The Use of Corrosion Resistant Alloy to Address Erosion Corrosion Problem in a Well in Mt. Apo Geothermal Field, Philippines

Abstract

Mt. Apo Geothermal Field, Philippines has been producing 104 MWe steam from two (2) power plants since 1997. At the onset of production, geothermal wells are discharging near neutral fluid, pH 5-6. In year 2013, a new well was completed which discharged erosive-corrosive fluids. The new well has a pH of 2.0 and total suspended solids of 15 mg/kg. Both the branch-line and wellbore liners were severely damaged with complete penetration in just three (3) months of continuous discharge. This paper presents the results on the use of corrosion resistant alloy (CRA) to address the erosion corrosion problem in both wellbore and surface facilities of the new well. The CRA liners are shown to be in good condition based on downhole survey. The wellbore CRA’s usable life is calculated to last up to 25 years. As for the above ground facility, a stainless steel wellhead separation system (WHS) was installed to isolate the erosive-corrosive discharge fluids from the existing facility. Based on the measurements conducted, no significant damage is noted in the wellhead separation system. To monitor effectiveness of the CRA materials, regular ocular inspections and caliper inspection surveys are being done.