FIELD: industrial wells for production of flowing medium and having compacted gravel for prevention of inflow of sand to recovered medium. SUBSTANCE: device includes casing string covering productive formation. Installed in casing is pipe made in form of supplying and perforated string. Placed in casing-perforated pipe string annulus is compacted gravel. Packer is placed on pipe above compacted gravel. Located between packer and compacted gravel on perforated pipe string is valve unit. Valve unit is made for opening of its shutoff members caused by fluctuating rise of differential pressure in compacted gravel and in perforated pipe string. Valve unit is installed in normally closed position. The method for preventing of loosening or displacement of compacted gravel is based on valve unit made for its closing at differential pressures during introduction of gravel into casing string and during recovery of fluid. Valve unit is opened under the action of uneven differential pressure of the preset value onto compacted gravel and in perforated pipe string. The preset value of uneven differential pressure is taken than calculated pressure of gravel loosening. EFFECT: higher efficiency. 8 cl, 5 dwg
