Geothermal Operations and Material Science

Transcription

1 Geothermal Operations and Material Science Einar Jón Ásbjörnsson, Ph.D. Materials Challenges in Geothermal Utilization Reykjavík University

2 if it ain't broke, don't fix it Engineering rule of thumb

3 Geothermal industry What is different with geothermal environment Geothermal brine can be oversalted, carbonated fluid with hydrogen sulfide Geothermal steam is sulfurous and can contain hydrochloric acid Cooling water can be a bacteria growing fluid

4 Three modes of utilizing material science Design Main parts of education in material science for engineers focuses on this part, e.g. material selection etc.

5 Three modes of utilizing material science Failure Basic failure analysis included in material science for engineers

6 Three modes of utilizing material science Operation

7 What are we looking for in operation Corrosion All types of corrosion Wells, pipelines, pumps, separators, cooling systems, etc. All parameters that can affect material degradation Change in material properties Brittle material due to hydrogen

8 Physical barriers There are some main factors that make material monitoring difficult in geothermal operations Access Underground structures, i.e. wells Insulation of pipelines and equipment Hot surfaces Scaling High capacity factor Few breaks in operations

9 Technical barriers Only NDT (non destructive test) are possible Visual (general conditions) Ultrasound (Thickness, cracks) Dye penetrant (cracks) Magnetic particle testing (cracks) X-ray (thickness, cracks) Eddie current (cracks) Mainly used for weld inspection during construction and for testing of drill components.

10 Methodology Direct methods Focus on one specific location Regular thickness measurement of a bend in steam pipe Indirect methods Focus on system stability Chemical analysis, ph, etc. Flow analysis Temperature in system

11 Direct methods The direct method fix on specific position Give indications on conditions at specific point in the system Interpretation is simple and action plan can be created fast. Thinning in a bend in a well head Change well head or decrease velocity and continue to monitor Usually discrete measurements Not possible to monitor large systems Risk assessment can identify critical points

12 Rotor inspection Position specific Visual, UT Action plan clear Use another period or change Low frequency Every x years

13 Indirect methods Focus on system as a whole Chemical analysis Often continuous measuring systems Hard to interpret Effects on system unknown ph below recommended value for a week Action: Adjust ph in system, start deviation plan Action plan for deviations hard to make System can be large

14 Chemical analysis Can provide false sense of safety Wellhead ph does not necessarily give indications of problems in the blending zones. Chemical analysis upstream in district heating system can be incorrect indicator downstream Large complex systems with many variables 1000 m 1600 m

15 Instrumental methods for corrosion monitoring Direct methods: NDT - Ultrasonic testing, radiography Indirect methods: Coupons test Electrical Resistance Measurements Linear Polarization methods NDT - Ultrasonic testing, radiography Hydrogen measurements Water analysis continuous ph and conductivity measurements etc.

16 External corrosion Studded PE sheet between insulation and aluminum. Not always used Critical points known At fixtures, outlet points The wetness in the insulation not monitored Not designed in the system

17 Conclusion One of the challenges in geothermal is to monitor material degradation during operation All design work (student or real life) should include a maintenance/monitoring plan. Implementation started in applied engineering Risk assessments of current systems should be done in order to identify critical points for direct monitoring

18 if it ain't broke, monitor it New Engineering rule of thumb

19 Thank you for your attention Photo: Gudmundur Steingrímsson