A dynamically positioned vessel (DPV) is located above an injection well, inject water or other fluids temporarily or for a short period of time, adjust the injection parameters, and either continue operating for the life of the system or as long as required to add permanent facilities on another platform. The DPV is connected to the potential injection well via a hybrid riser system. The hybrid riser system includes a rigid portion and a flexible portion. Injection using the DPV and the hybrid rise system can be more economical than injection using a conventional mobile offshore drilling unit (MODU) and a rigid riser.