Solubility data on BaSO4 and SrSO4 have been determined in the temperature range 353 to 393 K at pressures up to 41,4 MPa (6000 psi) and at ionic strength of NaCl brines between 0.1 and 2.0 M. The experiments were performed in a high temperature/high pressure test equipment by applying the dissolution technique. The experimental results confirm the general trend in solubility dependencies for both BaSO4 and SrSO4, determined at lower temperatures and pressures: pronounced increase in solubilities of BaSO4 and SrSO4 with increasing ionic strength, slight increase in solubilities when pressurizing the solutions up to 41.4 MPa. A temperature rise from 353 to 393 K causes an increase in BaSO4 solubility, but a decrease in SrSO4 solubility. Calculation of the solubility products reveals for BaSO4 an increase from 1.1 • 10−10 in pure water at 298 K and normal pressure to 5.1 • 10−8 in 2M NaCl brines at 393K and 41.4 MPa. For SrSO4 the solubility product increases from 2.8 • 10−7 in pure water at 298 and normal pressure to 18.2 • 10−7 at 373 K and 41.4 MPa and to 16 • 10−7 at 393 K and 41.4 MPa in 2M NaCl brines.

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