The objective of this paper is to present how Petrobras is successfully managing production losses due to mineral scale formation in subsea production wells from its biggest offshore field1 .

Marlim Field, discovered in 1985 with a STOIIP estimated at 1,012 million STD m3 (6,369 million STB) and a field area of 146 km2 is located in water depths ranging from 600 m to 1100 m.Current Marlim Field production, around 446,754 bpd is supported by injecting 761,971 bpd of sea water. The water production is 217,150 bpd (water cut = 32%) and GOR is 82 STDm3/STDm3. A total of 117 wells are on operation, with 73 producers and 44 water injectors. The field was developed using subsea completion through the vertical, deviated and horizontal wells, equipped with cased hole and open hole gravel packed screens.

Scale formation has occurred as a consequence of the incompatibility between the barium and strontium present in formation water and the high amount of sulfate in the injected seawater.

To avoid production losses a plan of water management was implemented, including frequent produced water chemical analyses to investigate the convenience for applying a chemical bullhead treatment to remove scale in the production wells (tubing, screen, gravel pack and near well bore)2,3,4 .

This paper presents results from dissolver treatments performed in the field and also from a special investigation using a rig in a horizontal well. Valuable information was obtained in this intervention, clearing up the scaling occurrence phenomena in this scenario, allowing therefore an improvement on productivity recovery of the wells.

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