To date, social sciences have devoted little attention to the processes of expert knowledge production related to the exploitation of unconventional hydrocarbon resources. In this article, we examine an epistemic experiment led by the European Commission, the European Science and Technology Network on Unconventional Hydrocarbon Extraction, which was aimed at producing authoritative knowledge claims on shale energy development. By developing the idiom of ‘co-production’, the article provides a more fine-grained understanding of the processes through which competing knowledge claims, forms of epistemic authority, and new energy publics co-evolve in a situation of highly-politicized controversy. Drawing on our first-hand observations as participants representing the social sciences in the expert network, this article provides an in-depth ethnographic account of the struggles of the European Union authorities to manage and delimit the controversy. In this way, the analysis develops our understanding of the challenges in improving the deliberation of shale gas as a transnational energy policy issue.