1. [ ENERGY / IN DETAIL ]
[ ENERGY / IN DETAIL ]
Smart Power Generation for
the oil and gas industry
AUTHOR: Junior Isles, Man in Black Media
Fig. 1 – A pumping station on the Baku-Tbilisi-Ceyhan pipeline in Turkey. The pipeline, for which Wärtsilä has supplied engines, crosses several
mountain ranges.
The oil and gas industry has a
tremendous need for prime movers
that can provide electrical power
or mechanical drive. With their
high efficiency and fuel flexibility,
combustion engines offer the most
competitive solution.
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in detail
The oil and gas business is a multi-billion
dollar industry with a huge need for
prime movers – whether in the form of
combustion (reciprocating) engines or
combustion turbines (rotating machines) to
deliver electrical power or mechanical drive.
As oil and gas become more difficult
to recover and operators attempt to
extract more from existing wells, the
demand for investment in power
generation will continue to increase.
The total investment in the upstream
segment is currently in the region of EUR
300 - 350 billion a year, a figure that is
expected to grow in the coming years.
The choice of whether to use rotating
or reciprocating machines is one that
operators need to consider carefully,
especially in the face of growing
environmental awareness and the need
for greater energy conservation.
Increasing energy demand continues to

2. WÄRTSILÄ TECHNICAL JOURNAL 01.2012
drive oil and gas exploration in regions such
as the Middle East, Russia, the Caspian and
Latin America. Underground gas storage
projects, and the development of gas
transport and distribution in Europe and
the U.S., are also increasing demand for
investment. For example, the U.K. is
planning to build many new underground
storage facilities to increase its severely
limited storage capability.
Applications
The market for combustion engines in
the oil and gas business can be split into
three segments: power plants, pumping,
and compression.
Power generation: Power plants are often
needed to provide power; the location can
be at an oil or gas field, a refinery, or even
at a compression or pumping plant in cases
when the compressor or pump is driven
by an electrical motor.
Such power plants are much the same as
in the electric utility industry. One of the
key differences, however, is the available fuel
to drive the power plant. Fuels can range
from associated gas to crude oil, have
varying quality and quantity, and often
cannot be burned in turbines.
This is where Wärtsilä’s technology comes
into its own. Wärtsilä has engines that can
run on gas or virtually any liquid fuel. It has
gas engines capable of running on normal
pipeline gas; liquid fuel engines that can run
on crude oil, heavy fuel oil (HFO) or light fuel
oil (LFO); and dual-fuel (gas-diesel) engines
capable of burning gas of varying quality
and liquid fuel at the same time. Gas-diesel
(GD) technology, which is unique to Wärtsilä,
is particularly well suited for oil field power
plants where there can be changes over
time in the quality of the associated gas, as
well as in that of the crude oil produced.
With engines ranging in size from 1 MW
to 23 MW, Wärtsilä can build oil or gas fired
power plants ranging from 1 MW up to 500 MW.
The modular design of Wärtsilä’s solutions
means that plant size can be increased by
adding additional units as the operators’
needs change.
Pumping: The same engines used for
generating electricity can be used for driving
pumps. Wärtsilä has large engines suited for
big pipeline projects. It has supplied engines
to projects such as the BTC Pipeline (see side
story) in Turkey, and the OCP Pipeline
in Ecuador.
An advantage of the Wärtsilä technology
is that its engines can run on the crude oil in
the pipeline without any refining or treatment.
Compression: Gas compression is a big
market for combustion engines. Gas
compression is a business worth several
billion dollars a year globally.
Smaller 0.5 - 2 MW engines are used for
small gas distribution lines, as well as in
the shale gas market, which are typically
very small fields.
Larger engines are used for underground
gas storage projects. Indeed, reciprocating
technology is better suited than centrifugal
technology for the high pressures needed
for underground storage.
Currently, the pipeline compression
sector has a prevalence of turbines driving
centrifugal compressors. The turbines used
for this application are typically 5-10 MW
but can also be bigger.
However, using combustion engines to
drive centrifugal compressors offers huge
savings in fuel. The arrangement would see
a gas engine driving the compressor directly,
or a power plant supplying electricity to
electrically driven compressors. Although
the latter would be a more expensive solution,
it would increase flexibility. Using a gas
engine in place of a gas turbine also provides
much better fuel efficiency. Lifecycle studies
of real cases show that such a solution could
deliver fuel savings of more than
EUR 100 million over a 20-year period.
Better efficiency
The efficiency argument presents a strong
case when comparing combustion engines
with other technologies. When a lifecycle
cost evaluation is made, the fuel cost over
the lifetime of a plant is many times that
of the capital expenditure cost.
