An oilfield worker from BP Exploration first noticed the acrid smell while driving near the Trans Alaska Pipeline System, which runs 1,300 kilometres from Prudhoe Bay in northern Alaska south to Valdez. It took three days to discover the source of the oil--a hole slightly larger than half a centimetre in a transit pipeline carrying crude oil to a pumping station. The leak spilled more than 5,000 barrels (about 800 cubic metres) of oil onto Alaska's North Slope. Pipeline operator BP paid US$111 million in fines, penalties and a lawsuit.
The main culprits behind the 2006 leak? Microorganisms, in the form of bacteria growing in a layer of sludge in the bottom of the pipe section, facilitated corrosive chemical reactions that ate through the metal. More than a decade later, the mechanisms and underlying chemistry that cause microbiologically influenced corrosion (MIC) in oil and natural gas pipelines are still not well understood. But this is about to change.
Federally funded Genome Canada has provided $7.9 million for a four-year, Large-Scale Applied Research Project called "Managing Microbial Corrosion in Canadian Offshore and Onshore Oil Production." The project involves four universities in Alberta and Atlantic Canada as well as InnoTech Alberta, a subsidiary corporation of the provincial Alberta Innovates, and 10 industry partners, including Enbridge and Suncor Energy. Aimed at a better understanding of MIC, the project will provide the industry with the knowledge and tools to better predict when, where and why the microbial corrosion occurs and how to prevent it.
Scientists in multiple disciplines, including microbiology, chemistry, engineering and computer science, are participating. They will make use of genomic techniques, such as DNA and RNA sequencing, to identify and catalogue the microbes, genes and associated metabolic activities responsible for MIC. For the first time, researchers will also make extensive use of actual field samples of microbial colonies, taken from upstream (called gathering) pipelines, larger transmission pipelines and offshore oil production platforms.
"While there have been a lot of studies on MIC done in the laboratory with pure microbial cultures under ideal conditions, it is not as well-known under field conditions and real operating systems," says project co-lead Lisa Gieg, associate professor of microbiology at the University of Calgary. The industry's current approach for identifying troublesome microbes is to sample fluids from pipelines and place them in closed containers called bug bottles to which glucose is added to culture any bacteria present. "The problem is that only up to five percent, at best, of all microorganisms in the world can be cultured this way in a bottle," Gieg says. "So it's difficult to really get a clear picture of all the microorganisms that might be in your sample. Genomic sequencing will give us a more complete picture of what kinds of organisms might be attaching to pipelines under different scenarios," she adds.
Project co-lead John Wolodko, an associate professor in the Faculty of Agricultural, Life & Environmental Sciences at the University of Alberta, likens MIC's complexity to bacterial diseases in humans. "We've only identified a small fraction of the microbial community that may, in fact, lead to microbial corrosion," says Wolodko, who also holds the Alberta Innovates Strategic Chair in Bio and Industrial Materials. Researchers from the U of A and InnoTech Alberta will conduct experiments on oilfield samples of microbes to test various species for their ability to influence corrosion. This will be done at InnoTech's corrosion engineering laboratory in Devon, Alta., using continuous-flow loops of pipe that simulate realistic flow conditions in a pipeline, says Tesfaalem Haile, a senior corrosion specialist at InnoTech. The project partners will also develop a computer model to simulate online microbial sludges, or biofilms, in actual pipelines.
The impact of MIC costs Canada's onshore and offshore petroleum sectors billions of dollars every year, Haile says. The cost in Alberta alone of maintaining, repairing and replacing pipelines amounts to more than $2 billion annually, with at least 20 percent due to MIC. Moreover, this is just the direct cost of pipeline corrosion; there are also indirect costs, such as cleaning up leaks and spills, which can double the direct cost, says Haile. (In the United States, corrosion of all types is one of the leading causes of failures in onshore transmission pipelines, according to the U.S. Department of Transportation, costing the country US$7 billion.)
Modelled on Responsible Care
In 2016, the 11 companies that belong to the Canadian Energy Pipeline Association (CEPA) spent $1.2 billion on monitoring and maintaining 118,000 kilometres of oil and gas transmission pipelines in Canada, says Patrick Smyth, CEPA's vice-president of safety and engineering. Through CEPA's Integrity First initiative--modelled on the chemistry industry's Responsible Care program--member companies are working together on safety and striving for zero incidents on their pipelines, Smyth says. Last year, CEPA members had three incidents that released 38 barrels (six cubic metres) of liquid products and 13 natural gas incidents that released 10,590 cubic metres. In 33 percent of cases, the cause was metal loss, although CEPA doesn't specifically track MIC versus other types of corrosion.
