A general coupled kinetic adsorption/precipitation transport model for scale inhibitor retention in porous media: II. Sensitivity calculations and field predictions

This paper describes the application of a generalised kinetic adsorption/precipitation (G/?) model for scale inhibitor (SI) retention and transport in porous media. The context of this study along with the chemistry and mathematics of the model itself are described in detail in the related Paper I (SPE 130702). Here, we describe a wide range of sensitivity calculations using this model which illustrate both (i) the consequences of this model in laboratory core floods, and (ii) the field predictions which results from various assumptions about field adsorption/precipitation processes. To our knowledge, this is the first time that such a dynamic coupled G/? model has been deployed in this way to scale inhibitor transport modeling. This model can describe any combination of retention mechanisms (adsorption and precipitation) in either equilibrium or under dynamic (non-equilibrium). conditions. The calculations presented here also clarify the roles of adsorption and precipitation mechanisms and how they affect field squeeze return curves. These results (and related experimental work, Kahrwad et al, 2009) show that precipitation is a more important process at higher SI concentrations going over to pure adsorption at lower concentrations. These modeling results indicate how we may then exploit the roles of each of these different mechanisms in the high SI and low SI regimes. Simulations of the type presented here can also help to provide the "target properties" for SI systems-(adsorption, precipitation and coupled adsorption/precipitation) of the future. This generalized model formulation also unifies the various approaches by different "schools of thought" by developing a scheme which can model any processes as appropriate. We believe that that this work resolves the controversy between adsorption vs. precipitation as the main mechanism of SI retention and replaces it with a clear generalised consistent model which may describe when (i) pure adsorption or (ii) coupled adsorption/precipitation occurs. © 2010, Society of Petroleum Engineers.