The Polymer Injection Project on Dalia field, one of the main fields of Block 17 in deep offshore Angola, is a world first for both surface and subsurface aspects. Thorough geosciences and architecture integrated studies led to decide to phase the project, with a polymer injectivity test on one single well, followed by a continuous injection of polymer on one of the four subsea lines delivering water to the field.

The single well injectivity test on DAL-710 was completed first quarter of 2009, just two years after first oil. Very successful results led to launch a polymer injection pilot on the full injection line of the Camelia reservoir.

The main objectives of the single line Camelia pilot were to confirm long term operability and injectivity of polymer in the specific conditions of this deep-offshore development, and measure the in situ viscosity (sampler well) of the injected polymer solution away from the injector, as key inputs to the evaluation of an extended project.

From February 2010 to August 2012, a 900 ppm polymer solution was injected through the three wells of the line. In summer 2012, a sampler well was drilled 80 m far from one of the injector, located behind the polymer front thanks to 4D seismic monitoring. MDT and bottom hole samples were done and analyzed.

The paper describes the main results of the pilot phase on injectivity, operability and polymer sampling. The pilot answered its objectives, but still a lower viscosity than expected was measured in the sampler well. Key deliverables were:

  • How to operate the whole process chain of viscosified water at topsides level

  • Better knowledge of polymer degradation from topside to deep into the reservoir

  • Data required to properly size an extended polymer project.

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