MS/AL Section
Groundwater Workshop Jackson, MS
August 2015
Presented By:
Mr. Bill Oakley, RPG
Consulting Hydrologist
&
Mr. G. Mark Teague, RPG
Consulting Geologist
Major Topics
• MS & AL Aquifer Systems
• Pump Tests
• Geophysical Well Logging
Gulf Coastal
Regional Aquifers
MS & AL Outcrop Systems Showing
Recharge Areas by Geologic
Formations:
• Oldest Paleozoic Rock
• Youngest Pleistocene Citronelle
sands & gravel
• Line of X-section NE to SW
• 15 Major Aquifers
• Oldest Located in NE
Mississippi (Paleozoic)
• Youngest Located in SW
Mississippi (Miocene)
• Variable Base of Fresh
Water
Ranges from 300’
in NE Mississippi to
Greater Than 3000’
in Hancock County
- Dome Size Ranges from ½
mile to 3 mile Diameter
- 30 Domes are Less than
4000’ below land surface
- Richton is the shallowest
at 700’ below surface
- Salts and some shales Behave in a
Plastic Manner and create Dome as
the Salt is more Buoyant
- Given the Plastic Nature of the
material(s) the structural influences
continues to migrate to the surface
until equilibrium is met
- Presently there are 5 gas storage
facilities inside salt domes in MS
- Is the Jackson Dome a Salt Dome?
The Jackson Dome
-Water Level Declines in MS:
Delta
Jackson Metro Area
NE Mississippi
Along MS Gulf Coast
-High Dissolved Solids Washington & Jackson Counties
- Near Base of Upper Cretaceous Aquifers in NE MS
-Little or No Fresh Groundwater in Kemper, Noxubee
Counties near AL State Line
1925 Land Surface- Top
1955 Land Surface-Middle
1977 Land Surface –
Man Standing at Base of Telephone Pole
San Joaquin Valley California at USGS Benchmark #S661
THE PUMPING TEST
• The single most important contribution the
water engineer can make to his Client is
the development and use of groundwater
resources is the specification and
achievement of more efficient watersupply wells.
THE PUMPING TEST
• For the water engineer the 1st step is to
recognize great room for improvement(s) to
efficiency & that many inefficient wells exist.
• An inefficient well is one in which the amount
of water level drawdown required to sustain a
given rate of discharge is substantially greater
than it should be for the aquifer involved.
2 Types of Pumping Tests
2 Types of Pumping Tests
Circular Orifice Weir
Specs generally
require 70 - 80 %
efficient; less
than 50% =
NO PAY!
Friction Loss
Lack of Development
Casing Size
Screen Size/Length/Slot
Improper Gravel Pack for Aquifer
Failure of Screen & Infilling
Unconfined / Confined Aquifers
Geophysical Logging & Groundwater Studies Uses:
• Help determine in-situ
water quality
• Help determine base of
fresh water zone based
upon TDS values
• Draw inferences about
aquifer production
• Help resolve issues of well
spacing
• Verify drilling depths of
contractor
Provide a graphical depiction of
geological formations vertically at
5”=100’
ALWAYS look at scales before
attempting to interpret data from
logs
Scales are located in the title bars at
the top & bottom of e-logs
Using Borehole GL to ID Water-Bearing
Strata for Optimum Screen Setting
• Critical when well yield or (max GPM) is
required
• Dependent on local and regional geology
• Should be considered when:
– Client’s desire is as much water as possible
– Geology of the site is not known
SPR= Black Curve at far right margin is not
affected by geometry and is best indicator of bed
boundaries.
R8, R16, R32, R64 = Colored curves at right
margin are affected by the geometry of the tool
spacing and is best illustrated in the 620’ – 640’
interval to the left.
Gamma Ray = Black Curve far left margin is a tool
that measures the natural radioactive minerals in
terms of counts per second with a good clean
beach sand reading in a range of (7.5-15 CPS)
and the scale increases in counts as clays can be
higher than 250 CPS!
SP= Blue Curve left margin; essentially compares
the fluids used to drill hole to that fluid within
the formations and provides indication of fresh
water zones verses salt.
Cur= Red curve left margin; is a manipulation of
Ohm’s law and is inverse function of the SPR
curve. Also, provides ground for the other
electrical operations of electrodes while
completing the circuit.
Scales are not shown here as they are based to Client preferences
when services are rendered. Unless otherwise specified by
stakeholders, technicians will adhere to log scales based on
professional experience in the region(s).
Commonly Used Geophysical Tools
• Natural Gamma
• Spontaneous Potential
• Full Waveform Sonic
– CBL after emplacement
• Resistivity (8,16,32,64)
– Formation
– Fluid
– Resistivity borehole logs
should be borehole corrected,
based on measured
resistivity, borehole diameter,
fluid resistivity, mud
resistivity, & temperature
Radioactive Source Tools
• Gamma-Gamma
• Neutron Density
Not commonly used
due to:
-Regulatory Issues
-Liability issues
-$$$$$$
Geophysical Logs & GW Data Helps
Quantify
• Aquifer Testing Data
– K(hydraulic conductivity), S (storativity),
T(transmissivity)
• Potentiometric Surface Maps
– Water Levels
• Water Quality (Lab)
– TDS
• Specific Yield (Sy-dimensionless value)
– Always a bit less than Porosity due to water retention during
production
– Estimate based upon porosity logs & derived permeability
• Hydraulic Conductivity (K) – determined using a resistivity logs
& surface conductivity
– Derivative of Sonic Porosity and R ratios
• Apparent Aquifer Thickness (b)
– Easily determined from Natural Gamma & Single Point Resistance Logs
• Transmissivity (T)
– Once we have the aquifer thickness (b) and (K) we have (T)!
Derive TDS from Resistivity Logs for Example
• TDS  (R8/R64) ) [56280/Rmf,T (Tmf + 7)]
•
•
Rmf= Resistivity Mud-Filtrate
Tmf= Temperature Mud-Filtrate
• TDS units are in PPM
• Values selected from E-Log Curves
• In this example. R8 = 62, R64=45, Rmf,t=2.1,
T=77
Elog from Fresh GW Sand in MS
TDS plot Derived from Previous Slides
Spontaneous
Potential (SP)
Responses
- Establish Clay base of Log
-Evaluate response relative to
clay base
- In this instance the Departure
is to Right of Clay Base
- Fresh Water Response
SP Departure from
Clay Base is
Negligible and
Overall Resistivity
Decreases Which
Indicates an
Increase in Salinity
SP Departure to
LEFT of Clay Base
= Increase in TDS
Oh
“Mudballs”