Gas Migration in EBS and Geosphere (GMT) - Subtask Modelling

During the experiment several teams of modelers supported by the partners of the GMT SubTask Modelling (NAGRA, Obayashi, RWMC, ANDRA and BGR) developed models of the field test from construction to excavation. Different modelling groups took different approaches.

CODE_BRIGHT modelling was initially supported by ENRESA and continued with the support of the GMT project. CODE_BRIGHT was used to simulate hydromechanically coupled two phase flow using unsaturated soil mechanics models. A strength of CODE_BRIGHT was that it was able to simulate the construction stages as well as the field test.

 

GETFLOW is a 3D two-phase flow code and the modelling for GMT was supported by RWMC. The figure shows a section of GETFLOW 3D Mesh

 

MHERLIN is a coupled two-phase hydromechanical model. The GMT modelling using MHERLIN was supported by ANDRA. MHERLIN used a large 3D mesh to model the EBS and shear zone. The figures shows the predicted water pressure in the EBS and shear zone during RGI2b (first series of gas injections).

 

ROCKFLOW modelling was supported by BGR. ROCKFLOW has developed from a two-phase flow code during the project into a coupled model. The first model was a 2D section, but a 3D model is now being developed using the latest coupled version of the code.

 

 

TOUGH2 was used throughout the experiment as a tool to help the design of the experiment and was typically used in a "history matching" mode in conjunction with ITOUGH2 the inverse model version of TOUGH2. TOUGH2 was used to simulate two-phase flow but detailed modelling showed that a better match to observation was achieved when a dilation/permeability enhancement around the vent was included in the models during the gas injections.

 


Participants of the Subtask Modelling Workshop November 2005 in Wettingen

 

The GTS underground facilities are also available to interested 3rd parties for underground testing and research. The GTS offers cost-effective access to a fully developed, well characterised underground research facility with round the year logistical support - please contact Dr. Ingo Blechschmidt, Head of the Grimsel Test Site, for further details.