Monterey Bay Aquarium Research Institute

 


Deep-sea chemistry
Day 4: We struck oil, but where's the gas?
August 13, 2011

Location: On the seafloor of Barkley Canyon
Latitude: 48° 18.6417 N
Longitude: 126° 3.9147 W

After painstakingly gathering oil from the bottom of the sea to learn about the behavior of gas-saturated oil, a seasoned group of ocean chemists (and one geophysicist) were astonished when the gas failed to materialize as the oil was slowly brought to the surface. The oil just sat there in its container—no fizzing, no bubbling, no escaping gas. What happened?

This group of scientists was attracted to this area off the coast of Vancouver in part because the high concentrations of methane and oil here make for an excellent natural laboratory to learn more about how methane-saturated oil behaves in the deep sea and when rising to the surface. They hope to add to the understanding of oil plume dynamics—for instance, the Deepwater Horizon event in the Gulf of Mexico last year resulted in the release of a large plume of methane gas along with the oil.

oil bubbling out of sediment
When the remotely operated vehicle (ROV) bumped the sediment, oil came bubbling out of the seafloor all around. The greenish dots all over this picture are oil. The ROV pilots had to chase these droplets and catch them in the funnel.

Most of the day was spent collecting oil from within these methane-rich sediments. Catching these oil droplets was no small feat. The ROV pilots were asked to hold a funnel contraption in one robotic arm and a metal rod in the other, all the while carefully monitoring the location of the vehicle or moving it quickly to follow the bubbles. The rod was used to stir up the mud, in hopes of loosening some oil. Sometimes they struck oil, sometimes they didn’t, but when they did, the pressure was on to catch as much as possible in the funnel before the droplets floated away.

poking the seafloor
The metal rod at right was used to stir up the mud to release the oil (the green blobs). The pilot would move the apparatus over to gather the oil in the funnel. In the background is a tip of a large deposit of methane hydrate, an ice-like compound formed when methane gas and seawater interact at the cold temperatures and high pressure of the deep sea. Oil has stained the hydrate yellow.
closeup of oil
A close-up look at the oil collected at the top of the funnel; the oil appeared red once it was inside the thick plastic container.

Because there is an abundance of methane in this area, both as a gas and as a solid ice-like hydrate, ocean chemist Peter Brewer was expecting to find oil that was saturated with methane gas. Once the oil was collected, it was brought up from the depths, until it was close to the surface so we could watch the gas separate out from the oil—gas would expand as the water got warmer and there was lower pressure. However, after the careful collection of a perfect sample of oil, there was no gas. Nothing. No bubbles came out of the oil, no expansion of the sample as the gas within expanded. What happened?

“There must be a reason for what we saw,” Brewer said. “It’s like a fight over who gets to use the methane gas.” The methane can be pulled toward the oil or toward the water. In this case, it appears the methane has been stripped from the oil and combined with the water to create the huge deposits of methane hydrate. The methane hydrates we can see are just the tips of the iceberg as the ice-like formations spread over large areas under the surface sediment. The formations that are yellow-tinged also contain oil.

To gain more of an understanding of what is happening in this area, the last task was to break up some chunks of the hydrate, bring it toward the surface, and wait for gas to evolve from the sample. That gas would then be tested for its chemical composition. This offered the pilots yet one more chance to fly around the seafloor trying to collect samples. Just think of it as using tweezers to grab a few ice cubes in a large lake. But the pool has a strong current and you have to manipulate a large boat to get close to the moving ice cubes. Well, it was something like that.

In any case, they were successful in gathering enough oily methane hydrate to run the test, which showed a complex gas signal similar to what would have been in the oil. Brewer and his group will do further study of their data and samples from today to learn more about these mysterious oil and gas behaviors, and how nature makes these deep-sea icebergs from rising oil and gas.

Randy welding
When he wasn’t busy chasing oil bubbles and gas hydrate all over the deep sea, pilot Randy Prickett welded a new handle for the a tripod used to insert a special laser into the seafloor.

