Geomechanical Analysis Key Features
Contents
Geomechanical Analysis
Key features and applications
The geomechanical code in ParaGeo is available in both explicit and implicit algorithms and may be applied to a wide range of geomechanical applications such as forward field-scale geological simulations over geological time frames, field-scale present day stress analyses, reservoir production modelling, wellbore stability analysis, cap rock integrity, slope stability, tunnelling and excavation analysis, geotechnical engineering, micro-mechanics, etc. You will be able to predict stress and strain distribution and magnitudes, deformations, strength, stiffness, failure and stability, etc. In pure geomechanical analysis, pore pressure and temperature distributions may be spatially prescribed. For field scale geological problems there is an option to perform a drained analysis with hydrostatic pore pressures with automatic computation of the vertical effective stress based on the integration of the effective density.
Some ParaGeo key features relative to the geomechanical field include:
•Material properties that evolve with compaction and damage over geological time frames
•Wide range of plasticity models that can capture the ductile and brittle behaviour of different rock types as well as creep and viscoplasticity
•Modelling of the diagenetic overprint on sediment properties
•Model the frictional properties of faults with the available contact models
•Gradual model initialization with several stages including recovery of the displacement resulting from initialization
•Assignment of material property dependencies on other properties
•Embedded fracture modelling for dense sets of fractures
•Geomechanical restoration modelling
Material models
Most geomechanical applications require non-linear material models in order to capture the constitutive response of the rocks involved. The material models available in ParaGeo for the mechanical field encompass:
Elasticity•Isotropic •Transverse isotropic •Orthotropic •Temperature dependent properties
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Poroelasticity•Cam-Clay poroelasticity •Stress and porosity dependent poroelasticity |
Plasticity•Pressure dependent Soft Rock 4 model (SR4) •Pressure dependent Soft Rock 3 model (SR3) •Isotropic Modified Cam-Clay model •Drucker-Prager •Rotating Crack •von Mises •Hill anisotropy •Maximum Tension model
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Viscoplasticity•Herschel-Bulkley •Temperature-dependent Herschel-Bulkley •Steady-state creep law (modified from Munson-Dawson model) |
Diagenesis•Exponential or Power law thermally controlled kinetic reaction model •Enhanced strength compaction model •Enhanced strength, hardening and stiffness compaction model •Cementation model |
Continuum Fracture•No compliant fracture •Elastic fracture •Bandis model •Mohr Coulomb shear strength model |
Contact mechanics and embedded fractures
Geoscientists often model faults and fractures following a discrete approach by using contact mechanics. In ParaGeo several contact models are available for the directions normal and tangential to the contact surface. Frictional properties of the faults can be modelled with the Mohr-Coulomb model, account for its cohesion or simply enable slip based on a maximum stress criteria for example. In addition you may chose to use constant contact properties or properties which vary with depth, with contact penetration distance and with time. For coupled simulations you may define contact fluid flow and contact thermal properties so that temperature transfer between fault planes and flow along and across faults can be modelled.
Some geologic systems may contain a dense set of fractures which may be impractical to model it via contact mechanics. ParaGeo also includes a continuum fracture approach by which several fracture sets with different orientations and properties may be assigned at material level. You can simulate the effect of fractures in the system in terms of the geomechanical response and also in terms of permeability enhancement and preferential flow pathways for coupled simulations.