[ ENERGY / IN DETAIL ]

[ ENERGY / IN DETAIL ]

Smart Power Generation for
the oil and gas industry
AUTHOR: Junior Isles, ...
WÄRTSILÄ TECHNICAL JOURNAL 01.2012

drive oil and gas exploration in regions such
as the Middle East, Russia, the Caspian ...
[ ENERGY / IN DETAIL ]

[ ENERGY / IN DETAIL ]

low as 50 percent. Gas engines lose virtually
no efficiency over time, and...
WÄRTSILÄ TECHNICAL JOURNAL 01.2012

Fig. 3 – One of four Wärtsilä pumping stations in the Turkey section of the BTC Pipeli...
[ ENERGY / IN DETAIL ]

[ ENERGY / IN DETAIL ]

the pipeline passes is mountainous. From
the lesser Caucasus Mountains on ...
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  1. 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. 4 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. 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 in detail 5
  3. 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 6 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. 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. in detail 7
  5. 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. 8 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.

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