Evaluation of inorganic scale deposition in an unconsolidated reservoir by numerical simulation

A good understanding of in situ brine mixing is important for offshore deep water fields under water injection. Incompatibility between the injection and formation waters may result in inorganic scale precipitation in the reservoir, in the well tubing and gravel pack, in flow lines and in surface equipment. In this work, we have used reservoir simulation to model injection brine/formation brine mixing and its effect on reservoir scaling. The objective of this work is to predict in situ brine mixing and its consequences using a simulator that models the kinetics of the scaling reactions. A semi-compositional simulator was used to model the barite deposition reaction which may occur in the reservoir and in the well. In this approach, we take into account the kinetics of the reactions, rather than assuming the traditional (equilibrium) thermodynamic model. Detailed near-well modelling using local grid refinement (LGR) was carried out to forecast of the level of barite precipitation which occurred in the gravel-pack and the consequent production losses. We have also modeled scale inhibitor treatments of the scaling well and a simplified "scale removal" treatment, again including additional preventive scale inhibitor squeeze treatments.