Following the shale gas boom in the United States, unconventional natural gas extracted from organic-rich shale rock formations has generated increasing attention in the European Union (EU). This considerable interest has been spurred by a range of optimistic volumetric appraisals of shale gas resource potential trapped beneath the European continent. The paper critically examines rationalities and practices through which states of resource availability and recoverability are made visible, measurable, intelligible, and thus rendered governable, namely open to new fields of possibilities to act upon. By implementing the concept of socio-technical imaginaries as governmentality approach, the analysis is guided by two objectives: first, to identify visions of shale gas potential contained in a range of resource estimates; second, to scrutinize rationalities of government, that is how shale gas resources are made knowable and purposeful, as well as technologies of government that operationalize these rationalities via practices of calculation, visualization, and inscription. The paper illustrates that, these highly speculative and uncertain assessments can forge powerful volumetric imaginaries of shale gas potential that yield specific governing effects concerned with securitization of unconventional hydrocarbons availability. Consequently, these imaginaries prescribe and legitimize techno-political hopes for certain post-conventional energy futures underpinning the fossil fuel abundance narrative.