NEW SAGD TECHNOLOGIES SHOW PROMISE
IN REDUCING ENVIRONMENTAL IMPACT
OF OIL SAND PRODUCTION
Vicki Lightbown1
INTRODUCTION
In Alberta, 80 percent, or roughly 135 billion barrels, of the oil sands are buried deep
below the surface and are not accessible by open pit mining. To access these valuable
resources, industries use an in-situ extraction method called Steam-Assisted Gravity
Drainage (SAGD) (shown in Figure 1). Because in-situ extraction takes place mainly
under the Earth’s surface, less land is disturbed during the extraction process than
surface mining.
In 2012, Alberta’s total in-situ bitumen production was about 990,000 barrels per
day, a 16 percent increase over 2011. This accounts for 52 percent of Alberta’s total
crude bitumen production. By 2022 in-situ production is expected to reach 2.2 million
barrels per day [1].
SAGD is a thermal in-situ production process where parallel wells are drilled
horizontally into an underground bitumen reservoir. Steam is produced at the surface
and injected into the reservoir through the shallower of the two wells (the injection
well). The steam heats the bitumen to a point where gravity allows it to flow down to
the lower well (the producer well) where the mixture of bitumen and water is then
pumped to the surface. The water and bitumen are separated at the surface.
Approximately two to four barrels of water are required per barrel of oil produced;
however, approximately 90 percent of the water used can be recycled back through the
process, so only half a barrel of new water (make-up water) is added to the process for
each barrel of oil produced. In comparison, oil sands mining operations use
approximately 2–4 barrels of make-up water and conventional oil operations use
approximately 0.1–0.3 barrels of make-up water per barrel of oil produced [2].
Treatment of the recycled water consumes energy and generates waste. Greenhouse
gas emissions for SAGD projects are around 0.06 tonnes of carbon dioxide equivalent
per barrel of bitumen produced [1]. As water becomes a more critical resource, operators
have had to start looking for and using alternative technologies to increase water recycle
rates while minimizing the amount of energy consumed in the water treatment process.
KEYWORDS
oil sands, produced water, steam-assisted gravity drainage, evaporator,
warm-lime softener, de-oiling, zero liquid discharge, Alberta, water treatment
1
Project Specialist, Alberta Innovates–Energy and Environment Solutions, Suite 1800, 10020 - 101A Ave | Edmonton,
Alberta | T5J 3G2. E-mail: vicki.lightbown@albertainnovates.ca. Company website: www.ai-ees.ca.
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FIGURE 1. SAGD process [1].
SAGD WATER TREATMENT PROCESS
When the bitumen and water mixture comes to the surface, the first step is to separate as
much of the bitumen from the water as possible. Next, any hardness and silica that may have
come from contact with the reservoir or come in with the make-up water is removed. The
water then goes through a polishing stage and is sent to the boiler to produce steam. Figure 2
shows two typical high level SAGD water treatment processes.
Oil/Water Separation
Typically, SAGD operations use a four phase oil/water separation process:
•
•
•
•
Free water knock-out
Skim tank
Induced gas flotation (IGF)
Oil removal filter (ORF).
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FIGURE 2. High level schematic of SAGD water treatment process.
The current oil separation process is unable to consistently provide oil-free produced
water, which creates reliability problems within the water processing facility. Oil that passes
downstream can cause upsets in warm lime softeners and fouling of heat exchangers and steam
generators. Upsets and fouling require downtime for cleaning and maintenance, resulting in
extra cost and loss of production. Efficient, reliable, cost-effective de-oiling technologies are
critical for water management in SAGD operations.
Hardness and Silica Treatment
The most common hardness and silica treatment process uses three treatment units:
• Warm lime softening (WLS)
• After-filters
• Weak acid cation (WAC) ion exchange.
WLS has a large site footprint and high capital cost for onsite installation. It requires
experienced operators to actively manage the treatment process in order to achieve stable
operation. WLS generally works well with water that has a lower total dissolved solids (TDS)
content (<7,000 ppm). As the TDS content increases, the amount of chemicals added
increases and the amount of treated water coming out of the unit decreases (i.e., more waste is
produced) [3]. After-filters are then used to remove precipitated solids from the treated water.
WAC units generally perform as designed and are not targeted for technology improvements. They can, however, have fouling issues if the oil removal process is not operating
reliably.
Some SAGD operators are now moving to evaporator technologies for silica and hardness removal. Evaporators use more energy than WLS and can be more expensive; however,
they can treat water with high levels of TDS while maintaining high water recycle rates and
producing a higher quality water output.
