New technologies and work ow for routine reservoir-scale geomechanical risk assessment in structurally and mechanically complex reservoirs

Camille Cosson and Jean-Daniel Lecuyer and Olivier Grosse and Romain Merland and Cedric Borgese and Zady Ouraga and Mélanie Morin and VILLARUBIAS Elsa and Emmanuel Gringarten and HAOUESSE Mahamed Aymen. ( 2018 )
in: 2018 Ring Meeting, ASGA

Abstract

Making a reliable assessment of geomechanical risk throughout reservoir lifecycle to plan field development and production with confidence is still challenging in the Oil and Gas industry. 1D or 2D models are used but often, they provide only a limited understanding of the 3D stress distribution in the subsurface. The need for 3D geomechanical models is an industry statement but current commercial software limitations prevent from fully integrating the key complexities required to accurately model reservoir geomechanical response to field production. Indeed, generating an optimized mesh for Finite Element simulations capturing geology ranges from hardly practicable for simple reservoir framework, to unpracticable, for more complex structures using classical structured meshing methods. Therefore, models currently used for geomechanical risk assessment are derived from simplified geological frameworks and do not relate anymore to static and flow simulation models. Most of the advanced meshing capabilities available on the market are usually disconnected from commercial modeling solutions and simulators. Thus, generating and simulating an advanced geomechanical model is time-consuming and painful. To overcome those O&G industry difficulties, we have developed a universal solution for easily assessing reservoir geomechanical risks in reservoirs while preserving the geological integrity. The geological framework and the associated mesh for geomechanical simulations is created within a commercial geomodeling solution widely used in the industry. The mesh is directly derived from the underlying geological framework including a sealed fault network. It takes the form of a 3D Hybrid Grid composed of structured and unstructured elements honouring stratigraphic deposition information. All petrophysical property needed for the mechanical computation can be directly modeled in the Hybrid Grid conformably with chronostratigraphy. The 3D grid is also optimized for simulation with next-generation flow simulators, avoiding approximations related to property scaling. Then the mechanical grid is exported from the geomodeler to a numerical solver. This approach allows us to combine a reliable representation of the subsurface with state-of-the art rock mechanics. The process automation for the construction of the geomechanical model and transfer to the simulator enables a fast and efficient workflow from geology to geomechanical simulation. In this paper, we will present an application of this approach to a North Sea case study. The reservoir is economic with hydrocarbons trapped inside stacked anticlinal sandy layers sealed by clay cap rocks. The overlying formations include chalk and the whole stratigraphic column is cut and offset by several faults resulting in a complex structural framework which could not be preserved with usual geomechanical modeling solutions. We will demonstrate that the solution presented in the article enables creating efficiently a reliable geomechanical model and assessing mechanical risks through production, focusing on risks related to fault reactivation.

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BibTeX Reference

@INPROCEEDINGS{,
    author = { Cosson, Camille and Lecuyer, Jean-Daniel and Grosse, Olivier and Merland, Romain and Borgese, Cedric and Ouraga, Zady and Morin, Mélanie and Elsa, VILLARUBIAS and Gringarten, Emmanuel and Aymen, HAOUESSE Mahamed },
     title = { New technologies and work ow for routine reservoir-scale geomechanical risk assessment in structurally and mechanically complex reservoirs },
 booktitle = { 2018 Ring Meeting },
      year = { 2018 },
 publisher = { ASGA },
  abstract = { Making a reliable assessment of geomechanical risk throughout reservoir lifecycle to plan field development and production with confidence is still challenging in the Oil and Gas industry. 1D or 2D models are used but often, they provide only a limited understanding of the 3D stress distribution in the subsurface. The need for 3D geomechanical models is an industry statement but current commercial software limitations prevent from fully integrating the key complexities required to accurately model reservoir geomechanical response to field production.

Indeed, generating an optimized mesh for Finite Element simulations capturing geology ranges from hardly practicable for simple reservoir framework, to unpracticable, for more complex structures using classical structured meshing methods. Therefore, models currently used for geomechanical risk assessment are derived from simplified geological frameworks and do not relate anymore to static and flow simulation models.

Most of the advanced meshing capabilities available on the market are usually disconnected from commercial modeling solutions and simulators. Thus, generating and simulating an advanced geomechanical model is time-consuming and painful.

To overcome those O&G industry difficulties, we have developed a universal solution for easily assessing reservoir geomechanical risks in reservoirs while preserving the geological integrity. The geological framework and the associated mesh for geomechanical simulations is created within a commercial geomodeling solution widely used in the industry. The mesh is directly derived from the underlying geological framework including a sealed fault network. It takes the form of a 3D Hybrid Grid composed of structured and unstructured elements honouring stratigraphic deposition information. All petrophysical property needed for the mechanical computation can be directly modeled in the Hybrid Grid conformably with chronostratigraphy. The 3D grid is also optimized for simulation with next-generation flow simulators, avoiding approximations related to property scaling. Then the mechanical grid is exported from the geomodeler to a numerical solver. This approach allows us to combine a reliable representation of the subsurface with state-of-the art rock mechanics. The process automation for the construction of the geomechanical model and transfer to the simulator enables a fast and efficient workflow from geology to geomechanical simulation.

In this paper, we will present an application of this approach to a North Sea case study. The reservoir is economic with hydrocarbons trapped inside stacked anticlinal sandy layers sealed by clay cap rocks. The overlying formations include chalk and the whole stratigraphic column is cut and offset by several faults resulting in a complex structural framework which could not be preserved with usual geomechanical modeling solutions. We will demonstrate that the solution presented in the article enables creating efficiently a reliable geomechanical model and assessing mechanical risks through production, focusing on risks related to fault reactivation. }
}