Reverse filling tool

The utility model discloses a reverse filling tool which comprises a well remaining part and a service tool part arranged in the well remaining part. The well remaining part enters a well along with apipe column before well cementation, after sand prevention construction is completed, a service tool is put into the well, the well remaining part is opened, and a circulation channel is establishedfor filling. The sand prevention device is researched and developed for meeting the sand prevention requirement of the horizontal well of the thick oil, high-mud and silty-fine sand loose sandstone oil reservoir, mortar can reversely flow in the sieve/lantern ring from bottom to top, sand setting does not exist, and a sand bridge cannot be formed; the technical problem that fractured reservoirs are self-selected according to the sequence of thin interlayers, multiple layers and pressing force from low to high which are severely heterogeneous between layers and in the layers is thoroughly solved. According to the utilit