Flow Resistance Analysis Of Combined Processing Slotted Liner Using Micro-EDM And ECM

Slotted liner sand control well completion is widely used in the development of loosen sandstone reservoirs,mainly using rectangular slot at present,but during application slotted liner prone to be sand-blocked,have the problem of serious erosion wear and short service life.The flow resistance emerges when viscous crude oil is flowing through slotted liner,obviously has an effect on the output of crude oil.So the selection of appropriate structure type and distribution of slit can effectively reduce the flow resistance,improve permeability and recovery rate.In this project a slotted liner flow resistance model was established,considered how structure type and distribution factors of slit influence formation pressure loss,used FLUENT software to calculate.This project adopted discharge electrolysis combined machining technology to produce slotted liner.This project also adopted a simulation test device using microscopic displacement principle to observed inlet pressure,outlet pressure and flow,and use real test result to compare with the simulation results.The compare results indicated that the simulated pressure difference values of rectangular slit is 7767 Pa when with sand.Because of the plug lead pressure to increase during measure process,measured values is 9510 Pa.The simulation results indicated that pressure loss mainly produced between inlet and outlet of slit and slit distribution has little effect on the formation pressure loss.For parameters of 0.2mm width and 80 mm length rectangular slit,when oil viscosity is 5mPa·s,velocity is 1m/s,its pressure difference is 2522 Pa.Increasing the length and width of the slit can increase the effective flow area,reduce the pressure difference between the inlet and outlet of slotted liner.Pressure difference between inlet and outlet has a linear relationship with the viscosity of crude oil.It also showed that pressure loss increases with the flow speed of crude oil.Flow velocity which is symmetrical distribution gradually decreases from the center to the two sides which is the sand-block reason.The process of using slotted liner to prove sand can be simplified as plane radial flow.0.2mm sand-proof accuracy of slotted liner permeability is 97m/d.The larger the width,the bigger the permeability.It also showed in the trapezoid slit simulation result that when the trapezoid angle is 1o,its pressure difference is 1108 Pa.Pressure difference can be effectively reduced when increasing trapezoid angle.Velocity in the axis forms a high velocity jet area.After the middle of the slit,flow velocity decreases along the direction,along the axis to be symmetrical.The trapezoidal slit is conducive to grit removal.Orthogonal test indicated that the primary and secondary sequence of factors which influence composite and stepped slit pressure difference is as follows: inlet width,the first runner(step)length,outlet width.For composite slit,the pressure decrease step by step.With the increase of the length of the first runner,the pressure difference increases gradually,and there is an obvious jet area in the first runner.The composite slit is also conducive to grit removal.For stepped slit,the pressure decrease in the first step,and it has a linear relationship with the first step length.The viscosity is larger in first step than the second,and there is a "speed failure zone" at the corner of the step in stepped slit which will lead to sand accumulation.