The present disclosure describes methods and systems, including computer-implemented methods, computer program products, and computer systems, for diagnosing reservoir health. One computer-implemented method includes receiving, from a client, a plurality of reservoir diagnostic data associated with a reservoir; computing, at a server, a plurality of reservoir health sub-indices based on the plurality of the reservoir diagnostic data; computing a reservoir health diagnostic index based on the plurality of reservoir health sub-indices and a predetermined category weighting factor; determining that a reservoir health sub-index is below a predetermined threshold; in response to the determining, generating an alert; and sending, to the client, the alert and a cause, wherein the cause indicates a reason that contributes to the reservoir health sub-index being below the predetermined threshold.