Fault Displacement Modelling Using 3D Vector Fields

In history matching and sensitivity analysis it is useful to study the effect of changing the position of horizons near faults and the resulting facies juxtaposition due to change in fault displacements. A new algorithm for calculating a 3D displacement field is developed. This is applicable to a wide range of faults due to a flexible representation and gives the possibility to apply this field to change the displacement and thereby moving horizons. The fault is represented as a surface in a local coordinate system defined by a centre point, dip and strike angles. The displacement of points associated with the fault outside the fault surface is described by a 3D vector field. The displacement on the fault surface can be found from the intersection lines between horizons and the fault surface (fault lines). Away from the fault surface the displacement field is defined by a monotonic decreasing function. The displacement for the fault can be changed by a user-defined factor. Then the whole displacement field is changed and points on horizons around the fault are moved by applying the modified displacement field. The interaction between faults influencing the same points are taken care of by truncation rules.