Improving hydraulic aperture estimations to inform discrete fracture network models

Quinn, Pat

Improving hydraulic aperture estimations to inform discrete fracture network models

Monday, September 23, 2019: 1:20 p.m.

Pat Quinn, PhD , School of Engineering, University of Guelph Guelph

John A. Cherry, Ph.D. , School of Engineering, University of Guelph, Guelph, ON, Canada

Beth L. Parker, Ph.D. , College of Physical and Engineering Science, G360, University of Guelph, Guelph, ON, Canada

Discrete fracture network numerical (DFN) models have long been available to simulate groundwater flow and transport in fractured rock, however these models are rarely applied at field sites because input fracture parameters are difficult to quantify. Because simulation results are strongly sensitive to fracture aperture there is need to decrease errors and uncertainty in aperture estimates. Hydraulic apertures derived using the cubic law using T values from straddle-packer tests are the most practicable way to obtain apertures. Over the last 10 years we have worked on improving our straddle-packer equipment design and test procedures to better understand the fluid mechanics of the water passing through the test equipment and in the fractures intersecting the tested interval. Insights concerning the nature of test conditions are obtained using a multiple-test approach to evaluate the inherent mathematical assumptions used to determine T, including validation of Darcian flow, cross-connection to the open borehole, and the steady flow assumption, to increase confidence in the calculated T values. However, further error in the calculated hydraulic aperture stems from uncertainty in the number of hydraulically active fractures in each test interval, and examples are provided showing how multiple datasets aid in the identification of the active fractures.

Pat Quinn, PhD, School of Engineering, University of Guelph Guelph

Pat Quinn completed a Ph.D. in Contaminant Hydrogeology at the University of Waterloo under the supervision of Beth Parker and John Cherry in September 2009, and is currently working as a research scientist in the School of Engineering at the University of Guelph in the G360 research group focusing on hydraulic testing in fractured rock environments.

John A. Cherry, Ph.D., School of Engineering, University of Guelph, Guelph, ON, Canada

John Cherry is the Director of the University Consortium for Field-Focused Groundwater Contamination Research, Associate Director of G360 Centre for Applied Groundwater G360–The Centre for Groundwater Research, and Adjunct Professor in the School of Engineering at the University of Guelph. He is a Distinguished Professor Emeritus at the University of Waterloo. Cherry co-authored the textbook Groundwater with R.A. Freeze (1979) and co-edited and co-authored several chapters in the book Dense Chlorinated Solvents and Other DNAPLs in Groundwater.

Beth L. Parker, Ph.D., College of Physical and Engineering Science, G360, University of Guelph, Guelph, ON, Canada

Beth Parker, Ph.D., University of Guelph Professor in the College of Physical and Engineering Sciences and Director of the G360 Centre for Applied Groundwater Research, has more than 30 years of experience investigating subsurface contamination at numerous sites around the world, using high resolution data sets for site conceptual model development and testing. Her current research activities emphasize developing improved field and laboratory methods for characterizations and monitoring of industrial contaminants in sedimentary rocks, clayey deposits, and sandy aquifers, and focus on the effects of diffusion in low permeability zones, plume attenuation, and hydrogeologic controls on remediation.