Finite Element Heat and Mass Transfer Code (FEHM)

A Versatile Tool for Simulating Groundwater and Contaminant Flow in Diverse Environments

FEHM supports a range of projects including CO2 sequestration, environmental remediation, and nuclear waste isolation.

FEHM models groundwater and contaminant flow in both deep and shallow, fractured and unfractured porous media. Created in the 1970s for geothermal and hot dry rock reservoir simulations, it has expanded to study flow and mass transport in saturated and unsaturated zones, including the Yucca Mountain nuclear waste repository. Today, FEHM supports U.S. Department of Energy projects such as environmental remediation at the Nevada Test Site, groundwater protection, CO2 sequestration, Enhanced Geothermal Systems, oil and gas production, nuclear waste isolation, and Arctic permafrost studies.

FEHM can model a wide range of subsurface physics, from single-phase fluid flow for large-scale groundwater aquifers to complex multi-phase fluid dynamics with phase changes like boiling and condensing. This versatility enables FEHM to simulate the unsaturated zones around nuclear waste storage or the leakage of CO2 or brine through faults and wellbores. The primary numerical approach used in FEHM is the control volume (CV) method, which ensures exact conservation of mass and energy in fluid flow and heat transfer equations. For more precise stress calculations, the finite element (FE) method is an option, particularly for displacement equations. FEHM also offers flexibility in choosing methods, with options for finite element and a simple finite difference scheme to meet the demands of specific simulation scenarios.

Capabilities

3-dimensional complex geometries with unstructured grids
Saturated and unsaturated media
Simulation of production from gas hydrate reservoirs
Simulation of geothermal reservoirs
Non-isothermal, multi-phase flow of gas, water, oil
Non-isothermal, multi-phase flow of air, water
Non-isothermal, multi-phase flow of CO2, water
Multiple chemically reactive and sorbing tracers
Preconditioned conjugate gradient solution of coupled linear equations
Fully implicit, fully coupled Newton Raphson solution of nonlinear equations
Double porosity and double porosity/double permeability capabilities
Control volume (CV) and finite element method (FE) methods
Coupled geomechanics (THM) problems (fluid flow and heat transfer coupled with stress/deformation) including non-linear elastic and plastic deformation, nonlinear functional dependence of rock properties (e.g. permeability, porosity, Young's modulus) on pressure, temperature and damage/stress