Gravel-packed wells

Gravel-packed wells

Up to now, we've been discussing naturally developed wells, where the formation adjoining the well screen is the aquifer itself which must be arranged to our liking.

It is possible, of course, to drill a wider borehole than our casing and fill this opening with just the sort of material we want to have next to the screen.

A properly designed gravel pack will allow water to move through it very, very easily — and therein lies one problem with the development of a gravel-packed well.

When a well is packed with gravel, the skin of impervious material which resulted from the drilling process is not next to the well screen, but outside the gravel pack.

This skin acts as a barrier between the pack and the water-bearing formation.

Surging action in attempts to develop this well must go first through the gravel.

Since it is so easy to move through the gravel (and so difficult to go through the skin), water is apt to slosh up and down through the gravel and away from the skin which the surge is aimed at breaking down.

Obviously, the thicker the gravel, the greater the problem.

The thinner the gravel, the more effective the surge.

The phosphates mentioned earlier can be especially useful in developing a gravel-packed well.

They assist in the removal of silt and clay.