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TABLE 1. Example SAGD water compositions (PW: Produced water, FW: Fresh water make-up,
BW: Brackish water make-up) [3].
Quality
Units
PW1
PW2
FW
BW1
BW2
BW3
TDS
ppm
1290
2870
1291
6961
17147
24532
Hardness
ppm
14
50
159
204
1411
2031
M-Alkalinity (CaCO3)
ppm
173
297
481
665
346
411
Calcium
ppm
4
11
44
34
302
432
Magnesium
ppm
1
5
12
29
159
231
Total Organic Carbon
ppm
300
350
8
6
4
8
Silica
ppm
188
261
14
7
7
7
Steam Generation
SAGD operations use two types of boilers to produce high-pressure, high-quality steam
(approximately 1000 psig): once-through steam generators (OTSG) and drum boilers. OTSGs
are the most commonly used boiler type as they are more robust and can handle feed water
with higher TDS content (<8,000 ppm) [4]; however, OTSGs can be unreliable and must
be followed by a vapor-liquid separator to increase the steam quality. Drum boilers are more
reliable and more efficient (use less energy) than OTSGs but can only be used in conjunction
with evaporators because they have lower limits on feed water quality parameters.
Water Composition
Water composition can vary widely depending on the formation being produced, the source
of make-up water (fresh or saline), and the technology being used. Example water compositions for various streams are shown in Table 1. The challenge with handling SAGD water is
the combination of hardness, silica, and oil.
REGULATIONS IN ALBERTA
The oil sands industry in Alberta is a highly-regulated industry. Thermal in-situ oil sands production can have environmental impacts such as use of water resources (both fresh and saline),
release of GHG to the atmosphere, and land fragmentation. Thermal in-situ water management regulations aim to minimize environmental impacts and maintain sustainable operations.
Directive 081: Water Disposal Limits and Reporting Requirements for Thermal In-Situ Oil
Sands Schemes is a recently released directive that consolidates various aspects of water management requirements for thermal in-situ oil sands schemes. The directive sets out water disposal limits, which require operators to recycle produced water efficiently and ensure that all
make-up sources are effectively used [5].
To increase transparency, thermal in-situ operators are required to report monthly on
annual water use. The reported numbers are summarized in the publicly-released Thermal
In-Situ Water Publication [5]. The report includes:
• Maximum annual water disposal limits and actual water disposal
• Produced water recycle and produced water-to-steam injection ratios
• Water productivity ratios (fresh water, brackish water, and disposal)
4www.oilgasandmining.com
• Make-up water use (fresh and brackish)
• Volumetric data (fresh water, brackish water, steam injection, water production, total
disposal, and bitumen production).
In addition to water regulations, Alberta has a Specified Gas Emitters Regulation
(SGER). In April 2007, Alberta became the first jurisdiction in North America to pass climate
change legislation requiring large emitters to reduce greenhouse gas (GHG) emissions. Emitters that produce more than 100,000 tonnes of GHGs a year are mandated to reduce emissions intensity by 12 percent. Companies have four choices to be in compliance [6]:
•
•
•
•
Make improvements to their operations
Purchase Alberta-based offset credits
Contribute to the Climate Change and Emissions Management Fund
Purchase or use Emission Performance Credits.
In 2012, 15 oil sands in-situ sites were required to comply with the SGER [7].
The challenge of balancing water management requirements with greenhouse gas emissions has led operators to look for innovative technical and operational solutions.
ALBERTA INNOVATES–ENERGY AND ENVIRONMENT SOLUTIONS
Alberta Innovates–Energy and Environment Solutions (AI-EES) is a provincial corporation
formed in 2010 as part of Alberta Innovates system. AI-EES’ goal is to help Alberta become a
global leader in sustainable energy production. AI-EES works with their partners to identify
critical technology gaps and apply world-class innovation management strategies and research
to develop solutions for the biggest challenges facing Alberta’s energy and environment sector.
As part of their portfolio, AI-EES works with industry, government, and technology developers to help find and develop innovative solutions to address the water versus energy challenge
that SAGD operators are faced with.
In addition to its own technical portfolio, AI-EES acts as the technical arm of the
Climate Change and Emissions Management (CCEMC) Corporation. The CCEMC is
funded through the Climate Change and Emissions Management Fund and invests money
from large-scale Alberta emitters into technology initiatives that reduce GHG emissions and
improve our ability to adapt to climate change.
Thermal In-Situ Water Conservation Study
In 2011, AI-EES and a consortium of industry partners commissioned the Thermal In-Situ
Water Conservation Study [3]. The purpose of the study, completed by Jacobs Consultancy,
was to evaluate the trade-off between water recycling, GHG emissions, and waste generation
to achieve various water recycling rates in thermal in-situ oil sands operations. The study also
considered new technologies with the potential to reduce energy consumption while maintaining a high rate of water recycling.
