Preliminary assessment of dolomite stringers in the Upper Jurassic Farsund Formation as a potential unconventional hydrocarbon reservoir

Abstract

With the increasing interest in the development of shale reservoirs in Europe, cross-border geoscience co-operation is undoubtedly pivotal in understanding the laterally extensive and vastly underexplored unconventional plays in and around the North Sea. The Upper Jurassic Volgian Farsund Formation is considered to be a key source rock in the North Sea. Organic-rich mudrocks are interbedded with distal silt- to sand-prone turbidites and are commonly punctuated by variably thick dolomitized stringers. The latter are locally hydrocarbon charged, and are considered to have better-preserved microporosity and pore connectivity and higher brittleness compared to the adjacent mudrocks. Hence, an improved awareness of their origin and distribution is essential to understanding this potential unconventional play. In this paper, the origin and lateral continuity of the dolomitized stringers within the Farsund Formation are considered based on the integration of borehole image, sedimentological, petrographical and geochemical data. While acknowledging the high level of uncertainty held in some aspects of this study, based on the restricted dataset, our main purpose is to share preliminary findings and thoughts, which are aimed at prompting wider cross-border discussion.