Approaches to Local Grid Refinement in TOUGH2 Models

Abstract

In many applications, local refinement of a TOUGH2 model grid is needed where smaller-scale details of the model behaviour must be resolved- for example, around production areas (or even individual wells) in a geothermal field. Because of its flexibility, TOUGH2 makes a range of approaches to local grid refinement possible. TOUGH2’s numerical formulation does implicitly require that the connection faces between grid blocks are orthogonal to the lines joining the block centres. However, not all approaches to local grid refinement satisfy this requirement. This paper surveys the available approaches to horizontal local grid refinement of TOUGH2 models, considering the merits and disadvantages of each with reference to model performance on a test problem. A new approach is also introduced, incorporating a non-linear optimization technique for ensuring maximum compliance with TOUGH2’s orthogonality requirement.