Balancing oil and gas activities with environmental protection measures is necessary while producing heavy oil. This is because; heavy oil is produced by either chemical or thermal recovery methods which pose harmful effects on the environment. In order to ensure that the oil and gas industry sustainable, there must be elimination of all factors that degrade the environment. Since heavy oil must be produced to meet increasing energy demands, environmentally friendly measures should be used to ensure that there is low carbon emission, little or no chemical retention in the formation. This paper presents mitigation measures for eco-friendly heavy oil recovery; they include the use of renewable energy for heat/steam generation during thermal recovery in order to reduce emission of fuels and use of plant based non-toxic and degradable chemicals to avoid pollution of ground water and formation. These chemicals include polymers, alkali and surfactant during chemical flooding. This ensures the oil and gas industry keeps up with the sustainable development goals.

1. Heavy Oil Recovery: Environmental Implications and Mitigation Measures
Heavy Oil Recovery: Environmental Implications and
Mitigation Measures
*Nwosi-Anele, Adaobi Stephenie1, Obuebite Ann Amalate2, Okoro, Evans Emmanuel3,
Onyekonwu Mike4
1,2World Bank African Center of Excellence, Center for Oil field chemical Research, Institute of Petroleum Studies,
University of Port Harcourt, Nigeria
3Emerald Energy Institute, University of Port Harcourt, Nigeria
4Department of Petroleum Engineering, University of Port Harcourt, Nigeria
Balancing oil and gas activities with environmental protection measures is necessary while
producing heavy oil. This is because; heavy oil is produced by either chemical or thermal recovery
methods which pose harmful effects on the environment. In order to ensure that the oil and gas
industry sustainable, there must be elimination of all factors that degrade the environment. Since
heavy oil must be produced to meet increasing energy demands, environmentally friendly
measures should be used to ensure that there is low carbon emission, little or no chemical
retention in the formation. This paper presents mitigation measures for eco-friendly heavy oil
recovery; they include the use of renewable energy for heat/steam generation during thermal
recovery in order to reduce emission of fuels and use of plant based non-toxic and degradable
chemicals to avoid pollution of ground water and formation. These chemicals include polymers,
alkali and surfactant during chemical flooding. This ensures the oil and gas industry keeps up
with the sustainable development goals.
Keywords: SAGD- Steam assisted gravity drainage, ES-SAGD – Expanded solvent steam assisted gravity drainage
INTRODUCTION
According to Nwosi-Anele and Iledare, (2016), the oil and
gas industry is said to be sustainable, if there is an
elimination of all factors that constitute harm to the
environment while exploiting the oil reserves. Oil and gas
activities around the world is not just restricted to the
conventional light and/medium crude oil recovery, it also
includes recovery of unconventional heavy and extra
heavy oil. Heavy and Extra heavy oil recovery involves
complex recovery methods compared to conventional
medium oil. The complex recovery used for heavy oil
recovery involves use of chemicals and heat. According to
US Geological Survey, Heavy oil is a complex
hydrocarbon having API gravity between 10OAPI –
22OAPI, while extra heavy has API gravity below 10OAPI.
World Energy council classifies heavy crude oil as crude
oil with API gravity below than 22oAPI and density above
920g/ml. The mode of recovery of heavy and extra heavy
oil is complex because they require enhanced oil recovery
methods, usually thermal and/or chemical recovery.
Chemical flooding (polymer, surfactant) reduces interfacial
tension between the oleic and aqueous phases and
increases the viscosity of the displacing fluid resulting in
favorable mobility and increased oil production. Thermal
recovery methods involve the use of heat/steam
generation to reduce the viscosity of the oil and increase
its mobility. Chemical recovery processes involve the
injection of various chemicals into the reservoirs. Alkali,
surfactant and polymers have proven successful for heavy
oil recovery (Obuebite et al, 2018) (Uzoho et al, 2015).
*Corresponding Author: Nwosi-Anele, Adaobi
Stephenie, World Bank African Center of Excellence,
Center for Oil field chemical Research, Institute of
Petroleum Studies, University of Port Harcourt, Nigeria.
