USE OF PROMOTER PIPE WITH DOWNHOLE HEAT EXCHANGER IN KLAMATH FALLS, OREGON

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USE OF PROMOTER PIPE WITH DOWNHOLE HEAT EXCHANGER
IN KLAMATH FALLS, OREGON

• John W. Lund Tonya Toni Boyd
• Geo-Heat Center
• Bill Hack Hachman Bruce Huffman
• Pacific Plumbers, Corp.

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BACKGROUND

• Downhole heat exchangers (DHE) used in Klamath
  Falls since the 1930s
• Also, used in Rotorua, New Zealand, Moana (Reno),
  NV, Turkey, Iceland, Hungary, Russia
• Consists of one or more closed-loop pipes
  circulating water suspended in a well extracting
  only heat
• Capacity from 100 kW to several MWt
• In wells up to about 500 ft (150 m) most
  economical, but have worked in depths to 1,500 ft
  (450 m)

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Typical DHE installation in Klamath Falls
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DHE in Klamath Falls
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TYPICAL DESIGN

• Well 10 to 12-in. (25 to 30-cm) diameter with
  8-inch (20-cm) diameter casing
• 2-inch (5-cm) diameter heating loop
• 2.5 to 3-inch (6 to 7.5-cm) diameter in larger
  installations
• ¾ to 1-inch (2 to 2.5-cm) domestic hot water loop
• Well completion must have space between casing
  and well bore
• Casing perforated at the bottom at live water
  flow and just below the minimum static water
  level at the top

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OPERATING CONDITIONS

• Rule of thumb 1,500 Btu/hr/ft (1.4 kW/m)
• 140oF (60oC) minimum well water temperature
• Thermo-syphoning gravity feed of water
• 15 - 25 gpm(1.0 - 1.5 L/s)
• 10 - 20oF (5 - 11oC) temperature change
• 3 5 psi (0.2 0.35 bar) pressure difference
  between supply and return lines
• Vertical velocity in well of 0.04 0.4 fps (0.01
  0.1 m/s) with maximum of 2 fps (0.6 m/s)

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Casing completion to provide vertical convection
cell
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PROBLEMS

• If casing not perforated home owners stimulate
  vertical flow by pumping and dumping into the
  storm sewer.
• Normally black-iron pipe used
• Corrosion at the air-water interface
• Cross-linked polyethylene (PEX) pipe used to
  solve corrosion problem and for ease of
  installation

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Temperature depth diagram before and after
perforating the casing.
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PEX pipes and corrosion of DHE
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NEW ZEALAND EXPERIENCE

• Rotorua high temperature wells up to 320oF
  (160oC) cannot be perforated or stand open due to
  several layers of cold water
• A system using promoter pipes was developed
• Pipe (convector) open at both ends suspended in
  the well below the water surface producing a
  convection cell bringing hot water up from the
  bottom.
• DHE installed next to the convector or inside the
  convector depending upon the room

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New Zealand promoter pipe installation
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KLAMATH FALLS BACKGROUND

• Many of the earlier wells were not cased to
  generated the vertical convection cell
• As a results about 60 pumper and dumpers
  installed to maximize heat exchange to DHEs
• Dumped water to storm sewer
• Cause water levels to drop approximately one foot
  (30 cm) per year
• A concern to well owners

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Steam rising from storm sewer
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KLAMATH FALLS BACKGROUND

• City of Klamath Falls pass an ordinance in 1985
  which prohibited surface disposal of geothermal
  fluids by July of 1990.
• A well owner either had to drill an injection
  well or use a DHE without pumping, if they wished
  to continue to use geothermal fluids for heating.
• A number of well owners abandoned their well, and
  OIT had to drill two injection wells

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OIT injection well drilling
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EARTHQUAKE OF 1993

• Two earthquakes of 5.9 and 6.0 magnitude occurred
  at depths of 7.5 miles (12 km) and 16 miles (25
  km) northwest of Klamath Falls in September,
  1993.
• Structures were damaged and water levels rose in
  zone of compression and fell in zones of
  extension
• Increases up to 3 ft (90 cm) and decreases up to
  7 ft (2.1 m) were recorded
• The Medical Clinic geothermal well started an
  artesian flow of 30 gpm (2 L/s) 1.5 months before
  the earthquake and increased to 150 gpm (9.5 L/s)
  after.
• Since this was a natural phenomena, the City
  allowed the Clinic to discharge the flow to the
  storm sewer.

