Techno-Economic Analysis of Geothermal Well Designs: Slim and Standard Hole Well Construction

Abstract Geothermal energy extraction, which is similar to hydrocarbon well developments, requires drilling and completion to access the heat from high-temperature subsurface zones. Even though geothermal energy has its environmental benefits, the economic viability of geothermal well construction may face challenges. These challenges may also include relatively higher complexities than oil and gas wells, because of the complex drilling mechanics and higher axial rating requirements for the casing strings. This study proposes a method to reduce geothermal well construction costs to improve the financial viability of enhanced geothermal systems (EGS) through a cost-effective well design. It is well acknowledged that geothermal systems typically require a producer and an injector well to harness the subsurface heat. While doublet’s philosophy has been refined, and there are fourth to sixth generations of doublets concepts, this paper proposes a new model that includes heat loss effects into the well cost model. The paper first shows the three main cases used for the analysis: classic triplets using three identical wells and the new concept using three smaller wells. Next, a well cost model will be created for each one of the concepts, highlighting the differences and advantages. Last, given the new proposed concept, the geothermal well farm concept will be discussed. The results indicate that the total deterministic cost for constructing a pair of slimhole injector wells could be comparable to that of a single standard or a big hole injector well. The novelty of this research lies in its examination of multiple injector-producer triplet EGS wells, emphasizing cost-effective drilling and completion techniques.