The SCALE2000 (V2.0) software (under Windows 95/98/NT) was specifically developed to predict quantitatively scale deposits induced by oil production operations. The conceptual model is based on the Pitzer's specific ion interaction formalism for Na-K-Ca-Mg-Sr-Ba-Fe-Cl-SO4-OH-H-Ac-CO3-HCO3-CO2-AcH-SiO2-H2O system under 25 - 250°C and 1 - 1000 bar conditions. SCALE2000 enables to perform four main kinds of calculations including solubility of the main known minerals responsible for scale problems in geothermal energy and oil productions (carbonates, sulphates, silicates, …), effect of temperature and pressure on the scale precipitations, effect of binary mixing of physico-chemical contrasted waters, quantitative predictions of scale formation based on a detailed kinetic formalism. As it was demonstrated by petroleum engineers, carbonate system is crucial for precise scale risk predictions. The reliability of SCALE2000 results was checked against measurements of individual mineral solubilities and kinetics found in the literature.

In this study, SCALE2000 was applied to the actual high temperature (164°C), high salinity (~ 84 g/l) and high pressure (320 bar) data of the Block 3 (Angola) oil-field. In agreement with observations, the precipitation of barite was predicted by SCALE2000. The mineralogical nature of deposits was intimately dependent on the reservoir water/seawater ratio. SCALE2000 simulations of the sulphate depositions on the tubing wall of the PAC 302B Pacassa well (block 3, Angola), as a function of the water produced, has permitted to predict the kinetics of barite precipitation for production P-T conditions (180 bar; 140°C). Simulation results were in good agreement with field observations.

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