— Nancy Barr



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Leg 1
 Equipment

R/V Western Flyer

The R/V Western Flyer is a small water-plane area twin hull (SWATH) oceanographic research vessel measuring 35.6 meters long and 16.2 meters wide. It was designed and constructed for MBARI to serve as the support vessel for ROV operations. Her missions include the Monterey Bay as well as extended cruises to Hawaii, Gulf of California and the Pacific Northwest.

ROV Doc Ricketts

ROV Doc Ricketts is MBARI's next generation ROV. The system breaks new ground in providing an integrated unmanned submersible research platform, with many powerful features providing efficient, reliable and precise sampling and data collection in a wide range of missions.

Laser Raman spectrometer DORISS2

By bouncing a specially tuned laser beam off of almost any object or substance—solid, liquid, or gas—a laser Raman spectrometer can provide information about that object's chemical composition and molecular structure.

Push cores

A push-core looks like a clear plastic tube with a rubber handle on one end. Just as its name implies, the push core is pushed down into loose sediment using the ROV's manipulator arm. As the sediment fills up the core, water exits out the top through one-way valves. When the core is pulled up again, these valves close, which (most of the time) keeps the sediment from sliding out of the core tube. When we bring these cores back to the surface, we typically look for living animals and organic material in the sediments.

Vibracores

Vibracoring is a common technique used to obtain samples from water-saturated sediment. These corers work by attaching a motor that induces high frequency vibrations in the core liner that in turn liquefies the sediment directly around the core cutter, enabling it to pass through the sediment with little resistance.

CO2 accumulator

Carbon dioxide is a liquid at the temperatures and pressures on the seafloor where hydrates are known to occur. Because of this, one cannot simply take down a tank of gas and expect to be able to release it at depth. Instead, the CO2 piston accumulator is used to deliver precise volumes of liquid CO,2 to experiments on the seafloor. The valves are operated hydraulically by remote control and hydraulic pressure is used to expel the liquid CO2 and deliver it to the experiments.

Heat-flow probe

MBARI's heat-flow probe is mounted on the side of the ROV Doc Ricketts inside the vertical stainless steel box. This both protects the delicate probe and provide the track so that the probe can be inserted into the sediment along a totally straight path.  The probe contains five high precision platinum sensors which are used to measure the vertical temperature gradient in the sediments. This gradient along with some knowledge of the heat capacity of the sediment allows scientists to calculate the rate of heat loss from the sediments into the ocean.

 Crew

R/V Western Flyer

Ian Young
Master


 

George Gunther
First Mate


 

Matt Noyes
Chief Engineer


 

Andrew McKee
Second Mate


 

Lance Wardle
First Engineer


 

Olin Jordan
Oiler


 

Paul Tucker
Second Engineer


 

Vincent Nunes
Bosun


 

Dan Chamberlain
Electronics Officer


 

Patrick Mitts
Steward


 

ROV Doc Ricketts

Knute Brekke
Chief ROV Pilot


 

Mark Talkovic
Senior ROV Pilot


 

Randy Prickett
Senior ROV Pilot


 

Bryan Schaefer
ROV Pilot/Technician


 

Eric Martin
ROV Pilot/Technician


 

 Research Team

Peter Brewer
Chief Scientist
MBARI

Peter has taken part in more than 30 deep-sea cruises, and has served as chief scientist on major expeditions and on more than 90 ROV dives with MBARI ships and vehicles. His research interests include the ocean geochemistry of the greenhouse gases. He has devised novel techniques both for measurement and for extracting the oceanic signatures of global change. At MBARI his current interests include the geochemistry of gas hydrates, and the evolution of the oceanic fossil fuel CO2 signal. He has developed novel techniques for deep ocean laser Raman spectroscopy, and for testing the principles and impacts of deep ocean CO2 injection.

