Geology: Can hydrocarbon source rocks be identified on seismic data?
As reported in this article from an energy & environment publication:
One of the world's leading energy companies, Norway's Statoil ASA, is going public this month with a scientific innovation that it says will drastically reduce the costs and risks of discovering new deposits of fossil fuels.
The innovation, a refined take on traditional sound-based seismic imaging, allows Statoil to detect -- before drilling any wells -- the presence of oil and gas sources in rocks miles underground. The technique, the company says, will work on deepwater oil or shale gas in unexplored regions and holdings once thought tapped out.
It is the first time, at least publicly, that an oil company has detailed a technique that provides reliable, direct acoustic evidence that these resources exist. In the past, these rocks would be deduced. Now, they can be seen.
Already employed by Statoil worldwide over the past few years, the technique especially improves the odds of finding oil and gas in unexplored regions that have never felt the bite of a drill's bit, said Helge Løseth, one of the Statoil geologists behind the innovation, published in the December issue of the journal Geology.
Everywhere, he said, "you increase the likelihood [of striking oil] quite significantly."
Independent geologists expect Statoil's seismic leap, while perhaps not exclusive to the company, will ripple through the industry, becoming a standard tool over the next few years. It will result in companies drilling fewer exploration wells, with each more likely to strike pay dirt than before. And given that one deepwater well can cost up to $100 million, paying for fewer "dry holes" can bring, in little time, stark savings.
"If you can identify the most important part of the petroleum system without having to deal with it [through drilling], it saves you a great deal of money," said Joe Macquaker, a petroleum geologist at Memorial University of Newfoundland who read the Statoil study. "You haven't drilled," he added again, with some wonder. "It just saves so much money."
The Statoil team's work is a nexus of older ideas, new data and the proper champion, said Carl Sondergeld, a petroleum engineer at the University of Oklahoma. It could revolutionize how the industry views oil systems, especially with broader use, he said. At the very least, "it allows an assessment of frontier areas through analysis of seismic data," Sondergeld added. "This is much more than we had previously."
Word of Statoil's success comes as the U.S. oil and gas industries have already been revitalized by the application of horizontal drilling and hydraulic fracturing to shale formations. Offshore, too, in regions like the Gulf of Mexico, oil explorers have improved their ability to see through salt formations that previously obscured hydrocarbons, though discovering oil in these depths remains a risky endeavor.
All of these innovations are a stark reminder for advocates of clean energy that the oil industry, and all its attendant greenhouse gas emissions, will remain a moving target. Driven by profits and, at some companies, scientific curiosity, engineers and geologists are continuously refining new and better ways to extract winnowing fuel from the earth. They have resources, and they will use them to keep prices manageable.
For better or worse, there is a boundless optimism in the industry that it is in fact entering a new era of plenty, said Matt Hall, a consultant at Agile Geosciences in Canada, who previously worked for Statoil as an exploration geologist.
"The way people talk nowadays, you never hear people talk about 'peak oil' anymore," he said. "Since 2005, you hear people say this is the beginning of the new petroleum age."
Petroleum, that is, and gas: While Statoil's work stems from its offshore oil traditions, it is directly applicable to the "unconventional" shale gas reserves currently upturning U.S. energy forecasts. It won't be long before such techniques spread to the shale business, if they haven't already, said Juergen Schieber, a geologist at Indiana University.
"Someone will probably try it on one of those unconventional plays in the Eagle Ford," he said, the Texas formation that originated the shale surge. Indeed, Schieber expects that some oil and gas explorers have already used similar approaches in secret.
"There are probably some guys at Exxon or Shell kicking themselves," he said.
While Statoil's seismic work will not eliminate the need for reconstructing geological records and the many other tools used to evaluate a rock basin, that's precisely why geologists, an incremental and conservative sort, admire the work.
"It's a perfectly reasonable extension of what is well known," Macquaker said.
Statoil will not say where it has applied the technique, but since 2009, its exploration wells have struck oil or gas 58 percent of the time; over the three previous years, that rate sat at 49 percent. Those strikes included a major discovery this year in the Barents Sea, an Arctic region that had previously defied exploration attempts.
