From Winter 2024 TAGD Business Meeting, January 30-31 at Embassy Suites Round Rock

1. Annual Fall Conference 2020
Jo
Borehole Magnetic Resonance
An Emerging Technology for Aquifer
Characterization for Water Resource Applications
Texas Case Studies
Jordan Furnans, PhD, PE, PG
Vice President – TX Operations
Jordan.Furnans@lrewater.com
512-736-6485

2. NOMENCLATURE:
• Nuclear Magnetic Resonance (NMR)
• Borehole Magnetic Resonance (BMR)
• Synonymous – Some people don’t like the word “nuclear”
• Magnetic Resonance Imaging (MRI)

3. • What is the AQUIFER YIELD?
• How much MOBILE WATER is available?
• How does the PERMEABILITY vary throughout
the aquifer?
Water Resource Needs:
– Production and Recharge Well Design
– Productivity/Injection Estimates
– Well Siting and Permitting
– Groundwater Model Calibration
Can BMR technology assist water managers in assessing
an aquifer for WATER RESOURCE INVESTIGATIONS?

4. BMR TECHNOLOGY
Permanent magnets in probe
polarize hydrogen in H2O
molecules
H2O
NMR Signal
S
0
∝𝜙 ∝pore size
T
2
NMR signal is generated and detected only
within a thin cylindrical sensitive volume
surrounding the center of the tool

5. What is BMR Logging?
• Characterizes the volume, structure, and type of fluids occupying the small
spaces (pores) within an aquifer unit.
• Important differences from other geophysical logs:
– Instead of lithologic indicators, BMR tells us about the spaces and fluids therein.
– Can provide a large array of information with one log
• Water Content
• Porosity (independent of lithology)
• Pore Size (volume/surface area)
• Pore Size Distribution
• Bound vs. Mobile Water
• Hydraulic Conductivity

6. BMR Log
Calculated porosity
distribution
Clay-bound water
Capillary-bound
water
Moveable water

7. BMR Log - K
Calculated porosity
distribution Calculated K

8. BMR Log – Specific Yield
Moveable water

9. Run Caliper Log First…
Borehole too large
to yield useful data

10. Borehole Geophysics
“NORMAL” SUITE “BMR” SUITE
• E-logs
• Natural Gamma
• Temperature
• Caliper
• Guard
• Sonic
• Neutron
• Density (gamma-gamma)
• E-logs
• Natural Gamma
• Temperature
• Caliper
• BMR (aka. NMR)
Switch can be made if field conditions are met: borehole < 12” diameter,
not a preponderance of large washouts. [Can be larger depending upon tool.]

11. Case Studies and Take Aways
Webb County
Wellsite in Texas

12. Texas Case Studies
Deep well
Large Potential
Screening Interval
Low Yield Expected
• Need to maximize yield
• Keep TDS < Target

13. Texas Case Studies
Deep well
Large Potential
Screening Interval
Low Yield Expected
• Need to maximize yield
• Keep TDS < Target

14. Texas Case Studies
Deep well
Large Potential
Screening Interval
Low Yield Expected
• Need to maximize yield
• Keep TDS < Target
TDS Calculated
From Resistivity Logs
And Mud Resistivity
HIGH K
HIGH TDS
HIGH K
Low TDS
Exclude This?

15. Texas Case Studies
Deep well
Large Potential
Screening Intverval
Low Yield Expected
• Need to maximize yield
• Keep TDS < Target
TDS Calculated
From Resistivity Logs
And Mud Resistivity
Excluded Upper
Portion – TDS Reasons
Too short to
Exclude

16. How’d we do?
Estimated Properties:
Transmissivity: 1,205-1,222 gpd/ft
TDS = 1790-2089 mg/L
Measured Properties:
Transmissivity: 1,152 gpd/ft
TDS = 1300 mg/L

17. Phoenix ASR
Well

18. 2016 2011
2002
TRADITIONAL METHOD:
HYDROLOGIC TESTING
A volume of water is
added, & the water-
level change is
recorded
• Falling head or
slug tests in
boreholes
• Aquifer tests only
in completed
wells

19. Slug Test K-values
Slug Test Estimated Productivity:
335 gpm with 100 ft of
Drawdown
Productivity Estimates Using Falling Head Test Data
Zone #
Depth Interval,
feet
Aqtesolv K-value,
ft/d
Applied Zone
Interval, feet
Calculated T-value,
gpd/ft
Estimated SC,
gpm/ft
Estimated capacity at
100 ft drawdown, gpm
Zone 1 1380-1410 0.83 45 279 0.19 19
Zone 2 1320-1350 1.08 67 541 0.36 36
Zone 3 1245-1275 1.08 68 550 0.37 37
Zone 4 1185-1215 1.45 57 617 0.41 41
Zone 5 1130-1160 1.10 68 562 0.37 37
Zone 6 1050-1080 1.55 103 1190 0.79 79
Zone 7 925-955 0.88 195 1289 0.86 86
SWL
Estimated Total Production Rate, gpm 335
where:
Q = gpm;
T = gpd/ft;
s = feet of drawdown
T
1,500
=
(gpm/ft) Q/s
Empirical Equation
T = Kb
Phoenix ASR Well

