One or more computer-readable media include computer-executable instructions to instruct a computing system to receive simulation results for future behavior of a reservoir that includes a material production well and a fluid injection site; define a virtual sensor as being located between the material production well and the fluid injection site; determine fluid saturation at the virtual sensor based at least in part on the simulation results; and issue a notification if the fluid saturation at the virtual sensor exceeds a fluid saturation limit. Various other apparatuses, systems, methods, etc., are also disclosed.