The seismic innovation could also help reduce the environmental risk posed by such deepwater wells, Hall added. Oil companies want to explore widely in the Arctic Ocean, off the coasts of Greenland and Alaska, ecosystems far more vulnerable to oil spills than the Gulf of Mexico. Industry is convinced productive oil systems are there, but there are few wells to gauge the region. Risks are rampant, and the public will not tolerate another eruption like the Deepwater Horizon.
"If you can change your risk by just 10 percent," Hall said, "that's important."
Most important variable in oil discovery
Like most energy innovations, Statoil's work is not easily grasped by laymen. Indeed, understanding it requires getting down in the literal mud.
Most of the oil discovered today has its origins in fine-grained shale rocks, which are essentially fossilized mud (Geologists prefer to call it "mudstone"). Flocks of ancestral algae died millions of years ago, their remains trapped in the seafloor's muck. Over time, these remains break down into organic debris that, when heated, cooks into oil and gas.
This buoyant oil and gas then escapes its mudstone home, until, in some cases, it becomes trapped in porous rock capped by impermeable strata, creating "conventional" oil and gas reservoirs. The upshot of this migration has been that these reservoirs are the primary pursuit of oil drillers, while the mudstone source for these fuels, deeper down, has remained neglected, Memorial's Macquaker said.
"These are the places where the earth, if you like, would naturally sequester organic carbon to remove CO2 from the atmosphere," he said, albeit on geological time scales. Yet despite this importance, he said, "the rocks aren't terribly well known."
While these carbon-rich mudstones, called "source rocks" in industry argot, are the most important variable in discovering oil, explorers have traditionally used models to guess at their presence, drilling suitable oil traps and hoping for strikes, Macquaker said. Other explorers place more emphasis on the source rocks, arguing that if they are not present, drilling has little point. One of those companies is Statoil, he said.
Controlled by the Norwegian government, Statoil is under constant pressure to squeeze more oil from the country's dwindling reserves, a burden that has spurred its scientific work. The company has intimately explored the North Sea over the past few decades, plunging well after well into the seafloor, taking the time to drill into the source rocks that fed their oil finds, the type of core data that underlies their seismic work.
"They take the time and resources to do things like this properly," Agile's Hall said.
Like all oil companies, Statoil uses acoustics to probe uncharted rock. Blasting the ground with vibration, companies tow long strands of geophones in parallel along the ocean floor, listening to sound waves reflected by Earth's deep places. Interpreting the resulting charts, which resemble an abstract artist's take on a crumpled doubledecker sandwich, can be an equal mix of science, engineering and art.
Typically, these surveys focus on structural geology: identifying rocks that could house oil, not the oil itself. While at times flashes of fuels can be divined in this resounding noise, especially gas leaks, these indicators remain easily confounded. Instead, oil seeps are used to hint at possible hydrocarbons, and a basin analysis of the region's geological history is constructed to judge whether source rocks could exist.
"So, at the beginning, there's a lot of homework," said Frans Kets, a visiting research fellow at the United Kingdom's University of Leeds and a former geophysicist with Shell.
Statoil's innovation, which builds off work by, among others, Jose Carcione, an Italian geophysicist, bends the grading curve on this homework, allowing the company to better gauge whether source rocks exist in a region using solely seismic surveys.
The acoustic signature of source rocks -- the velocity and density of sound waves as they speed back upward -- is controlled by the presence of oil and gas precursors, they found. The signal, first proven in Norway, has held true in a wide array of mudstone, young to old.
As long as you have organic material, Løseth said, the waves will be reliably altered. While the algorithm may have a hard time divining between different concentrations of carbon, a flaw several geologists noted in the paper, that does not matter as much in exploration, Løseth added. The sheer presence of carbon is the thing.
"It's more important whether you have 4 percent, or zero percent," he said.
Statoil's aggressive move into U.S. shale
If only applied to deepwater oil, Statoil's work would be notable. But as the company refined the technique, a new reality emerged for the oil and gas business: The reservoir became the source rock.
The shale gas reserves that companies are now eagerly fracturing around the United States are called "unconventional" for a reason. Rather than their fuels migrating out to a reservoir, they have remained home, ripening in the mudstone. Indeed, most shale gas reservoirs are simply over-mature source rocks that once produced oil.
