As a supplier of advanced versatile solutions to oil field operators, Wärtsilä participates in the Global Gas Flaring Reduction Partnership, a public-private partnership supporting the efforts of the petroleum industry and national governments to reduce the flaring of gas.
During the last decade, global institutions and organisations, as well as the world´s energy industry, have awakened to the realization that huge amounts of energy are being wasted in flaring. At the same time, flaring also poses a severe threat to
the environment.
“The World Bank-led Global Gas Flaring Reduction partnership (GGFR) estimates that globally, around 150 billion cubic meters (bcm) of gas are flared or burned every year, causing some 400 million tons of carbon dioxide in annual emissions. That is equivalent to 30 per cent of the European Union’s gas consumption.
Gas flaring not only harms the environment but also deprives developing countries of an energy source that is often cleaner and cheaper than others available. During the drilling for crude oil, gas usually comes to the surface as well and is often vented or flared instead of used, particularly in countries that lack effective regulations, gas markets, and the necessary infrastructure to utilise the gas.
The U.S. EPA estimates that over 100 bcm of methane is vented or lost through fugitive emissions in the oil and gas sector each year. As methane is a more potent greenhouse gas than CO2, this adds the equivalent of over 1 billion tons of carbon dioxide annually. Altogether, annual emissions from flaring and venting are equivalent to more than twice the potential yearly emission reductions from projects currently submitted under the Kyoto mechanisms.
The major flaring region in the world is Russia and the Caspian (about 60 bcm); followed by the Middle East and North Africa (about 45 bcm). Sub-Saharan Africa (about 35 bcm) is the third-biggest flaring region, followed by Latin America with some 12 bcm of gas flared annually.”
The magnitude and volumes of flared and vented gases are globally monitored, including by satellites, but the exact figures are a matter of discussion. The general understanding, however, is that the GGFR figures are conservative.
GGFR in practice
Detailed and comprehensive lifecycle plans for hydrocarbon production will be made for each oil field in order to specify the facility equipment and resources for each production stage, defining mainly:
- Upstream flow development in the production stages, e.g. production wells hooking-up programme
- Water cut development in the production stages
- Oil production in the production stages, starting from “early oil” through one or more “oil production plateaus” (the continuous constant production of each stage) into field depletion
- GOR (gas-oil ratio) through the production stages
- Total cumulative oil recovery target from the reservoir
- Power demand in the production stages will be an outcome of these plans.
The basic concept is electrical power generation for the field facility processes from the upstream to downstream oil shipping pumps. The power generation can be combined with heat recovery (combined heat and power – CHP), if needed.
The oil production plateaus will be the core of the field economy, usually as “BOPD”, barrels of oil-per-day. The revenue to the operator is based on these BOPD, and the production costs are also commonly calculated based on these BOPD.
Naturally, there will be fixed costs, and the major reductions will come from the host country in taxes, royalties etc. The utilisation of AG will be further evaluated to determine its affect on the cost-per-barrel.
Each oil field is individual and different, notably in terms of the production cost structure in general, and the energy consumption in particular. Energy may constitute a significant cost factor, if procured from the electricity grid. Some of the produced crude oil can be used as fuel for the field facility power plant, in which case the cost can be valued as “lost revenue”. The most economical means is to use waste, i.e. the associated gas if available, as power plant fuel.
Technology solutions
The specific solution for power production in oil fields is based on Wärtsilä gas-diesel (GD) technology, for AG-fuelled applications in particular.
The GD technology was introduced in 1987 with the Wärtsilä 32GD, the first gas engine in the Wärtsilä portfolio. GD technology makes it possible to run the engine on either gas or oil liquids; associated gases of almost any quality and liquid oils from diesel oil to heavy fuel oils, including even crude oils.
GD engines use the diesel combustion cycle in both gas and liquid fuel operation, which gives them the characteristics and rating of a diesel engine at all site conditions. In the gas mode, 4% of the fuel is needed as liquid pilot fuel to initiate combustion. GD technology also provides the excellent efficiency and minimal derating of a modern diesel engine.
An enhanced innovation in the use of GD technology, called fuel sharing, was introduced in 2002 for plant operation where the gas supply is not constant, or where the quality of the gas varies.
The fuel sharing system allows the engine to run on gas and liquid fuel in different proportions, in order to optimize plant operation according to the availability of the fuels. If, for example, only 30% of the rated output can be achieved with the available gas, the engine makes up the balance of 70% of the output with fuel oil. The operator can freely change the set point of the fuel share, and the control system will ensure that the actual operating point is within the specified operating windows.
An 11 MW power plant at a field facility in Ecuador has been in operation since 2003 using two Wärtsilä 16V32GD units. The plant has been fuelled by the associated gas and crude oil from the processing facility, and it utilises the fuel sharing system. The fuel sharing is becoming very important now that the AG production is decreasing, and the gas flow has been very limited and highly variable. Thus, the plant can continue full output operation with a higher share of the liquid fuel, the crude oil. The generating sets had each amassed over 35,000 hours by October 2008, and the power plant has produced more than 300 GWh of electricity. The main components of the AG have been varying.
GD-engines can be also utilised to drive gas compressors for the re-injection of the excess AG into the well structure to maintain the pressure, to enhance oil recovery, or even to be stored for later gas production, as discussed above.
The economics of the development and lifecycle of a particular oil field are complex and difficult to model with a conventional feasibility study. There are many parameters that influence the model of the various options, and these parameters may change dramatically during the life of the field. For example, the levels of investments needed for the various options are different. The ultimate consideration for the operator is the cost of producing a barrel of oil, but clearly what works for one site may not work for another.
A study of the gas management of oil production was conducted for a 12-year operation cycle, with the oil production plateau being 50,000 bpd. The associated gas utilisation consists of fuelling the field facility power plant, and the re-injection compressing of the excess gas. The reinjection compressors were also powered with the AG fuelled GD engines. The total installed power of the GD engines was 36 MW, but the utilisation varied according to the gas production.
The total gas production during that 12-year cycle is 6400 mln.nm³ and the peaking GOR is about 1400 scf/bbl. The total fuel gas for the power plant and the re-injection compressors is 700 mln.nm³, corresponding to about 11% of the produced gas during the 12-year cycle.
In addition to the stored gas, savings in carbon credits will be about 17 million tons, as opposed to flaring that stored gas throughout the 12-year cycle.
Conclusion
As a supplier of advanced versatile solutions to oil field operators, Wärtsilä is participating in the Global Gas Flaring Reduction partnership to promote the reduction in flaring.
Wärtsilä can be the one-stop supplier for each of these field facility power applications, for both power generation and gas compression. For each of these associated gas utilisation applications, the first choice for the driver would be the Wärtsilä GD-engine, not forgetting Wärtsilä’s wide range of other diesel and gas engines, depending on the available fuels. The scope of supply will be tailored from machinery delivery to turnkey plants, and combined with lifecycle maintenance support worldwide.
