Reinjection of geothermal water into reservoirs could help maintain the reservoir pressure but may lead to thermal breakthrough. Therefore, the calculation of an optimal distance between the production and reinjection wells is required to balance the changes of pressure and temperature in the reservoir. In this work, a procedure has been designed to optimize well-doublet placement by integrating numerical simulations and economic analyses. The procedure is composed of two subsequent steps, which makes the method more flexible. The first step is the numerical simulation, which incorporates the geological and physical processes. The second step is to optimize the cost by varying the well distance. An example shows that it is better to place the reinjection well in the downstream of the production well. A distance of 400 m between the wells was found to be optimal for the given scenario. Through a further comparison with economic parameters in different countries, the optimal distance was found to be more relevant to the ratio of heat price over electricity than a single parameter for heat or electricity prices.