Losing Water in the Well

Losing Water in the Well

In general, drilling procedures are normal through the various sand and gravel formations. Occasionally a formation is encountered which "drinks" the drilling water faster than it can be supplied to the pit. This type of formation, and runny formations such as quicksand, must be shut off if drilling is to progress and the hole is to be preserved. One method of cutting off, or at least slowing down, the water loss is by muddying up the formation with drilling mud or clay as is used in conventional mud rotary drilling. The mud is added while the drilling fluid is circulating in the well. As the rate of loss decreases, drilling penetration is resumed slowly until the zone is passed and sealing has taken effect.

When it is impossible to stop the water loss, it becomes necessary to case the hole to the bottom of the troublesome area. The casing diameter, however, must be such that it does not interfere with the designed completion of the well. Should the screen setting zone be the area requiring casing while drilling, the casing must be set in order to set the string of screens and the gravel pack material. After this, the casing is pulled back to properly expose the screens.

In some cases, the natural clays through which the hole passes will help to mud-up a runny formation. There are cases, too, where the natural clays are too effective and cut down the yield of the potential water bearing sand aquifers. Care must be taken to keep the drilling water as thin as possible while penetrating clays. Thinning means delay in penetration as clear water is added and the clays circulated out of the hole. Such delays can be expensive both in labor costs and in penalties if the job is running behind.

There are areas where the clay formations are naturally "dry". Once they are broken through by the bit and wetted by the drilling water, they tend to swell and close in on the hole. As they close in, reaming action is necessary. This may delay downward progress and cause binding and breaking of the reamer blades.