Expert Viewpoint - Commercial Biogenic Gas Production
Heavyoilinfo.com talked to Profero Energy about its projects to commercialize natural gas production from depleted heavy oil fields by accelerating biodegradation activity.
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Research indicates that much of the world’s heavy oil has been formed from the biodegradation of lighter oils by microscopic organisms over millions of years. This is an anaerobic process that produces natural gas (methane). Profero Energy believes that, by injection of nutrients into a reservoir, the in-situ process can be accelerated to produce commercial volumes of gas from abandoned oil resources. The company is developing technologies to recover additional value from heavy oil fields that are otherwise no longer economically viable. |
Pictured above: Dr. Ian Head and Dr. Steve Larter, Profero Energy
Profero Energy
Profero Energy Inc., founded in 2007, is based in Calgary. Its proprietary technology is based on research into biodegradation by scientists at the University of Calgary (UofC), Canada, and the University of Newcastle, UK. This article is based primarily on an interview with Peter Santosham, the company’s Business Development Director; Ian Head, Chief Microbiologist; and Steve Larter, Chief Scientific Officer. Head is a Professor at the University of Newcastle, UK, and Larter is a Professor at the University of Calgary. Both are senior members of the Profero team that has been working with oil companies to study the origins of heavy oil since the 1990s.
Biodegradation of oil
Professors Head and Larter estimate that 95% or more of the world’s heavy oil, including the Canadian oil sands bitumen, is formed through the in-situ biodegradation of lighter oil producing methane as a by-product. The process has also occurred in the North Sea Troll and Frigg gas fields which contain biodegraded oil. Some of the largest gas accumulations on Earth may have been formed by heavy oil alteration.
An anaerobic process
In 2003, the Newcastle research group published a paper in Nature about its discovery that the biodegradation process is anaerobic. They describe two types of microbe, found naturally in environments containing crude oil, that are responsible for converting it into methane. First, bacteria called Syntrophus digest the oil and produce hydrogen gas and acetic acid. Secondly, methanogens, a type of organism known as archaea, combine the hydrogen with carbon dioxide to produce methane.
Accelerating the process
The biodegradation process occurs naturally in reservoirs over millions of years, but is slow because the organisms have an imbalanced diet, starved of nutrients such as nitrate and phosphate. The addition of a mixture of nutrients, dissolved in water, enables the microbes to grow, multiply, and digest the oil at a greatly increased rate, with a corresponding increase in gas production. In the laboratory, the research team was able to reduce geological timescales to a few hundred days. By extension, if the nutrients are pumped into an oil reservoir, the team predicts that similar results could be obtained in an oilfield in a timescale of a year to tens of years.
Candidate reservoirs
All commercial hydrocarbon deposits will have contained life-forms at some time, but those that have experienced temperatures above 80–90 degC will be “paleo-pasteurized”, and microbes are unlikely to regenerate. However, Profero estimates that more than 90 percent of global heavy oil and bitumen reservoirs have remained sufficiently cool throughout their history to contain the required microbes. While steam-assisted processes such as SAGD may cause local pasteurization, they are unlikely to sterilize a whole reservoir. In any case, a simple test of a sample will quickly confirm the presence of the required organisms.
Feasibility tests
Profero is preparing to perform trials of its accelerated biogenic gas creation process in several sites in shallow fields in Western Canada. These sites are in reservoirs containing oil of gravity around 12–30 API, previously produced using cold primary methods and CHOPS. The company is “cautiously optimistic” and hopes to have field results some time in 2010.
Profero has performed reservoir simulation to predict the distribution of the injected nutrient-enriched waterflood through the subsurface. Watered-out fields, where water saturation has hampered primary production, are considered to present ideal situations for the biodegradation process. High water mobility is beneficial, helping stranded pockets of oil to be targeted.
Head and Larter stress that Profero is not involved with microbially-enhanced oil recovery (MEOR), where new organisms are introduced into the subsurface. Instead, the company is seeking to enhance oil and gas recovery by accelerating the activity of organisms that are currently living in situ. The low recovery ratios usually experienced with heavy oil make these assets particularly suitable, along with its abundance in shallow, easily accessible, onshore fields.
