The Bakken/Three Forks is the largest oil field (in square miles) in the world. It underlies approximately 18,000 square miles of North Dakota and is about the size of theState of West Virginia. Throughout most of the Williston Basin, the Bakken Formation consists of three layers, or “members” that lie approximately two miles underground. The upper member is a layer of black marine shale approximately 23 feet thick. The middle member is composed of sandstone, limestone, siltstone and dolomite about 85 feet thick, and the lower member is black marine shale about 50 feet thick.
The shale members have high levels of organic material that converts to oil and natural gas under the proper conditions and contains concentrations of natural occurring radioactive material, or NORM, that is brought to the surface during the drilling and extraction process.
What is NORM?
Naturally occurring radioactive materials, or NORM, are radioactive substances that exist in all natural media, including soils, rocks, water, air, and even in many of our foods like bananas, white potatoes, and peanut butter, and as radioactive potassium in our own bodies.
Higher concentrations of NORM is uncovered in byproducts of oil and gas development, including sediment, silt and other particulates that are carried to the surface with produced water. This is because radioactive elements, such as radon, radium and uranium are dissolved during normal reactions between water and rock, and concentration becomes higher during long periods of water-to-rock contact.
Why does Bakken Shale have NORM?
Millions of years ago, North Dakota was once covered by an inland sea. As animals and organisms died, their bodies sunk to the bottom and were covered with layers of rock and sediment deposit, becoming a layer of black marine shale that we call the Bakken. The Bakken, like other oil and gas-bearing shale, experienced long periods of water-to-rock contact to produce higher concentrations of NORM. NORM exists in the oil, rocks, and formation water, or the briny solution contained in reservoirs of oil and gas.
How is NORM brought to the surface?
During drilling, a mixture of oil, gas, and formation water is pumped to the surface. The water is separated from the oil and gas into tanks where it is referred to as “produced water.” Sediment, silt and other particulates are also brought to the surface. These byproducts of oil and gas development are considered waste.
Are these byproducts radioactive?
Though you may have never been aware of it, radiation is, and always has been, all around us. Natural, “background” radiation has been with us since the birth of the universe. Naturally-occurring radioactive elements, such as radon, radium, uranium, and cadmium that have been present in the rocks and minerals of the earth’s crust since it was formed, so some radioactivity may be associated with almost all minerals, rocks, ores and water. Therefore, it is important to differentiate between different types of radioactivity.
Radioactive materials are classified under two headings, man-made and naturally occurring radioactive materials. Radioactive materials that are naturally occurring in rocks, soil, water and air are considered NORM. Formation water, produced water, drill cuttings and other waste that is brought to the surface during oil and gas production are considered technologically (human) enhanced naturally occurring radioactive material, or TENORM.
In addition, it is important to define what constitutes “radioactive waste.” Radioactive waste comes from a number of sources, with the majority of it originating from the nuclear fuel cycle and nuclear weapons reprocessing. Another source includes medical and industrial wastes, and a third source is NORM, which includes the wastes generated by oil and gas development.
Radioactivity is measured in picocuries and its concentrations are generally reported in picocuries per gram (pCi/g). Most natural soils and rocks contain between 0.5 and 5 pCi/g of radium. In North Dakota, NORM is defined as material with radioactivity exceeding 5 pCi/g.
How is NORM regulated and disposed?
NORM is not federally regulated in the United States. The Nuclear Regulatory Commission (NRC) has jurisdiction over a relatively narrow spectrum of radiation, and the Environmental Protection Agency (EPA) has jurisdiction over NORM. Since no federal entity has implemented NORM regulations, NORM is variably regulated by the states, primarily those with oil and gas development. For those that do not, EPA has several activities underway that will help provide guidance.
In North Dakota, NORM is defined as materials exceeding 5 pCi/g, and cannot be disposed of in the state, nor are the proper meters or equipment being used in direct correlation to picocuries.
Other oil-producing states define NORM at higher levels and have specially designated and permitted landfills, disposal wells, and/or injection wells to provide for the proper handling and disposal of the radioactive waste byproducts of oil and gas production.
When industries extract or handle minerals or utilize large quantities of water, rocks and soils containing NORM, there is a higher likelihood of exceeding the 5 picocurie threshold. For this reason, the oil and gas industry in North Dakota must spend tens of thousands of dollars per load of radioactive material to ship outside of the state to have it properly disposed of in others that have specific NORM regulations and permitted disposal sites, including Colorado, Idaho and Texas.
“Naturally Occurring Radioactive Material,” Energy and Environmental Research Center
“Doses in our daily lives,” U.S. Nuclear Regulatory Commission
“Radiological Dose and Risk Assessment of Landfill Disposal of Technologically Enhanced Naturally Occurring Radioactive Materials (TENORM) in North Dakota,” Argonne National Laboratories
“Radiation Dose Calculator,” U.S. Nuclear Regulatory Commission
“Understanding Naturally Occurring Radioactive Material in the Marcellus Shale,” Marcellus Shale, Issue 4. Paleontological Research Institution