Email: nwosi.adaobi@aceuniport.org
Review Article
Vol. 4(1), pp. 034-039, July, 2019. © www.premierpublishers.org, ISSN: 0767-0974
Journal of Oil, Gas and Coal Engineering

2. Heavy Oil Recovery: Environmental Implications and Mitigation Measures
Nwosi-Anele et al. 035
Only little quantities of these chemicals are expected to be
recovered with the produced oil. The interaction of the
chemicals left in the subsurface geologic formations with
connate fluids, brines, and rocks are not completely
understood nor can it be positively stated that toxic
substances or hazardous materials are not produced by
the decomposition of such chemicals (Donaldson,1989).
Such toxic or hazardous substances may be confined to
the reservoir, and no doubt transfer toxins to the
environment, since the environment is part of the
ecosystem (Ellis et al, 2017). This paper reveals that
pollution could occur in the recovery of heavy and extra
heavy oil because of the technologies used, the
implications of the pollution and control and mitigation
measures. It employs the use of environment
management system techniques to aid the regulation of
environmental best practices for the total efficiency of the
oil and gas industry. This paper is necessary because it
reveals how the recovery of heavy and extra heavy oil
affect the environment and result in emission of hazardous
materials into the environment.
LITERATURE REVIEW
Heavy and Extra heavy oil is formed by the cenzoic and
mesozic tectonic movement that damaged the paleo-
reservoirs, causing conventional oil to migrate the shallow
formations or earth surface. These migrated conventional
oil experience micro degradation along with oxidation by
free oxygen thereby forming heavy oil (Caineng et al,
2013). Heavy and Extra-heavy oil are characterized by
high density, high viscosity, consisting of carbon, oxygen,
hydrogen, nitrogen and sulphur where carbon and
hydrogen are the dominant components. Metallic elements
such as Nickel, Vanadium, Copper, and Iron occur in trace
quantities.
Heavy oil has been found to be a good alternative to
light/medium crude oil in this era of increasing energy
demand and reducing light and medium crude oil reserve
base. Countries like Canada, Venezuela, Trinidad and
Tobago heavy oil recovery have begun to yield millions of
barrels and meeting their countries energy demand.
Recovery methods that have been applied with great
success are:
Chemical Recovery Methods
• Polymer flooding
• Alkali-surfactant and polymer flooding
Thermal Recovery Methods
• Steam assisted gravity drainage
• Expanded steam assisted gravity drainage.
• Steam flooding/injection
• Cyclic steam stimulation
• In situ combustion
• Toe to heel air injection
CHEMICAL RECOVERY METHODS
Polymer Flooding
Many heavy-oil reservoirs in Canada are relatively small,
thin and are not good candidates for expensive thermal
recovery methods. This has made Polymer, Alkali and
Surfactant flooding relevant for thin and small reservoirs.
Polymer flooding involves the injection of high viscous
polymer fluids into the reservoir to act on the thick oil
layers. Polymers act as the displacing fluid, effectively
displacing (pushes out) the oil thereby increasing the
sweep efficiency due to its high viscosity resulting in
improved oil recovery. This method has been applied in
Nigeria by Mogbo, (2011) in a reservoir located in the Niger
Delta with a gas cap and little water aquifer. It was found
that there was incrémental oïl production of 7% but a lot of
polymers were lost in the subsurface formation which is
hazardous to the environment.