All of a sudden, understanding how source rocks work has become vogue.
"Over the last few years, it's actually become very clear that your source rock can be a trap and can be a reservoir," Indiana's Schieber said. "That's not something you have to beat to death down in Houston anymore."
The interest in source rocks has been a boon for scientists like Memorial's Macquaker, who spends "a lot of time worrying how you get organic carbon in mudstone." The field is moving quickly, and already Macquaker's research has demonstrated that source rocks will form in far more situations than previously suspected. Geologists used to say that, in an ocean, low-oxygen conditions were needed to preserve the dead algae.
"These notions are wrong," he said, adding "all you have to do is bury it rapidly."
Statoil itself entered the U.S. shale market in a big way last month, buying Austin-based Brigham Exploration Co., which has holdings in North Dakota and Montana, for $4.4 billion; in the past two years, it has also inked billion-dollar deals for shale reserves in Texas and the Northeast. While this move was likely driven by market fundamentals, having the seismic technique certainly did not hurt.
"People are going to be very excited about [Statoil's] method for shale gas," Hall said.
The interest will stem out of the fact that, for shale gas, no measure is more important to gauge than what is called the reservoir's "total organic carbon" -- the exact ingredient that Statoil says it can now detect and measure. While many U.S. shale formations are already so riddled with wells that pure seismic exploration is unnecessary, Oklahoma's Sondergeld suspects Statoil's technique will allow for better well placement, he said.
It is the type of innovation of that, built out of many incremental advances, could change the industry. While horizontal drilling and fracturing are one example, Sondergeld is reminded of another, similar seismic advance, known as "3D seismic," when companies began deploying multiple acoustic sensors in parallel to monitor reflected noise. Such refined data was necessary for Statoil's current work.
"I can't tell you how many times, based on 2D seismic, we just missed our play," he said.
While Statoil will be applying the technique, which it secured a worldwide patent on last year, throughout its holdings, Løseth is especially excited with how it will allow Norway's offshore oil fields, the definition of a declining petroleum system, to be reinvigorated.
"As long as we're using seismic data," he added, "I think this technology will be used."
As reported in this article from an energy & environment publication:
One of the world's leading energy companies, Norway's Statoil ASA, is going public this month with a scientific innovation that it says will drastically reduce the costs and risks of discovering new deposits of fossil fuels.
The innovation, a refined take on traditional sound-based seismic imaging, allows Statoil to detect -- before drilling any wells -- the presence of oil and gas sources in rocks miles underground. The technique, the company says, will work on deepwater oil or shale gas in unexplored regions and holdings once thought tapped out.
It is the first time, at least publicly, that an oil company has detailed a technique that provides reliable, direct acoustic evidence that these resources exist. In the past, these rocks would be deduced. Now, they can be seen.
Already employed by Statoil worldwide over the past few years, the technique especially improves the odds of finding oil and gas in unexplored regions that have never felt the bite of a drill's bit, said Helge Løseth, one of the Statoil geologists behind the innovation, published in the December issue of the journal Geology.
Everywhere, he said, "you increase the likelihood [of striking oil] quite significantly."
Independent geologists expect Statoil's seismic leap, while perhaps not exclusive to the company, will ripple through the industry, becoming a standard tool over the next few years. It will result in companies drilling fewer exploration wells, with each more likely to strike pay dirt than before. And given that one deepwater well can cost up to $100 million, paying for fewer "dry holes" can bring, in little time, stark savings.
"If you can identify the most important part of the petroleum system without having to deal with it [through drilling], it saves you a great deal of money," said Joe Macquaker, a petroleum geologist at Memorial University of Newfoundland who read the Statoil study. "You haven't drilled," he added again, with some wonder. "It just saves so much money."
The Statoil team's work is a nexus of older ideas, new data and the proper champion, said Carl Sondergeld, a petroleum engineer at the University of Oklahoma. It could revolutionize how the industry views oil systems, especially with broader use, he said. At the very least, "it allows an assessment of frontier areas through analysis of seismic data," Sondergeld added. "This is much more than we had previously."
