Modeling Flow in the Fault Zone Using Local Grid Refinement

1
Modeling Flow in the Fault Zone Using Local Grid
Refinement

• Erlend Øian
• with
• I. Garrido, M. S. Espedal,
• G. E. Fladmark

20th SUPRI-B Industrial Affiliates Meeting, May
5-6, 2003
2
Introduction

• Fault outcrop, Kilve, England

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Overview

• Geological data
• Conceptual fault zone model
• Numerical laboratory
• 3D, multiphase flow simulator ATHENE
• Domain decomposition based local grid refinement
• Parallel version
• Ongoing work
• Develop accurate FD models for the fault zone
• Comparison with discrete fracture models

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Fault zone - conceptual model

• Fault core
• Modeled as porous medium
• Heterogeneous
• Damage zone
• Fracture sets

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Mathematical model

• Modified basin model
• Compositional or black-oil formulation
• Primary variables
• Temperature
• Water pressure
• Molar mass of each component
• Constitutive relations

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Numerical formulation

• Control volume finite difference scheme
• Two-point flux
• Multi-point flux
• Sequential solution procedure

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ATHENE simulator

• Implemented in C
• Main modules
• TimeStepping
• Basin
• Geometry
• Matrix/vector and iterative methods
• SparseLib, MV, IML

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Domain decomposition

• Underlying coarse grid
• Defined based on large-scale geological features
• Final composite grid
• Selected coarse domains are refined

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Parallelization

• Parallelization on sub-domain simulator level
• MPI for communication

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Parallel communication
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Portability

• Simulator runs on several platforms
• IBM p690 Regatta
• HP
• SGI Origin
• Linux clusters

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Example

• Permeable bed with faults
• Faulted blocks are locally refined
• Solved in parallel on SGI 2000
• Scales almost linearly

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Fault core example - permeability
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Fault core example flow results

• Oil saturation

• Gas saturation

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Fault core example flow results

• Oil saturation

• Gas saturation

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Fault core example - parallelization

• Load balancing needs further development

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Damage zone - scales

• Fracture sets can be identified
• length (size)
• orientation
• fracture density
• Hierarchy of scales

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Finite difference modeling issues

• Gridding
• Applicability of Cartesian models
• Techniques for capturing coupling between scales
• Partial upscaling

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Damage zone - flow calculations

• Ongoing work
• Compare results with discrete fracture network
  models
• Karimi-Fard et al. (2003)

ATHENE result
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Summary

• Continuing development of parallel compositional
  simulator with domain decomposition
• Demonstrated reasonable level of parallel
  efficiency
• Currently benchmarking against discrete fracture
  model

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Future directions

• Complete benchmarking study
• Assess applicability of finite difference model
  for complex fault zones
• Large-scale simulations
• Load balancing
• Solvers
• Upscaling