Historically, operators of power plants,
and compression or pumping stations,
have paid little attention to fuel efficiency
as the fuel is often provided free of charge
from the owners of the field. With free fuel
meaning low operating costs, the main
impact on profitability is capital investment
i.e. the cost of equipment. Operators have
therefore opted for the cheapest equipment,
which is usually not the most fuel-efficient.
But this is changing. As energy prices
continue to increase, efficiency is becoming
an important part of the evaluation process.
In order to save energy, reduce the
environmental impact and cost, energy
efficiency programmes are now common
in the production of oil and gas.
As a traditional industry, oil and gas
operators have a tendency to use technology
they are familiar with. This often means that
when issuing tenders, only turbine
technology is specified, despite their much
lower efficiency compared to combustion
engines.
Although some larger gas turbines can
demonstrate efficiencies of around 40
percent, the smaller turbines (around 10 MW)
typically used in many applications have
an efficiency of about 30 percent or less,
depending on operating conditions.
Efficiency decreases during part-load
operation, and there is a significant dropoff in power as the ambient temperature
increases. Gas turbines also lose output
and several percentage points in efficiency
due to wear between overhauls.
By comparison, Wärtsilä’s gas and diesel
combustion engines have shaft efficiencies
of around 45-48 percent. Efficiency above
40 percent is maintained even at loads as
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3. [ ENERGY / IN DETAIL ]
[ ENERGY / IN DETAIL ]
low as 50 percent. Gas engines lose virtually
no efficiency over time, and liquid fuel
engines lose only about one percent between
overhauls of the fuel injection system.
Unlike combustion turbines, combustion
engines do not derate over time but
maintain full output during their lifetime.
Fuel flexibility
The ability to burn almost any liquid or
gas fuel in a Wärtsilä engine can help to
drastically reduce the cost of fuel, even from
a purely logistical standpoint.
The ability to run on a wide range of fuels
is why combustion engines are playing a
major role in the drive to reduce flaring.
Gas flaring is a practice that is coming
increasingly under the spotlight due to
environmental concerns and the need for
energy conservation.
In 2010, Wärtsilä became the first solution
provider to become a member of the Global
Gas Flaring Reduction Partnership (GGFR).
The GGFR was formed by the World Bank
in 2002 to support the efforts of oil producing
countries and companies to increase the use
of associated natural gas, and thus reduce
flaring and venting. It estimates that over
138 billion cubic meters (or 4.9 trillion cubic
feet) of natural gas is being flared and vented
annually.
This is equivalent to 25 percent of the
United States’ gas consumption, 30 percent
of the European Union’s gas consumption,
or 75 percent of Russia’s gas exports. The gas
flared yearly also represents more than
the combined gas consumption of Central
and South America.
At a gas price of about USD 4 per million
Fig. 2 – Wärtsilä's gas-diesel technology offers the opportunity to reduce flaring of associated
gases, thereby enabling fuel savings and a reduction in greenhouse gas emissions.
Btu, the value of the gas flared in oil fields
and refineries today is around USD 20
billion a year. This wasted associated gas
could produce 65 GW of electricity a year.
With Wärtsilä’s gas-diesel technology,
associated gas can be used for power
generation or gas re-injection at the oil field.
Its fuel sharing technology allows
the engines to cope with variations in gas
quantity and quality.
Reliability
Another key benefit of using combustion
engines is the high reliability they provide.
Oil and gas are highly valuable
commodities and any failure in, for example,
pump or compression equipment can have
serious financial consequences.
Operators, therefore, always install spare
or backup engines or turbines to ensure
there is no interruption in oil or gas
production.
There is a general perception that a
turbine is more reliable than an engine due
to its fewer moving parts. However, modern
Wärtsilä engine technology
Gas engines: Wärtsilä gas engines are
suited to normal pipeline quality gas.
They are spark-ignited (SG) engines
that use the lean-burn Otto cycle.
In this process, the gas is mixed with air
before the inlet valves. During the intake
period, gas is also fed into a small prechamber, where the gas mixture is rich
compared to the gas in the cylinder. At
the end of the compression phase the gas/
air mixture in the pre-chamber is ignited
by a spark plug. The flames from the
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in detail
nozzle of the pre-chamber ignite the gas/
air mixture in the whole cylinder. After
the working phase, the cylinder is emptied
of exhaust and the process starts again.
Oil-fired engines: Wärtsilä liquid fuel
engines can run on crude, heavy fuel
oil (HFO) or light fuel oil (LFO). In the
diesel process, liquid fuel is injected into
the cylinder at high pressure by camshaftoperated pumps. The fuel is ignited
instantly due to the high temperature
resulting from the compression.
Combustion takes place under constant
pressure with fuel injected into the cylinder
during combustion. After the working
phase, the exhaust gas valves open and
the cylinder is emptied of exhaust gases.
