A common flow assurance problem during waterflooding operations is the deposition of mineral scale due to mixing of incompatible brines. Deposition of mineral scale can occur anywhere in the production system (reservoir, near wellbore, wellbore, surface facilities) if certain conditions for deposition of scale are present (composition of mixed brine, dynamics of mixing, pressure, temperature and kinetics). Understanding where and how scale will deposit and its impact on production and operations is important especially for the mega offshore field development projects which use new generation of high value wells (long/multi laterals, MRC) associated downhole equipment (ICD, ICV, etc) and surface facilities. In this paper, we present a systematic approach to assessing the scale deposition risk with an example of the application to a giant carbonate field, offshore Abu Dhabi.
The giant oil field subject is the subject of this paper was discovered in the early 1960's and is located offshore Abu Dhabi. The reservoir is an undersaturated reservoir with initial pressure of 3,850 psi at 7,550 ft TVDSS and formation temperature of 210 Deg F. The field covers a large area extending about 35 km in the East-West direction and 20 km in the North-South direction. The reservoir is laterally sub-divided according to permeability variations into three regions- Eastern, Central and Western. In the Eastern region, permeability ranges from 20-60 mD. The permeability deteriorates in the central region to 10-15 mD. In the Western region, permeability is low (<3 mD). Permeability-thickness (kh) map of the reservoir is depicted in Fig.1.
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