We performed a modeling study to compare the feasibility of three geothermal designs: a closed- loop heat exchanger, a closed-loop heat exchanger with hydraulic fractures engineered to contain thermally conductive material, and an open-loop two-well doublet with multistage fracturing along horizontal laterals. The study was performed with a fully integrated hydraulic fracturing, reservoir, and wellbore simulator. Simulations were performed at a variety of temperatures and operating conditions. The findings show that the closed-loop heat exchanger designs yield very low energy production per foot of wellbore drilled. These designs would require a huge decrease in the cost of drilling to be economically competitive. In contrast, the simulations show that open-loop designs with horizontal laterals and multistage fracturing are capable of sustaining high energy production rates and temperatures over the long-term.