Erosion is a material degradation at the surface of exposed material and is caused by mechanical action such as friction and impact caused by solids carry over in the fluids. This is also caused by the implosion of bubbles during flashing causing cavitation, and liquid droplet impingement. The solids from the geothermal fluids can be material from a reservoir or wellbore that has been carried to the surface due to being lifted by the fluids. Solids can also be from precipitates in the chemical reaction in the fluids as the fluid rises to the wellbore and chemical reactions occur due to the separation of steam and brine in the geothermal fluids.
Erosion removes the exposed surface of the material gradually until the critical thickness is reached. To mitigate corrosion, the solution is to do weld-overlay cladding of the exposed surface with a wear-resistant material. However, the wear-resistant material is very hard when applied as cladding is prone to cracking. To solve this phenomena, the base material is cladded first with Inconel Alloy 625. Once the Inconel alloy 625 is set, the wear-resistant alloy layer is then added on top. Inconel alloy 625 exhibits high corrosion resistance and high ductility which makes it a material of choice for base surface modification.
The erosion in geothermal production can also be due to changing geothermal reservoir characteristics. Each wellhead component and branch line piping design is usually according to the initial discharge characteristic of the well. Geothermal reservoir drawdown will occur over time. The well will produce more steam which increases its steam velocity and lifts more solid material to the surface. This will increases the likelihood of erosion. Erosion can also be process-specific and can be due to inappropriate piping configuration. As the geothermal fluids flow downstream with changing pressure, thermodynamic plays in the propagation of implosion of bubbles during flashing and cavitation, and liquid droplet impingement.
Wilclad solution for erosion mitigation is problem-specific. Our first approach is design modification specific to client requirement and our sustaining solution is the application of weld-overlay cladding with wear-resistant material for long-term erosion mitigation.