Word of Statoil's success comes as the U.S. oil and gas industries have already been revitalized by the application of horizontal drilling and hydraulic fracturing to shale formations. Offshore, too, in regions like the Gulf of Mexico, oil explorers have improved their ability to see through salt formations that previously obscured hydrocarbons, though discovering oil in these depths remains a risky endeavor.
All of these innovations are a stark reminder for advocates of clean energy that the oil industry, and all its attendant greenhouse gas emissions, will remain a moving target. Driven by profits and, at some companies, scientific curiosity, engineers and geologists are continuously refining new and better ways to extract winnowing fuel from the earth. They have resources, and they will use them to keep prices manageable.
For better or worse, there is a boundless optimism in the industry that it is in fact entering a new era of plenty, said Matt Hall, a consultant at Agile Geosciences in Canada, who previously worked for Statoil as an exploration geologist.
"The way people talk nowadays, you never hear people talk about 'peak oil' anymore," he said. "Since 2005, you hear people say this is the beginning of the new petroleum age."
Petroleum, that is, and gas: While Statoil's work stems from its offshore oil traditions, it is directly applicable to the "unconventional" shale gas reserves currently upturning U.S. energy forecasts. It won't be long before such techniques spread to the shale business, if they haven't already, said Juergen Schieber, a geologist at Indiana University.
"Someone will probably try it on one of those unconventional plays in the Eagle Ford," he said, the Texas formation that originated the shale surge. Indeed, Schieber expects that some oil and gas explorers have already used similar approaches in secret.
"There are probably some guys at Exxon or Shell kicking themselves," he said.
While Statoil's seismic work will not eliminate the need for reconstructing geological records and the many other tools used to evaluate a rock basin, that's precisely why geologists, an incremental and conservative sort, admire the work.
"It's a perfectly reasonable extension of what is well known," Macquaker said.
Statoil will not say where it has applied the technique, but since 2009, its exploration wells have struck oil or gas 58 percent of the time; over the three previous years, that rate sat at 49 percent. Those strikes included a major discovery this year in the Barents Sea, an Arctic region that had previously defied exploration attempts.
The seismic innovation could also help reduce the environmental risk posed by such deepwater wells, Hall added. Oil companies want to explore widely in the Arctic Ocean, off the coasts of Greenland and Alaska, ecosystems far more vulnerable to oil spills than the Gulf of Mexico. Industry is convinced productive oil systems are there, but there are few wells to gauge the region. Risks are rampant, and the public will not tolerate another eruption like the Deepwater Horizon.
"If you can change your risk by just 10 percent," Hall said, "that's important."
Most important variable in oil discovery
Like most energy innovations, Statoil's work is not easily grasped by laymen. Indeed, understanding it requires getting down in the literal mud.
Most of the oil discovered today has its origins in fine-grained shale rocks, which are essentially fossilized mud (Geologists prefer to call it "mudstone"). Flocks of ancestral algae died millions of years ago, their remains trapped in the seafloor's muck. Over time, these remains break down into organic debris that, when heated, cooks into oil and gas.
This buoyant oil and gas then escapes its mudstone home, until, in some cases, it becomes trapped in porous rock capped by impermeable strata, creating "conventional" oil and gas reservoirs. The upshot of this migration has been that these reservoirs are the primary pursuit of oil drillers, while the mudstone source for these fuels, deeper down, has remained neglected, Memorial's Macquaker said.
"These are the places where the earth, if you like, would naturally sequester organic carbon to remove CO2 from the atmosphere," he said, albeit on geological time scales. Yet despite this importance, he said, "the rocks aren't terribly well known."
While these carbon-rich mudstones, called "source rocks" in industry argot, are the most important variable in discovering oil, explorers have traditionally used models to guess at their presence, drilling suitable oil traps and hoping for strikes, Macquaker said. Other explorers place more emphasis on the source rocks, arguing that if they are not present, drilling has little point. One of those companies is Statoil, he said.
Controlled by the Norwegian government, Statoil is under constant pressure to squeeze more oil from the country's dwindling reserves, a burden that has spurred its scientific work. The company has intimately explored the North Sea over the past few decades, plunging well after well into the seafloor, taking the time to drill into the source rocks that fed their oil finds, the type of core data that underlies their seismic work.
