This chapter explores the relationship between geoscientific knowledge production and geopolitical agencies in the making of new subsurface resources, specifically unconventional fossil fuels. Focusing on recent controversies surrounding the assessment of potential shale gas resources in Europe, we analyse the ways in which highly speculative and contested resource estimates have come to inform the geopolitical imagination of many EU states and, in turn, provided a new impetus for geoscientific inventories and exploration of shale formations. In the first part of the chapter, we engage with recent volumetric accounts in political geography and cognate disciplines to conceptualize these epistemic struggles of resource-making as a case of “subterranean geo-politics”. The empirical analysis in the second part then traces the geo-politics of shale gas prospecting in Poland and the UK, describing how volumetric projections of resource abundance have become undermined by diverse materialities and socio-political constructions of the subsurface. This is evidenced by the difficulties of translating knowledge across geo-economically disparate sites of resource development, notably the failure to apply the US-based expertise to the European context. Finally, we document more recent efforts by the European Commission and other epistemic authorities to overcome the deficiency and incompatibility of local resource estimates by developing standard, EU-specific geo-metrics for shale energy assessment.