Groundwater Exploitation Well Construction
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Transcript of Groundwater Exploitation Well Construction
3/3/08
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Groundwater Exploitation
• Today
– Well Drilling
– Well Completion
– Well Development
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For deeper wells,
more intricate methods are needed,
as we will review here.
Fletcher Driscoll, 1986,
Groundwater & Wells,
Johnson Div.
National Ground-water Association
http://www.ngwa.org/
Good resources:
Australian Drilling Industry
Training Committee Ltd., 1997,
Drilling: The Manual of Methods,
Applications, and Management,
Lewis Publishers.
How are wells constructed?
• Drilling
• Completion (casing, screen,
surface features)
• Development
For shallow wells/piezometers(total depth <100 ft):
• Hand digging
• Augering
• Drive point
• Jetting
Well Construction
WaterAid /Jim Holmes
www.wateraid.org
3/3/08
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http://coastlinemachinery.com/
Drilling
http://coastlinemachinery.com/
bbwater.com http://en.wikipedia.org/wiki/Water_well
Completion w. screen
dnrc.mt.gov/wrd/water_op/bwwc
Cable tool drilling Rotary drilling
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(Harlan et alii, 1989)
Mast
Cable Tool Drilling
Well construction: drilling
http://en.wikipedia.org/wiki/Water_well
3/3/08
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Advantages:• Low cost
• Minimal alteration of permeability or water quality
• Doesn’t require large amounts of water
Disadvantages:• Slow (especially for deeper wells) 100 ft/d (good), but 10 ft/d (poor)
• Slow in soft sediment
• Casing loss (casing must typically be used to support the
hole; it might not be possible to recover this)
Cable Tool Drilling
http://coastlinemachinery.com/This method is disappearing.
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Mud pitMud pit
Rotary Drilling
(Harlan et alii, 1989)Well construction: drilling
http://www.youtube.com/watch?v=Y_dEzSa6I4E
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(Todd, 1980)
(Driscoll, 1986)Well construction: drilling
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Advantages:• Fast drilling rate
(300-500 ft/d if soft; 30-50 ft/d in very hard rock)
• Little loss of drilling rate with depth
• No casing loss (fluid keeps hole open)
Disadvantages:• High cost of rig
• More labor intensive
• Drilling mud can clog formation, change water quality
• Can lose fluid circulation
(caverns in limestone, lava tubes in basalt)
• Development time is high
Rotary Drilling
http://coastlinemachinery.com/
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Bowman Irrigation WellDrilled with mud rotary
12 inch diameter, 116-ft deep
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Reverse Rotary Drilling
Mud has a higher velocity
through the drill string
than it does in the annular
space around the drill
string—it can thus lift
coarser particles
This is ideal for
formations that form large
clasts; helps prevent
clogging in general
(Harlan et alii, 1989)Well construction: drilling
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Air Rotary Drilling
The same principle as
rotary drilling, but uses
air as the drilling fluid:
often it is actually air with
a foaming agent
Can’t be used in
materials that collapse or
materials that form
coarse particles(Harlan et alii, 1989)
Well construction: drilling
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Similar to air rotary drilling, but uses a hammer action instead of
rotary action
Pneumatic (air hammer) Drilling
Advantages:• Fast drilling rate in hard rock (50-100 ft/d)
• No plugging (or water quality change)
Disadvantages:• Most expensive method
• Only good in hard rock
• Can’t use in high permeability intervals
below the water table (can’t lift water)
http://coastlinemachinery.com/
3/3/08
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13(Harlan et alii, 1989)
Drilling with Auger
Augering:
hollow stem
or solid stem
(Harlan et alii, 1989)
A fast and cheap
method for
unconsolidated or
poorly-consolidated
sediments.
Using a hollow-stem
auger allows core
sampling.
The auger will bounce
off boulders, so this
method is not ideal for
alluvial fan sediments.
Well construction: drilling
http://www.geology.sdsu.edu/
classes/geol552/hollowstem.htm
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“Mobile B-59 is a versatile medium-duty drill rig. It can run hollow stem augers or perform
using mud rotary, air rotary or down-the-hole hammer drilling techniques. It is
accompanied by one of six available late-model support trucks which can carry all of the
support equipment needed to complete your project. This drill rig is mounted on a 1993
Ford F800 Series truck, has 12,000 foot pounds of torque enabling it to drill with up to 12
V4-inch diameter hollow stem augers capable of sampling soils and rock coring up to a
depth of 1,000 feet, installing 2-inch and 4-inch diameter monitoring wells and recovery
wells to 10-inch diameter. This rig is supported by a 1995 GMC Topkick 9400 Series truck
with a 24-foot box to handle all supplies necessary to complete projects.”
