Molecular factor computing sensor for intelligent well completion

A molecular factor computing sensor for use in a subterranean well can include a thermal detector, a layer of an electromagnetic energy absorptive composition, and an electromagnetic energy source. The thermal detector is sensitive to electromagnetic energy from the electromagnetic energy source and absorbed by the electromagnetic energy absorptive composition. A method of identifying at least one chemical identity of a substance in a subterranean well can include positioning at least one molecular factor computing sensor in the well, and the molecular factor computing sensor outputting at least one signal indicative of the chemical identity of the substance. A system for use with a subterranean well can include at least one molecular factor computing sensor that outputs a signal indicative of a chemical identity of a substance in the well. The substance flows between an earth formation and a wellbore that penetrates the formation.