The geological reservoir characterization of a calcite-cemented, heterolithic shoreface reservoir, Ben Nevis formation, Hebron Asset

Depositional and diagenetic heterogeneities control reservoir quality and performance and a better understanding of their distribution and impacts on fluid flow will improve reservoir development planning and maximize hydrocarbon recovery. Shoreface deposits within the Ben Nevis Formation at the Hebron Asset consist of alternating beds of facies with contrasting reservoir quality that are diagenetically overprinted with the precipitation of calcite cement. Lower quality fairweather facies are interbedded with higher quality sandstone beds that record periodic pulses of sediment into a quiescent shoreface environment by storm activity. The heterolithic nature of the reservoir and diagenetic alterations caused by calcite cement have implications on reservoir continuity and the spatial distribution of reservoir properties that control fluid behaviour. It is difficult to understand and quantify this distribution from subsurface data alone, and outcrop analogue studies aid in reservoir characterization and modelling by revealing information at the interwell-scale about facies architecture, continuity and distribution. An outcrop study of cemented shoreface parasequences in the Book Cliffs, Utah quantified the dimensions and distributions of calcite concretions and calculated variograms with a horizontal:vertical anisotropy ratio of 5:1. This ratio was used in the stochastic population of facies in the Hebron reservoir model to calculate horizontal variograms from vertical variograms that are well-defined from well log data. Streamline simulation demonstrates the importance that a geologically-realistic representation of cementation has on reservoir performance. Streamlines indicate that concretions act as baffles, making flow paths more tortuous and causing earlier breakthrough