Geothermal energy is certainly one of the most interesting renewable energy options. There are many countries in the world that have excellent geothermal energy resources at their disposal but regardless of excellent global potential geothermal power is still a scarcely used renewable energy resource.
This is because of the geothermal drilling which is very complicated and very expensive process, even despite the recent technological advancements.
In most cases, oil and gas drilling is significantly less complicated than geothermal drilling. Oil drilling is normally done in softer and less-fractured rock, resulting in fewer problems with fluid circulation while on the other hand geothermal drilling often goes through igneous and metamorphic rocks, which are harder and lot more fractured than the sedimentary rocks through which most oil wells are drilled.
Drilling through fractured rocks is extremely difficult because these rocks can change the impact loading on drills and cause significant damage.
Also, oil drilling in most cases doesn't involve dealing with very high temperatures which is a common thing associated with geothermal wells.
Geothermal energy industry still doesn't have enough funds to invest in research and improve the process of drilling under increasingly difficult conditions. Geothermal drillers create only a small number of new geothermal wells each year which makes it very difficult and expensive to support innovation in this field. On the other hand oil and gas industry creates lot more wells per year and this gives them the resources needed to invest in further research.
Due to the increasing global hunger for oil, the oil industry has started going for much deeper reservoirs which means it has started experiencing the same difficulties the geothermal drilling has to go through. This will likely lead to further research and some new solutions that could hopefully be applied in geothermal energy industry too.