Scale deposition in surface and subsurface production equipment is one of the major operational problems encountered during oil production, which results in equipment corrosion, wellbore plugging, production rate decline, and requires frequent squeeze treatments. Oil field scales mainly result from changes in the physicochemical properties (pH, temperature, and pressure), mixing with incompatible brine compositions, and mixing with inhibitors. Meanwhile, comprehensive modeling and prediction of scale formation has remained challenging due to the complexity of the geochemical reactions that occurs in real fields.
For the first time and to overcome the lack of comprehensive geochemical-based tools, a robust, accurate, and flexible coupled reservoir and wellbore model is developed, and then, integrated with a geochemical tool (i.e. IPhreeqc) to predict scale formation from injection wells through the reservoir to production wells. IPhreeqc, the United States Geological Survey (USGS) geochemical tool, has the capability of modeling homogenous and heterogeneous, reversible and irreversible, and ion-exchange reactions under non-isothermal, non-isobaric, and local equilibrium or kinetic conditions. In this work, by integrating IPhreeqc with the compositional reservoir (UTCOMP) and wellbore simulator (UTWELL), the geochemical capabilities of IPhreeqc is used in a multi-physics reservoir/wellbore models for comprehensive prediction of carbonates and sulfates scales deposition. Moreover, the effects of weak acids and hydrocarbon phase dissolution in the aqueous phase were included to accurately predict the carbonate scale profile.
To the best of our knowledge, there is no comprehensive simulator available in the industry through which scale deposition in the reservoir and wellbore can be predicted accurately. In this paper, scale deposition profile in the field is estimated by including 1) the interaction of the hydrocarbon and aqueous phases and its effect on the aqueous-scale geochemistry 2) effects of parameters that vary greatly in the field (i.e. pressure, temperature, and pH) and 3) comprehensive geochemistry simulation (provided through coupling of the simulators with IPhreeqc). The outcome of this study yields a comprehensive tool for prediction of scale deposition profile and will help scale deposition risk management and mitigation plans.
