Method
|
Scale
|
Examples
|
Instrumentation/Description
|
Darcy-based methods
|
- generally, ~10 m to ~100m separation between wells
- local to regional investigations common
- risk of misleading interpretation unless the equivalent porous medium (EPM) assumption is validated
|
- conventional site investigation based on water level survey and estimation of hydraulic conductivity (K)
|
- wells and water level tapes or sondes
- measure head in wells for gradient across domain and obtain domain K value - data collection requires minutes per well
- packer testing may be performed to characterize hydraulic properties of fractures to support Darcy calculations
|
Tracer tests
|
|
|
- tracer poured into well or recharge site
- tracer detected by water sampling or with passive solid sorbent samplers
|
|
- active injection followed by water sampling
- sampling only following tracer introduction by spill or natural source
|
- salts (Luhmann et al., 2012)
|
- active injection followed by water sampling
|
- colloids (McKay et al., 2000)
|
- active injection with a two-well injection-withdrawal system
|
- dissolved gases (e.g., He, SF6) (Gupta et al., 1994; Vulava et al., 2002)
|
- active injection followed by water sampling
|
Single borehole techniques
|
- centimeter-scale measurements geared to locations where fractures cross the borehole
- larger scale flow patterns possible with multiple wells and complimentary information from other methods
|
- borehole dilution and FVPD (Brouyere et al., 2008)
|
- packers to isolate the borehole section of interest, tracer injection system, sampling/datalogging
|
- Flute liner
- pressure log
- temperature profile (Peheme et al., 2010)
|
- pressure profiling during installation can identify depths of major fractures
- temperature profiling next to liner to identify zones of high water-flux - with heating and subsequent return to background temperatures, flow rates may be inferred
|
- FRPFM (fractured rock PFM) (Levison and MacDonald, 2014)
|
- instrument supplied by vendor, suspended in well for days to weeks, packer system required
- return to vendor for analysis
|
- ORP (oxidation-reduction profiling)
- (Sale et al., 2020)
|
- sensors suspended in borehole and passively sense variations in water redox chemistry with depth - depths of greatest variations suggest depths of water flux from fractures
- requires datalogger for longer-term data collection
|
- IWPVP
- (Osorno et al., 2018)
|
- instrument positioned across fracture for testing
- requires injection system and datalogger
|