Seismic modelling of metre-scale normal faults at a reservoir-cap rock interface in Central Spitsbergen, Svalbard: implications for CO2 storage

Abstract

On Svalbard (Arctic Norway), a pilot-scale research project has been established to investigate the feasibility of storing locally produced CO2 in geological aquifers onshore. Drilling, geophysical and geological data acquisition and water-injection tests confirm the injectivity and storage capacity of the naturally fractured and compartmentalised siliciclastic storage unit that is located at c. 670–1000 m depth below the proposed injection site in Adventdalen, Central Spitsbergen. Excellent outcrops of the reservoir-caprock units 15 km from the planned injection site allow for detailed sedimentological and structural studies, and complement 2D seismic data acquired onshore and offshore. In this contribution, we focus on small-scale (metre-scale displacement) normal faults present in both reservoir and caprock to quantify their seismic detectability. We generate synthetic seismic sections of structural models based on high-resolution virtual outcrop models populated with elastic parameters from wireline log data. We address a number of geological scenarios, focusing on CO2 migration within the compartmentalised reservoir, its baffling by normal fault zones and migration of CO2 along a hypothetical fault in the caprock. Our results indicate that while the small-scale faults are unlikely to be imaged on conventional 2D seismic data, the fluid effect associated with CO2 migration along the fault zone will generate considerable reflectivity contrasts and should result in good definition of the extent of the CO2 plume even in such structurally confined settings.