"They take the time and resources to do things like this properly," Agile's Hall said.
Like all oil companies, Statoil uses acoustics to probe uncharted rock. Blasting the ground with vibration, companies tow long strands of geophones in parallel along the ocean floor, listening to sound waves reflected by Earth's deep places. Interpreting the resulting charts, which resemble an abstract artist's take on a crumpled doubledecker sandwich, can be an equal mix of science, engineering and art.
Typically, these surveys focus on structural geology: identifying rocks that could house oil, not the oil itself. While at times flashes of fuels can be divined in this resounding noise, especially gas leaks, these indicators remain easily confounded. Instead, oil seeps are used to hint at possible hydrocarbons, and a basin analysis of the region's geological history is constructed to judge whether source rocks could exist.
"So, at the beginning, there's a lot of homework," said Frans Kets, a visiting research fellow at the United Kingdom's University of Leeds and a former geophysicist with Shell.
Statoil's innovation, which builds off work by, among others, Jose Carcione, an Italian geophysicist, bends the grading curve on this homework, allowing the company to better gauge whether source rocks exist in a region using solely seismic surveys.
The acoustic signature of source rocks -- the velocity and density of sound waves as they speed back upward -- is controlled by the presence of oil and gas precursors, they found. The signal, first proven in Norway, has held true in a wide array of mudstone, young to old.
As long as you have organic material, Løseth said, the waves will be reliably altered. While the algorithm may have a hard time divining between different concentrations of carbon, a flaw several geologists noted in the paper, that does not matter as much in exploration, Løseth added. The sheer presence of carbon is the thing.
"It's more important whether you have 4 percent, or zero percent," he said.
Statoil's aggressive move into U.S. shale
If only applied to deepwater oil, Statoil's work would be notable. But as the company refined the technique, a new reality emerged for the oil and gas business: The reservoir became the source rock.
The shale gas reserves that companies are now eagerly fracturing around the United States are called "unconventional" for a reason. Rather than their fuels migrating out to a reservoir, they have remained home, ripening in the mudstone. Indeed, most shale gas reservoirs are simply over-mature source rocks that once produced oil.
All of a sudden, understanding how source rocks work has become vogue.
"Over the last few years, it's actually become very clear that your source rock can be a trap and can be a reservoir," Indiana's Schieber said. "That's not something you have to beat to death down in Houston anymore."
The interest in source rocks has been a boon for scientists like Memorial's Macquaker, who spends "a lot of time worrying how you get organic carbon in mudstone." The field is moving quickly, and already Macquaker's research has demonstrated that source rocks will form in far more situations than previously suspected. Geologists used to say that, in an ocean, low-oxygen conditions were needed to preserve the dead algae.
"These notions are wrong," he said, adding "all you have to do is bury it rapidly."
Statoil itself entered the U.S. shale market in a big way last month, buying Austin-based Brigham Exploration Co., which has holdings in North Dakota and Montana, for $4.4 billion; in the past two years, it has also inked billion-dollar deals for shale reserves in Texas and the Northeast. While this move was likely driven by market fundamentals, having the seismic technique certainly did not hurt.
"People are going to be very excited about [Statoil's] method for shale gas," Hall said.
The interest will stem out of the fact that, for shale gas, no measure is more important to gauge than what is called the reservoir's "total organic carbon" -- the exact ingredient that Statoil says it can now detect and measure. While many U.S. shale formations are already so riddled with wells that pure seismic exploration is unnecessary, Oklahoma's Sondergeld suspects Statoil's technique will allow for better well placement, he said.
It is the type of innovation of that, built out of many incremental advances, could change the industry. While horizontal drilling and fracturing are one example, Sondergeld is reminded of another, similar seismic advance, known as "3D seismic," when companies began deploying multiple acoustic sensors in parallel to monitor reflected noise. Such refined data was necessary for Statoil's current work.
"I can't tell you how many times, based on 2D seismic, we just missed our play," he said.
While Statoil will be applying the technique, which it secured a worldwide patent on last year, throughout its holdings, Løseth is especially excited with how it will allow Norway's offshore oil fields, the definition of a declining petroleum system, to be reinvigorated.
"As long as we're using seismic data," he added, "I think this technology will be used."