CEPA members are mainly big companies that operate the large-diameter, long oil and gas transmission pipelines where water and sediment content are strictly limited by the National Energy Board. But in Alberta, there are many dozens of pipeline companies operating about four times the total length of pipelines compared with CEPA members. Most of these pipelines are the smaller-diameter, shorter pipelines that contain both water and crude oil or gas. It is these companies whose pipelines are responsible for the lion's share of the 460 incidents recorded in Alberta in 2016: hits, leaks and ruptures along 422,000 kilometres of oil and gas pipelines. These incidents released more than 4,860 cubic metres calculated as total liquid volume, according to the Alberta Energy Regulator (AER). (Natural gas releases are also included in this total liquid volume.) Of these incidents, 32 were rated by the AER as of "high consequence," meaning that the public, wildlife and/or environment were significantly impacted. Most of these incidents consisted of non-fresh water, such as saline water or water extracted along with oil and gas from geological reservoirs. About 750 cubic metres were hydrocarbons. The majority of all incidents were related to pipeline integrity, with internal corrosion representing 36 percent of total pipeline incidents in 2015, the AER says. Other causes of pipeline incidents included incorrect operation, operating conditions, external corrosion (outside the pipe), external interference (such as damage by a third party), material degradation and natural force damage.
The role of water
The National Energy Board (NEB) regulates oil and gas transmission pipelines that cross provincial and international borders. On these pipelines, there were 114 incidents in 2016, including four hydrocarbon liquid releases totalling about seven cubic metres and 47 natural gas releases totalling about 690 cubic metres, according to the NEB. Internal corrosion was the cause of only one incident. MIC-related corrosion is less of a problem (although it still occurs) in these transmission pipelines than in gathering pipelines. On large-diameter, long transmission pipelines, the amount of water and sediment content entering the pipelines is strictly limited. In Western Canada, however, smaller-diameter, shorter gathering pipelines transporting raw crude oil and natural gas from wells can contain significant quantities of water, which is produced along with the oil from the geological reservoir. Offshore production platforms in Atlantic Canada, where MIC is a growing problem, also contain large amounts of water.
Microbes inside pipelines are anaerobic; they don't need oxygen to survive. But they do need water. Oil-water mixtures, or emulsions, carry the nutrients--including hydrogen sulphide ([H.sub.2]S), carbon dioxide (C[O.sub.2]), salts and acids--that the bugs require for growth. Many of these chemical species are also produced by bacteria through their metabolic activity. One particularly troublesome substance is [H.sub.2]S, which not only facilitates the growth of microbes but is also corrosive on its own.
The microbes often form a biofilm in areas where a pipeline has low or stagnant flow. Once established, these biofilms are difficult to dislodge, even with mechanical scrubbers, called pigs, sent through pipelines. Some microbial species have even developed resistance to chemical biocides. "They are smarter than us when it comes to surviving in harsh environments," Haile says.
However, it is not the microbes themselves that actually cause the corrosion, says project co-lead Faisal Khan, professor and department head of process engineering and the Vale Research Chair of Process Risk and Safety Engineering at Memorial University of Newfoundland in St. John's. "What the microbes do is facilitate that degradation process, which is actually caused by the environment that they're in."
There is debate within the scientific community about what types of reactions are the key drivers of MIC, Khan says. To answer that question, his research group will do molecular modelling to identify the microbes' metabolite chemistry and how it reacts with a pipeline's metal surface. Researchers will then produce a computer tool to predict the rate of MIC-related corrosion and how long it will take to create a hole in specific pipelines.
Massive data collection
The four-year project will produce an enormous amount of metagenomic, chemical, environmental and other data. All of this will be managed by Robert Beiko and his research group at Dalhousie University in Halifax. "Our primary role is to develop the ontology and the database, to bring the very large amounts of data together as they're collected and house, integrate, query and visualize all this information," says Beiko, associate professor in computer science and Canada Research Chair in Bioinformatics. Elvira Mitraka, a postdoctoral researcher, will create the ontology that structures the database, enables a machine to query the information and allows the entire team's researchers to interpret and analyze the data using a common vocabulary.
Project scientists will develop new standard operating procedures for preventing MIC, including protocols for sampling microbes in the field, which they hope industry will adopt as part of pipeline integrity management plans. New regulations are also possible. Genome Canada says the knowledge and tools developed from the project could save Canada's oil and gas industry $300 to $500 million per year in capital costs spent on fighting MIC and replacing infrastructure.
"The stars have aligned to bring this problem to fruition, with new technology, industry players and a collaborative network of multidisciplinary researchers," Wolodko says. "It is very unique that we have all this coming together, and it's unique that we're doing it in Canada."
Please Note: Illustration(s) are not available due to copyright restrictions.
Caption: The petroleum industry uses mechanical pigs, like the one shown here, inside a pipeline. The pig, used to clean the inside pipeline wall, gets pushed along by the flow of oil or natural gas.
Caption: Microbiologist Lisa Gieg uses genomic tools to analyze corrosion-inducing microbes in her University of Calgary laboratory.
Caption: Alberta oilfield technicians install a mechanical scrubber, called a pig, that helps clean bacteria out of pipelines.
Caption: A corrosion coupon is a strip of metal placed inside an operating pipeline to monitor microbial corrosion.
Caption: Severe microbial corrosion inside a crude oil pipeline.
Caption: Faisal Khan and colleagues at Memorial University are undertaking chemical modelling of microbes' metabolite chemistry and how it reacts with a pipeline's metal surface.
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|Title Annotation:||Chemical Engineering: Microbial Corrosion|
|Publication:||Canadian Chemical News|
|Date:||Sep 22, 2017|
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