Speaker
Description
Mineral scaling is a well-known problem in geothermal applications often caused by changes in the temperature of the fluid while moving to the surafce and/or by alterations in its composition and chemistry. If no precautions are taken, geothermal power plant components (wells, pipes, equipment) can be subject to the formation of deposits. More precisely, precipitation may disturb flow regimes, limit fluid flow, have an impact on the efficiency of geothermal energy production and increase maintenance costs. Thus, the ability to predict mineral precipitation can lead to active reservoir management strategies and better design of the process with the ultimate aim of improving production and minimizing costs. Obviously, precise calculation of the local temperature, pressure and composition of the fluid is crucial. In this study, a geochemical model is integrated into a thermo-hydraulic model to draw scaling risk tendencies in the production wells as a function of the host rock composition and aqueous solution chemistry while producing from magmatic geothermal systems.
The approach includes the coupling between three internal tools: the well flow model GWellFM, the geochemical calculator Arxim, and the thermodynamic library Carnot to estimate the deposition under subcritical conditions. Initially, different representative fluid compositions associated with magmatic systems are defined, and then the scaling risk along the production wells is estimated based on a calculated temperature-pressure path. Fluids from different geothermal fields were chosen to cover chemical compositions representative of different magmatic geothermal systems that may be encountered, considering the following ranges: (1) aqueous solutions characterized by salinity ranging from meteoric water to seawater, (2) log(pCO2) and log(pH2S) ranging from near equilibrium to undersaturated concentrations, and (3) host rock compositions covering the calc-alkaline and alkaline magmatic series. Three groups of minerals as potential scaling risks in the production wells are considered in the study: carbonates, sulfates, and amorphous silica.
