Handling natural complexity in 3D geomechanical restoration, with application to the recent evolution of the outer fold-and-thrust belt, deepwater Niger Delta.

Pauline Durand-Riard and Chris A. Guzofski and Guillaume Caumon and Marc-Olivier Titeux. ( 2013 )
in: AAPG Bulletin, 97:1 (87-102)

Abstract

3D geomechanical restoration provides an accurate deformation history accounting for contrasts in rheologies in a model. Complex models including unconformities, thin or pinched-out layers have been successfully restored using implicitly de fined stratigraphic and erosive surfaces. However, the only suggested way of approaching flexural slip in restoration is to localize slip along some horizons. To take full advantage of the implicit approach while being able to account for flexural slip folding, we investigate the integration of new geomechanical properties in the 3D restoration. We consider the flexural slip folding as a result of the stacking of rigid layers interbedded with thin weak layers, for which the geomechanical properties can be upscaled to a transversely isotropic material. The restoration of a transversely isotropic anticline is compared to the results computed using isotropic properties and to a stack of rigid isotropic layers with non-frictional slip between the layers. This shows that the use of transversely isotropic properties reasonably approximates the fl exural slip folding. We then propose to demonstrate how new volumetric restoration tools can be used to understand the recent geologic evolution of a complex geological natural system located in the toe of the Niger Delta, West Africa. This 30x42 km system includes compressional structures such as a detachment fold, a forethrust fault-bend fold and a structural wedge formed in series. The structural history is recorded by growth stratigraphy and erosional surfaces that delimit the kinematics of deformation. In this system, 3D gradients of fault slip, vertical variations in mechanical strength, regional erosive surfaces, and variable lateral boundary conditions motivated the use of new techniques of 3D geomechanical restoration. The restoration of two growth units results in a better understanding of the structural evolution of the system, reinforcing the interpretation that the area is behaving as a deforming thrust sheet at critical taper, but also highlighting coeval activity on both the hinterland structures and the toe of the thrust belt.

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BibTeX Reference

@ARTICLE{,
    author = { Durand-Riard, Pauline and Guzofski, Chris A. and Caumon, Guillaume and Titeux, Marc-Olivier },
     title = { Handling natural complexity in 3D geomechanical restoration, with application to the recent evolution of the outer fold-and-thrust belt, deepwater Niger Delta. },
   journal = { AAPG Bulletin },
    volume = { 97 },
    number = { 1 },
      year = { 2013 },
     pages = { 87-102 },
       doi = { 10.1306/06121211136 },
  abstract = { 3D geomechanical restoration provides an accurate deformation history accounting for contrasts in rheologies in a model. Complex models including unconformities, thin or pinched-out layers have been successfully restored using implicitly defined stratigraphic and erosive surfaces. However, the only suggested way of approaching flexural slip in restoration is to localize slip along some horizons. To take full advantage of the implicit approach while being able to account for flexural slip folding, we investigate the integration of new geomechanical properties in the 3D restoration.
We consider the flexural slip folding as a result of the stacking of rigid layers interbedded with thin weak layers, for which the geomechanical properties can be upscaled to a transversely isotropic material. The restoration of a transversely isotropic anticline is compared to the results computed using isotropic properties and to a stack
of rigid isotropic layers with non-frictional slip between the layers. This shows that the use of transversely isotropic properties reasonably approximates the fl exural slip folding. We then propose to demonstrate how new volumetric restoration tools can be used to understand the recent geologic evolution of a complex geological natural system located in the toe of the Niger Delta, West Africa. This 30x42 km system includes compressional structures such as a detachment fold, a forethrust fault-bend fold and a structural wedge formed in series. The structural history is recorded by growth stratigraphy and erosional surfaces that delimit the kinematics of deformation. In this system, 3D gradients of fault slip, vertical variations in mechanical strength, regional erosive surfaces, and variable lateral boundary conditions motivated the use of new techniques of 3D geomechanical restoration. The restoration of two growth units results in a better understanding of the structural evolution of the system, reinforcing the interpretation that the area is behaving as a deforming thrust sheet at critical taper, but also highlighting coeval activity on both the hinterland
structures and the toe of the thrust belt. }
}