Research On Mechanism Of Hydraulic Cavitation Treatment Of Oilfield Fracturing And Returning Fluid

This paper mainly focuses on the phenomenon of hydrodynamic cavitation.The degradation of fracturing fluids by hydraulic cavitation technology was studied.The effects of parameters such as the selection,pore size,number of orifices and opening area of the hydrodynamic cavitation device on the degradation were analyzed.It is concluded that the hydrodynamic cavitation device can effectively degrade the COD content in the fracturing fluid.The main findings are as follows:(1)Through the measurement of oilfield fracturing and returning liquid,it is found that its composition is complex,has strong stability,high concentration,high COD and high viscosity.Hydrodynamic cavitation is the pressure drop as the liquid flows through a retraction device(such as a geometric orifice,venturi,etc.)and the gas dissolved in the liquid is released.When the pressure is about to the saturated vapor pressure or below,a large amount of cavitation bubbles are generated due to the intense vaporization of the liquid,and the bubbles are instantaneously destroyed when the pressure is restored,accompanied by a transient high pressure(5×10~7 Pa)high temperature(1000-5000 K),and A local high concentration of oxidant is generated in the solution,and the organic pollutants in the solution are oxidized and degraded into harmless substances to achieve the purpose of purifying water.(2)The flow field and cavitation intensity of the hydrodynamic cavitation device with different parameters were simulated by Fluent software.The velocity field,pressure field and gasification rate in the tube were obtained and the simulated values were compared with the experimental values.The results show that the gasification rate of the 7~#orifice plate can reach the maximum value under the same fracturing and returning liquid working conditions,and the results are consistent with the experimental results.(3)Through the construction of hydraulic cavitation experimental platform,analyze and compare the effects of hydrodynamic cavitation devices with different parameters on the treatment of oilfield fracturing fluids.The results show that the decrease in the pore size of the orifice plate type hydrodynamic cavitation device contributes to the improvement of the treatment performance.The decrease in the number of holes the orifice plate type hydrodynamic cavitation device can enhance the cavitation effect within a certain range,and can improve the degradation rate of the COD value.