A model has been developed to predict the density of a brine containing CaCl2, CaBr2) and ZnBr2 from its composition. The model accounts for the effects of pressure and temperature using experimental results and literature data. The theoretical framework and equations used are presented.

Brine completion fluids are used to control wells during gravel-packing and other open perforation completion work. Since they are usually filtered to minimize particulate invasion, careful adjustment of the overbalance pressure is required to minimize fluid loss to the formation. The methods presented here will allow the engineer to more accurately estimate the density requirements for the fluid.

The model has been compared to published brine density data and matches that data well. The model predicts the effects of temperature on CaCl2, CaBr2 and ZnBr2 solutions. The effect of pressure on these fluids is small and less documented, but where data are available for comparison purposes the model matches the data well up to 200°F.

Methods of predicting the density of brine completion fluids are needed for well control pressure calculations and cost control of fluids, and are major factors in brine completion fluid optimization. This work represents the first application of modern solution thermodynamics to field completion brine problems.

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