In Brazil’s presalt fields, the demand for large volumes of freshwater for acidizing operations, coupled with logistical constraints, has led to the adoption of seawater in the formulation of stimulation fluids. Although seawater traditionally has been avoided because of concerns about calcium sulfate (CaSO4) precipitation and scaling, this study reviews existing literature, the operator’s records, service companies’ data, and simulation studies conducted by Petrobras’ R&D Center (CENPES) to assess the true risk of using seawater in carbonate acidizing. The replacement of freshwater with seawater resulted in logistical, operational, and environmental benefits, as well as enhanced availability of stimulation vessels.
Background
To assess the use of seawater in acidizing fluids, data were collected from published papers, theses, and scaling simulations conducted by CENPES using commercial software. In the literature, a relationship was established between damage susceptibility, sample permeability, and injection rate in laboratory experiments, demonstrating that higher permeability and flow rates can mitigate the effects of sulfate precipitation.
