Vector Field Based Fault Modelling and Stratigraphic Horizons Deformation

Abstract

Abstract Consequent choices during hydrocarbon exploration and field developement depend on 3D numerical models of the main geological interfaces and the major faults in the area of interest. Such structural models provide decisive informations like reservoir rock volume or compartmentalization, and are unavoidable stages to build the reservoir grids used for resources estimation, flow simulations and well planning. However, these models need to be continually modified, either to integrate new information from well drilling and production history or to consider several hypotheses about the most uncertain features of the fault network. To do so, petroleum engineers involved in reservoir modeling need flexible and efficient tools to easily edit parts of structural models while preserving their general consistency. In a first step to handle structural model edition challenges, we propose a new way to numerically model a fault object and deform previously modelled stratigraphic horizons. This method is inspired by the "Vector Field based Shape Deformations" (VFSD ) techniques used by the Computer Graphics community. Our approach considers a fault as a 3D vector field, interpolated thanks to several scalar fields linked to the fault geometry and few scattered data points if available. This vector field is then integrated into path lines able to drive the deformation of the surrounding objects in a purely geometrical manner. The so-obtained deformation is limited to an influence region neighboring the fault and can affect several horizons simultaneously in a consistent and reversible way. Moreover, self-intersections can be prevented and both the first order smoothness and the fine-scale features of the deformed horizons are conserved. The vector field interpolation methodology we present is based on a user-defined conceptual model for deformation attenuation and a direction constraint on the displacement. It was implemented in common geomodelling software. The resulting tool is applicable on a wide range of fault geometries, and can be added as a new exit condition for fault network stochastic simulation algorithms. Last, some derived applications, related to salt diapir modelling or paleotopography restoration, are also conceivable.