The sand trap is the bottom plain casing pipe with the cone-shaped end cap. It is screwed to the
bottom of the pipe that is lowered in the well. The sand entering the well over the period due to over-pumping is collected in the sand trap pipe without blocking the screen pipes, which will affect the well yield.
Gravel packing is the filling of the annular space between the final reamed hole and casing pipe
using gravel of appropriate size.