water well screens - Botti Elio Perforazioni

WATER WELL SCREENS
Sébastien BART – Bruno BENAGLIA
Padova 15 Febbraio 2010
DEFINE SCREENS
• Objectives
• Yield consistent with aquifer capabilities
• Longer well life
• High well efficiency with minimum
drawdown
• Good sand free water quality
• Improved rehabilitation and treatment
• Shorter development time
• Keep good aquifer quality
• Reduced costs and pumping costs
© 2008 All rights reserved to Johnson Screens (Europe) Pty Ltd. No information contained in the presentation is allowed to be copied without the approval of Johnson screens (Europe) Pty Ltd.
WELL DESIGN
With bad design, risks are :
• Low productivity
• Sand up
• Short service life, corrosion
• Clogging
• Production stoppage
• Collapse
© 2008 All rights reserved to Johnson Screens (Europe) Pty Ltd. No information contained in the presentation is allowed to be copied without the approval of Johnson screens (Europe) Pty Ltd.
TYPES OF SCREENS
•Keep water well long time with best efficiency
•Facilitate cleaning and rehabilitation in the future
•Important to accede behind screens with :
– large open area
– drawing of screens
© 2008 All rights reserved to Johnson Screens (Europe) Pty Ltd. No information contained in the presentation is allowed to be copied without the approval of Johnson screens (Europe) Pty Ltd.
INFORMATION
• Hydrogeological context
• Aquifer type
• Water quality
• Grain size analysis
• Efficiency, static and dynamic level
• Drilling methods
© 2008 All rights reserved to Johnson Screens (Europe) Pty Ltd. No information contained in the presentation is allowed to be copied without the approval of Johnson screens (Europe) Pty Ltd.
TYPE OF SCREEN
• Vee wire screen
• Large % of open area
• Possibility small slot
• Drawing of wire limit clogging
• Easy to develop and rehab
• Efficient well with high flow rates
© 2008 All rights reserved to Johnson Screens (Europe) Pty Ltd. No information contained in the presentation is allowed to be copied without the approval of Johnson screens (Europe) Pty Ltd.
TYPE OF SCREEN
• Pipe based / Wrapped on pipe
•Strong tensile and collapse
strength
•For deep WW
•Expensive
© 2008 All rights reserved to Johnson Screens (Europe) Pty Ltd. No information contained in the presentation is allowed to be copied without the approval of Johnson screens (Europe) Pty Ltd.
TYPE OF CONNEXIONS
Connection on site with :
• Thread connection : diameter ?
• ZSM : easy and quickly to install
• Welding procedure : process, filler
metal, velocity, chamfer, qualification of
welder
© 2008 All rights reserved to Johnson Screens (Europe) Pty Ltd. No information contained in the presentation is allowed to be copied without the approval of Johnson screens (Europe) Pty Ltd.
QUALITY
For stainless steel :
• Microscopic surface layer of protection : Cr, Ni
• Welded area
protection decreases
• So we have to :
– Pickling and passivating + connection
– Welded on site with gas backing
*ZAT : Zone Affectée Thermiquement
© 2008 All rights reserved to Johnson Screens (Europe) Pty Ltd. No information contained in the presentation is allowed to be copied without the approval of Johnson screens (Europe) Pty Ltd.
NATURALLY DEVELOPPED WELLS
•Create a more permeable zone
around screen in aquifer
• Increase hydraulic permeability
near water well with select particle
remove
• Good for non homogeneous aquifer
and not corrosive
• Slot retains 40 à 50 % of sediment
© 2008 All rights reserved to Johnson Screens (Europe) Pty Ltd. No information contained in the presentation is allowed to be copied without the approval of Johnson screens (Europe) Pty Ltd.
NATURALLY DEVELOPPED WELLS
• Not recommended :
– For fine and/or uniform aquifer
– For corrosive water
– If no sieve analysis
© 2008 All rights reserved to Johnson Screens (Europe) Pty Ltd. No information contained in the presentation is allowed to be copied without the approval of Johnson screens (Europe) Pty Ltd.
ARTIFICIAL GRAVEL PACK WELLS
• For very fine and uniform sediments
• For highly rolled aquifer
• For incrusting water
• To increase slot size /
auto-development
GRAVEL
PACK
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GRAVEL PACK
•Slot retains min. 90% of filter pack
• Filter pack needs :
– to be clean
– rounded grains and uniform size to reduce drawdown
– siliceous >90 % to limit risk of dissolution
• Use of centralizer to keep a good annulus around screen (2”– 4”’)
• Control of gravel pack if possible (pressure, volume…)
© 2008 All rights reserved to Johnson Screens (Europe) Pty Ltd. No information contained in the presentation is allowed to be copied without the approval of Johnson screens (Europe) Pty Ltd.