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High angle normal faults
Major earthquake epicenters
Klamath Falls
EARTHQUAKE MAP OF 1993
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EARTHQUAKE

• The artesian flow at the Clinic dropped below the
  casing top with time
• A suction pump was then installed to bring up
  heat from the bottom of the well and the water
  discharged to the storm sewer.
• Finally, the City in 2008, served notice to the
  Clinic that they would have to cease pumping and
  dumping to the sewer.

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Artesian flow from well suction pump
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MEDICAL CLINIC PROJECT

• Pacific Plumbers of Klamath Falls was hired to
  solve the pump and dump problem.
• Geo-Heat Center was consulted as to possible
  solutions, as only the bottom of the 12-inch
  (30-cm) diameter casing was perforated for the
  live flow thus, no convection cell produced
• Ripping perforations at the casing top
• Installing a smaller, perforated casing inside
• Lengthening the DHE
• Installing a promoter pipe

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MEDICAL CLINIC DHE

• Well has 12-inch (30-cm)
  a 10-inch (25 cm) casing
• SWL at 8 feet (2.5 m)
• Well drilled to 364-ft (111 m)
• temperature 204oF (96oC)
• artesian flow 280 gpm (18 L/s)
• DHE of 2.5-inch (6.4-cm)
• Decided to use a 4-inch (10-cm) diameter
  promoter pipe to save removing the DHE

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MEDICAL CLINIC HEATING

• They were having trouble heating the facility
  even with the pump and dump system running.
• Especially true for cold morning and warm
  afternoons where the system had to adjust
  temperature down to 100oF (38oC) inside building
• During the winter of 2007-2008 temperatures as
  low as 5oF (-15oC) with average low of 20oF
  (-7oC) and average highs of 40oF (4oC) and max.
  of 50oF (10oC)
• Clinic area of 12,000 ft2 (1,115 m2) with a peak
  heating load of 240,000 Btu/hr (252,000 kJ/hr)
  (70 kW) domestic hot water heating

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PROMOTER PIPE

• March, 2008 installed 355 ft. (108 m) of 4-inch
  (10-cm) diameter promoter pipe.
• One-inch (2.5-cm) diameter holes torch cut near
  top and bottom over a 3 to 5 ft. (1-1.5 m)
  length
• Well water temperature measured inside the pipe
  before and after cutting the holes.
• Pipe suspended off the bottom to avoid fines
  sloughing at the bottom and covering the holes.
  (10 foot 3 m) of open hole at bottom.

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Installing the promoter pipe and temperature
logging the well
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Installing promoter pipe and cutting holes
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RESULTS

• Temperature profile before showed 155oF (68oC) at
  the top of the well and increasing to 193oF
  (89oC) at the bottom, thus the DHE was only
  exposed to the cooler well water with no
  convection cell
• With the promoter pipe installed the temperature
  was 170 to 180oF (77 to 82oC) over the entire
  well depth in March, 2008
• Temperature inside the building was increase to
  around 170oF (77oC)
• Outside low temperature around 28oF (-2oC) and
  highs around 50oF (10oC)

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Before
After
Well temperature profiles
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RESULTS II

• A 2nd set of reading taken in August, 2008.
• Artesian flow had increased, flooding the cellar
  around the well
• Water level has come up about 7 feet (2 m)
• Temperature profile increased from191 to 193oF
  (88 to 89oC)
• 190oF (88oC) inside the building
• The system is working too well!!!

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August temperature profile
Temperature profile in August, 2008
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CONCLUSIONS

• Installing a promoter pipe solved the problem of
  pumping and dumping to the storm sewer
• Increased the temperature of the well water
  throughout the water column
• Increased the temperature of heat supplied to the
  building
• Cost to the Medical Clinic 10,000
• Annual savings in heating 7,000

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Thank You