Trenton, NJ
http://www.talon.bizland.com/index.html
“Talon installs monitoring wells, production wells, and piezometers using
Air and Mud Rotary, Air percussion rotary, Hollow Stem Augers, ODEX
and Rock coring techniques.”
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(Driscoll, 1986, Groundwater & Wells)
http://coastlinemachinery.com/
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It is often hard to drill
‘straight’ or ‘plumb’.
Survey the well (vertically)
in order to
determine configuration.
Why?Imagine all calculations we do
(potentiometric mapping, well
test analysis, etc)
that depend on knowing where
the well is located at the depth
of measurement.
(Driscoll, 1986)
Drilling “straight”
http://coastlinemachinery.com/
3/3/08
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17Well construction: completion
Surface Features
casing
gravel
pack
18Well construction: completion
Surface Features
(Todd, 1980)
If no precautions are taken, runoff
can move down to the aquifer,
traveling along the outside of the
casing—this can lead to
groundwater contamination, or
casing collapse from erosion
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Unless in hard rock, something
has to keep the hole open at
depth—the casing is typically
steel; in shallow wells, PVC or
some other plastic
Well construction: drillingWell construction: completion
Casing
(Todd, 1980)
Completion with casingJohnson Screen
PVC Monitoring
Well Casing
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In the aquifer, there has to be a
way to let water in to the well;
we must still typically keep the
hole ‘propped’ open, though;
also we don’t want the well bore
to fill up with particulates
Well construction: drillingWell construction: completion
Screen
Johnson Screen (Todd, 1980)
bbwater.com
Completion w. screen
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“Home-made screens”—these involve making openings
in regular casing
•torch cut
•knife cut
•shot perforated
These types of screens are cheap, but open area is
low (1-2 %); there is poor control of opening
dimensions.
In many locations and for many purposes handcut
screens are now illegal.
Well construction: drillingWell construction: completion
Homemade Screen
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(Nielsen, 1991)
Milled slots: similar to torch cut,
but done with a milling machine
at the factory
2-3 % open area
Good control on slot size
Well construction: drillingWell construction: completion
Milled Slot Screen
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ScreenThree patterns of shutter screen, continuous slot, bridge slot, and mill slot screens
Roscoe Moss Company http://www.roscoemoss.com/
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(Nielsen, 1991)
Well construction: completion
Wire Wrap Screen
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Wire Wrap Screen
Johnson Screen
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(Driscoll, 1986)
Well construction: completion
Screens
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Wire-wrapped screens help prevent clogging
(Driscoll, 1986)
Well construction: completion
Screens
28Production Well
(Schwartz and Zhang, 2003)
Helps well production
by increasing hydraulic
conductivity around
the screen
Well construction: completion
Filter (Graval or Sand) Pack
USGS monitoriing well;
pouring & tamping
a sand pack
http://il.water.usgs.gov/nawqa/uirb
Roscoe Moss Company
“Well screen is an important component of well
design. It must be realized that it is not an answer
to all well problems. In a gravel envelope well, it is
the gravel that filters the formation material and not
the screen. The screen simply retains the gravel
pack. Screen selection must be based not only on
theoretical considerations, but on a practical
relationship to the design and construction of an
efficient, durable installation. The best screen
design cannot automatically correct incompleted
gravel installation or well development. Screen can
only facilitate the construction of an efficient well
and help assure its satisfactory operation” Roscoe
Moss Company
http://roscoemoss.com/tech_manuals/gwwc/
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A well is developed to give better production; this is
especially important in wells where drilling mud was used
Development removes fine particles, leaves only particles
that are bigger than the screen opening size
• surge block
• surge pumping
• overpumping
• jetting
• compressed air injection
Well construction: development
Development
Surging one way (leaving sand bridges) v. back-and-forth.
(Driscoll, 1986)(Driscoll, 1986)
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www.nps.gov/hafo/hydrology/stage/stage7.htm
Jetting
Well construction: development
Development
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Centrifugal pump performance curves
PumpsSubmersible (downhole) Pump Turbine PumpCentrifugal Pump
http://www.goulds.com/pdf/Bturbine.pdf
http://www.goulds.com/pdf/BSPMSPH.pdf
http://www.goulds.com/pdf/B5-25GS%201%20.pdf
Turbine pump performance curves
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Bowman Irrigation Well12-in casing, 116-ft deep
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Bowman Irrigation Well12-in casing, 116-ft deep
casing casing
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Well Completion Report
Well construction: completion