Worldwide applications
The biogenic process could be applied to depleted conventional oilfields such as Troll in the North Sea, where both oil and gas production continue. In such cases there is potential not only to recover stranded oil as gas, but also to mobilize some residual oil due to increased pressure caused by gas generation. Such fields also have the benefit of an existing infrastructure. Laboratory tests using samples from the North Sea were able to convert 10 % of the oil in 2 years. Adding nutrients to injected water during primary or secondary production would give the biodegradation process an early start, accelerating levels of activity once oil production is abandoned, while also helping to maintain or increase reservoir pressure.
Gas prices are currently depressed, due in part to an excess of shale gas in the USA, however this is likely to be temporary and several issues favor its long-term value. These include geopolitical factors and environmental issues such as carbon trading. CO2 emissions from burning methane are about 50 % of those involved in producing, processing, and burning coal or bitumen to generate the same amount of energy.
Growing interest
An estimated 90 % of the microorganisms on Earth are in the subsurface, but few oil companies have microbiologists. Those that do are often more concerned with corrosion and flow assurance. The first oilfield microbiological studies were in 1923, but then and since, the work has mostly been esoteric. Profero observes that, over the last 5 years, there has been an increase in serious interest, not only by producers but also among investment companies.
Head and Larter note how little the industry knows about the composition and origins of heavy oil and how much upside potential exists from a better understanding. Very heavy bitumen is probably less likely to produce commercial quantities of gas than oils at the lighter end. However, there are enormous volumes of suitable heavy oil, much of it in fields that are considered non-economic or that have been abandoned with 80 to 90 % of the resources still in the ground. Scaling-up from the laboratory to an oil field raises several challenges, such as how to collect the produced gas, so in addition to increasing understanding of biodegradation of oil into methane, Profero is investigating optimized gas recovery processes. The company believes that these technologies could significantly extend the economic operating lifespans of many types of hydrocarbon reservoirs. The biodegradation process is also being applied to abandoned coal mines, as currently being tested by companies such as Luca Technologies.
Within a few years, Profero expects to know a lot more about how its technology works in practice and what proportion of unrecoverable oil could be converted to methane gas. Even a small fraction could be a very attractive commercial proposition.
For more information, visit the Profero Energy website.
References:
Head, I.M., Jones, D.M. and Larter S.R.: “Biological activity in the deep subsurface and the origin of heavy oil,” Nature (2003) No. 426, 344–352.
Head, I.M., Larter, S.R., Gray, N.D., Sherry, A., Adams, J.J., Aitken, C.M., Jones, D.M., Rowan, A.K., Huang, H. and Röling, W.F.M.: “Hydrocarbon Degradation in Petroleum Reservoirs,” Handbook of Hydrocarbon and Lipid Microbiology (Vol 3), Timmis, K.N., McGenity, T., van der Meer, J.R. and de Lorenzo, V. (eds.), Microbes and Communities Utilizing Hydrocarbons, Oils, and Lipids, Heidelberg, Germany, Springer, (2010), 4500.
Jones, D.M., Head, I.M., Gray, N.D., Adams, J.J., Rowan, A.K., Aitken, C.M., Bennett, B., Huang, H., Brown, A., Bowler, B.F.J., Oldenburg, T., Erdmann, M. and Larter, S.R.: “Crude Oil Biodegradation Via Methanogenesis in Subsurface Petroleum Reservoirs,” Nature (2008) No. 451, 176–180.
Larter, S.R., Adams, J., Cherry, A., Fay, M., Gates, I., Gray, N., Head, I., Jones, M., Rafter, D.,Santosham, P. and Zhang, X.: “Low Emission Microbial Upgrading and Recovery (LEMUR)—Potential Route to Low or Zero Emission Energy Recovery from Oilfields,” Expanded Abstracts, (2009) CSPG CSEG CWLS Convention, Calgary, Canada.
Roadifer, R. E.: “Size distributions of the world's largest known oil and tar accumulations,” in Exploration for Heavy Crude Oil and Natural Bitumen, AAPG Studies in Geology no. 25, R.F. Meyer (ed.), Tulsa, USA, American Association of Petroleum Geologists, (1987), 3–23.
