Effect of Flow Rate and Wellbore Geometry on Pyrite Scale Formation in Geothermal Well

Abstract

Mineral scale morphology and texture are significantly influenced by the physicochemical conditions in their formation environment, making these key indicators for interpreting mineral formation processes. In geothermal systems, these features vary greatly depending on whether minerals form through direct crystallization, during boiling, or other cooling mechanisms. Among the factors that impact mineral morphology, fluid flow rate and wellbore geometry play essential roles, particularly in the development of pyrite scales. This study examines pyrite deposits from production wells in the Tiwi Geothermal Field, Albay, Bicol, Philippines, each characterized by distinct flow conditions and wellbore geometry. Comparative analysis reveals that lower flow rates and larger wellbore diameters encourage crystal growth, leading to the formation of larger, well-defined euhedral pyrite crystals. In contrast, higher flow rates and smaller wellbore diameters favor rapid nucleation over crystal growth, resulting in the development of fine-grained, disseminated anhedral pyrite. These observations underscore the effect of flow rate and wellbore geometry on the morphology of pyrite scale and provide insights into a better understanding of the mechanism of pyrite scale formation.