Releasing and Circulating Overshot
The overshot is fishing the pipes externally, especially for drill collar, drill pipe, tubing and subs. The fluid can circulate with the high pump pressure after catching the fish as seals. The top of fish will be milled by under mill shoe. It can also work with jars to catch the stuck fishes. If the catched fish can’t be released from sticking, an overshot can be released to lift the drill string.