The Thermal In-Situ Water Conservation Study found [3]:
• WLS has the lowest GHG emissions. The produced water recycle rate was limited
to 87 percent with fresh make-up water. The recycle rate dropped quickly when the
TDS concentration of the make-up water exceeded approximately 7,000 ppm.
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• Evaporators can achieve a produced water recycle rate in excess of 90 percent even
with TDS levels exceeding 24,000 ppm; however, GHG emissions were 7 to 8
percent higher than WLS.
• Technologies that minimize water use, such as evaporation and zero liquid discharge,
will increase GHG emissions between 3 to 10 percent on an overall SAGD plant.
• Zero liquid discharge increased the produced water recycle rate by 1 to 3 percent,
but increases GHG emissions between 2 to 6 percent over evaporators. Zero liquid
discharge also increases capital costs and operational complexity for operators.
• New technology options examined in the study offer the potential to better balance
the trade-off between GHG emissions and water recycle; however, the changes
are evolutionary and incremental over the best commercial technologies available.
Improved reliability and operability could be potentially larger drivers for water
treating technology selection than reductions in GHG emissions and water use.
Figure 3 and Figure 4 show the produced water recycle rate (PWRR) and GHG emissions for the evaporation and WLS cases at various TDS levels.
RJ Oil Sands De-oiling
RJ Oil Sands (RJOS) is an Alberta-based company developing game changing solutions for
enhanced oil recovery from waste streams in the oil and gas industry. AI-EES, Pengrowth
Energy Corporation (Pengrowth), and Laricina Energy Ltd. (Laricina) have partnered with
RJOS to pilot a high-temperature, high-pressure de-oiling technology.
RJOS has developed a low energy separation technology that does not require heat,
chemicals, or rely on density of the oil to remove the oil out of liquid and slurry streams. At
the heart of the RJOS process is a patented Phase Separation Device that induces dissolved
FIGURE 3. Produced water recycle rate vs. make-up water TDS concentration for WLS and
evaporators [3].
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FIGURE 4. GHG emissions vs make-up water TDS concentration for WLS and evaporators [3].
and entrained gas into the feed water to separate oil and oil wet solids from the process water.
The process is fully automated and can respond to variable flow rates and slugs of oil (upsets).
Water coming out of the unit has an oil content of <10 ppm in SAGD applications [8].
Figure 5 shows a schematic of the RJOS process.
RJOS has two commercial-scale installations of their process operating at low temperature
(approximately 90°C). The objective of the current pilot is to test the RJOS process at higher
temperature (approximately 140°C) and pressure. The benefits of operating at a higher temperature include:
• The elimination of a common operational challenge: in this process water will not
need to pass through a heat exchanger prior to de-oiling. Using current processes,
heat exchangers often require regular maintenance to address fouling issues.
• Energy savings and GHG emissions reductions: in the current water treatment
process water comes from a reservoir and is cooled to approximately 90°C before
FIGURE 5. Schematic of RJOS process [9].
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treatment, then reheated to create steam for injection. With the RJOS hightemperature de-oiling process the water can circulate through the water treatment
process without cooling which reduces the reheating load during steam generation.
A high-temperature hardness/silica removal technology will need to partner with the
RJOS process to achieve the full benefit.
The RJOS high-temperature, high-pressure de-oiling pilot skid is constructed and operating at a Pengrowth SAGD facility. To date, the pilot has been operating as expected. Final
results will be reported in the middle of 2014.
IDE Technologies Falling Film Evaporator
IDE Technologies (IDE) is a world-leading water treatment company specializing in the
development, engineering, construction, and operation of enhanced desalination facilities and
industrial water treatment plants. The company is headquartered in Israel and holds subsidiaries around the world. AI-EES, Alberta Innovation and Advanced Education, and the Canadian Oil Sands Innovation Alliance (COSIA) have partnered with IDE to pilot their unique
horizontal falling film evaporator. The technology has been used in treating heavy oil produced water for over 20 years. It is now being adapted and optimized to the meet the unique
needs of the oil sands market. Figure 6 shows a schematic of the IDE design.
The IDE horizontal evaporator is a multi-effect (multi stage) evaporator that offers different chemical conditions in each stage and reduces the exposure of parts to concentrated brine.
The IDE evaporator design is unique in that the interior tube bundles are oriented horizontally, as opposed to vertically as is the case in evaporators currently being used in SAGD.
