the gradual increasement of the layers in the water injection scheme. But the conventional fixed-nozzle blanking plug has many defects such as the hard work of the flow measure and adjustment, instable water flow rate and so on. So the requirement for new technique is urgent now.The constant flux blanking plug has many advantages such as convenient application, simple structure and low cost. But current constant flux blanking plugs have some problems in the flow characteristics and reliability. This raises the difficulty of the application. Based on theories in the mechanical engineering, electronic engineering and materials engineering together with the methods such as the theoretical analysis, computer simulation and experimental analysis, a new type downhole constant flux blanking plug has been developed. This research is financed by the Heilongjiang Key Science and Technology Project of China"Research and Development on the Constant Flux Blanking Plug Used in the Separated Layer Water Injection"(GC05A508).The pressure-reducing first constant flux blanking plug has been put forward, and its merits in internal leakage and vibration are analyzed. The kinetic model of the constant flux blanking plug has been established with the full consideration on the influence of the leakage, damping force, hydraulic lock force, and local flow field, which provides the theory foundation for research the static or dynamic characteristics of the pressure-reducing first constant flux blanking plug.The mixed-simulation method on the pressure-reducing first constant flux blanking plug has been brought forward on the basis of the computational fluid dynamics and hydro-mechanics. The static characteristic and stability of the pressure-reducing first constant flux blanking plug have been analyzed by this simulation method. The experiments show that the simulation results are precise and reliable. The structural optimization has been done effectively to reduce the production cost and enhance the flow control precision.The main failure mechanisms of the constant flux blanking plug have been studied. The contaminant wear and lock simulation method has been established based on the theories of fluid-particle two phase flow, particle dynamics, contaminant wear and contaminant lock. The simulations on the wear rates and lock forces have been done using the Matlab software. And the influences of the clearance height and valve spool vibration have been studied. The particle-induced erosion near valve ports and cavitation in the valve pocket have been calculated by the Fluent software, and their influences on the flow characteristic have been analyzed. The simulation results are reasonable and helpful to the design.The test bench has been designed, and the properties including the flow characteristic and reliability of the pressure-reducing first constant flux blanking plug have been tested by ground and downhole experiments. The structures, materials and surface treatment of the constant flux blanking plug have been optimized on the basis of the theoretical analysis, simulation and experiments to achieve better combination property. The experimental results show that: i) the adopted theoretical and numerical methods are effective in the analysis of the flow characteristic and the reliability; ii) the designed constant flux blanking plug has high performance both in the flow control precision and in the service life.A new type downhole flow regulating scheme which combines the constant flux blanking plug and downhole testing and regulating system has been brought forward. The practicability has been analyzed, and the preliminary studies on the overall scheme, machine construction, circuit framework, software configuration have been done.