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PETROMAKS2-Stort program petroleum

Optimizing Water Chemistry for Enhanced Oil Recovery

Tildelt: kr 11,1 mill.

We propose to quantify the impact of injected water chemistry on the recovery of oil on the field scale. This will be done by building a streamline model for the chemical changes that occur as the injected fluid moves from injection to a production well. The main focus will be on fractured chalk reservoirs, such as the Ekofisk and Valhall reservoirs, however the methods developed will be general. The chemical changes will be calculated assuming that the flow occurs in flow zones (fractures or permeable st rata). Along the flow zone the chemistry of the water changes when the chemical components diffuse into the surrounding matrix rock and react with the matrix rock minerals, or when chemicals in the matrix pores diffuse into the flow zone. The imbibition o f water within the flow zone into the matrix, and the expulsion of oil from the matrix into the flow zone, will also be considered. To reach the main objective the effect of water chemistry will be studied on three different scales, pore-, core-, and fie ld-scale. The three models will be integrated together, because it is important that the effect of water chemistry is not limited to be studied at a single scale. The chemical changes along the flow zone may have such a pronounced effect on oil production that modelling precisely the pore or core scale factors are not of great importance for the effect on oil production. On the other hand the reverse could also be true. The pore models will be tested against the observed distribution of oil and water in pore structures from cryo SEM images. The core models will be tested against imbibition experiments. The final product of the combined pore, core, and streamline model will be a set of theoretical streamline model predictions of how changes in injected w ater chemistry impacts oil recovery. The methods developed in this project will also give basic understanding of chemical water weakening and production well scaling.

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PETROMAKS2-Stort program petroleum