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You are here: EPA Home Radiation Protection Programs Naturally-Occurring Radiation 

TENORM Oil and Gas Production Wastes 

Oil and Gas Production Wastes 

The geologic formations that contain oil and gas deposits also 

contain naturally-occurring radionuclides, which are referred to 

as "NORM" (Naturally-Occurring Radioactive Materials):

uranium (and its decay products) 

thorium (and decay products)

radium (and decay products) 

lead-210

Geologists have recognized their presence since the early 

1930s and use it as a method for finding deposits (Ma87).

Much of the petroleum in the earth's crust was created at the 

site of ancients seas by the decay of sea life. As a result, 

petroleum deposits often occur in aquifers containing brine 

(salt water). Radionuclides, along with other minerals that are 

dissolved in the brine, precipitate (separate and settle) out forming various wastes at the 

surface:

mineral scales inside pipes 

sludges

contaminated equipment or components

produced waters.

Because the extraction process concentrates the naturally occurring radionuclides and 

exposes them to the surface environment and human contact, these wastes are classified as 

TENORM. 

On this page:

How are drilling wastes produced? 

How much radiation is in the wastes?

Waste Types and Amounts 

Produced Waters 

Scale

Sludge

Contaminated Equipment 

Disposal and Reuse: Past Practices 

Recycling of Metals

Disposal of Wastes 

Radiation Protection 

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Disposal and Reuse: Current Practices

Recycling of Metals

Waste Disposal 

Exposure Risks

Oil/Radiation Waste Disposal Workers

Nearby Residents/Office Workers

What is being done?

Resources 

How are drilling wastes produced?

The briney solution contained in reservoirs of oil and gas is known as "formation water." 

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 or pits, where it is referred to as "produced 

water." As the oil and gas in the reservoir are removed, more of what is pumped to the 

surface is formation water. Consequently, declining oil fields generate more produced water. 

While uranium and thorium are are not soluble in water, their radioactive decay product, 

radium, and some of its decay products are somewhat soluble. Radium and its decay 

products may dissolve in the brine. They may remain in solution or settle out to form 

sludges, which accumulate in tanks and pits, or mineral scales, which form inside pipes and 

drilling equipment. 

How much radiation is in the wastes?

Because radium levels in the soil and rocks vary greatly, so do their concentrations in scales 

and sludges. Radiation levels may vary from background soil levels to as high as several 

hundred nanoCuries per gram. The variation depends on several factors:

concentration and identity of the radionuclides

chemistry of the geologic formation

characteristics of the production process (McA88).

The table below shows the range of activities in these wastes:

Wastes Radiation Level [pCi/g]

 low average high 

Produced Water 

[pCi/l] 0.1 NA 9,000

Pipe/Tank Scale 

[pCi/g] <0.25 <200 >100,000 

The Radiation in TENORM Summary Table provides a range of reported concentrations, and 

average concentration measurements of NORM associated with various waste types and 

materials. 

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Waste Types and Amounts

Each year the petroleum industry generates around 150,000 cubic meters (260,000 metric 

tons) of waste including produced water, scales, sludges, and contaminated equipment. The 

amount produced at any one oil reserve varies and depends on several factors:

geological location

formation conditions

type of production operation

age of the production well. 

An estimated 30 percent of domestic oil and gas wells produce some TENORM (McA88). In 

surveys of production wells in 13 states, the percent reporting high concentrations of 

radionuclides in the wells ranged from 90 percent in Mississippi to none or only a few in 

Colorado, South Dakota, and Wyoming (McA88). However, 20 to 100 percent of the facilities 

in every state reported some TENORM in heater/treaters. 

Produced Waters

The radioactivity levels in produced waters are generally low, but the volumes are large. The 

ratio of produced water to oil is approximately 10 barrels of produced water per barrel of oil. 

According to the American Petroleum Institute (API), more than 18 billion barrels of waste 

fluids from oil and gas production are generated annually in the United States.

Produced waters contain levels of radium and its decay products that are concentrated, but 

the concentrations vary from site to site. In general, produced waters are re-injected into 

deep wells or are discharged into non-potable coastal waters. 

Scale 

Scale is composed primarily of insoluble barium, calcium, and strontium compounds that 

precipitate from the produced water due to changes in temperature and pressure. Radium is 

chemically similar to these elements and as a result is incorporated into the scales. 

Concentrations of Radium-226 (Ra-226) are generally higher than those of Ra-228.

