Modelling and design of scale inhibitor squeeze treatments in complex reservoirs

This paper describes the formulation and application of a simulation tool for modeling scale inhibitor adsorption squeeze treatments in realistic reservoir formations. In this simulator, a three-dimensional (3D), three-phase black oil reservoir model is used to calculate the larger scale reservoir flows such as the local well layer flow rates and watercuts, and the near wellbore area water saturations. However, a very accurate fine grid near well simulation model is embedded into this reservoir scale calculation which models all of the inhibitor transport, including adsorption/desorption behaviour and dispersion, within the maximum penetration distance of the injected inhibitor. Since this penetration distance may only be tens of feet which is generally much smaller than a single grid block in a reservoir model, a fine radial subgrid is used to accurately track the injection and back-production of the inhibitor. It is demonstrated that this approach provides a vast improvement over any previous methods of modeling this process. In the paper, the one layer single well radial model is first presented with examples of its application. This is followed by the description of the full reservoir inhibitor squeeze simulator combining the black oil model and the fine grid radial squeeze model. The application of this simulator to some realistic near-well inhibitor squeeze treatments and the key factors governing the process in a heterogeneous formation are then examined. The issues studied include the following; the form and type of inhibitor adsorption isotherm, the equilibrium/non-equilibrium adsorption/desorption processes, the effect of degree and type of reservoir heterogeneity, the concentration of the injected inhibitor slug and the significance of overflush size.