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Modeling Mineral Scaling In Matalibong Sector of Tiwi Geothermal Field, Albay, Bicol, Philippines
Mineral scaling is one of the major problems often encountered in geothermal fields, such as in the Tiwi Geothermal Field in Bicol, Philippines. Identification of appropriate mitigating measures is critical to properly address this problem. This paper aims to understand and identify the mechanisms and processes leading to the formation of calcite, pyrite, and anhydrite as mineral scales in one well located in Tiwi Geothermal Field using CHIM-XPT (2016). With the reconstructed reservoir water, cooling, boiling, fluid-fluid mixing, and isothermal simulations were performed. Results of the geochemical modeling showed that the mineral scaling in well located in the Matalibong sector could be a product of boiling and cooling of mixed cold groundwater and the reconstructed reservoir water. Aside from established temperature and pressure, fluid flow rate velocity and wellbore geometry (inner diameter and length of the production casing), were also considered in this study as factors in the formation of mineral scales. The fluid flow rate velocity was calculated using the Hagen-Poiseuille equation where the inner diameter and the length of the production casing together with the pressure were used as parameters. A decrease in fluid flow rate velocity can trigger adiabatic boiling in the system. The result shows that at a constant temperature, a boiling event happens when pressure decreases due to low fluid flow rate velocity with respect to its depth leading to the formation of minerals, specifically anhydrite. This shows that not all types of mineral scaling-forming processes, such as boiling, are driven by thermodynamic changes. Kinetics can also promote adiabatic boiling where pressure changes due to fluid flow rate velocity conditions leading to the formation of mineral scales. With this understanding of how calcite, pyrite, and anhydrite were formed, it is necessary to monitor and control the fluid flow rate velocity in the well to avoid adiabatic boiling leading to the formation of the mineral scales.