Chemo-poroplastic analysis of a borehole drilled in a naturally fractured chemically active formation

A coupled chemo-poroplastic model is developed to investigate the change in ion transfer and its effect on pore pressure and effective stresses in chemically active fractured media. The equivalent permeability tensors are calculated using the boundary element method for an arbitrary oriented fractur...

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Vydané v:International journal of rock mechanics and mining sciences (Oxford, England : 1997) Ročník 52; s. 82 - 91
Hlavní autori: Roshan, H., Fahad, M.
Médium: Journal Article
Jazyk:English
Vydavateľské údaje: Oxford Elsevier Ltd 01.06.2012
Elsevier
Predmet:
Applied sciences
Buildings. Public works
Chemically active rock
Computation methods. Tables. Charts
Density
Exact sciences and technology
Geotechnics
Mathematical analysis
Mathematical models
Naturally fractured shale
Osmotic flow
Plastic zones
Plasticity
Porosity
Soil investigations. Testing
Stress tensors
Stresses
Structural analysis. Stresses
Well drilling
Chemically active rock
Osmotic flow
Plasticity
Naturally fractured shale
Chemical analysis
Site analysis
Shale
Borehole
Osmosis
Permeability
Modeling
Stress distribution
Flow(fluid)
Formulation
Jointed rock
Numerical simulation
Porosity
Computing method
ISSN:1365-1609, 1873-4545
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Shrnutí:A coupled chemo-poroplastic model is developed to investigate the change in ion transfer and its effect on pore pressure and effective stresses in chemically active fractured media. The equivalent permeability tensors are calculated using the boundary element method for an arbitrary oriented fractured system, and used in the chemo-poroplastic model. An explicit modified Euler algorithm with substepping including a yield surface correction scheme is used to integrate the plastic stress–strain relation. Super-convergent patch recovery method is also used to accurately evaluate the time dependent nodal stress tensors from the stress tensors of gauss points. From the results of this study it was revealed that the pore pressure drops around the wellbore due to chemical osmotic back flow. The drop in pore pressure, however, becomes a function of fractures' orientation and density. The state of stresses reach the yield strength of the rock in fractured shale, thus forming a plastic zone around the wellbore. The relaxation of effective tangential stresses in the plastic zone, therefore, has a potential to cause stability problems. ► We modelled the chemo-poroplastic behaviour of a naturally fractured shale using FEM. ► We efficiently calculated permeability tensors for a shale fractured system using BEM. ► The change in solute transfer, pore pressure and stresses were analysed. ► Solute transfer and pore pressure were significantly altered in presence of fractures. ► The plastic deformation occurred in fractured shale but not in homogeneous shale.
Bibliografia:ObjectType-Article-1
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ISSN:1365-1609
1873-4545
DOI:10.1016/j.ijrmms.2012.03.004