increase in the effective density of particles in the fluid slurry each of which is a hindrance to particle transport to locations further along screen assembly 60 positioning exit ports 106 out of phase with slurry passageways 98 reduces the liquid leak off by increasing the pressure required to push the liquid through the porous matrix and reduces the velocity of the liquid near exit ports 106 thereby reducing the rate of liquid leak off this rate of liquid leak off is further reduced by using a liquid in the fluid slurry that is thixotropic such that its viscosity increases with reduced velocity through the porous matrix even though fig2 has depicted exit ports 106 as being circular it should be understood by those skilled in the art that exit ports 106 could alternatively have other shapes without departing from the principles of the present invention those shapes being considered within the scope of the present invention also it should be noted by those skilled in the art that even though fig2 4 have depicted three slurry passageways 98 at 120 degree intervals around screen assembly 60 other numbers of slurry passageways either greater or fewer and other intervals between such slurry passageways may be used without departing from the principles of the present invention and are considered within the scope of the present invention likewise even though fig2 and 5 have depicted three exit ports 160 at 120 degree intervals around manifold 102 other numbers of exit port either greater or fewer and other intervals between such exit ports may be.