20. Phoenix ASR Well
Productivity Estimates using NMR Data
Zone #
Depth,
feet
NMR K-
value, ft/d
Applied Zone
Interval, feet
Calculated T-
value, gpd/ft
*Estimated SC,
gpm/ft
Estimated
Capacity at 100 feet
Drawdown, gpm
Zone 1 1412 1.49 25 278 0.19 19
Zone 2 1387 0.33 25 62 0.04 4
Zone 3 1362 0.51 25 95 0.06 6
Zone 4 1337 1.28 25 240 0.16 16
Zone 5 1312 0.88 25 165 0.11 11
Zone 6 1287 0.78 25 145 0.10 10
Zone 7 1262 0.98 25 184 0.12 12
Zone 8 1237 1.34 25 251 0.17 17
Zone 9 1212 1.73 25 323 0.22 22
Zone 10 1187 6.33 25 1185 0.79 79
Zone 11 1162 2.85 25 534 0.36 36
Zone 12 1137 6.15 25 1149 0.77 77
Zone 13 1112 8.07 25 1509 1.01 101
Zone 14 1087 1.60 25 299 0.20 20
Zone 15 1062 6.75 25 1262 0.84 84
Zone 16 1037 2.30 25 431 0.29 29
Zone 17 1012 22.67 25 4239 2.83 283
Zone 18 987 0.92 25 172 0.11 11
Zone 19 962 0.96 25 179 0.12 12
Zone 20 937 0.67 25 125 0.08 8
Zone 21 912 2.05 25 384 0.26 26
Zone 22 887 2.79 25 522 0.35 35
Zone 23 862 2.48 25 463 0.31 31
Zone 24 837 7.21 25 1348 0.90 90
Zone 25 812 7.53 5 282 0.19 19
SWL 807 605
Estimated Total Production Rate, gpm 870
Well Screen Interval
NMR Zone Estimated
Productivity:
870 gpm with 100 ft of
Drawdown

21. Phoenix ASR Well
335 gpm
100 ft of Drawdown
Slug Test Estimated Productivity:
870 gpm
100 ft of Drawdown
NMR Zones Estimated Productivity:
Aquifer Test Productivity:
1,095 gpm
100 ft of Drawdown

22. Phoenix
ASR Well
Kslug - 1.55
Knmr - 4.43
Kslug - 0.88
Knmr - 0.83
Kslug - 1.08
Knmr - 1.08
Kslug - 1.08
Knmr - 1.13
Kslug - 1.10
Knmr -5.79
Kslug - 1.45
Knmr - 0.63
Kslug - 0.83
Knmr - 1.35

23.  Significant underestimation of
hydraulic conductivity from slug
tests
 NMR fills in gaps in hydraulic
conductivity rather than interpolation
 Lack of zone development can impact
zonal slug test results
 Projecting underestimated K-values
exacerbates the problem (i.e.,
underestimated productivity)
 Evaluation of NMR K values was not
quick nor simple. This would often need
to be done “on the fly” for well design.
Phoenix ASR Well Take Away

24. Production and Exploration Sites
Ave. NMR in monitor well
K = 13 ft/day 280 – 500 ft bls
K = 4.9 ft/day 500 – 750 ft bls
NMR conducted after
monitor well was
constructed inside 5”
PVC casing & screen
Aquifer test K in
shallow well
= 16.6 ft/day
Aquifer test K in
deeper well
K = 2.6 – 4.7 ft/day
Metro Water District’s
OJ2 Replacement Well
in Tucson, AZ

25. Hydraulic Conductivity
– Aquifer Testing
Aquifer test
K = 60.7 ft/d
BMR Log
Geo. Mean: KSDR = 3.3 ft/d
Geo. Mean: KTIM = 11.5 ft/d
BMR Log
Geo. Mean: KSDR = 1.6 ft/d
Geo. Mean: KTIM = 3.0 ft/d
Aquifer test
K = 28.4 ft/d
Aquifer test
K = 94 –106 ft/d

26. Specific Yield
Aquifer test
Sy = 0.14
BMR Log
Arith. Mean: Sy = 0.12
Geo. Mean: Sy = 0.11
BMR Log
Arith. Mean: Sy = 0.13
Geo. Mean: Sy = 0.10
Aquifer test
Sy = 0.12
Aquifer test
Sy = 0.11

27. Benefits
 Direct detection and quantification of water
content and porosity
 Determination of bound versus mobile water
 Quantitative estimates of hydraulic
conductivity, transmissivity, specific yield, and
pore-size distribution
 Sy is a difficult parameter to achieve, and NMR
seems to be a good source.
Challenges
o Confidence of dataset, especially for K
o Borehole diameter limitations
o Requires pre-project planning to ensure
limitations are understood, adequate data is
collected, proper constants are applied for
data processing
o K estimates will get better if it’s used more in
a geographic area
Conclusions

28. Jordan Furnans, PhD, PE, PG
Vice President – TX Operations
Jordan.Furnans@LREwater.com
512-736-6485