Advances in 3D implicit modeling of complex faulted geological structures.

Laurent Souche and François Lepage and Gulnara Iskenova. ( 2013 )
in: Proc. 33rd Gocad Meeting, Nancy

Abstract

In the frame of 3D structural modeling, approaches based on the interpolation of one or several implicit functions recently emerged to overcome the limitations associated with traditional surfacebased techniques when dealing with complex faulted reservoirs. Techniques based on implicit function formulation efficiently minimize the variations of dip and thickness of the created geological layers while ensuring that all seismic and well data are properly honored. They also tend to preserve the consistency of the stratigraphic pile throughout the model, by preventing conformable surfaces to cross each-other. Finally, the use of a topologically discontinuous support, such as a faulted tetrahedral mesh, for interpolating the implicit function(s) makes it possible to account for complex fault networks. Moreover, additional constraints can easily be defined to honor e.g. dip or fault displacement data. There are, however, several drawbacks associated with the use of implicit methods for the modeling of stratigraphically and structurally complex reservoirs. For example, proper control of the interpolation of the implicit function in presence of large variations of layer thicknesses and correct management of the activity of faults vs. deposition in presence of unconformities are difficult to achieve. Rapid areal and vertical variations of the thickness of geological layers may indeed introduce a conflict between the constraints controlling the fit to interpretation data and those ensuring the smoothness of the interpolated implicit function. This can result into non-monotonic implicit functions, and therefore into artifacts in extracted horizon surfaces. Similarly, accurate control of the portion of the stratigraphic pile which should be affected by – or erode – a set of faults cannot be achieved when using a single, invariant support (e.g. a faulted unstructured mesh) for interpolating all the stratigraphic sequences. After briefly reviewing the various steps of a typical implicit modeling workflow, this paper describes algorithmic and numerical improvements over traditional techniques for creating, reliably and automatically, detailed 3D structural models in presence of large thickness variations, independently from the complexity of the tectonic and depositional history. Various aspects of implicit structural modeling are addressed: interpolation constraints, regularization terms and topological editions of the interpolation support. These improvements are demonstrated using real and synthetic interpretation data and compared with results obtained by traditional implicit modeling techniques.

Download / Links

BibTeX Reference

@INPROCEEDINGS{SoucheGM2013,
    author = { Souche, Laurent and Lepage, François and Iskenova, Gulnara },
     title = { Advances in 3D implicit modeling of complex faulted geological structures. },
 booktitle = { Proc. 33rd Gocad Meeting, Nancy },
      year = { 2013 },
  abstract = { In the frame of 3D structural modeling, approaches based on the interpolation of one or several implicit functions recently emerged to overcome the limitations associated with traditional surfacebased techniques when dealing with complex faulted reservoirs. Techniques based on implicit function formulation efficiently minimize the variations of dip and thickness of the created geological layers while ensuring that all seismic and well data are properly honored. They also tend to preserve the consistency of the stratigraphic pile throughout the model, by preventing conformable surfaces to cross each-other. Finally, the use of a topologically discontinuous support, such as a faulted tetrahedral mesh, for interpolating the implicit function(s) makes it possible to account for complex fault networks. Moreover, additional constraints can easily be defined to honor e.g. dip or fault displacement data.
There are, however, several drawbacks associated with the use of implicit methods for the modeling of stratigraphically and structurally complex reservoirs. For example, proper control of the interpolation of the implicit function in presence of large variations of layer thicknesses and correct management of the activity of faults vs. deposition in presence of unconformities are difficult to achieve. Rapid areal and vertical variations of the thickness of geological layers may indeed introduce a conflict between the constraints controlling the fit to interpretation data and those ensuring the smoothness of the interpolated implicit function. This can result into non-monotonic implicit functions, and therefore into artifacts in extracted horizon surfaces. Similarly, accurate control of the portion of the stratigraphic pile which should be affected by – or erode – a set of faults cannot be achieved when using a single, invariant support (e.g. a faulted unstructured mesh) for interpolating all the stratigraphic sequences.
After briefly reviewing the various steps of a typical implicit modeling workflow, this paper describes algorithmic and numerical improvements over traditional techniques for creating, reliably and automatically, detailed 3D structural models in presence of large thickness variations, independently from the complexity of the tectonic and depositional history. Various aspects of implicit structural modeling are addressed: interpolation constraints, regularization terms and topological editions of the interpolation support. These improvements are demonstrated using real and synthetic interpretation data and compared with results obtained by traditional implicit modeling techniques. }
}