Optimized Grids for Accurately Representing Geology in Geomechanical Simulations
- Emmanuel Gringarten (Paradigm) | Jean Daniel Lecuyer (Dassault Systèmes) | Elsa Villarubias (Paradigm) | Camille Cosson (Paradigm) | Wan-Chiu Li (Paradigm)
- Document ID
- Society of Petroleum Engineers
- SPE Annual Technical Conference and Exhibition, 9-11 October, San Antonio, Texas, USA
- Publication Date
- Document Type
- Conference Paper
- 2017. Society of Petroleum Engineers
- 5.6 Formation Evaluation & Management, 5.1.2 Faults and Fracture Characterisation, 7.2 Risk Management and Decision-Making, 0.2 Wellbore Design, 1.6 Drilling Operations, 7.2.1 Risk, Uncertainty and Risk Assessment, 5.1.5 Geologic Modeling, 7 Management and Information, 0.2.2 Geomechanics, 5 Reservoir Desciption & Dynamics, 5.6.9 Production Forecasting
- geomechanics, unstructured grids, fault reactivation, reservoir modeling
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- 205 since 2007
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To reliably quantify changes in the in-situ stresses due to oilfield exploitation, it is necessary to start from a representative description of the subsurface and simulate both fluid movement and geomechanical effects. For this purpose, a new 3D "hybrid" grid is presented. This grid accurately honors geological features, with no unwarranted simplifications, while being ideally suited for geomechanical simulators and the new generation of flow simulators.
The new 3D Hybrid Grid is dominated by hexahedrons arranged in a structured manner except around faults, where it is made up of tetrahedrons. The grid is constructed from the underlying geological model and the sealed fault network. Both structured (hexahedrons) and unstructured (tetrahedrons) parts follow stratigraphic deposition information. For geomechanical simulations, each compartment is considered as an independent mesh part allowing sliding effects along the faults. At the interfaces between the hexahedrons and tetrahedrons in a fault block, shared nodes are used to ensure stress equilibrium and displacement continuity.
Uncertain states of stress and unforeseen changes in the integrity of the subsurface can have grave economic and environmental consequences. Understanding these helps mitigate development risks, and optimally develop the field. Today, geomechanical studies are not routinely performed and are often based on simplified descriptions of the subsurface. With this new Hybrid Grid, we propose to combine a reliable representation of subsurface with state-of-the art rock mechanics to assess how reservoirs respond to drilling, completion and production. Simplifications in either can lead to incorrect assessment of risks or production forecasts. The grid presented in this paper aims at honoring geology accurately while also being optimal for numerical computations. The zones of tetrahedrons enable the inclusions of even the most complex faulting systems, while the structured hexahedrons precisely follow the stratigraphy and are most efficient for geomechanical simulations.
The gridding technology presented enables a coherent representation of the subsurface for constructing geological models for simulating both flow and geomechanics. Although such meshing schemes exist for modeling manufactured objects, these are difficult to apply to geological formations; our approach now enables them by guiding the meshing using the chronostratigraphic parameterization of the subsurface. It will allow engineers to routinely include the effects of stress changes during production and will build confidence in development plans.
|File Size||2 MB||Number of Pages||13|
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