Abstract
Espadarte is an oilfield located offshore in the Campos Basin, Brazil, in water ranging from 750 to 1,500 m depth. The first development plan took place in the beginning of 2000. This plan consisted of 8 producers and 4 injectors. The first oil was produced in Espadarte FPSO in August 2000. In 2002, the well (#1) had shown the first strong presence of Barium Sulphate deposits inside the tubing. After trying to chemically remove the scale without success, the solution was to change the entire tubing string, followed by a displacement of a scale inhibitor. As a precaution, it was decided to stop the water injection in order to reach better understanding of the problem.
The Petrobras Research Center gave the necessary support and few months later a scale treatment was designed. With this inhibitor treatment formulation, the operational procedure adopted consisted to inject the inhibitor in a remote way, using stimulation vessels, in order to by-pass the high costs associated with the use of a dedicated rig, since all the wells in Espadarte have wet completion.
A detailed plan was prepared in order to cover all the aspects involved in an operation like this, collecting samples of water produced before and after the injection of the inhibitor. Due to the availability of stimulation vessels, the first campaign took place only in 2005 and permitted the return of the water injection in the field.
This paper presents the methodologies adopted to prevent, and in some cases to remove, the BaSO4/SrSO4 scale in Espadarte wells.
