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1
Presentation title to go here.
City of Surrey, Groundwater Exploration
Program Sunnyside Production Well 3 Screen
Design
  • Subtitle to go here.Date

35th B.C. Groundwater Association
Convention March 2005 Lee Ringham, P.Geo.
Client/Partner Logo
2
Talk Outline
  • Introduction
  • Groundwater Exploration Program Overview
  • Sunnyside Production Well 3 Drilling
  • Screen Design Criteria and Decisions
  • Clayton Intermediate Well
  • Lessons Learned
  • Conclusions

3
Project Summary
  • Project involved drilling seven test wells and
    one production well.
  • Project was under very tight timelines. Drilling
    started Dec 15, 2003 and ended April 16, 2004.
  • Needed to develop a comprehensive geological
    framework of the study area, as this did not
    exist.
  • Needed to complete pumping test, water quality
    analyses and reporting within 2 weeks of well
    completion.

4
Map of Surrey
Selected Drilling Target Areas
5
Project Approach
  • Developed the hydrogeologic model of the study
    area, based on the simplified geology
  • Water well database data distribution and
    quality highly variable focus on wells deeper
    than 15m
  • Digital mapping City provided topographic
    mapping, aerial photographs, property ownership,
    current water supply pipelines, land use
  • Quaternary geology mapping is available digitally
    from GSC. Mapping quality is very good but is
    limited to upper 2m of unconsolidated material.
    We were interested in unconsolidated aquifers at
    depths of 50 to 200m
  • Other geological information from reports was
    added to database

6
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7
Sunnyside Production Well
  • Site selected as there were several nearby wells,
    so stratigraphy and well yield was known.
  • Well was to replace a production well that was no
    longer capable of being used.
  • Well was sited to provide additional water to
    already existing infrastructure.
  • Desired well yield was 1,000 USgpm.

8
Sunnyside Park
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10
Site Stratigraphy
  • Well 1
  • 0 397 Till with sand and gravel
    interbeds
  • 397 - 406 Cemented sand/gravel
  • 406 - 414 Sand and gravel
  • 414 492 Fine sand and silt
  • Well 2
  • 0 401 Till with boulders, gravel and
    sand layers
  • 401 422 Sand and gravel
  • 422 500 Fine uniform sand
  • Well 3
  • 0 396 Till with gravel layers
  • 396 406 Cemented sand/gravel
  • 406 411 Sand and gravel
  • 411 482 Fine sand and silt

11
Drilling target depth
12
Sunnyside Production Well
  • Target aquifer was Pre-Semiahmoo sediments,
    located roughly 440 ft below ground elev -65 ft
    a.s.l.
  • Well started with 18 ft of 24 inch casing to act
    as a surface seal.
  • 20 inch casing to 180 ft, 16 inch to 436 ft.
    Looked for sand and gravel in cuttings to signify
    top of aquifer.
  • Drilling with dual rotary rig took 6 days.
  • 16 inch casing advanced with cable tool to 495
    ft, looked for blue clay in samples, signify
    bottom of aquifer.
  • Cable tool drilling took 3 days.

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15
Sample Results
  • 11 samples collected over 5 foot intervals from
    438 492 ft.
  • Samples were uniform, fine grained silty sand.
  • Sieve results indicated lt 20 retained by 17 thou
    sieve but 50 76 retained by 10 thou sieve.
  • Lab supplied 50 passing sizes for each sample
    interval, ranged from 9 to 13 slot.

16
UC D40/D90 D40 10 to 13 thou D90 5 to 8 thou
17
Review Existing Reports
  • Looked at previous well completion reports and
    screen designs for guidance.
  • Well 1 screen sizes were 10, 18 and 20 slot,
    with a 60 slot length in the upper gravel layer.
  • Well 1 broke down after 1 yr due to heavy wear
    from sand abrasion. On-going problems included
    excessive wear and sand accumulation in nearby
    reservoir.
  • Well 2 was completed with 30 slot, 10 inch
    diameter screen with a sandpack
  • No problems associated with this well, but yield
    was not what the client wanted.

