| Abstract |
Economic feasibility of a geothermal power plant relies on continuous and constant operation of the geothermal loop. Constraints of operational performance like unscheduled shut-down periods, intense maintenance operations and follow-up costs reduce their reliability. Once geothermal wells are drilled and completed they are considered in most cases as fixed equipment of the geothermal loop designed for a service life of twenty and more years. When it comes to maintenance issues, well casings are most difficult to access after completion and if required, work-over operations are time-consuming and costly. To make sure that the wells are fully operable, regular inspections of casing integrity are performed at soultz. Casing integrity of the inner casing of gpk-2 was evaluated amongst other wells in july 2015 by ultrasonic measurements, gamma-ray detection and camera inspection. After more than fifteen years of operation, the calculated wall thickness of the gpk-2 9”5/8 casing shows a maximum loss of 2.2 mm within the first 500 m which indicates a corrosion rate of less than 0.2 mm at production conditions. Down to approximately 300 m, gr values are low and show a higher variation which indicates a strong heterogeneity of the scaling layer at the pipe interior. This finding was confirmed by camera inspection. Gpk-2 inner casing interior is mainly covered with scales. Frequently, parts of the scale layer are mechanically removed by lsp installation/De-installation and logging operations which leave long vertical scratches on the pipes. There is no indication at all for scale spalling due to subscale corrosion processes. During the camera logging, no holes or other signs of casing integrity impairment was discovered. Down to 120 m uniform corrosion is frequently visible and to the final logging depth uniform corrosion is visible only randomly. |