Even Harry Houdini wouldn't be able to escape NETL's comprehensive MVA program. The MVA techniques NETL is developing are the critical "trick" to make geologic sequestration a safe, effective, and acceptable method for greenhouse gas control.

When we talk about making things disappear, it calls to mind well-rehearsed feats of legerdemain—quarters lost to a magician’s deft hands, doves well hidden with a sweep of a cape, and rabbits vanishing into a deep, black hat. But making carbon dioxide (CO₂) emissions “disappear” is no act. Carbon sequestration energy research requires a scientific—and permanent—approach. Capturing and sequestering CO₂ is today’s most promising solution to global climate change and a key to environmentally responsible energy generation. Ensuring the sequestered CO₂ doesn’t hop back out of the hat is a major focus of NETL’s work.

Now You See It...
Plants and animals all generate CO₂, either through respiration or decomposition. Before the Industrial Revolution, CO₂ “sinks,” such as oceans and terrestrial plants, absorbed all the CO₂ emitted to the atmosphere, keeping the carbon cycle in balance. Unlike other animals, however, humans rely on industrial power generation in order to thrive. This additional energy production emits excess CO₂. In fact, fossil fuel power generation is a major contributor of the greenhouse gas (GHG). Now, CO₂ emissions have outgrown the capacity of natural sinks to absorb them, and we require a manmade solution to this manmade problem.

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  NETL's Carbon Sequestration Program is helping to develop technologies to capture and store CO₂ that would otherwise reside in the atmosphere for long periods of time. NETL's MVA efforts ensure this CO₂ storage is safe and permanent.  

NETL researchers are developing technologies to capture CO₂ at fossil fuel power plants and store it underground in a process called geologic carbon sequestration, thereby avoiding its emission into the atmosphere. In this process, CO₂ is separated from emissions sources and recovered in a concentrated stream. The CO₂ stream can then be transported and sequestered, or stored, underground in such a way that it will remain there permanently. Voila! CO₂ emissions disappear—at least to the casual observer. But, behind the scenes, scientists are keeping a close watch on the sequestered gas. Did you ever wonder where the rabbit went after it disappeared into the hat? NETL researchers are observing this phenomenon with the CO₂ in storage.

Ensuring the permanency of the CO₂ containment is where monitoring, verification, and accounting (MVA) techniques come into play. MVA is essential to making geologic sequestration a safe, effective, and acceptable method for GHG control. So, how do you monitor something you can’t see?         

Out of Sight, Never Out of Mind—
One of the challenges of underground CO₂ storage is predicting how securely it is stored or trapped. Openings or leaks provide an escape path through which the CO₂ might travel from its repository back into the atmosphere. NETL is developing the technologies and protocols needed to monitor every move of the incarcerated gas and ensure the CO₂ stays put.

   

Observation wells monitoring injected CO₂ at a SECARB site. SECARB is one of seven NETL Regional Carbon Sequestration partners.

MVA techniques help ensure the safety and efficacy of geologic sequestration. With these techniques, researchers can measure the amount of CO₂ stored at a specific sequestration site, monitor the site for leaks, track the location of the underground CO₂ plume, and verify that the CO₂ is stored safely and permanently.

How do these capabilities perform on the practical stage? The Southeast Regional Carbon Sequestration Partnership (SECARB)—one of seven NETL-managed regional carbon sequestration partnerships—offers a good example. SECARB has identified the following MVA strategy. The first step is to ensure that the well is leak-proof. The wellbore provides the most likely pathway for CO₂ to leak from the injection zone to the ground surface or even into underground sources of drinking water. To ensure well integrity, researchers evaluate the cement bond between the well casing and the rock, test the injection wells’ mechanical integrity, and monitor tubing and annular pressures. The second step is to ensure safe CO₂ injection operations. Researchers will perform this feat by monitoring pressure changes, since changes in pressure are a good indicator of CO₂ migration or leakage. Third, researchers will verify the location and migration of the injected CO₂ plume using a variety of methods including seismic data (underground vibrations) and underground fluid sampling. Finally, researchers will drill wells into underground sources of drinking water and sample the groundwater chemistry periodically to detect indications of any CO₂ leakage.

MVA efforts also evaluate greenhouse gas reduction goals. Because they are essential for determining the long-term safety of this technology, MVA measures will ultimately define the success of geologic carbon sequestration efforts. A successful MVA program will enable sequestration project developers to ensure human health and safety and prevent damage to the ecosystem.

In general, MVA for geologic sequestration has the following objectives:

• Improve understanding of storage processes and confirm their efficiency and effectiveness.
• Evaluate the interactions of CO₂ with formation solids and fluids.
• Have a monitoring system in place that will detect a leak early in the process, and assess environmental, safety, and health impacts in the unlikely event that a leak to the atmosphere or groundwater does occur.
• Evaluate and monitor any required remediation efforts should a leak occur.
• Provide a technical basis to assist in legal disputes resulting from any impact of sequestration technology, such as groundwater contamination, seismic events, crop losses, etc.

  NETL's monitoring, verification, and accounting research is helping ensure the environmental safety and efficacy of carbon capture and storage.

