Abstract: A down hole shut-in device effects a stoppage of effluent from a blown-out oil well by freezing a plug of the effluent within the well. The down hole shut-in device is installed within a conventional tubing string or casing string and includes a tubular member having a structural outer wall and a relatively thin, heat-exchanging inner wall. During normal operations, a substantially non-compressible fluid is maintained within the volume bounded by the outer and inner walls for transmitting pressure exerted upon the thin inner wall to the structural outer wall. During a blow-out or other loss of well control, the substantially non-compressible fluid is replaced by a refrigerated fluid for removing heat from the effluent flowing within the tubular member. A series of flow deflectors are mounted to the inner wall and are normally flush therewith.