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A new method for conditioning stochastic groundwater flow models in fractured media

Milne, Andrew; Cliffe, Andrew; Holton, David; Houston, Paul; Jackson, C. Peter; Joyce, Steve

Authors

Andrew Milne pmxam3@nottingham.ac.uk

Andrew Cliffe Andrew.Cliffe@nottingham.ac.uk

David Holton David.Holton@serco.com

Paul Houston Paul.Houston@nottingham.ac.uk

C. Peter Jackson CPeter.Jackson@sercoassurance.com

Steve Joyce Steve.Joyce@serco.com



Abstract

Many geological formations consist of crystalline rocks that have very low matrix permeability but allow flow through an interconnected network of fractures. Understanding the flow of groundwater through such rocks is important in considering disposal of radioactive waste in underground repositories. A specific area of interest is the conditioning of fracture transmissivities on measured values of pressure in these formations. This is the process where the values of fracture transmissivities in a model are adjusted to obtain a good fit of the calculated pressures to measured pressure values. While there are existing methods to condition transmissivity fields on transmissivity, pressure and flow measurements for a continuous porous medium there is little literature on conditioning fracture networks. Conditioning fracture transmissivities on pressure or flow values is a complex problem because the measurements are not linearly related to the fracture transmissivities and they are also dependent on all the fracture transmissivities in the network.

We present a new method for conditioning fracture transmissivities on measured pressure values based on the calculation of certain basis vectors; each basis vector represents the change to the log transmissivity of the fractures in the network that results in a unit increase in the pressure at one measurement point whilst keeping the pressure at the remaining measurement points constant. The fracture transmissivities are updated by adding a linear combination of basis vectors and coefficients, where the coefficients are obtained by minimizing an error function. A mathematical summary of the method is given. This algorithm is implemented in the existing finite element code ConnectFlow developed and marketed by Serco Technical Services, which models groundwater flow in a fracture network. Results of the conditioning are shown for a number of simple test problems as well as for a realistic large scale test case.

Journal Article Type Article
Journal Advances in Water Resources
Print ISSN 0309-1708
Electronic ISSN 0309-1708
Publisher Elsevier
Peer Reviewed Not Peer Reviewed
APA6 Citation Milne, A., Cliffe, A., Holton, D., Houston, P., Jackson, C. P., & Joyce, S. A new method for conditioning stochastic groundwater flow models in fractured media. Manuscript submitted for publication
Publisher URL http://www.elsevier.com/wps/find/journalabstracting.cws_home/422913/abstracting
Copyright Statement Copyright information regarding this work can be found at the following address: http://eprints.nottingh.../end_user_agreement.pdf

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Copyright Statement
Copyright information regarding this work can be found at the following address: http://eprints.nottingham.ac.uk/end_user_agreement.pdf





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