- Students’ Column
- War and Military
Nowadays, the problem of energy efficiency and energy saving stands in the forefront of the global agenda. Each of us is engaged in the process of conserving resources. We save electricity by installing high-efficient LED lamps, power production companies purchase new generation equipment in order to increase the coefficient of performance of the plants and engineers are continuously working to make fuel consumption in our cars more effective. However, have you ever thought how much of these natural resources is wasted without any use? In this article I will try to cover the problem of associated petroleum gas flaring.
I am sure everyone knows that natural gas is one of the major energy sources. Associated petroleum gas (APG), or associated gas, is a form of natural gas as well. It is found with deposits of petroleum, either dissolved in the oil or as a free “gas cap” above the oil in the reservoir under high pressure reservoir conditions (1). When oil is extracted, the pressure decreases and associated gas separates from the oil. However, traditionally this gas is considered as a waste product and is simply burnt off in gas flares. This process is called flaring and when it occurs this gas is referred to as flare gas. Taking example of Russia, which is one of the largest producer of oil and gas in the world, currently for each tonne of oil produced in Russia about 150 cubic metre of associated gas is released and this value is rising each year (2). This situation can be explained by the fact that oil production in Russia is moving to the east and north of the country. In such regions average gas/oil ratio is higher than in traditional production regions and can reach several hundred cubic meters per tonne of oil.
However, not all amount of APG is flared. Major share, that is 60% approximately, is sent from the oil field to gas processing plants and to other consumers. APG is usually separated to stripped gas (methane, or general natural gas) and NGL (natural gas liquids, which commonly consist of propane, butane and other heavy gas fractions). Further, natural gas can be used for wide range of needs, while NGL is commonly used as a raw material in chemical industry.
In Russia NGL is usually purchased by chemical companies for polyethylene and polypropylene production. 22% Of associated gas is used for oil field’s own needs, that includes utilizing APG for electricity and heat generation in steam or gas turbine power plants, and pumping APG to the reservoir in order to support extraction pressure. Also, associated gas can be used for synthetic fuel production on site via GTL (Gas-To-Liquid) conversion, however, there is almost no experience of this method application in Russia so far. Finally, 17% of APG is flared, and losses accounts for remaining 1% (2).
It should be taken into the consideration, that these figures are average among Russia and regions around it. In some states APG efficient use is almost equal to 100%, while in others it barely exceeds 50% (3). Low APG utilization levels are observed in the oil fields that are situated in remote underpopulated areas with severe climate and weather conditions. In such regions APG transporting from the field is very expensive and does not pay back. The use of associated gas for oil field’s own needs is limited. The main problem is that APG extraction is not constant, its variation is significant during the project lifetime, and coefficient of performance and other parameters of power plants are usually low at part loads. Furthermore, expensive gas pre-treatment facility must be installed in order to purify APG from sulphur, nitrogen and other harmful compounds. Such investment also can be unsustainable for medium and small scale oil production facilities. So, these factors causes flaring of significant APG amount without any use.
It is worth noting, that today efficient associated petroleum gas utilization level is rising every year in the country (2). Nevertheless, Russian Federation still takes the first place in the world in terms of gas flaring according to Worldbank. Each year Russian oil extraction industry flares up to 17 billion cubic meters of APG according to official Russian statistics (2). In order to show you how significant this value is, I would like to note that this can be compared to annual natural gas consumption of a typical European country. However, Worldbank estimates total gas flaring in Russia (what is mainly associated gas flaring) at much higher value: 35 billion cubic meters annually (4).
Associated gas flaring is not only a huge resource waste. It causes water, soil, air, and thermal pollution in the neighbourhood. When APG is utilized at flare facility about 10% of its value is vented directly into the atmosphere. As methane (the major component of APG) has global warming potential (GWP) coefficient 21 times more than CO2 (5), such 10% vented volume accounts for greenhouse gas emissions equivalent to CO2 emissions from remaining 90% of APG burned completely. On the basis of official Russian statistics on APG flaring in 2014, it can be estimated that flaring in Russia accounts for 30 million tonnes of annual CO2 emissions. This value can be compared to the total CO2 emissions generated annually by an entire European country such as Sweden or Norway. Among the emissions, apart from methane leaks and CO2, harmful components such as sulphur, nitrogen oxides, carbon monoxide, soot, benzyl, phosgene, toluene, heavy metals (mercury, arsenic, chrome), sulphuric anhydrite, and others are also present (6).
But how can we deal with such enormous resource waste? Is there any possibility to avoid loosing precious natural resource?
Firstly, I would like to discuss current situation in oil and gas production in Russia. Today as I already noticed oil and gas production shifts to the north and east of the country, to Western Siberia and Far East, and new exploration fields are mainly medium or small. Traditionally, such oil fields are supplied with energy from diesel generators. However, the fuel is usually very hard to deliver in remote areas. For example, in many regions helicopter is the only one mean of transportation. Hence, diesel fuel cost rises up to several times during the delivery process. This situation calls for the need of reliable energy generation methods using available local fuels. In this respect, APG would be a very attractive source of energy.
If we take into account high gas-oil ratio in new exploration regions, it turns out that electricity production from APG from turbines exceed power consumption value by several times. Such energy excess is hard to utilize in remote areas. Moreover, this methods does not solve the problem of fuel supply for vehicles that are working continuously on the field. Good option could be the use of associated gas partly for electricity production and partly for other needs. After conducting analysis of different APG utilization methods, it was concluded, that GTL conversion plant can be good solution for effective associated gas utilization in remote areas on small and medium scale facilities. What is special about GTL method is the possibility to use heat of the conversion reaction to produce electricity, which covers own needs of the plant and oil field’s as well. Also, significant amount of synthetic liquid hydrocarbons is produced. Part of it can be used for high quality diesel fuel generation which can be further consumed by cars and other vehicles in the oil field. The remaining can be mixed with recovered oil and send to the pipeline. This is very attractive method, don’t you think so? But there has to be catch. Why this solution is not applied at Russian oil fields? The answer is simple: no experience of implementing this technology and high capital and operating investments. Although today modern small scale GTL cost effective technologies have started to appear and surely they will play important role in solving the problem of gas flaring.
I hope that in the future we would utilize finite natural sources more carefully and the term «gas flaring» will remain only as an relic of the past.
1. Glossary of Terms Used in Petroleum Reserves/Resources Definitions. – 14 p. – http://www.spe.org/industry/docs/GlossaryPetroleumReserves-ResourcesDefinitions_2005.pdf.
2. Российский статистический ежегодник 2015. [Russian Statistical Yearbook 2015]. – 728 p. – http://www.gks.ru/free_doc/doc_2015/year/ejegod-15.pdf
3. Регионы России. Социально-экономические показатели. [Regions of Russia. Socio-economic Indicators]. – 1266 p. – http://www.gks.ru/free_doc/doc_2015/region/reg-pok15.pdf.
4. Worldbank. Global Gas Flaring Reduction Partnership (GGFR) Top 20 gas flaring countries. – http://www.worldbank.org/content/dam/Worldbank/Programs/GGFR%20Presentation%20March%202015.pdf
5. Climate Change 1995, The Science of Climate Change: Summary for Policymakers and Technical Summary of the Working Group I Report. – 572 p. – https://www.ipcc.ch/ipccreports/sar/wg_I/ipcc_sar_wg_I_full_report.pdf.
6. Попутный нефтяной газ в России: «Сжигать нельзя, перерабатывать!» [Associated Petroleum Gas in Russia: «Do not Flare, Utilize!»]. – 88 p. – https://www.wwf.ru/data/pub/oil/wwf_png_net_corrected.pdf.