The municipality of Heerlen has launched a heating and cooling network project based on medium-depth geothermal energy from former coal mines that are now flooded. This project initially focused exclusively on the supply of heat and cold to consumers, but it then developed to evolve into a 5th generation heating network focused on the exchange of heat between its various actors. For the transposition of this type of project to other regions such as Wallonia, we have identified the opportunities and the obstacles (technical, sociological, geographical, political, legal) which have made the success of this project.