Simulating seismic chimney structures as potential vertical migration pathways for CO2 in the Snøhvit area, SW Barents Sea: model challenges and outcomes

Abstract

Carbon Capture and Storage (CCS) activities at the Snøhvit field, Barents Sea, will involve carrying out an analysis to determine which parameters affect the migration process of CO2 from the gas reservoir, to what degree they do so and how sensitive these parameters are to any changes. This analysis will aim to evaluate the effects of applying a broad but realistic range of reservoir, fault and gas chimney properties on potential CO2 leakage at various depths throughout the subsurface. Fluid flow might take place through parts of or the entire extent of the overburden. One of the aims of the analysis is assessing the potential of CO2 reaching the seabed. Using the Snøhvit gas reservoir and overburden in the Barents Sea, a series of geological models were built using seismic and well-log data. We then performed numerical simulations of CO2 migration in focused fluid flow structures. Identification of potential migration pathways and their extent, such as gas chimneys and faults, and their incorporation into these models and simulations will provide a realistic insight into the migration potential of CO2. In the simulations the CO2 is injected over a 20 year period at a rate of 0.7 Mt/year and migration is allowed to take place over a 2000 year time frame for domains of approximately 21 Km 2 for the caprock fault models, 24 Km 2 for the realistic gas chimney models and 35 Km 2 for the generic gas chimney models, in a layered sedimentary succession. The total mass of CO2 injected in the reservoir during the 20-year injection period is 14 Mt. There is a strong interaction between the various parameters but the parameter that had the most influence on the CO2 migration process was probably the permeability of the reservoirs, especially the average permeability (k). Also, for the faulted caprock scenarios, it should be noted that at near surface depths the permeability of 765 mD is already adequate for a good CO2 flow. At the chimney top level (600 m) however, a further increase in permeability has an additional effect on improving CO2 flow. Overall, considering the slow upward migration velocity of the plume, this geological setup can be regarded as a suitable storage site.

Role of Faults in Hydrocarbon Leakage in the Hammerfest Basin, SW Barents Sea: Insights from Seismic Data and Numerical Modelling

“…The leakage along the fault planes has been previously reported as main link between deep thermogenic reservoirs and the shallow subsurface [13,17,32,33]. In this study, we have shown that the intrinsic fault properties (capillary entry pressure and permeability) play a major role in hydrocarbon leakage from reservoirs during deglaciations.…”

“…With this approach, we aim to reveal the impact of Pliocene-Pleistocene glaciations on hydrocarbon remigration and leakage from the Snøhvit and Albatross fields, which could serve as the analogue for de-risking of petroleum prospects in the Barents Sea. The results will also have implications for CO 2 capture and storage efforts and associated risks at Snøhvit field [8,32]. …”

“…Past petroleum system modelling studies were coarse and first focused on the implementation of glacial cycles in 2D [10], followed by a 3D PSM study at a 2 km × 2 km scale grid resolution, where petroleum leakage was addressed explicitly by capillary leakage though seal failure. Moreover, recent studies of the Barents Sea revealed that the key regional faults (Figures 1 and 3) in the Hammerfest Basin, namely NS, SW-NE and NW-SE faults [13,17], play a key role in petroleum migration from deeper Jurassic reservoirs ( Figures 3 and 4) to the shallow stratigraphy and up to the seabed [16,17,30], resulting in pockmarks (Figures 4 and 5), inferred gas hydrates [30,31], amplitude anomalies, gas chimneys ( Figures 3 and 4) and shallow gas accumulations [16,30,32,33]. Evidence of condensate type light hydrocarbons charging the seabed sediments also indicate a deep origin of the fluids and present-day microseepage [34].…”

Modelling of CO2 storage in geological formations with DuMux, a free-open-source numerical framework. A possible tool to assess geological storage of carbon dioxide in Romania

“…Walter et al [33] provides estimates of the risk of brine discharge into freshwater aquifers due to CO2 injection into geological formations. Key parameters influencing the CO2 migration process from the gas reservoir in the Snøvit area, Barents Sea were determined by means of numerical modelling with DuMu x [34]. The authors identify potential migration pathways and their extent, i.e., faults, gas chimneys in an off-shore mostly sandy reservoir located in the Tubåen Formation (at 2560-2670 m below sea surface).…”

Coupled Basin and Hydro-Mechanical Modeling of Gas Chimney Formation: The SW Barents Sea

“…The numerical modeling of the gas leakage and chimney forming mechanisms is very challenging. Tasianas et al [20] modeled the gas leakage along pre-existing conducting geological structures on the reservoir scale. They considered the flow along three types of structures preliminary set up in the model: faults, fracture network penetrating the reservoir's caprock, and high permeable fluid conduits.…”