Outcrop-based reservoir modeling of a naturally fractured siliciclastic CO2 sequestration site, Svalbard, Arctic Norway

We present a geological model of an unconventional siliciclastic reservoir projected for CO2 sequestration near Longyearbyen, Svalbard. The reservoir is characterized by a substantial sub-hydrostatic pressure regime, very low matrix porosity and -permeability values, extensive natural fracturing and the presence of igneous dykes and sills. Due to the poor reservoir properties of the matrix, flow in the reservoir is largely governed by fracture properties. Input data to the model includes four boreholes, partly or completely penetrating the reservoir section, offshore and onshore 2D seismic profiles and structural and sedimentological data collected from nearby outcrops of the target formation. Combined, these datasets provide firm modeling constraints with respect to the regional geometry, sedimentology and fracture patterns. Previous work has shown that the observed fractures can be grouped into five distinct lithostructural units (LSUs), each exhibiting a characteristic set of properties (fracture density, orientation etc.). The spatial distribution of these LSUs is incorporated into the model. Initial first-order water injection tests using a commercial streamline simulator validate the applicability of this model for further fluid injection tests, including the long-term monitoring of injected CO2.