Halite Precipitation

[DFhidro]

Hello,
I have some chemical samples that I enter into phreeqc to see the saturation index and it tells me that it is zero or slightly negative with respect to halite. However, during the process of obtaining the chemical sample in my well I had salt precipitation aggressively. How can I interpret that in reality salts precipitate and the saturation index is zero or negative?

PD: I'm using Pitzer.

[dlparkhurst]

Rapid precipitation of halite would produce equilibrium, so it seems reasonable to have a near-zero saturation index.

My guess is that the in situ temperature is greater than the sampling temperature. If halite is saturated at the higher temperature, lowering the temperature during transit in the well and sampling would produce precipitation.