GRAVEL PACK
• Complex for depth water well
• Difficult to control pressure, volume and
position
• Have to limit direct contact between screen
and aquifer
© 2008 All rights reserved to Johnson Screens (Europe) Pty Ltd. No information contained in the presentation is allowed to be copied without the approval of Johnson screens (Europe) Pty Ltd.
OPEN AREA
• He must be highest possible :
– To increase productivity and limit head losses
– Limit clogging with small velocity
– Improve efficiency of cleaning and rehabilitation
– Long life of water well with good performance
© 2008 All rights reserved to Johnson Screens (Europe) Pty Ltd. No information contained in the presentation is allowed to be copied without the approval of Johnson screens (Europe) Pty Ltd.
EFFICIENCY OF SCREENS
• Objective : limit well losses
Q=20m3/h
Drawdown = BQ + CQ²
BQ
BQ
CQ²
CQ²
Large open area
Small open area
© 2008 All rights reserved to Johnson Screens (Europe) Pty Ltd. No information contained in the presentation is allowed to be copied without the approval of Johnson screens (Europe) Pty Ltd.
Q=20m3/h
EFFICIENCY OF SCREENS
Q=35m3/h
Q=20m3/h
BQ
BQ
CQ²
CQ²
Large open area
Small open area
© 2008 All rights reserved to Johnson Screens (Europe) Pty Ltd. No information contained in the presentation is allowed to be copied without the approval of Johnson screens (Europe) Pty Ltd.
ELECTRICAL ENERGY
• CAS n°1 :
Q = 50 m3/h
- 48 318 Kwh/year with SP60-7
•CAS n°2 :
- 43 561 Kwh/year with SP60-7
10 h/day et 365 j/year
NS =
20 m
ND = 40 m
- 39 080 Kwh/year with SP60-5
ND = 50 m
Difference 10 to 20%
CAS N°2
(Grundfoss study)
© 2008 All rights reserved to Johnson Screens (Europe) Pty Ltd. No information contained in the presentation is allowed to be copied without the approval of Johnson screens (Europe) Pty Ltd.
CAS N°1
LAMINAR / TURBULENT FLOW
• Exploitation :
• Entrance velocity must be < 3 cm/s :
- To stay in laminar flow
- To stop sand
- Reduce corrosion
and mineral incrustation
© 2008 All rights reserved to Johnson Screens (Europe) Pty Ltd. No information contained in the presentation is allowed to be copied without the approval of Johnson screens (Europe) Pty Ltd.
DETERMINING ENTRANCE VELOCITY
• 1) OA = (slot / (slot + wire width)) x 100 = %
• 2) SA = OD x
x length x OA = m²
• 3) Velocity = flow rate / SA = cm/s
• Ex : Slot = 0,7 mm – Wire width = 2,5 mm – Length = 20 m –
Flow rate = 50 m3/h – diameter 219 mm
• 1) OA = (0,7 / (0,7 + 2,5)) x 100 = 21,8 %
• 2) SA = 0,219 x
x 20 x 0,218 = 3 m²
• 3) Velocity = (50 / 3) / 36 = 0,46 cm/s
© 2008 All rights reserved to Johnson Screens (Europe) Pty Ltd. No information contained in the presentation is allowed to be copied without the approval of Johnson screens (Europe) Pty Ltd.
EFFICIENCY OF WATER WELL
Specific capacity
Specific capacity m3/h/m
25
20
15
10
5
0
0
2
4
6
8
10
12
14
Year
© 2008 All rights reserved to Johnson Screens (Europe) Pty Ltd. No information contained in the presentation is allowed to be copied without the approval of Johnson screens (Europe) Pty Ltd.
16
EFFICIENCY OF WATER WELL
Specific capacity
Specific capacity m3/h/m
25
20
15
10
5
0
0
2
4
6
8
10
12
14
16
Year
CLEANING OPERATION
© 2008 All rights reserved to Johnson Screens (Europe) Pty Ltd. No information contained in the presentation is allowed to be copied without the approval of Johnson screens (Europe) Pty Ltd.
CLOGGING - REHABILITATION
© 2008 All rights reserved to Johnson Screens (Europe) Pty Ltd. No information contained in the presentation is allowed to be copied without the approval of Johnson screens (Europe) Pty Ltd.
CLEANING OPERATION
How to limit clogging :
• Total disinfection :
– material, pipes,
pump….
• Entrance velocity
screen,
gravel
pack,
– maxi 1,5 to 3 cm/s
• Pumping regime
– steady flow
• Quality of maintenance
© 2008 All rights reserved to Johnson Screens (Europe) Pty Ltd. No information contained in the presentation is allowed to be copied without the approval of Johnson screens (Europe) Pty Ltd.
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