| Abstract |
Corrosion of both surface and sub-surface equipment has been a perennial problem in the commercial operation of the Palinpinon Geothermal Field. Acidic discharge either inherent or induced by prolonged exploitation of the field is the major cause of corrosion that triggers not only the undue replacement of the wellhead assembly components but also the excessive thinning of the wellbore casing. The severity of corrosion varies from well to well depending largely on the chemical characteristics of the discharging fluids. At least 10 from a total of 39 commercially producing wells in Palinpinon are affected by acid intrusion and have been the subject of continuous chemical monitoring, particularly the pH, SO4, Mg and Fe levels. Of these, PN-20D, PN-22D and BL1-D showed higher thinning levels based on Ultrasonic Test (U.T.) measurements and Casing Inspection Caliper (CIC) surveys. The corrosion attack was so severe in well BL-1D that the production liner eventually parted just below the PCS. Compounding this problem was the erosive action of the corrosion products and suspended solids consisting of minute formation particles entrained in the discharging fluids. Despite the low pH of and high Fe concentration in the discharging fluids, well BL-1D was utilized for commercial operation almost continuously for over six years since its commissioning in November 1994. Within this period, a number of operational interventions, e.g. spring water injection and the adoption of the sweep bend section into the wellhead assembly, were implemented to address the problem on high iron levels and excessive thinning of the wellhead tee. |