A process for stimulating microbial methane production in a petroleum-bearing subterranean formation, comprising: (a) analyzing one or more components of the formation to determine characteristics of the formation environment; (b) detecting the presence of a microbial consortium, comprising at least one methanogenic microorganism, within the formation; (c) assessing whether the formation microorganisms are currently active; (d) determining whether the microbial consortium comprises one or more methanotrophic microorganism; (e) characterization of one or more microorganisms of the consortium, at least one of the members of the consortium being a methanogenic microorganism, and comparing the members of the consortium with at least one known microorganism having one or more known physiological and ecological characteristics; (f) characterization of one or more methanotrophic microorganisms of the consortium (if present), and comparing the members of the consortium with at least one known microorganism having one or more known physiological and ecological characteristics; (g) using information obtained from steps (a) through (e) for determining an ecological environment that promotes in situ microbial degradation of petroleum and promotes microbial generation of methane by at least one methanogenic microorganism of the consortium; (h) using information obtained from steps (a) and (f), if methanotrophic microorganisms are present, for determining an ecological environment that demotes in situ microbial degradation of methane by at least one methanotrophic microorganism of the consortium; and (i) modifying the formation environment based on the determinations of steps (g) and (h), if methanotrophic microorganisms are present, to stimulate microbial conversion of petroleums to methane while minimising methane destruction by adverse processes.