Scales are normally found on the inside of piping and tubing. The API found that the highest 

concentrations of radioactivity are in the scale in wellhead piping and in production piping 

near the wellhead. Concentrations were as high as tens of thousands of picocuries per gram. 

However, the largest volumes of scale occur in three areas:

water lines associated with separators, (separate gas from the oil and water)

heater treaters (divide the oil and water phases)

gas dehydrators, where scale deposits as thick as four inches may accumulate .

Chemical scale inhibitors may be applied to the piping complexes to prevent scales from 

slowing the oil extraction process. If the scales contain TENORM, the radiation will remain in 

solution and eventually be passed on to the produced waters. 

Approximately 100 tons of scale per oil well are generated annually in the United States. As 

the oil in a reservoir dwindles and more water is pumped out with the oil, the amount of 

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Oil drilling rig.(click for 

larger image.)

scale increases. In some cases brine is introduced into the formation to enhance recovery; 

this also increases scale formation.

The average radium concentration in scale has been estimated to be 480 pCi/g. It can be 

much higher (as high as 400,000 pCi/g) or lower depending on regional geology.

Sludge

Sludge is composed of dissolved solids which precipitate from produced water as its 

temperature and pressure change. Sludge generally consists of oily, loose material often 

containing silica compounds, but may also contain large amounts of barium. Dried sludge, 

with a low oil content, looks and feels similar to soil. 

Oil production processes generate an estimated 230,000 MT or five million ft3 (141 cubic 

meters) of TENORM sludge each year. API has determined that most sludge settles out of the 

production stream and remains in the oil stock and water storage tanks.

Like contaminated scale, sludge contains more Ra-226 than Ra-228. The average 

concentration of radium in sludges is estimated to be 75 pCi/g. This may vary considerably 

from site to site. Although the concentration of radiation is lower in sludges than in scales, 

sludges are more soluble and therefore more readily released to the environment. As a result 

they pose a higher risk of exposure. 

The concentration of lead-210 (Pb-210) is usually relatively low in hard scales but may be 

more than 27,000 pCi/g in lead deposits and sludge. 

Contaminated Equipment

TENORM contamination levels in equipment varied widely among 

types of equipment and geographic region. The geographic areas 

with the highest equipment readings were northern Texas and the 

gulf coast crescent from southern Louisiana and Mississippi to the 

Florida panhandle. Very low levels of TENORM were found in 

California, Utah, Wyoming, Colorado, and northern Kansas. 

According to an API industry-wide survey, approximately 64 percent 

of the gas producing equipment and 57 percent of the oil production 

equipment showed radioactivity at or near background levels. TENORM radioactivity levels 

tend to be highest in water handling equipment. Average exposure levels for this equipment 

were between 30 to 40 micro Roentgens per hour (μR/hr), which is about 5 times 

background. Gas processing equipment with the highest levels include the reflux pumps, 

propane pumps and tanks, other pumps, and product lines. Average radiation levels for this 

equipment as between 30 to 70 μR/hr. Exposures from some oil production and gas 

processing equipment exceeded 1 mR/hr. 

Gas plant processing equipment is generally contaminated on the surface by lead-210 (Pb210). However, TENORM may also accumulate in gas plant equipment from radon (Rn-222) 

gas decay. Radon gas is highly mobile. It originates in underground formations and dissolves 

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in the organic petroleum areas of the gas plant. It concentrates mainly in the more volatile 

propane and ethane fractions of the gas. 

Gas plant scales differ from oil production scales, typically consisting of radon decay products 

which accumulate on the interior surfaces of plant equipment. Radon itself decays quickly, 

(its half-life is 3.8 days). As a result, the only radionuclides that affect disposal are the radon 

decay products polonium-210 (Po-210) and lead-210. Polonium-210 is an alpha emitter with 

a half-life of 140 days. Pb-210 is a weak beta and gamma emitter with a half-life of 22 years. 

Disposal and Reuse: Past Practices

Recycling of Metals 

Before the accumulation of TENORM in oil production equipment was recognized, 

contaminated materials were occasionally recycled for use in making steel products:

load-supporting beams in house construction

plumbing for culinary water

fencing materials

awning supports

practice welding material in class rooms. 

Disposal of Wastes 

When sludge fouling in water and oil storage tanks became a problem, the tanks were 

drained and the sludge disposed of in waste pits:

Burn pits

Earthen pits were previously used for temporary storage an periodic burning of nonhazardous oil field wastes collected from tanks and other equipment.

