Stratigraphic reservoir compartmentalization: causes, recognition, and implications for the geological storage of carbon dioxide

Abstract

The impact of carbon capture and storage (CCS) in mitigating anthropogenic emissions of greenhouse gases is potentially great, but its success is strongly dependent on identifying suitable geological storage sites. One of the key uncertainties in this regard is the degree of compartmentalization of the target storage horizon. Many studies have examined reservoir compartmentalization in oil and gas fields and its implications to hydrocarbon production, but few have looked at compartmentalization from the perspective of CCS storativity. Using case studies from the oil and gas industry, this paper examines the predictability of reservoir compartmentalization and the techniques used to assess it. It then focusses on stratigraphic compartmentalization in saline aquifers, a major category of potential carbon storage sites, examining in particular the Triassic Bunter Sandstone Formation of the UK North Sea. It is clear that the analysis of stratigraphic, seismic and fluid compositional data can provide early evidence of reservoir compartmentalization. The available data indicate that the Bunter Sandstone has a low risk of stratigraphic and structural compartmentalization. However, the presence of compartments in oil and gas fields is often confirmed only once well production data are available. As such, though the broad likelihood of compartmentalization in a CCS site can be forecasted, understanding its exact nature may be dependent on injection data.