apparatus arrives at the well site with numerous apertures 34 prefabricated therein inserts 43 having various inner diameters are also supplied the inserts 43 are also manufactured from erosion resistant materials such as tungsten carbide or ceramic and made to fit the apertures 34 before the wellscreen 30 is inserted into the wellbore the apertures are pre sized 62 using inserts to determine the optimum entry and exist points for the slurry based upon the location of highly permeable portions of formations surrounding the wellbore if permeable formations exist apertures 34 are sized by placing inserts 43 to decrease the diameter of the aperture so as to limit the amount of slurry reentering the annulus 16 the apertures 34 can also receive insert that is blocked thereby completely sealing the aperture to the flow of material therethrough further if an abrasive sand packing procedure will be utilized or if the particles encountered will be highly abrasive erosion resistant inserts 43 are added to minimize the erosion of the apertures 34 the erosive resistant inserts 43 may be made of materials such as ceramic or tungsten carbide the embodiment allows for more accurate control of when where and how much of the slurry reenters the annulus 16 from the alternative pathway while foregoing is directed to the preferred embodiment of the present invention other and further embodiments of the invention may be devised without departing from the basic scope thereof and the scope thereof is determined by the claims that follow for example the apparatus can be used in any wellbore where a portion of the wellbore is to be by passed by a slurry of particulate matter one example includes a water bearing formation located.