Seismic-derived geomechanical properties of potential CO₂ storage reservoir and cap rock in Smeaheia area, northern North Sea

Abstract

Geologic CO2 storage site selection requires reservoir, seal, and overburden investigation to prevent injection- and storage-related risks. Three-dimensional geomechanical modeling and flow simulation are crucial to evaluate these mechanical-failure-related consequences; however, the model input parameters are limited and challenging to estimate. This study focuses on geomechanical properties extracted from seismic-derived elastic property cubes. The studied reservoirs (Middle Jurassic Sognefjord, Fensfjord, and Krossfjord formation sandstones) and cap rocks (Heather and Draupne formation shales) are located in the Smeaheia area, northern North Sea, and are evaluated for a potential CO2 storage site. From the elastic property cubes, i.e., acoustic impedance, P- to S-wave velocity ratio, and bulk density, we obtained geomechanical property cubes of Young's modulus, Poisson's ratio, shear modulus, lambda-rho, and mu-rho. Petrophysical property cubes such as porosity and shale volume were also available and were extracted from the elastic property cubes using deterministic methods. We evaluated the geomechanical properties to observe their relationship with depth, compaction/cementation, and petrophysical properties to characterize the cap and reservoir rocks. We found good coherence between the geomechanical and petrophysical properties and their relationship with compaction as a function of depth. The brittleness analyses using elastic property crossplots reveal that both the cap and reservoir rocks are mainly ductile to less ductile, posing lower fracturing risk during CO2 injection. This also indicates lower risks of associated microseismic and possible CO2 leakage.

Structural traps and seals for expanding CO2 storage in the northern Horda platform, North Sea

“…While the results associated to trap and seal presence within the northern Horda Platform assessed herein were favorable, several other factors should also be considered with respect to CO2 containment. For instance, we did not undertake an in situ or induced mechanical top seal failure, however, no pervasive fracturing has been reported within the Lower and Upper Jurassic top seal intervals to date, and recent petrophysical and geophysical studies suggest that both possess adequate seal integrity (e.g., Rahman et al, 2020;Fawad et al, 2021b). Another important derisking measure is to evaluate the reactivation potential for preexisting faults, as this can generally lead to the breach of potential seals (e.g., Jones and Hillis, 2003;Lyon et al, 2005;Osmond and Meckel, 2020).…”

Influence of Depositional and Diagenetic Processes on Caprock Properties of CO2 Storage Sites in the Northern North Sea, Offshore Norway

“…A detailed, pre-stacked, seismic-inverted, property-based analysis was carried out in the Aurora injection site (mainly focusing on the proposed injection well location). The pre-stacked seismic inversion was carried out using an algorithm based on three modified Fatti et al [53] reflectivity terms [54][55][56]. The pre-stacked simultaneous inversion method assisted in generating P-impedance (AI), S-impedance (SI), and density (ρ) cubes.…”

Impact of Fluid Distribution and Petrophysics on Geophysical Signatures of CO2 Storage Sandstone Reservoirs

“…More recently, the Norwegian government, in partnership with oil and gas industry, has committed to large‐scale CO 2 sequestration in the Norwegian Continental Shelf (Global‐CCS‐Institute, 2021). Promising sites have been identified in Smeaheia (Fawad et al., 2021) and Aurora (Aker et al., 2021) areas, with high‐quality sandstone reservoirs with a certain degree of heterogeneity (i.e., variable clay content and porosity).…”