Thomas Kwader says developing horizontal wells is difficult for a number of reasons, mainly because the bentonite drilling mud used during the drilling of the borehole is extremely efficient at plugging holes or slots on the screen..
The introduction of a polyphosphate (see a drilling mud supplier for different brands available) will help breakdown the gel strength of the mud, but the bentonite and natural clays still need to be removed from the borehole annulus. Another method used to place the polyphosphates outside the screen is to pull a tremie pipe (3/4- or 1-inch) attached to the outside of the well casing. Small diameter holes drilled in the tremie pipe along the screened area allow for the polyphosphates to be injected where they are needed. Leaving the polyphosphates overnight helps break down the gel.