Alkali-Surfactant-Polymer Flooding (ASP)
This method involves the injection of alkali -surfactant into
the reservoir to obtain an ultra-low interfacial tension and
enhance oil recovery. In Enhanced oil recovery,
Surfactants are primarily used to reduce the tension
between the fluids at the interface. Alkalis (high pH
chemicals) form natural surfactant upon reaction with the
napthenic acid in the crude oil. They are less expensive
than the synthetic surfactant and reduces the absorption
of synthetic surfactant. In Nigeria, Avwioroko et al, (2014)
applied alkali-surfactant and polymer flooding for heavy oil
recovery. Alkali used was sodium hydroxide, surfactant
was Tween (polysorbate), and polymer used was Gum
Arabic and salt. The Gum Arabic used as polymer is a local
plant found in the wild rain forest in Nigeria and other parts
of Africa. An incremental recovery of 57% was observed
with ASP in Nigeria. The advantage of this method is that
a local plant is used and such polymer even though lost in
the formation may not be of any harm to the environment
and the ecosystem.
THERMAL RECOVERY METHODS
Steam Assisted Gravity Drainage (SAGD)
This is an advanced method of heavy oil production. It
utilizes steam as an agent to conduct heat through thermal
conduction and convention while being produced through
a gravity drainage. According to Delamaide, (2015) SAGD
can be applied in three different ways:
• Two horizontal wells are drilled near the reservoir
bottom with one on top of another. The upper well is an
injector while the bottom well is a producer.
• A horizontal well is drilled alongside two or more vertical
wells. The horizontal well is drilled at the bottom of the
reservoir with the vertical wells above it. The vertical
well serves as the injectors while the horizontal well is
the producer.

3. Heavy Oil Recovery: Environmental Implications and Mitigation Measures
J. Oil, Gas Coal Engin. 036
• The third way is to use only one horizontal well with a
steam string running into it to introduce steam into the
reservoir. This method is more economical than the
other two; it enhances Gas oil ratio and oil production
rates.
SAGD has been found to be uneconomical in certain
formation especially in North America (Amirian et al,
2018). Hence SAGD can be said to be not economical and
environmentally friendly, because steam generation
results in increasing carbon emission into the environment
and is also costly. Thermal methods may by
environmentally friendly if carbon emission via steam
generation is eliminated. Steam generation can be done
using solar power. This can be applied to all the thermal
methods.
Figure 1: Steam assisted gravity drainage
(source: oilfield team)
Expanded Steam Assisted Gravity Drainage (ES-
SAGD)
This method is similar to SAGD, but it involves the
combination of steam with solvent injected via the injection
well to aid production of oil. The solvent injected could be
either an alkali, surfactant or a polymer (this reduces the
interfacial tension between oil and water, capillary
pressure and alter wettability). It has shown improved
heavy oil recovery rates. Encana Corporation of Canada
has tried ES-SAGD pilot scheme at its Senlac thermal
project in 2002 for heavy oil (Nasr, 2005). Solvent-assisted
SAGD can lead to lower steam usage and energy intensity
than that of SAGD. This has several implications. First,
less steam use means less energy consumption which in
turn implies less fuel gas emissions to the atmosphere.
Second, less steam use means less water handling,
production and treatment. Third, produced solvent can be
separated and re-injected into the oil sand formation, i.e.,
it can be recycled. The injected steam keeps the region
near the well bore hot, making the solvent to remain in the
vapor phase which in turn promotes its transport (Gates,
2010). The major disadvantage of this method is the
retention of the solvent in the shallow reservoir which is
likely to cause pollution of ground water.
Steam Flooding/Injection
Dry steam is injected into the reservoir through the
injection well to supply energy and heat the oil layers
reducing the oil viscosity, making thick oil layers mobile to
flow into the production well. This method is effective in
heavy oil reservoirs with bottom aquifer and large gas cap.
Figure 2: Steam injection
(source: oilfield team)
Cyclic Steam Stimulation
Steam is injected into a drilled well in the formation; the
well is shut for six (6) days to allow the steam to soak for a
few days. The steam soaks the formation, mobilizing the
oil and building up reservoir pressure. After six (6) days,
the oil is produced from the same well
Figure 3: Cyclic Steam injection
(source: oilfield team)

4. Heavy Oil Recovery: Environmental Implications and Mitigation Measures
Nwosi-Anele et al. 037
In-situ Combustion
This method is one of the earliest methods used in heavy
oil recovery. It was patented in the United States in the
year 1920. It is sometimes referred to as fire flooding.
Air/oxygen is introduced into the reservoir; the well ignites
the oil in the reservoir and starts a fire. Heat is generated
as a result of oil oxidation, increasing the temperature. The
heat generated by burning the heavy hydrocarbons in
place produces hydrocarbon cracking, vaporization of light
hydrocarbons and reservoir water in addition to the
deposition of heavier hydrocarbons known as coke. As the
fire moves, the burning front pushes ahead a mixture of
hot combustion gases, steam and hot water, which in turn
reduces oil viscosity and displaces oil toward production
wells.
Toe to Heel Air Injection (THAI)
Toe to heel air injection (THAI) process is a new enhanced
oil recovery process used in the recovery of heavy oil
formulated by Petro bank Energy and Resources limited of
Canada. It is a thermal recovery method that integrates
advanced reservoir technology and horizontal well
concepts for heavy oil recovery. It burns the heavy coke
fraction of the reservoir to produce heat required to
increase the temperature of the oil-bearing formation, this
reduces the viscosity of the oil, making it mobile (Fatemi et
al, 2011). THAI is similar to in-situ combustion in operation
but the injector well is a vertical well, while the producer
well is a horizontal well, more of the mobile oil penetrates
the producer well because it is a horizontal well as seen in
Figure 4. Recovery efficiency is high with toe-to heel air
injection compared to in-situ combustion.
Figure 4: Toe to heel air injection
(source: oilfield team)
Table 1: Environmental implication of heavy oil recovery
S/N RECOVERY METHOD ENVIRONMENTAL IMPLICATION MITIGATION
1. Polymer Flooding Polymer retention in the formation
causing ground water pollution and
pollution of ecosystem resulting from
water cycle processes.
Use of environmentally friendly
natural polymers sourced from plants
or trees e.g. Gum Arabic
2. Alkali-Surfactant-Polymer
Flooding
Alkali-Surfactant-Polymer retention
in the formation causing ground
water pollution and produced water
pollution.
Use of locally sourced/
environmentally friendly alkali-
surfactant. Typically sourced from
plants and trees. e.g. Lecithin
3. Steam Assisted Gravity Drainage Carbon emission resulting from fuel
used to generate steam.
Use of renewable energy (wind, solar,
hydro) as source of steam generation
4. Expanded Steam Assisted Gravity
Drainage
Carbon emission resulting from fuel
used to generate steam and
retention of injected solvent
Use of renewable energy (wind, solar,
hydro) as source of steam generation
and use of eco-friendly solvent.
5. Cyclic steam stimulation, Steam
Injection, In-situ combustion and
Toe to heel air injection
Carbon emission resulting from fuel
used to generate steam.
Use of renewable energy (wind, solar,
hydro) as source of steam generation
CONCLUSION
Heavy oil recovery methods are mainly thermal and/ or
chemical method, only a few reservoirs are successfully
recovered using artificial lifts systems. The use of synthetic
chemicals and harmful solvent to enhance oil recovery is
a threat to the environment and the climate. To mitigate
this challenge, use of environmentally friendly chemicals
(green fluids) that are mostly plant based and the
generation of heat/ steam using renewable energy sources
(wind, solar, hydro) is a way to ensure that a balance of
Energy - Economy- Environment is attained complying
with Sustainable Development Goals.

5. Heavy Oil Recovery: Environmental Implications and Mitigation Measures
J. Oil, Gas Coal Engin. 038
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Accepted 24 July 2019
Citation: Nwosi-Anele AS, Obuebite AA, Okoro EE,
Onyekonwu M (2019). Heavy Oil Recovery: Environmental
Implications and Mitigation Measures. Journal of Oil, Gas
and Coal Engineering, 4(1): 034-038.
Copyright: © 2019 Nwosi-Anele et al. This is an open-
access article distributed under the terms of the Creative
Commons Attribution License, which permits unrestricted
use, distribution, and reproduction in any medium,
provided the original author and source are cited.