Overburden Fluid Migration along the Vette Fault Zone, North Sea, Using Different Fault Permeability Models

Abstract

Summary To qualify fault bonded traps for CO2 storage, risk assessment of both across- and along-fault fluid migration needs to be performed. Existing fault models focus on the across-fault sealing in the reservoir section, whereas the permeability up along the fault in the overburden is less well understood. In the current study two different methods assigning fault zone permeability from host rock properties are compared. The geocellular model consists of stochastically generated isotropic cells within the fault zone, whereas the smear models are characterized by permeability anisotropy with a lower across fault permeability due to clay smear and deformation bands, compared to along-fault. The two fault permeability models are included in a flow simulation for the Vette Fault Zone on the Horda Platform, Norway, to demonstrate the effect on flow rates in the overburden related to the fault. The brine flow rate above the fault zone is found to range from 5–95 kg/year per meter horizontal fault trace for the range of properties tested with only minor variation in flow rates between the two models. The results demonstrate limited potential for fluid transport along the overburden section of the Vette Fault Zone due to high clay content and limited fault width.