Application of Chemical and Wellbore Modelling to the Corrosion and Scaling Properties of Ohaaki Deep Wells

Abstract

Thermodynamic models are used to calculate the chemistry of the inflow into existing deep wells from measured surface chemistry and enthalpy. This information, together with wellbore simulation, allows the calculation of chemical conditions throughout the wellbore. Estimates of the chemistry are incorporated into predictive phase-stability models of protective corrosion products and mineral scales. These models assist in defining the risk of corrosion and scaling in the existing deep wells. Ohaaki deep wells have produced waters having a similar chemistry to those in the shallow reservoir. This New Zealand experience can be contrasted with occasional acid fluids being experienced in other shallow geothermal fields and more acid fluids being encountered in deep wells in other fields.