Block 3 reservoirs in Angola are dolomitic reservoirs with temperatures ranging from 150 to 164 °C with a nearly constant pressure (320 bar). They are all affected by scale precipitation that forms into the tubings and the topsides.

Modeling was applied to find quick correlations between physical measurements and the predicted risk of scaling. Information from wire line reports, maintenance operations and gamma campaigns were gathered in order to draw up a list of risky wells, and to validate the found correlations. The water cut, the composition of the produced water, the well head temperature and the drawdown can be used to determine the risk of scaling and roughly the location of the deposits. In this paper, on one hand, we present the relation between drawdown, water cut and Calcium carbonate precipitation and on the other hand between salinity and barium sulphate scaling.

The kinetic module of the SCALE2000 software was used to explain why the injected seawater does not produce any Calcium carbonate inside the tubing even if it is supersaturated at surface conditions. Finally, a new version of this software has been tested; it includes a model that uses simplified hydrodynamic approach based on a scheme of chemical reactors connected in series.

The model thus takes into account the cumulated effects of water flow in terms of Pressure and Temperature variations, and changes in dynamic water composition due to the mixing. It is then possible to estimate both the thickness of the scale deposits and their location along a production or injection well.

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