Study On Structure Optimization Of Two Cluster Hydraulic Injector Based On Erosion Analysis

Hydraulic jet fracturing technology is the main technique to increase production of low permeability oil and gas field.Compared with the single stage injection tool,double cluster hydraulic injector can fracture two oil and gas reservoirs at the same time,fracture could be used in two oil or gas reservoirs at the same time by double cluster hydraulic injector,which could improve the efficiency of fracturing.However,high-speed flow of sand-laden fluid will cause severe erosion damage to the double cluster hydraulic ejector.The erosion are different between the upper and lower spray gun,cause overall damage to the injector.Based on the problem of erosion in the application of double cluster hydraulic ejector,The erosion experiment of the 35 CrMo steel,which is the injector body material,was accomplished by using a jetting experimental installation.The influence of injection angle and jet velocity of sand-laden fluid on the weight loss of sand fracturing fluid was studied.The results show that the erosion loss of 35 CrMo steel increases with the increase of injection angle,reaches the peak value when the jet angle is 45 degrees,then decreases with the increase of injection angle.A erosion calculation formula suitable for hydraulic injection is obtained by fitting the test dates.The liquid-solid two phase flow field is analyzed by the numerical simulation method of discrete multiphase flow.The erosion calculation formula based on erosion experiment was used to predict the wall thickness loss on the inner wall of the injector.It is found that the liquid flow rate through the upper nozzles of are greater than that of the lower nozzles;while the sand flow rates through the lower nozzles of are greater than that of the upper nozzles.The erosion thickness of the outer wall of the spray gun is less than that of the inner wall.The wall thickness loss of the lower gun wall is greater than that of the upper spray gun.The maximum erosion wall thickness loss occurs at the inner wall of the lower gun.In order to improve the difference the of flow rates and erosion losses between the upper and lower spray gun,structural optimization schemes are proposed,which contain the changing nozzle quantity and diameter and cluster spacing of the upper and lower sprays.Through the numerical simulation of the same working conditions,the more effective schemes are determined by comparing the difference of the sand flow rates and the erosion wallthickness losses between the upper and lower nozzles.The optimization scheme which is used6×6mm nozzles in the upper spray and 6×5mm nozzles in the upper spray,can improve the difference of sand flow and the erosion loss.However,the cluster spacing of the upper and lower sprays has little effect on the mass flow rate and the erosion thickness of the inner wall.It is innovatively proposed a structural optimization scheme of the short section which is built spiral groove inside of the wall and installed in the front of the upper spray.The structure parameters of the spiral groove in the short circuit are optimized by numerical simulation.The optimization scheme of the combination of the external flow short section and the nozzle diameter can relative fully improve the sand flow rate of the nozzles and the difference of the erosion thickness.