Innovative stochastic probability distribution of fault permeabilities in 3D geo-pressure modelling

Understanding the sealing capabilities of faults provide vital information for underground carbon dioxide storage to hydrocarbon exploration and production. The sealing properties of faults are dependent on several parameters controlled by lithologies, overlap, throw, fault width, burial history, thermal regime and diagenesis in the sedimentary basin. All these input parameters hold large uncertainties, and different processes will influence the fault permeabilities.

In this work we are using a Monte-Carlo approach, varying the input parameters with a certain distribution, and simulate the fault permeabilities for a North Sea case study. The 3D simulated mean geo-pressures are compared with measured overpressures in sandstone units from wells. To carry out the 3D simulation, the in-house Pressim2.0 software has been used to simulate pressure generation and dissipation over geological time scale. The fluid flow dynamics can be represented and described by pressure compartments laterally delineated by mapped faults from seismic. Lateral flow is modelled between the reservoir units and the vertical fluid flow in the overburden is modelled below, in between and above the reservoir units. Depth-converted maps of the overlying sediments are used to reconstruct the burial history that is adjusted for decompaction.

In this work we will present stochastic probability distribution of key input parameters defining the fault permeability and transmissibility for a study area. The simulated fault permeabilities will be compared with published data. We will also use misfit analysis, to evaluate what fault permeabilities that will be give the lowest misfit/deviation compared to measured overpressures from wells.