To accomplish these tasks, NETL employs three layers of technology in its MVA portfolio. Primary technologies are proven, mature monitoring applications. The secondary layer is techniques that have the potential to improve accounting efforts for the injected CO₂ and provide insight into CO₂ behavior; secondary technologies also help refine the primary technologies as scientists learn more about the injected CO₂. Technologies in the third layer are geared towards answering fundamental questions concerning the behavior of CO₂ underground; these may provide benefits as monitoring tools after field testing. These three technology layers combined provide a comprehensive method of understanding and monitoring the stored CO₂. Armed with these tools, NETL tailors its MVA packages to site-specific characteristics and geological features.

Each geologic sequestration site varies significantly in risk profile and geology, including features such as formation depth, porosity, permeability, temperature, pressure, and seal formation. These variables complicate MVA efforts, since what works at one site may not work at another. Because no “cookie cutter” strategy would work, scientists tailor MVA efforts to each specific site. The task is as monumental as it sounds, and so NETL is leading the National Risk Assessment Partnership (NRAP), which teams five DOE national labs to integrate scientific insights across the sequestration research community:

• NETL conducts research on wellbore risk assessment.
• Lawrence Berkeley oversees research for risk assessment monitoring.
• Lawrence Livermore is responsible for systems modeling for risk assessment.
• Los Alamos’s research focuses on natural seal integrity.
• Pacific Northwest is coordinating research on risk to groundwater systems.

Our Talented Associates—
NETL’s MVA research is working to ensure that injected CO₂ does not disappear without a trace. NETL-managed research projects put CO₂ in the limelight to keep it in line. Here are a few examples:

Act One: Monitoring. With funding and guidance from NETL, Planetary Emissions Management, Inc., in partnership with AXYS Technologies, Inc., DOE’s Kansas City Plant (a national secure manufacturing R&D facility), Lawrence Berkeley National Laboratory, LI-COR, Inc., and Rutgers University are commercializing an innovative, field-ready carbon-14 analyzer. Carbon-14—a naturally occurring radioisotope of carbon—is a “ready-made,” sensitive tracer of fossil-fuel derived CO₂. The analyzer works at surface and subsurface locations over large areas and with great precision. The technology will allow researchers to track sequestered fossil fuel directly and accurately at lower costs than existing approaches. Currently, the analyzer is deployed for testing at two sites, one where CO₂ leaks from natural geologic reservoirs and a pilot CO₂ injection site.

Act Two: Verification. Again, with funding and guidance from NETL, Schlumberger Carbon Services researchers in partnership with Anadarko Petroleum Company, Princeton University, Rocky Mountain Oilfield Testing Center, and Los Alamos National Laboratory are developing models to establish the overall probability that a given well will leak. Leaky wellbores are a notable risk to secure storage, and this project will develop methods to quantify this leakage risk in both active and abandoned wellbores. Data will help researchers determine the risk of leakage at the start of a project—prior to injection—thereby providing a clearer picture of how a particular site will behave. This higher level of certainty will, in turn, enable better decisions on repairing wells and help determine appropriate MVA technologies.

Act Three: Accounting. NETL also funds and manages a project with Stanford University’s Stanford Rock Physics Laboratory, ExxonMobil, and Ingrain, Inc., who are developing methods that use seismic data to map injected CO₂. Using rock-fluid models, researchers are studying chemical changes in the rock, pore pressure changes, and gas saturation. Feeling a bit dazzled? Let’s break it down: when CO₂ is pumped into a reservoir, it affects chemical changes in the rock. Existing minerals and compounds change form, and researchers can use these changes to account for the stored CO₂. Pore pressure changes also occur when gas is first injected. As the gas is taken up into the surrounding rock, the pressure reduces. Similarly, gas saturation is high when it’s initially sequestered, but thins out as long-term chemical reactions take place and the gas is absorbed. By examining these three areas, researchers can accurately follow the movement, presence, and permanence of CO₂ in its intended storage location.

Results from these well-mastered MVA research areas are helping to further scientists’ understanding of various carbon sequestration options. By helping provide cost-effective, environmentally sound technology options, these projects may lead to a reduction in CO₂ emissions.

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  This 3-D geologic model represents one of the tools researchers use to monitor CO₂ storage in geologic formations. This particular model was constructed from wells in the Weyburn field (Saskatchewan, Canada), which stores CO₂ transported from a North Dakota gasification plant.

MVA Goals: The Grand Finale
NETL’s carbon sequestration research program aims to retain 99 percent of CO₂ in underground reservoirs for over a century. DOE’s goal is to demonstrate, by 2012, 99 percent retention of CO₂ and the ability to detect leakage into the atmosphere at levels of 1 percent or less of the amount of CO₂ stored. By 2012, researchers are poised to offer new technologies that will enable modifications and improvements to monitoring protocols—improvements that are also expected to reduce the cost of geologic sequestration.

These are aggressive goals. But with the pervasive exigency of global climate change and energy demand increasing worldwide, the goal is not only ambitious, it is imperative. MVA technologies will help mitigate our carbon footprint and protect our planet and our quality of life for generations to come. It’s no wonder that, as NETL’s research continues, scientists are providing us with great levels of confidence that sequestered CO₂ remains in place—when the magician reaches into his hat, the rabbit is there, right where it’s supposed to be.