Collaborating for Net Zero: Driving the Climate Transition with Geothermal Energy

Abstract

Mineral scaling is a common occurrence in the Leyte geothermal field. A frequent cause of the scaling issues in Mahanagdong is due to mixing of incompatible high-mineral, low-pH fluids and neutral-pH fluids. Scales formed vary depending on the composition of the fluids involved, but the most common are amorphous silica, metal sulfides and metal oxides. A recently documented scale deposition due to low-pH and neutral-pH fluid mixing was found in a two-phase line where an additional low-pH well was cut-in. The well was mixed with five other production wells, with one of them a high water flow, neutral-pH fluid well. The mixture resulted in the precipitation of a significant amount of iron oxides within the pipeline. After one month, it reduced the cross-sectional area of the 42-inch diameter pipe by around 65%. The scale-filled pipelines were cut and replaced to allow the return of the production wells online without obstruction. An online chemical inhibitor was added to the low-pH well — to minimize the scale deposition — since the low-pH well is now continuously cut-in to the two- phase line. Regular monitoring of the line shows that scale deposition is still ongoing and further studies and adjustments are needed to maximize the effect of the chemical dosing.