With the piston in its upper position, the
inlet valves open just before the exhaust
gas valves close, and the cylinder is filled
with air. In Wärtsilä engines the inlet
valves close just before the piston reaches
the bottom dead centre. This method,

4. WÄRTSILÄ TECHNICAL JOURNAL 01.2012
Fig. 3 – One of four Wärtsilä pumping stations in the Turkey section of the BTC Pipeline.
medium speed engines have been proven to
provide reliability equal to that of turbines.
With the clear benefits of better
reliability, greater fuel flexibility and lower
operating costs, it is time for the oil and
gas industry to change its conservative
mindset and focus on using the more
efficient and environmentally friendly
solutions that combustion engines provide.
called “Miller timing”, reduces the work
of compression and the combustion
temperature, which results in higher
engine efficiency and lower emissions.
Dual-fuel engines: Fuel flexibility and
high efficiency are the main advantages
of the dual-fuel technology. They can
be characterised as “anything in, and
anything out”. They can run on crude
and other liquid fuels as well as gas of
varying quality, and can be used for
Pumping for BTC
As one of the longest of its kind in the world,
extending across three countries from the
Caspian Sea to the Mediterranean coast,
the Baku-Tbilisi-Ceyhan (BTC) Pipeline is
described as one of the great engineering
endeavours of the new millennium.
Designed for the transport of 1 million
barrels (50 MTPA) of crude oil per day, the
pipeline is of regional and international
significance and is the main export route
power generation, combined heat and
power, pumping or compression.
Wärtsilä dual-fuel engines are unique
because they have two different injection
systems. A micro pilot injection system
injects a very small amount of liquid
fuel when the engine is operating in
gas mode. The micro pilot system is of
the common rail type, which allows
for very small injection amounts.
This makes it possible to meet very
stringent emission regulations, which
for Azeri crude to world markets.
Commissioned in 2006, the state-of-theart pipeline was built by a consortium led
by B.P. It extends from Baku on the Caspian
Sea, through Azerbaijan, Georgia and Turkey,
to the port of Ceyhan on the Mediterranean
coast of Turkey. From here the crude is
further shipped via tankers to European
markets.
Much of the route through which
would be impossible if a normal injection
system were used. A conventional injection
system is used when the engine is run on
liquid fuel. The engine transfers from gas
to fuel oil operation (LFO, HFO) at any
load instantaneously and automatically.
Because the gas is injected to the
engine at high pressure, the engine
is not sensitive to the methane
number or other gas components.
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5. [ ENERGY / IN DETAIL ]
[ ENERGY / IN DETAIL ]
the pipeline passes is mountainous. From
the lesser Caucasus Mountains on the border
with Georgia, the pipeline heads west across
the Anatolian Plateau before crossing south
through the Taurus Mountains. At this point
it follows a steep descent to the Cukurova
plain on the north shore of the Gulf of
Iskenderun.
The Anatolian Plateau forms the
principal landform on the route. The terrain
comprises a number of broad plains at
elevations between 1500 m and 2000 m
above sea level, and upland mountains
rising to 3000 m. With a total length of
1769 km, the major portion (1076 km) of
the pipeline’s route is located in Turkey.
Pumping oil across such a vast distance
and high elevations called for the installation
of eight pumping stations – two in
Azerbaijan, two in Georgia and four
in Turkey.
The BP consortium awarded the entire
design and construction of the Turkish
section of the pipeline, including the
pumping stations, to BOTAS, the Turkish
Petroleum Pipeline Corporation.
In 2002, BOTAS awarded a contract to
Wärtsilä for the equipment for the four
stations in Turkey. The scope of the contract
covered the supply of nineteen 18-cylinder
Wärtsilä 34SG engines in V-configuration
with selective catalytic reduction (SCR)
systems, a starting air system, lube
oil systems for the engine, and for the
pump and gear box, cooling radiators,
auxiliary modules for heat exchangers
and filters, air intake ducts, exhaust gas
systems, and pump seal oil systems.
The BTC pump stations in Turkey,
installed along the pipeline from the Georgia
border down to the Ceyhan Marine Terminal,
are designated PT1, PT2, PT3 and PT4 and
Fig. 4 – BTC pump station with five pump sets driven by Wärtsilä 34SG engines.
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in detail
are at elevations of 2140 m, 1720 m, 2028 m
and 1595 m, respectively above sea level.
The gas fired reciprocating engines offer
several significant benefits. Compared to
gas turbines, reciprocating engines have
the main advantage of retaining high
efficiency at high altitude. A reciprocating
engine has an efficiency of about 40 percent
compared to less than 30 percent for a gas
turbine driver. Gas turbines experience a
significant loss of power at higher altitudes
and are further handicapped by a steep drop
in efficiency at deviations from the design
point.
Following more than five years of
operation, BTC and Wärtsilä are considering
modernising the engine automation
system with the introduction of a torque
measurement system. This would allow the
engines to automatically adjust according
to the flow of oil in the pipeline.