Introduction

Deep offshore exploration has been very successful in Bloc 17 Angola. After a first discovery with Girassol in the Oligocene levels, Total operator discovered the Dalia field in 1997 in the Miocene levels containing moderately viscous oils (up to 10 cP).

Very early in the geosciences studies, the oil viscosity was identified as the main limiting factor to the water injection recovery. Considering the key parameters of the reservoir: medium viscosity, low temperature, high permeability sandstones, polymer injection was positively screened as a potential EOR method for the Dalia Field.

Polymer injection is a mature technique on shore as more than 170 polymer field tests were registered in 2000, with many more projects put on stream since .More than 200 000 barrels of polymer EOR oil were daily produced in 2010, mainly in China on the giant Daqing field. Offshore implementation has on the other hand been extremely limited with only one single implementation, again in China, in the Bohaï Bay (Zhou et al – 2008). The project is still active but remained limited to a few wells.

Extensive integrated architecture and geosciences feasibility studies of polymer flooding started in 2003 on the Dalia field, three years before production start-up. Many challenges needed to be addressed as no EOR or polymer project had ever been implemented in deep offshore conditions.

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