Determining static reservoir connectivity using noble gases

Determining the connectivity of fluids in hydrocarbon reservoirs is a key challenge during the appraisal stage. Such information is critical for assessing the economic viability and planning reservoir development. Although several tools exist to determine static connectivity and the fluid column organisation post-hydrocarbon emplacement, it is extremely difficult to determine the extent of the connectivity between fluids of different phases. Conventional connectivity studies on the Tormore field, West of Shetland Basin, UK have resolved the vertical connectivity of one well (T2) but have been unable to resolve further vertical or lateral connectivity. Here, we outline a new tool for assessing hydrocarbon connectivity by completing the first intra-field connectivity study of the noble gas composition (He, Ne, Ar, Kr and Xe) of fluids from individual reservoir units, allowing the resolution of both the vertical and lateral connectivity within the Tormore field. To achieve this, we obtain fluid samples from archived PVT vessels rather than from the wellhead or platform separators, allowing sampling of the individual reservoir units encountered during drilling. Our findings corroborate previous connectivity studies undertaken on the oil well, T2, confirming that the reservoir unit of T2-A is isolated from the lower reservoir units. We apply the same method to the gas well, T3, finding that unit T3-A is isolated from the lower reservoir units. In addition, we identify a previously unknown connection between the gas and oil phase that is separated by a poorly constrained fault. These findings confirm the effectiveness of using noble gas fingerprints to assess the connectivity of fluids in different phases, providing a new tool for understanding connectivity in hydrocarbon and non-hydrocarbon settings (e.g. Carbon, Capture and Storage).