A Practical Field Test and Simulation Procedure for Prediction of Scaling in Geothermal Wells Containing Noncondensable Gases

Abstract

Scaling in a hydrothermal type of geothermal well reduces or interrupts the production of geothermal energy. Calcite is one of the most common scales in geothermal wells. The reason for its formation in geothermal production wells is clear. The flowing up of geothermal water causes a change in the pressure and temperature, which results in the escape of CO2 gas from the geothermal water, causing a rise in pH and the supersaturation of CaCO3 in the solution. To predict scaling in a new geothermal well, conditional data for geothermal well simulations are required. It is important to determine what field data are needed and how to obtain them. It is necessary to deal with some parameters that are hard to measure and that have not been described in detail in the existing literature. In this study, a two-phase flow model and a chemical reaction equilibrium model are integrated to simulate the scaling process in production wells. Based on the simulation, a comprehensive and practical approach, including a novel noncondensable gas content measurement method, is applied to predict the depth of the first gas bubble using simple field test data and does not require reservoir permeability and earth conductivity. The result shows good agreement with the location of scaling detected in the field.