Innovative tools for continuum discretization, better management of TOUGH2 input data and analysis of the numerical simulation results

In the numerical simulation of the geothermal reservoir behaviour and of its exploitation, the domain discretization is one of the factors affecting the delta between predicted and measured values. Increasing the grid resolution of the numerical model around the volumes of interest can reduce the above mentioned delta, but that requires computational and operating costs whose entity depends on the complexity of the model. The simulation of 3D models characterized by a huge number of blocks produces a large amount of data that are difficult to analyze without adequate post-processing and visualization tools. The difficulties increase when we adopt unstructured grids (Voronoi) and local refinement in spatial discretization. In order to enhance spatial discretization and data management, a pre-processor (TOUGH2GIS) has been developed using GRASS GIS (Geographical Information System [1]) and AMESH [2] open source codes. This new pre-processor significantly reduces operating errors, the time required by pre-processing activities and locally refined unstructured grids generation and its update. Thanks to GIS approach, conceptual model elaboration and its conversion into a numerical model have been integrated under a software (TOUGH2GIS) so that updates and changes to the conceptual and numerical models can be made quickly. TOUGH2GIS is a suite of tools (BASH scripts and C codes with tcl-tk graphical user interface) for automating several operations such as domain discretization, rock types assignment, mesh file generation, simulation's output import and link to the numerical model as database attribute tables. In a few words, TOUGH2GIS represents an efficient tool supporting the whole operations required by model calibration. TOUGH2Viewer is a post-processor (written in Java, developed in NetBeans 7.1 environment and mainly based on Java3D libraries) that allows a three dimensional graphic reconstruction of the numerical model and let the user to explore, through a simple and intuitive graphical interface, the output of TOUGH2. Originally thought for unstructured grids visualization, the post-processor can also manage structured grids created with the MESHMAKER module. In particular, the software handles the visualization of 3D grid (structured and unstructured), 3D vector representation of mass and heat transfer, isosurfaces of the simulated variables, 2D contour maps. It is possible to browse simulated model data in a 3D view through rotation, pan, zoom, horizontal and vertical sections. The user can display the variables simulated or the rock types assigned to the nodes of the grid in colour scale. Moreover, the user can import isosurfaces in shape file format and view them along with the 3D model. Finally, the user can get space and time profiles of the thermophysical properties present in the output file by selecting the node or column of interest. The 3D visualization of the mass and heat transfer between adiacent grid nodes is obtained as vector sum of the flows in input / output to the node. All display functions can be customized through a simple and intuitive graphical interface, in order to optimize simulation analysis and to produce high quality printouts. The performances of TOUGH2GIS and TOUGH2Viewer have been tested executing history matching and developing exploitation scenarios for a Tuscan high enthalpy geothermal field. [1] http:// grass.fbk.eu [2] http://esd.lbl.gov/research/projects/tough/licensing/free.html