A well tool device includes a housing having an axial through bore. The well tool device further includes a sleeve section axially displaceable relative to the housing; a fluid flow preventing frangible disc; and an axial fluid passage bypassing the frangible disc when the well tool device is in an initial state, thereby allowing a fluid flow between a first location above the frangible disc and a second location below the frangible disc. The sleeve section includes an axial through bore aligned with the axial through bore of the housing. The axial fluid passage is closed when the well tool device is in a subsequent state. The fluid flow preventing frangible disc is provided in the bore of the sleeve section in sealing engagement with the sleeve section. The well tool device further includes a disc supporting device for supporting the frangible disc in relation to the sleeve section. The disc supporting device is releasably connected inside the sleeve section by means of a releasable connection device. The well tool device further includes a disintegration device disintegration of the frangible disc, wherein the well tool device is in a final state when the frangible disc has been disintegrated by the disintegration device.