Management of NORM has become a rising issue to stakeholders and regulators. ERM has expertise at all stages of the management of NORM to assist in resolving these issues and to identify sustainable solutions for the Oil and Gas industry.
What is NORM and TENORM?
The heat flow from our planet’s interior is estimated to be almost twice as high as the world’s primary energy consumption. The source of that heat, which fuels plate tectonics and keeps volcanoes active is to a large extent the decay of radioactive materials that occur naturally in our planet’s mantle and crust. Radioactive isotopes are ubiquitously present in our environment at various levels. The exposure to such radiation is responsible for the majority of a person’s yearly radiation dose and is not usually considered of any special health or safety significance. However, certain industries handle and bring to the surface significant quantities of Naturally Occurring Radioactive Materials (NORM), which usually end up in their waste streams. Various industries generate radioactive byproducts, from obvious areas such as the mining for uranium, mineral sands or coal to the less well known area of the production of oil and natural gas. NORM containing media within which radioactivity has been concentrated and/or exposed to the accessible environment as a result of human activities is referred to as Technologically Enhanced Naturally Occurring Radioactive Materials, or TENORM. The presence of NORM in oil production has been known since more than 100 years, but industry associations, agencies or dedicated governmental committees have only been addressing the issue in a more coordinated manner during the past decade, compounding which there is rising public awareness. This article focuses on the occurrence of NORM associated with the oil and gas industry and highlights some of the key issues and solutions.
Source and reservoir rocks of oil and gas deposits can contain high concentrations of radioactive elements that are mainly the decay products of uranium and thorium. Of particular relevance are elements with a long half-life, such as radium-226 (226Ra) or lead-210 (210Pb) that occur in the uranium-238 decay series and radium-228 (228Ra), which is a thorium progeny (Figure 1). The most common isotope, 226Ra, is an alpha emitter, with accompanying gamma radiation, and has a half-life of about 1600 years. 228Ra is principally a beta emitter with a half-life of 5.76 years. Stable lead is the final product of this lengthy radioactive decay series. Radon (222Rn), a radioactive gas, can be present in the gas stream in varying degrees and many of its decay products are attached to ambient aerosols or airborne particulates, which can be inhaled. Figure 2 shows the origins of NORM in oil and gas production and indicates where radionuclides may accumulate in the recovery process.
Figure 1 (Source: World Nuclear Association)
Figure 2 (Source: OGP Report No. 412, 2008)
Key challenges in NORM waste management
Radioactive materials, together with many other constituents, become dissolved in saline formation water and are brought to the surface with the oil, gas and water mixture during production. Equally, drilling and injection fluids can take up some NORM. Depending on the formation characteristics, also cuttings may exhibit minor levels of radioactivity. Although concentrations of NORM in produced fluids or cuttings are usually quite low and thus rarely present a risk to human health or the environment, this can change significantly when the fluids are processed. Pressure and temperature changes in oil or gas wells and in production piping lead to a precipitation and the build-up of mineral scale, most of which is sulphates such as BaSO4, SrSO4 and carbonate scale such as CaCO3. As radium behaves chemically similar to barium (Ba), strontium (Sr) and calcium (Ca), the radium co-precipitates with the other mineral scale forming radium sulphate or radium carbonate. Activity concentrations, measured in Becquerel per gram, have been reported to reach up 15,000 Bq/g for 226Ra and almost 3,000 Bq/g for 228Ra in hard scales (OGP Report 412, 2008). Not all NORM nuclides end up in scale but accumulate in sludge from tanks or separators (210PB and 210Po), produced sand and to a very large extent in produced water. In gas processing facilities and condensate, high activity concentrations of 222Rn can be observed, often as a thin film plated onto surfaces.
The build-up of scale in production piping has serious implications for efficiency because of the significantly reduced throughput. Such pipes and other equipment need to be replaced or descaled. While equipment that contains NORM scale can hardly be disposed of or recycled legally and hence frequently ends up in secured storage yards, descaling is the most reasonable option but results in the generation of radioactive waste that can exhibit elevated radiation levels and requires proper disposal. The same applies to sludge that contains NORM with higher activity concentration. A particular issue that tends to become overlooked is the accumulation of radioactive materials in produced water evaporation or brine pits, which are abundant in arid, remote regions and are often very large scale. While the water evaporates, it leaves NORM in salts and bottom sludge from years and sometimes decades of production. Such evaporation pits are occasionally used to deposit scale or sludge from pipe and equipment cleaning. Since residual oil is present in produced water and does not get entirely removed by separators, an oily layer frequently covers the fluids in the pit. Efforts to clean such “oil pits” can unwittingly expose workers to radiation if no measurements are undertaken prior to planning such activities. According to U.S. EPA, the activity of radionuclides in such soils have been reported to be in the range from 10 to 40 Bq/g and could thus pose a potential radiological health risk.
The Regulatory Background
Regulations on the disposal of oilfield waste containing NORM vary greatly, and so does the availability of suitable or dedicated landfills. Another complication is the fact that different standards exist for waste originating from natural sources and those out of the nuclear industry. Oil and gas waste is even exempt under some jurisdictions. Generally, NORM can be classified as Low Specific Activity (LSA) material or Low Level Radioactive Waste (LLRW). At present, there are no clear rules that define LSA for the purpose of disposal. This may change in the future due to new Basic Safety Standards (BSS) Directive (2013/59/Euratom) that call for new standards for exemptions from regulatory control and stipulates for example an activity threshold of 1.0 Bq/g for NORM waste. However, most pertinent regulations relate to human exposure to radiation and thus to dose rates, which are a function of radiation type, material, time and distance and can’t be converted directly from activity concentrations. Current threshold levels of exposure are set at 0.3 – 1 mSv/a (Millisievert per year) for the general public and 5 – 50 mSv/a for specialized radiation workers that undergo continuous monitoring. This is in addition to other radiation exposure from natural sources, cosmic radiation or medical x-rays.
ERM’s NORM Services – How we can help you
ERM has developed significant expertise in all stages of NORM management in various geographies. They comprise
- Compliance assessments and regulatory review
- Identification of best practices, technically and regionally
- Permitting assistance
- Baseline studies and measurements
- NORM Management Systems
- Health and safety management
- Health and environmental risk assessments
- Waste Management Plans, disposal and treatment options
- Feasibility studies
- Remedial planning
- Project management and implementation
We have developed a workflow that ensures any project is set up to deliver reliable and comprehensive results and solutions, and which can be entered at different stages and adopted to a variety of tasks.
ERM Workflow for NORM Related Projects within the Oil and Gas Industry
An element of particular importance is the identification, the assessment and the quantification of risks to human health, which can involve the heat mapping of sites or activities, an options risk analysis or a bow-tie analysis with NORM controls. Such assessments of present conditions and the simulation of possible handling, remediation or disposal options allow for the development of prevention, control or mitigation measures.
To coordinate the delivery of NORM-related services at the best quality, ERM has set up a dedicated team of NORM experts that get engaged across all business units.
To set up a topic specific discussion, or to find out more about ERM's expertise in relation NORM, please contact: