Tertiary oil recovery is also sometimes known as
enhanced oil recovery because many oil companies have now abandoned the
conventional approach of oil recovery using primary recovery followed by
secondary followed by tertiary in that order so sometimes the recovery is now
started with tertiary oil recovery hence the name has been changed to enhanced
oil recovery in literature. In this blog post I aim to analyze the
environmental implications with a focus on climate change of one of the
traditional methods of enhanced oil recovery using Carbon Dioxide, as well as
the method’s other implications. This method requires injecting CO2 gas into
the well to increase the pressure and thus make oil come up to the surface or
to make CO2 mix with the remaining oil thus making it more volatile and also
causing it to come up to the surface.
CO2-EOR can help in the reduction of CO2 emissions and
simultaneously improve the security of energy supply. There are no current
implications of this technique in Europe. Not implemented in Europe yet due to
high costs of CO2 thus increasing the operating and capital expenses of
offshore projects of oil extraction and making oil economically unprofitable to
extract using this method. However Kyoto protocol is pressuring Europe to think
seriously about decreasing CO2 emissions together with higher oil prices
suggest that this method of oil recovery might be implemented in the near
future. The oil fields in the North Sea are also running out of oil that may be
extracted using primary or secondary recovery thus they either need to be
abandoned or more investments made into them in terms of enhanced oil recovery.
This technique is already quite widely used in the USA, which is known to
increase oil recovery by 9-18% more from the reservoir beyond what is
achievable using the conventional primary and secondary methods of recovery.
For this blog post, one of the readings I did was examine the European
Commission’s Report together with the Institute of energy on the potential of
the implication of this technique in Europe. The report focused it’s study on
the region in the North Sea which included 81 active oilfields and produces 73%
of crude oil produces in the EEA (European Economic Area) at 4 million barrels
of oil per day. These oil fields belong to UK, Norway and Denmark.
Crude oil production in the EU reached approximately
1.05 billion barrels in 2003 which corresponds to 4% of world oil production
(European Commission, 2005).
However we have to remember that Norway is not part of the EU hence these
figures are not as easy to interpret as not all of Europe is included yet the
report considered Norway when it was created as territorially Norway, is, in
fact in Europe and it’s also part of the EEA. The inland consumption of oil in
the EU in 2003 was at approximately 4.78 billion barrels hence 78% of oil
(European Commission, 2005)
was supplied by imports which increases the price of oil available for use in
the EU. Most of the imports of this oil came from OPEC countries 40.3%,
followed by Russia at 24.8% and Norway at 22.0%. Despite the high levels of
imports of oil into the EU already, the European production of it is actually
decreasing, which means the prices of the essential raw material- oil will rise
further within the EU. This is shown by Figure 1 below. Furthermore, the fact that
The North Sea is running out of the easily recovered oil adds an urgency to the
matter as otherwise the already struggling EU economies will be effected. Thus
in this blog post I examine the advantages and disadvantages of using one of
the enhanced oil recovery methods with regards to Europe.
Figure 1.
Source: European Commission, 2005 Crude oil production, net gross consumption and import dependency in the EU
during the period of 1990-2030.
At first sight, this method of oil recovery seems more
eco friendly than other methods and if fact even helps the environment to a
certain extent reducing the emissions of CO2 into the atmosphere and hence
reducing the anthropogenic climate change. It includes injecting CO2 into the
oil reservoirs to obtain the oil out of them, which means also creating
underground CO2 stores. Carbon capture and storage (CCS) underground are
currently a field of active research as little is actually known about the
implications of such practice. But the main advantage is that CO2 is captured
from power plants and other anthropogenic CO2 sources that massively effect
climate change due to very high emissions of this GHG and it is injected into
the oilfields that nearly reached the end of their lives. AS a result of this
process CO2 is stored underground decreasing that country’s and global CO2
emissions and additional oil is produced thus creating income that helps the
economy in this environmentally helpful process. This environmental fact certainly
gives this method of oil recovery an advantage over other methods of enhanced
oil recovery.
