An injection pipe string (4) in a well (2) for the injection of a fluid into at least one reservoir (6) intersected by the string (4), in which at least parts of the injection string (4) opposite the at least one reservoir (6) are provided with one or more outflow positions/-zones. At least one pressure-loss-promoting flow control device is provided to each outflow position/-zone. In position of use, the flow control device(s) control(s) the outflow rate of the injection fluid to a reservoir rock opposite said position/zone. The flow control device(s) is (are) disposed between an internal flow space (18) of the injection string (4) and the reservoir rock opposite said position/zone, and said device(s) is (are) hydraulically connected to at least one through-going pipe wall opening (28, 86) in the injection string (4), and to said reservoir rock. By using such flow control devices, the outflow profile of the injection fluid may be appropriately controlled along the injection string (4).