INTERVIEW with Larry Wickstrom, Chief Division of Geological Survey

What do you do to support sustainable development in Ohio?

Ohio relies heavily on coal, oil and natural gas to produce energy required for development. Our division has a long history of identifying and mapping the locations of oil and natural gas resources and coal deposits in Ohio. We are currently applying our expertise in geological mapping and research to address the problem of global warming and carbon dioxide emissions, so Ohioans can use their energy sources more efficiently.

What is this problem?

There are many sources of green house gases that contribute to global warming as depicted in the illustration. Although carbon dioxide, or CO₂ is a naturally occurring gas, the majority of climate scientists believe that continuous increases in earth’s CO₂ levels are major contributors to global warming.

Within the United States, Ohio is the fourth largest emitter of CO₂, behind California, Texas and Pennsylvania. One potential way of reducing carbon emissions from large industrial point-sources of CO₂, such as coal burning power plants and steel mills, is to capture and sequester CO₂ before it is emitted into the atmosphere.

How do we know that carbon dioxide sequestration is possible?

Sequestration is a method of capturing and securely storing CO₂ before it would otherwise be emitted to the atmosphere. Natural geologic reservoirs have held oil, natural gas, water and even CO₂ for millions of years with minimal to no leakage. These natural reservoirs provide the basis for assuming that large quantities of CO₂ can be contained underground.

Carbon Sequestration Process

In addition, substantial experience with geologic injection operations already exists.

Waste industries use deep natural reservoirs for disposal and storage of industrial and hazardous wastes. Natural gas is stored in geologic reservoirs to withdraw later during peak winter usage. The injection of CO₂ in oil fields to stimulate additional oil production has been taking place since the early 1970s.

How does geological carbon sequestration work?

Geological sequestration involves injecting CO₂ into appropriate rock units in the deep subsurface, generally greater than 2,500 feet deep, where it is securely stored or trapped. Our division has been researching Ohio’s CO₂ sequestration capabilities since 2000 as part of the Midwest Regional Carbon Sequestration Partnership funded by the federal government. The primary attraction of geologic sequestration is the potential for direct and long-term storage of captured CO₂ emissions in close proximity to large CO₂ generators, such as ethanol plants and power plants. This process is illustrated in the diagram.

How do you identify appropriate reservoirs for sequestration?

Three primary types of rock formations can serve as reservoirs for storing CO₂ underground: deep saline formations, oil and gas fields and unmineable coal seams. Deep saline formations are natural salt-water bearing intervals of porous and permeable rocks that occur beneath the level of potable groundwater. Oil and gas fields represent known geologic traps containing hydrocarbons within a confined reservoir with a known cap or seal. Within deep unmineable coal seams, the CO₂ forms a molecular bond with the carbon in the coal.

The potential capacity of any geologic reservoir needs to be verified by detailed regional assessments as well as by site-specific investigations. We collect data about reservoir depth, porosity, permeability and injectivity, reservoir pressure and integrity, water chemistry and other variables that control the sequestration potential. We also collect data about cap rock units as they must be relatively impermeable and sufficiently thick to arrest any appreciable vertical movement of the CO₂ within the reservoir.

To further our understanding of these deep reservoirs, we have initiated a fact-finding project in Tuscarawas County in collaboration with the U.S. Department of Energy, the Battelle Memorial Institute and the Ohio Air Quality Development Authority. The test well site appears in the photos above, one of which includes several of the scientists involved in the project. The project requires drilling 8,700 feet underground to search for hydrocarbons, analyze rock types and collect important data on how much CO₂ the deep rock layers can hold.

This is interesting, how do you obtain deep reservoir data in this project?

First, the well is drilled using a drill bit seen in the photo above. This bit is attached to the end of drill pipes that you can see stacked on a rack in the second photo.

During the drilling process, various digital logs of data are acquired. Three of these logs are shown in the photo to the right. The Mud log, in the lower right corner of the photo, provides data about drilling time with depth, gas shows and rock type from well cuttings that are taken at 10-foot intervals during the drilling process.

The Gamma Ray, Neutron/Density log, in the middle, records data about the porosity of different rock types.

The more colorful log in the photo is a Formation Microscanner Image log that produces a detailed visual image of most of the borehole wall to help us evaluate the different reservoirs. Analysis of the logs helps us determine where to take sidewall cores.

The sidewall coring process enables us to extract individual core plugs from the sides of the well. These plugs, separated by metal markers, are gathered into a chamber.

Core Plugs

Microscopic Examination of Plugs

Geographix

The plugs can be examined under a microscope. Microscopic analysis, which is conducted in a laboratory reveals rock type, color, grain size and shape, porosity, permeability, sedimentary features and the presence of oil staining or gas shows to provide clues about the environment in which the rocks were deposited and their potential to store hydrocarbons or sequester CO₂.

The digital logs can be further utilized by importing them into Geographix, a special type of computer software. This software is being used in the photo below left to examine a vertical slice of the test well subsurface based on Gamma Ray, Neutron/Density logs. The subsurface rock units in the test well are being correlated to other wells in eastern Ohio. Overall, our data from the test well site is considerable and can be compared with data about other wells in the state.

What have you discovered so far?

We have been analyzing data from tens of thousands of wells and producing dozens of maps of some of the most favorable reservoirs and cap rocks for Ohio. Our initial assessments of Ohio’s deep storage capacity indicate that we can potentially sequester approximately 45 billion tons of CO₂, representing about 350 years of our current output of CO₂ from stationary point sources.

However, that capacity is not equally distributed around the state. Some areas have large potential, while other areas have little to no potential. This is important information to guide future plans for building large CO₂ point-source industries and, perhaps, building pipelines to distribute the CO₂ from sources to appropriate storage sites.

We still have much to learn about how the rate at which these deep rocks will accept CO₂ and the pressure buildup from injection operations will interact. This information is vital to allow planning of how many wells will be needed at what spacing, which determines compression needs, pipeline lengths; basically the overall distribution of operations.

What is the most challenging aspect of your job?

Communications! I coordinate the work of the division and our partnerships with a number of other Ohio agencies, Battelle Memorial Institute, federal agencies and a number of other state geological surveys. Communication between these various parties is critical to keep all working in concert toward common goals and to prevent duplicate efforts and minor disputes. We also must communicate our technical findings to technical and non-technical audiences. That is a lot of communicating!