Modelling of stochastic faults and fault networks in a structural uncertainty study

Abstract

Modelling faults from seismic data for a 3D depth model is a difficult task because of the multiple sources of uncertainty. The uncertainty may be attributed to migration velocities, picking of faults and organization of the fault network in 3D. Faults are generally not migrated from time to depth domain like horizons are, but modelled in the depth domain from the depth migrated horizons. For this reason, a new data structure has been designed that is targeted for fault modelling. Taking uncertainties into account, this structure allows for rapid modelling of faults from depth migrated horizons. The input data and the parameterization of the new data structure will be described. Following this, a way to incorporate uncertainties during the interpretation process is proposed and a description of different stochastic methods used to compute new shapes and locations inside a given uncertainty volume will be made. Finally, the method and the results obtained will be described while studying uncertainties on more complex fault networks. The influence of fault uncertainties on the reservoir volumetric estimates will be shown as one possible result of the simulation process.

Fault displacement modelling using 3D vector fields

“…Caumon et al [4] use a set of techniques to model structural uncertainty by perturbing stochastically the geometry of a reference structural interpretation. This extends the work presented in Lecour et al [11] where stochastic modelling of fault locations in reservoir grids is used to perform sensitivity studies on volume calculations in the 3D earth model. Thore et al [19] underline the importance of assessing the sources of uncertainty in the structural modelling and show how this has impact on gross rock-volume calculations, well planning, flow simulation and history matching.…”

“…The joint effect from faults close to each other is taken care of by truncation rules applied on the fault operator defined from the displacement fields. Caumon et al [4], Lecour et al [11] and Holden et al [9] focus on stochastic perturbation of fault geometries and fault throw, but in a history matching workflow a deterministic way of perturbing the fault geometry and throw is desired. Effects of changing fault throw on reservoir flow can implicitly be represented by changing the throw used in the fault seal calculations as shown by Manzocchi et al [13], however, an explicit change of fault throw is needed for volume calculations and for well planning.…”

Dynamic data integration for structural modeling: model screening approach using a distance-based model parameterization

“…The method is designed to perturb the position of horizons and faults from the "best" structural model obtained by expert's interpretation, accounting for uncertainties from different sources. Lecour et al [2] applied this method to complex fault network modeling, focusing only on the uncertainty resulting from interpretation. Similar applications are also found in Samson et al [3], Corre et al [4], Charles et al [5], and Holden et al [6].…”

Stochastic simulations of fault networks in 3D structural modeling

“…In explicit modeling, geological interfaces are represented as polygonal surfaces. Lecour et al [16] propose to modify the geometry of a surface by perturbing its nodes along an uncertainty bar defined at each node. The perturbation is correlated along the surface using the probability field method [17], in order to obtain realistic geometries.…”

“…For a whole model, each surface is perturbed according to its structural uncertainties and all connections (horizon to horizon, horizon to fault and fault to fault) are stored. Once all geological objects have been perturbed, connections are honored so that the topology is preserved [16]. In practice, this raises a number of challenges to maintain model consistency in the case of large uncertainties, for interferences between surfaces and large mesh distorsions may occur.…”