High levels of hardness will result in flocculation of bentonite with associated severe increases in viscosity. Subsequently, as the cation exchange process continues, the clay particles will aggregate and the result will be a low viscosity fluid.

The main effect of hardness on polymer fluids is precipitation of polymers at high pH (>11) in which viscosity may decrease and fluid loss increase.

Sources of Contamination

Hardness in water is due to dissolved calcium and magnesium ions.

Diagnosis

Use the calcium and total hardness tests.

Treatment

1.  Increase the pH to 10.5 with caustic to precipitate out magnesium as magnesium hydroxide

2.  Treat calcium with soda ash at 0.16 bbl per 100 ppm calcium.

Note:   Cement mixwater must be checked and treated for hardness before use.