The energy industry itself creates very high pollution
levels due to combustion of fossil fuels for energy production thus it is
responsible for air, water and soil pollution so surely it should take at least
some responsibility for its actions?! Furthermore oilfields are proven fluid
traps, providing a certain level of certainty that they could serve as good CCS
stores to try and mitigate the effects of climate change. If CCS was one of the
techniques of mitigation of climate change, the oilfields (due to their
economic profitability) are the geological reservoirs that have had the most
research done to them thus there is better data available about them than any
non-commercially profitable geological storage options for carbon such as
aquifers. CO2 has to be stored in formations that occur at approximately 800m
below the surface thus oilfields and aquifers are the best carbon storage
options available on Earth CCS was used to combat climate change (Gough, 2006).
A saline aquifer is a geological formation in the rock
found both below sea beds and ground and it consists of a layer of porous rock
bearing saltwater. Oilfields are underground traps that used to store oil and
gas or still do before it is extracted mostly without leakages over millions of
years and they include already built infrastructure built around the sites
already for the purposes of oil recovery that could now also be used for CO2
storage pumping.
Experience from CO2- EOR (Enhanced Oil Recovery) use
in USA has shown that approximately 0.33 tones of CO2 are required to produce a
barrel of oil miscible EOR operations and up to 0.8-1.1 tones per barrel of oil
for immiscible CO2-EOR operations (European Commission, 2005).
There are two types of oil EOR- miscible and immiscible which differ in the way
and process oil is forced from under the ground but either way, it is evident
that CO2 would be stored under the ground.
However there have also been studies done trying to
assess CCS implications for our planet as well as humanity in general. They use
SRES scenarios, which are Special Report on Emissions Scenarios produced by the
IPCC and often used to model climate change in studies or what if studies under
different future conditions due to climate change. I shall look at them more
closely in my next blog post as they are fairly important. The good thing here
is that the use of SRES by CCS studies also means that they consider climate
change when looking at the implications of CCS as well as the fact they
consider different projections of climate change and not just the implications
of CCS today.
One of the worries of CCS is that although it makes
CO2 “disappear” it is also not the ultimate solution of CO2 emissions and high
anthropogenic production as we have to be careful not to just hide this problem
“under the carpet”. The timescale of how long we can keep CO2 under the ground
stored in these reservoirs is not certain and not enough research has been done
into the area. The key security issue is the integrity of bedrock. As Figure 2
below shows, oil and gas cavity in bedrock or where CO2 is advised to be stored
is covered by a cap rock, which is an impermeable layer of rock that acts as a
seal. However longterm security relies on a continuous layer of cap rock
extending far from the points of injection of CO2 into the ground through the
oil wells. The oil wells themselves may represent weak points but these could
potentially be monitored to avoid leakages and rapidly sealed if a leak was to
occur but what if a leak occurred in some other place along the reservoir? The
reservoirs sometimes extend over large geographical areas and hence it would be
very difficult and expensive to monitor the whole thing over ground.
Source: European Commission, 2005. A typical “anticline” oil reservoir resulting from the upward folding of
geologic strata (left) and a schematic of an oil occurrence within the
reservoir (right).
Furthermore the specific store capacities of the
reservoirs remain unknown. The potential capacity for storage in an aquifer are
calculated from estimates of volumetric sweep efficiency (the displacement of
water by CO2) based on modeled simulations of the reservoirs (Gough, 2006).
However as we remember from the oil reserves blog post, it is very difficult to
determine the size of the reservoir and the current technology does not provide
detailed estimates thus they often change from the moment an oil reserve is
discovered and all through its lifetime. Furthermore the pore volume that can
be used for CO2 storage in the reservoir is very specific on each reservoir and
depends on factors such as rate of injection, relative permeability, density
and mobility of the fluids and rock heterogeneity. However this would require
detailed research of each reservoir, which is currently lacking and thus only
very generic estimates are used so it is uncertain how much CO2 we could
actually “bury” under the ground and whether it is worth it. The extent of
reversibility of CO2 back to the surface from the reservoirs also currently
remains a mystery so the talk of using this CO2 in the future for new methods
of energy creation and thus CCS being an early investment into something
potentially very good for the economy remains a mystery.
Adverse impacts to human health and ecosystems are
also a potential. Although CO2 is not toxic or too dangerous for humans in small
concentrations, potentially leakages from the reservoirs can be very dangerous
to humans because being a gas, CO2 would rapidly spread until the leak is
discovered and high quantities of the gas have the potential to cause such
severe conditions as asphyxiation (difficulties in breathing due to lack of
oxygen) which potentially further leads to coma or death (Gough, 2006).
The effects of CO2 that would be pumped into the reservoirs on any
micro-organisms that might inhabit the reservoirs are also unknown thus
potentially some ecosystems could get damaged although research suggests that
oil and gas deposits would have already killed said ecosystems or caused them
to adapt.
Finally there is also uncertainty that remains about
the impacts on the large-scale earth systems due to CCS. There are some
concerns that it would cause disruptions in the balance or weight distribution
between ice caps and oceans thus effecting geology. Furthermore the increased
pressures within the reservoirs could induce new seismicity in complete
different parts of the world. So not only would we experience the effects of
more natural disasters in terms of earthquakes and volcanic eruptions but also
the whole environment on Earth is interlinked so by dis balancing the oceans,
CCS could create a potential greater positive feedback to climate change
compared to CO2 emissions into the atmosphere.
However despite all the uncertainties and under
research of CCS, it is currently quite widely used in the USA for EOR and it is
seen as a rather positive method of EOR compared to other methods so the
question of why it is not yet implemented in Europe remains.
Firstly there are still some technical difficulties
that remain with using this method in the North Sea such as the fact that in
the US it is only used on the onshore oil fields whilst we are talking about
offshore fields in Europe and hence the method requires research and monetary
investment into this research as well as time before it can be implemented.
Also the reservoir stratigraphy in the North Sea is very different to that in
the US and it contains faulted blocks and steeply dipping beds. In the US the
reservoirs are located in the low permeability and low dipping formations
unlike the North Sea which are dominated by high permeability dipping
reservoirs which means that gravity effects in the North Sea will be more
important than viscous flow in the US so yet again more research into the
effects of geology would be required (Gough, 2006).
Then there are also the economic reasons that not only
would money have to be invested into all the extra research but also the costs
of CO2 supply itself. Due to North Sea fields being offshore, there are no
major combustion plants near by and thus infrastructure would have to be put in
place to deliver CO2 to the oilrigs. Close monitoring of the wells would
further be required to avoid the danger of leakages thus also increasing costs
of recovery of oil this way. All of these make oil recovery this way
potentially uneconomically viable for the purpose. Seeing as CCS is not yet
seen as a major climate change mitigation policy, government has little
incentive to invest in any of these projects either.
On top of all of these, environmental concerns by the
public from such major new technology projects also remain and especially in
the democratic countries of Europe where the public has a potential to stop
such projects from going ahead thus they would require scientific proof and
hence detailed research into the projects to convince them of safety and
positive outcomes of such a project especially if public budgets were to be
invested into these. Legal reasons also remain and albeit the fact there are no
current legal limitations on the use of CO2 in EOR projects, there could be legal
worries that CO2 is not used for EOR but with the aim of purely under
researched CCS which has not yet been given a green light.
Overall, despite CO2 being a very questionable method
of EOR with lots of uncertainties and potential disadvantages especially
regarding CCS, I think CO2 as a method of EOR as well as just pure CCS is a
very interesting topic that requires more research and potentially it is very
important in mitigation of current climate change. Especially, let’s face it,
humanity is not going to reduce its emissions of CO2 into the atmosphere any
time soon or not to the significant amount that is needed to reduce climate
change in our energy based society today thus some alternative solutions on
what to do with all the CO2 produced in fossil fuel combustion are very
important. Also I think that since USA have started using this method already,
it obviously must be economically viable and profitable so Europe needs to do
some research into it and seriously consider it especially on the verge of having
to use EOR for oil extraction anyway or otherwise the European economy will be
left lagging behind the USA one once again.
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