Flow Field Analysis And Structure Optimization Of Eccentric Injection Mandrel

With the rapid development of China’s economy,the total amount of petroleum oil required is gradually increasing.Improving the recovery of crude oil from oil fields through stratified water injection is one of the commonly used means at present.Since the required injection volume of each oil layer varies due to different permeability and pressure,water dispensers are needed to control the flow rate of each layer in the process of stratified water injection.At present,the injection accuracy of injection mandrel is not precise enough and its flow characteristics have not been studied thoroughly,therefore,a technical study on eccentric injection mandrel is carried out in the paper.A method combining theoretical analysis,numerical simulation and experimental research is used in this paper.At first after analyzing the development process and current situation of the layered water injection process in oil fields at home and abroad,an eccentric injection mandrel is selected as study object,and the structure and working principle of the improved eccentric injection mandrel are elaborated.Secondly,a computational fluid dynamics model of the eccentric injection mandrel is established through theoretical analysis,and the pressure and velocity distribution and pressure loss inside the eccentric injection mandrel under different nozzle opening and flow rate are analyzed by simulation method,and the pressure loss at the nozzle is determined to be the largest,and the relationship between flow rate and differential pressure between inlet and outlet under different nozzle openings is derived.Through data processing and analysis,it is concluded that the flow rate and differential pressure in the eccentric injection mandrel are quadratic,the flow rate is linearly related to the open side of the differential pressure.In order to verify the reliability of the simulation results,the consistency between simulation and experiment is verified by building a test bench and comparing the test data simulation results.The water injection process is simulated by MATLAB to calculate the relationship between the injection volume,the nozzle opening and the injection pressure.The results show that: when the injection volume increases,the adjustment space of the adjustable spout also becomes larger,and it is easy to meet the injection requirements;when the injection volume is smaller,the pressure difference generated at the nozzle is smaller,and the effective adjustment of the injection volume will make the opening of the nozzle relatively small,which will easily cause the spout to be clogged;the smaller the injection pressure is,the more favorable the adjustment of the nozzle.It can provide a basis for the adjustment of the spout in the water injection process.Using single-factor test method,the influence law of the import of each structural parameter for the eccentric injection mandrel on the speed,the differential pressure between the inlet and outlet and the maximum deformation is studied,and the most suitable parameter index is initially selected.Based on the theory of orthogonal analysis and design,orthogonal tests are designed for the number of injection holes,the diameter of injection holes and the shape of the nozzle for the eccentric injection mandrel,and an orthogonal test table with three factors and five levels of the eccentric injection mandrel is established.The results are processed and analyzed to obtain the influence law on the performance of the eccentric injection mandrel when multiple influencing factors are changed,so as to determine the relatively optimal parameters of the eccentric injection mandrel.After comparing the results,the simulation analysis shows that the eccentric injection mandrel has relatively better performance when the number of injection holes is 36,the diameter of injection holes is 3.2mm and the shape of the nozzle is semi-circular.The optimized model is compared and analyzed with the original model,and the results show that under the condition of the inlet pressure 15 MPa and the nozzle opening 100%,when the steady state is reached,the differential pressure between inlet and outlet before optimization is 0.21 MPa,and the differential pressure between inlet and outlet after optimization reach 0.09 MPa,and the decrease of differential pressure between inlet and outlet after optimization is 57.14%,and the decrease of the average shear stress on the fluid is 3.88%.There are 57 pictures,7 tables and 55 references.