Hydromechanical Well Tests
Conventional hydraulic well tests involve stressing a well and 
interpreting the resulting changes in pressure in the vicinity. The
pressure changes cause small displacements in the porous or fractured medium, however, and this provides a potentially useful signal that can be interpreted along with the pressure transients. We have been developing methods for conducting and analyzing hydromechanical well tests in an effort to improve understanding of fractured rock.
The field technique requires an extensometer for measuring the small axial displacements accompanying pumping. We built our first working prototype in 2002, and new designs were developed in 2003 and 2004. The early prototype is shown to the left and below, and the current status of the extensometer development is described here.
Field response
A distinctive characteristic of hydromechanical well tests is the hysteretic relationship between displacement and well bore pressure. This is shown below in some data from an early pumping test (the figure appeared in a 2003 AGU presentation). Interestingly, the loop-like shape of these data appears in nearly all the field tests we have conducted thus far, and in the theoretical analyses. The shape of the loop differs between these tests, however, and appears to be related to aquifer characteristics
Theoretical analysis
The analysis of hydromechanical well tests requires using an analysis that can account for the coupled displacement and fluid flow through fractured material. The analysis we are currently using is described in a recent paper.
Paper from Witherspoon Conference, 2004
Paper describing theoretical analysis, 2006
We appreciate the support of the National Science Foundation, although they are certainly not responsible for neither our opinions nor our errors. The initial research was supported by NSF EAR 0001146, and we are currently supported by NSF EAR 0609960.
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Last Updated:
August 28, 2006
-- Questions or comments, contact Larry Murdoch.
School of Environment, Department of Geological Sciences
340 Brackett Hall, Clemson, SC 29634 USA -- Telephone: (864) 656-3438, Fax: (864) 656-1041
© 2004-2005 Clemson Univeristy, Clemson, SC, USA. All rights reserved.