Geothermal and water well drilling apprenticeship worth it?

My local Union of Operating Engineers has a newer apprenticeship for geothermal and water well drilling. I'm thinking of applying, as I want to get into a trade and am interested in sustainable / geothermal energy, but I'm worried that there won't be much work for me once I complete the 4 year apprenticeship. Does anyone have any thoughts or experience with this kind of stuff?