Mineral encrustation problems in groundwater from Oman and the Eastern United Arab Emirates

Abstract EN

We report upon scaling problems associated with the Semail nappe of Northern Oman and the UAE.

The most common encrusting mineral is calcite (CaCOj).

This is deposited much more rapidly than in a normal carbonate environment, due to the unusual process of mixing between hydroxide- and bicarbonate-type groundwaters.

Very occasionally the mix ratios and chemistries of these contrasting groundwaters results in a pH of > 10.5, which induces brucite (Mg(OH)2) precipitation.

Encrustation with brucite is well known from boilers and other high temperature industrial plants, but has not previously been reported from boreholes at ambient groundwater temperatures.

This brucite scaling is not amenable to treatment by acidification, but can be avoided by appropriate borehole siting and construction.