Fluid level indication system and technique

A technique that is usable with a well includes disposing a distributed temperature sensor in a conduit that traverses a region of the well. The region contains at least two different well fluid layers. The technique includes circulating a fluid through the conduit and using the distributed temperature sensor to observe at least one temperature versus depth profile of the fluid. Based on the observation, the depth of a boundary of at least one of the well fluid layers is determined.