Abstract
The Geo-Drill project aims to save time, increase service life of equipment and instrumentation, and reduce costs during drilling of geothermal wells by improving drilling methods with new materials and novel design of a down-the-hole (DTH) drill hammer. In the project polymer coatings (PTFE/PPS) with added graphene oxide (GO) nano-particles were corrosion tested at high temperature and pressure to evaluate the corrosion resistance in simulated geothermal drilling environment. The results from the corrosion testing of the PTFE/PPS-GO coatings in simulated geothermal drilling environment at two different conditions that can be encountered during drilling operation are reported here. One set of samples with various GO content was tested in moderately alkaline water, pH = 9, at 120 °C and 50 bar for 14 days; simulating normal drilling conditions. A second set of samples were tested at harsh conditions at 250 °C, 50 bar for a duration of 7 days in water (vapor and liquid phases) with CO2 and H2S gasses added, which are conditions that can be encountered during geothermal well drilling if loss of circulation of the drilling fluid occurs with the subsequent ingress of corrosive gases into the well. To evaluate corrosion resistance, weight changes were measured, and microstructural and chemical composition analyses were performed with scanning electron microscope with an attached energy-dispersive X-ray spectroscopy equipment before and after testing.
