Study On Structure Design And Characteristic Analysis Of Asymmetrical Pulse Generator

With the development of oilfields exploitation, waterflooding became a proventechnique, resulting in more and more emphasizing on the importance of well washing.Conventional well washing technique is unsatisfying for its low efficiency and likely initiatedsecondary pollution. Negative pressure pulse jet can not only periodically decreasebottom-hole pressure but also results in high pressure and velocity gradient. By asymmetricaldesign, the pulse generator can improve its efficiency and energy utilization.Asymmetrical pulse generator is preliminary designed. Influences of asymmetricalstructure parameters on pulse characteristics are studied by numerical simulation andmodulation test. Numerical simulation results suggest asymmetrical design slightly decreasespulse frequency. Asymmetrical distance difference, wedge diameter and signal way have littleinfluence on pulse amplitude while can significantly affect fluid diversion, specifically2:1ratio can be realized by asymmetrical design of signal way. Widths of control way and outputports are deterring parameters, fluid diversion ratio correspondingly increases with theirincrease and1:0.32can be reached. Considering pulse amplitude, they are respectivelydesigned as0.4W and (0.3-0.35) W,1.0W and (0.8-0.9) W. Results of modulation testbasically consist with numerical simulation results, with the greatest pulse amplitude of1.05MPa. To further amplify pulse amplitude, oscillation cavity is designed and studied. Theconclusion comes to that, pulse amplitude amplifies effect decreases with the increase ofcavity length and the optimized size is2.1times of inlet diameter. Pulse amplitude issignificantly influenced by output port diameter, and the optimized size is1.2times of inletdiameter. Slightly change of output length can significantly influence pulse amplitude, and1.49MPa can be realized when it is1.8times of output diameter. Results of evaluationexperiments show the advantages of asymmetrical pulse jet, especially when the rock is harder. When the sample cement sand ratio is2:1, conventional jet can increase rockpermeability by2.107%while asymmetrical pulse jet can increase it by8.729%.