The horizontal orientation improves energy efficiencies and allows for easier removal and
cleaning of the tube bundles. IDE expects their horizontal evaporator to use 30 percent less
power than current evaporator technologies [10].
FIGURE 6. Schematic of IDE horizontal falling film evaporator [10].
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IDE has designed the evaporator so that it is modular and can be prefabricated offsite.
The modular design reduces site installation time by multiple months. Reduced site installation time can have signification labour cost savings in the oil sands region where labour costs
are known to be high.
The IDE horizontal evaporator is currently being tested at lab scale (1 m3/day) using feed
water streams from various SAGD sites. Initial tests show positive results, as shown in Table 2.
Lab testing is expected to run through the middle of 2014. Once lab testing is complete,
the evaporator will be scaled up to a field demonstration at an Alberta SAGD facility. The
field demonstration is expected to treat approximately 250 m3/day of produced water.
TABLE 2. Pilot performance with produced water as feed water [11].
Parameter
Feed Water (ppm)
Brine (ppm)
Distillate (ppm)
Total Organic Carbon
492
8583
10–20
Silica (as SiO2)
260
5124
1.5–3
Calcium
2.6
48
0.02–0.09
Magnesium
0.6
2
0.01–0.02
1,400
39,000
5–10
Total Dissolved Solids
FIGURE 7. IDE pilot 1 m3/day pilot unit [11].
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Saltworks Technologies Zero Liquid Discharge
Saltworks Technologies (Saltworks) is a British Columbia–based company that develops innovative water purification, desalination, and brine treatment systems. Saltworks has developed
a zero liquid discharge technology, called SaltMaker, that treats challenging industrial waste
waters to produce fresh water and salts. Saltworks is partnered with the CCEMC and SAGD
operators to pilot the SaltMaker using concentrated SAGD boiler blow down water.
The SaltMaker would replace crystallizers that are currently being used for zero liquid
discharge at some SAGD facilities that don’t have the option of deep well disposal. The SaltMaker is expected to be lower cost, use less energy, and be more reliable than the crystallizers.
The SaltMaker uses waste heat to treat the water through four humidification–dehumidification steps, which is expected to have a large reduction on energy consumption. The energy
requirements of the process are 8 kWhe/m3 (electrical) and 150–200 kWht/m3 (thermal at
85°C) [12]. A schematic of the treatment process is shown in Figure 8.
The SaltMaker is modular in design, uses no membranes, has non-metallic wetted parts
(minimizes corrosion), and includes an automated self-cleaning process. The modules can be
removed for inspection via a simple cart without confined space entry. Figures 9, 10, and 11
show the SaltMaker modules and module assembly.
Pilot testing is in progress and results are generating increased interest from SAGD operators. The pilot is expected to be completed by December 2015.
FIGURE 8. Schematic of Saltwork’s SaltMaker process [12].
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FIGURE 9. SaltMaker Modules
and Mass Production [12].
FIGURE 10. Assembled module (left) and moduling loading/unloading by forklift (right) [12].
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FIGURE 11. SaltMaker under construction at site: modules based on ISO container “blocks” [12].
SUMMARY
Thermal in-situ oil sands operators are faced with the challenge of balancing water management requirements with GHG emissions. The challenge has led operators to look for innovative technical and operational solutions.
Current technologies under development have the potential to improve water conservation while reducing energy use and costs. AI-EES, technology developers, industry, and government are partnering to advance these technologies through the development process. As
technologies reach commercialization, the thermal in-situ oil sands industry should expect to
see improved environmental performance while maintaining economic production.
REFERENCES
1.http://www.energy.alberta.ca/OilSands/pdfs/FS_SAGD.pdf
2. In-Situ Oil Sands Water Treatment and Reuse Optimization 2014, conference proceedings, January
22–23, 2014.
3.http://www.ai-ees.ca/media/6868/thermal-in-situ-water-summary-report.pdf
4.http://www.tundrasolutions.ca/files/Evaporators%20in%20SAGD%20DP.pdf
5.http://www.aer.ca/about-aer/spotlight-on/oil-sands/in-situ-impacts
6.http://esrd.alberta.ca/focus/alberta-and-climate-change/regulating-greenhouse-gas-emissions/greenhousegas-reduction-program/default.aspx
7. AESRD, personal communication
8.http://www.rjoilsands.com/tech/
9. RJ Oil Sands, personal communication
10. IDE Technologies, personal communication
11. COSIA Oil Sands Water Conference 2014, conference proceedings, March 11–13, 2014.
12. Saltworks Technologies, personal communication
12www.oilgasandmining.com