In Deep Offshore Fields, the injection of chemicals demands the installation of expensive and complex systems.

When the Girassol and Dalia projects, on the Block 17 in Angola, were undertaken, the Operator decided to limit the number of liners for continuous injection to one.

Through this liner, a Scale and a Corrosion inhibitor will be injected at the bottom of the well. In the near future, when the water cut becomes relevant, a demulsifier could be also injected.

The liner can also be used occasionally, for the injection of methanol, in order to remove the hydrate plugs.

The paper presents the research and development undertaken to determine the different molecules (scale and corrosion inhibitors plus demulsifiers) and their compatibilities, as well as the compatibility with any other fluid that could come in contact with the additive.

The multifunctional chemical that has been especially formulated for this application, contains three different products dissolved in the same solvent, even if, generally, they are soluble in different fluids.

The advantage of such a solution is that the percentages of each of the three base compounds can be adapted to the production conditions and the evolution of the water cut, without affecting their stability.

The solution of the compatibility problems has represented a real challenge. The three active substances should not only be mutually compatible, but the product itself has to be compatible with other fluids likely to be injected through the liner. These would include methanol, used for the prevention of hydrates, or glycols, for the preservation of the liners during the shut-down periods.

The last major challenge was to obtain a stable blend presenting a very low viscosity, capable of being injected over long distances and at low temperatures with a minimum pressure drop.

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