This paper analyzes the relation between well spacing and Net Present Value of a Hot Sedimentary Aquifer geothermal doublet. First, a sensitivity analysis is carried out to evaluate the effect of uncertainty of geological and production parameters on the Net present Value. Second a finite-element approach is utilized to study the effect of fluvial facies architecture on geothermal energy production. For this purpose detailed fluvial facies architecture models are created utilizing a process-based facies modelling approach. These models and reservoir properties are based on a geological dataset of the Lower Cretaceous Nieuwerkerk Formation in the West Netherlands Basin (WNB). Results of the sensitivity analysis show that a 10% variation in well spacing from a 1000m base case scenario could vary the NPV by 10%. The minimal required well spacing is dependent on the reservoir thickness, flow rate and the allowed production temperature drop. The simulations results show that the theoretical advantage of a reduction in well spacing could be balanced by a poor well connectivity between the wells because of the characteristic of fluvial reservoir architecture. @en