18
Consult the Textbook!
  • Screen design criteria in Groundwater and Wells
    (Driscoll, 1986)
  • Select a slot size allowing 60 of aquifer
    material to pass through.
  • Entry velocity into screen 0.1 ft/sec (0.03 m/s)
  • More conservative sizes may be used when
  • doubt concerning reliability of samples
  • Aquifer is thin and fine grained
  • Development time is at a premium
  • Formation is well sorted
  • Use slot sizes that retain 40 50 of aquifer
    material.

19
Naturally Developed Well
  • Possible to install a naturally developed well
  • 10 ft of 12 slot, 14 inch
  • 5 ft of blank
  • 10 ft of 10 slot, 14 inch
  • 30 ft of 12 slot, 14 inch
  • Install a sandpack filter from surface, use a 20
    slot, 10 inch, 50 ft screen
  • In both cases yield was not 1,000 USgpm

20
Driller Recommendation
  • Drilling contractor also sieved samples
  • Results
  • To retain 50 of aquifer material 13 slot
  • To retain 40 of aquifer material 14 slot
  • To retain 30 of aquifer material 15 slot
  • Flow rates
  • 10 slot screen 10 gpm/ft 500 USgpm
  • 15 slot screen 12 gpm/ft 600 USgpm
  • Yield too low

21
Back to Driscoll
  • Filter pack screens may be considered under the
    following conditions
  • Fine, uniform sediment
  • Slot size smaller than 10 slot
  • Filter packs should retain 90 of the aquifer
    material
  • Filter packs should be at least 3 inches thick
  • Screen slots should retain at least 90 of the
    filter pack
  • At 495 ft depth, how to ensure that the sand pack
    goes where it should?
  • Screen 20 slot, 10 inch, 50 foot already
    rejected as not enough yield.

22
Still more Driscoll
  • Look at pre-pack screens
  • Contact screen manufacturers to discuss situation
    with them
  • Calculate size of pre-pack material, size outer
    and inner screens accordingly
  • Prepare for sticker shock!

23
Pre-Pack Screen Design
  • Discussions with screen manufacturers
  • Outer screen 14 in OD, 20 slot
  • Pre-pack material was 2 inches of 8 12 ceramic
    fill (0.066 x 0.094 inch)
  • Inner screen 10 inch ID, 20 slot
  • Screen length 50 feet
  • Calculated maximum yield was 888 USgpm was deemed
    acceptable by client.

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25
Damage to screen during transit
26
Torn packer, damaged in transit
27
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28
Development
  • Development time was 12 hours
  • Less than 1 foot of sand in screens
  • Pumping test indicated that the well would
    produce 888 USgpm, but recommended pumping rate
    was lower.

29
Clayton Intermediate Well
Selected Drilling Target Areas
30
Clayton Intermediate Well
  • Well sited to take advantage of sand and gravel
    deposit.
  • Stratigraphy
  • 0 36 ft Clay
  • 36 190 ft Fine to coarse sand
  • 190 195 ft Clay
  • 195 232 ft Medium coarse sand
  • 232 286 ft Blue clay with sand interbeds
  • Aquifer screened - 243 280 ft.

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33
Grain Curves Differences
  • Different positions of grain size curves, reflect
    sampling method.
  • Cable tool sampling gives more representative
    samples with a complete distribution of grain
    sizes.
  • Errors in screen design possible with air rotary
    method only.
  • Still need to rely on drillers experience.

34
Lessons Learned
  • Not surprisingly, dual rotary drilling is very
    fast and drill very straight or true holes.
  • Cable tool rigs, although slower, provide more
    representative aquifer samples.
  • Use all available information to identify
    potential problems, including driller advise
    BUT.
  • Be prepared to consult other sources of
    information.

35
Lessons Learned
  • Sieving aquifer samples can reveal subtle
    considerations for screen design.
  • Pre-pack screens may be advisable, depending on
    aquifer characteristics

36
Conclusions
  • Water well record database is VITAL!
  • Simple geological/hydrogeological models may be
    suitable for various purposes.
  • Choose drill rig carefully.
  • Driller input is important in screen design, but
    be prepared to sieve samples and use other
    sources of information in conjunction with their
    knowledge.

37
Thank you. Questions?
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