GEOSIM

GEOSIM® is a coupled reservoir, geomechanics, fracturing and reservoir damage software for the analysis of reservoir problems which include strong coupling between reservoir flow and formation stress, deformations, compaction or stress-dependent properties, or interactions with fractures resulting from stimulation treatments, waterflooding or waste injection. The system is currently capable of modeling both single well and full field problems.

GEOSIM was originally developed at SIMTECH Consulting Services in early 1990s and later at Duke Engineering & Services (DE&S). It is now owned, developed, used for studies and leased by TAURUS. New products that have been released since 2003 include the version using Eclipse® simulator as the reservoir module, version with treatment of formation damage for sea water and produced water injection, and a pseudo-continuum rock mechanical model suitable for coupling to a dual-permeability reservoir model for naturally fractured reservoirs.

Typically, the reservoir grid is a subset of the finite element stress grid, which will cover the overburden, flanks and possibly base rock. Each component has its own input and, correspondingly, the user can build the model input data in several parts pertaining to the reservoir model (Eclipse or TRS), the stress-strain model and its interface (FEM3D and GEOINT), the fracture interface (GEOFRAC) and the damage module. Depending on the problem solved, only the relevant parts of the system need to be used.

GEOSIM has been used extensively for full field compaction studies, fault reactivation studies, waterflood and waste injection studies, and geomechanical modeling of conventional and thermal fracturing for a variety of reservoirs throughout the world.

Stress Strain Model – FEM3D

Modeling of geomechanical response of the formation is performed by the GEOSIM module which consists of the stress analysis modules and the interface to TERASIM. The modular design allows optional stress codes to be utilized. Currently the principal module is the FEM3D code with the ENHANS 3 code as an option. FEM3D is a poroelastic and thermoelastic finite element code, which treats elasticity and plasticity. It also utilizes a Newton algorithm with variable stiffness scheme to handle general non-linear and elasto-plastic problems. Its features include:

• Choice of linear, hyperbolic, hypo-plastic, orthotropic or tabular constitutive model for linear or non-linear type material
• Elasto-plastic constitutive model with Mohr Coulomb or Drucker Prager shear failure criteria with nonlinear friction function, elliptical cap for compressive failure (compaction) with smooth transition to cone, non-associated plasticity on the cone with hardening and associated plasticity with hardening on the compaction cap
• Regionally dependent constitutive models
• Three methods of solving plasticity equations
• Brick e