Johansen Formation: VE Model Versus 3D Simulation
In this example, we compare the accuracy of a VE simulation to a series of 3D simulations with increasing vertical resolution.

The Johansen formation is a deep saline aquifer in the North Sea, which is considered for storage of CO2 in a future pilot project for CCS at Mongstad, Norway. Here we compare simulations of a 2D cut of the Johansen formation using a 3D simulator with different vertical grid resolutions to a simulation with a vertical equilibrium model. The focus is on the post-injection dynamics, or equivalent, the behavior of the plume far from the injector.

Simulation setup:

  • vertical slice from the Johansen formation,  vertical resolutions in 3D simulator: 5 (original), 10 and 20 cells
  • initial plume: placed in stratigraphic trapping region with an identified spillpoint (right figure)
  • simulation time: 2000 years
  • simplifications: no residual trapping, simple relative permeability, no-flow conditions on all edges
  • permeability/porosity: 200 mD/20 %

The plots in the figure below compare the three 3D simulations with a VE simulation, to which the 3D simulations seem to converge.



Initial CO2 saturation distribution for the 3D simulation with 20 vertical cells.

The CO2 distribution after 2000 years of simulation computed with the full two-phase simulator for different z-resolutions (nz=5, 10, 20) compared with a simulation based on vertical equilibrium model (far right). A rather fine z-resolution is needed to get accurate results for the 3D simulator.

Published February 1, 2016