Rock Physics Analysis of EOS Well Caprock Shale for the Northern Lights CCS Project, Offshore Norway

Abstract

Summary This study focuses on seal characterization of Lower Jurassic Drake Formation shale from the Northern Lights project’s CO2 confirmation well Eos (31/5-7) from the Horda Platform area, the northern North Sea using the Young’s Modulus-Poisson’s Ratio) rock physics template. A rock physics model which computes theoretical values of dynamic elastic properties for common constituents of shales is utilized to construct Young’s Modulus-Poisson’s ratio template. The template shows the variations in Young’s Modulus and Poisson’s Ratio and for a combination of mineralogical mixtures versus porosity or effective stress. Results show that the lower part (DIMSAM-Drake Intra Marine Shale of Acoustic Marker, 53 m thick) of the Drake Formation shale in Eos is a good seal, although the upper part of the shale (Drake 2) has relatively high brittleness values. The evaluation of caprock by rock physics template is challenging as the caprock properties are site-specific and also influenced by many factors such as mineralogical composition, maximum burial, exhumation, in-situ stress conditions, the existence of faults, natural fractures, and their orientations. Therefore, though the brittleness indices estimate based on elastic parameters are easy to use but require calibration with lab investigation.