Ed Peltzer
Senior Research Specialist
MBARI

Ed is an ocean chemist who has been with MBARI since 1997. He has been involved in developing in situ laser Raman spectrometry instruments and lab based analytical techniques to study the composition of gases in gas hydrates and deep-sea vents. He has collaborated on the development of new instrumentation for the measurement of temperature and pH from ROVs and deep-sea observatories. As the group's project manager, Ed is also responsible for expedition planning and logistics.

Peter Walz
Senior Research Technician
MBARI

Peter has worked as a research technician for a variety of scientists at MBARI. Most recently he has supported the research efforts of Dr. Peter Brewer and his interests in the ocean chemistry of greenhouse gases such as methane and carbon dioxide. Peter assists with the design, testing and deployment of the ocean going science hardware and works closely with the marine operations group to integrate new equipment to work with MBARI's ROV's.

Andreas Hofmann
Postdoctoral Fellow
MBARI

Andreas is a MBARI Postdoctoral Fellow in the Brewer lab. He obtained a PhD in marine biogeochemistry in the Netherlands after his biology undergraduate and bioinformatics graduate studies in Germany. Andreas' specialty is pelagic and benthic biogeochemical modeling with a focus on pH and proton cycling. At MBARI, Andreas is working amongst others on the characterization of marine hypoxic and suboxic zones, focusing on the explicit description of physical limitations to aerobic respiration. On this cruise, Andreas will be involved in obtaining and processing Raman spectra, as well as in various other tasks supporting the objectives of the group.

Nancy Barr
Web/Print Project Manager
MBARI

Nancy manages the editing, design, and production of the MBARI annual report and participates in a variety of editorial and communication projects. She also oversees the institute website. Nancy has been to sea with several MBARI research groups, helping them to carefully remove worms from whale bones, annotate video, sift seafloor sediment, and collect and process water samples. For this expedition she will be in charge of the daily reports that will be posted to this website and will assist with other science crew tasks.

Elizabeth Coward
Summer Intern
MBARI

Elizabeth is an MBARI summer intern in the Brewer lab. She is a senior at Haverford College, PA, where she is obtaining her undergraduate joint degree in biology and chemistry. Elizabeth's prior research has been principally concerned with the bioavailability and geochemical dynamics of oil in marine sediments. Her interest in oceanic fossil fuels and greenhouse gases has brought her to the Brewer lab, where she will be using laser Raman spectroscopy to investigate methane and carbon dioxide signatures, the dynamics of gas hydrates and ocean acidification.

Michael Riedel
Research Scientist
Natural Resources Canada - Geological Survey of Canada

Michael Riedel was part of an international team of scientists supported by the Integrated Ocean Drilling Program (IODP) which completed a unique research expedition in 2005 aimed at recovering samples of gas hydrate, an ice-like substance hidden beneath the seafloor off Canada's western coast. As IODP Expedition 311's co-chief scientist, Michael explored his interest in gas hydrate; he believes such deposits have played an important role in ancient global climate change.

Laura Lapham
Postdoctoral Researcher
National Energy Technology Lab, U.S. Department of Energy

Laura's research is concentrated on studying methane cycling at cold seeps, biogeochemcial cycling of methane and sulfer in deep sea sediments, development of deep sea instrumentation to collect novel samples, stable isotope geochemistry, modeling of biogeochemical processes and temporal variability of dissolved methane concentrations. The focus of her research has been mainly on gas hydrate environments, but she is also interested in other systems that relate to the carbon cycle. Her research seeks to understand how methane is distributed between different pools, e.g. dissolved or hydrate phases, and also to understand how local biogeochemical processes affect this methane, mostly through anaerobic methane oxidation.

Jon Furlong
University of Victoria

Jon is a graduate student at the University of Victoria studying with Michael Riedel. His bachelor's degree was completed in Earth Sciences from Memorial University in Newfoundland before he moved from one coast to the other. Jon's research focuses on neo-tectonic faulting offshore Vancouver Island and its links to gas hydrate formation and fluid migration.