Brine pits

Lined and/or earthen pits were previously used for storing produced water and other 

nonhazardous oil field wastes, hydrocarbon storage brine, or mining wastes. In this 

case, TENORM in the water will concentrate in the bottom sludges or residual salts of 

the ponds. Thus, the pond sediments pose a potential radiological health risk. The 

radionuclides in these soils have been reported to be in the range from 270 to 1100 

pCi/g.

Disposal and Reuse: Current Practices 

Recycling of Metals 

Now that the petroleum industry is aware of the potential for contamination, they take a 

number of precautions before recycling: 

Loads of scrap metal are surveyed for hidden radioactive sources and TENORM.

Piping and equipment are cleaned before release for recycling at smelters.

Pollution control devices, such as filters and bubblers, are installed in smelter stacks 

to reduce airborne radiation releases.

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Although much of the NORM-contaminated equipment is presently stored in controlled areas, 

some companies are now cleaning the equipment and proposing to store it at designated 

disposal sites.

Waste disposal 

The average concentration of the radium in the oil and gas wastes at offsite and onsite 

disposal facilities is approximately 120 pCi/g. 

Sludges containing elevated TENORM are now dewatered and held in storage tanks for later 

disposal. 

Produced waters are now generally reinjected into deep wells or, in the case of offshore 

production facilities, are discharged into non-potable coastal waters. No added radiological 

risks appear to be associated with this disposal method as long as the radioactive material 

carried by the produced water is returned in the same or lower concentration to the 

formations from which it was derived. As of 1992 there are 166,000 injection wells in 31 

states. 

Pipes contaminated with scale are cleaned at pipe yards either by sandblasting them with 

high pressure water or by scraping out the scale with a rotating drill bit. The removed scale is 

then placed in drums and stored for later disposal.

Contaminated equipment may either be cleaned and reused by the petroleum industry; 

disposed; or, if radiation levels are sufficiently reduced, sold for recycle. If equipment cannot 

be further decontaminated to acceptable levels, it is sent to a landfill licensed to accept 

NORM materials. 

In some cases contaminated steel may be reprocessed via smelting. During the smelting 

process molten steel separates from the NORM which vaporizes and is released as a gas. If 

the steel mill has pollution control equipment, most of the NORM is trapped in the baghouses 

and scrubbers. A typical smelting operation is capable of capturing 99 percent of the 

particulate releases. 

Exposure Risks

TENORM contamination in oil production waste came to the attention of industry and 

government in 1986 when, during routine well work in Mississippi, barium sulfate scale in 

tubing was found to contain elevated levels of levels of radium-226, and thorium-232. 

Because of concerns that some pipes may have contaminated the surrounding environment, 

radiological surveys were conducted by EPA's Eastern Environmental Radiation Facility. These 

surveys showed that some equipment and disposal locations exhibited external radiation 

levels above 2 mR/hr and radium-226 soil contamination above 1,000 pCi/g. Some 

contamination had also washed into a nearby pond and drainage ditch at one site, as well as 

into an agricultural field with subsequent uptake of radium by vegetation.

Because TENORM contaminated wastes in oil and gas production operations were not 

properly recognized in the past, disposal of these wastes may have resulted in environmental 

contamination in and around production and disposal facilities. Surface disposal of radioactive 

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sludge/scale, and produced water (as practiced in the past) may lead to ground and surface 

water contamination. 

Those at risk include:

oil/radiation waste disposal workers

nearby residents/office workers.

Oil/Radiation Waste Disposal Workers 

Disposal workers include those who work directly on top of uncovered waste sites. Potential 

risks assessed for these workers include exposures due to direct gamma radiation and 

radioactive dust inhalation. In addition, they may inhale radon gas which is released during 

drilling and produced by the decay of radium, raising their risk of lung cancer. Workers 

following safety guidance will reduce their total on-site radiation exposure. 

Nearby Residents/Office Workers 

Risks evaluated for members of the public working or residing within 100 meters of a 

disposal site are similar to those of disposal workers. They include: direct gamma radiation, 

inhalation of contaminated dust, inhalation of downwind radon, ingestion of contaminated 

well water, ingestion of food contaminated by well water, and ingestion of food contaminated 

by dust deposition. 

Risks analyzed for the general population within a 50 mile radius of the disposal site include 

exposures from the downwind transport of re-suspended particulates and radon, and 

exposures arising from ingestion of river water contaminated via the groundwater pathway 

and surface runoff. Downwind exposures include inhalation of re-suspended particulates, 

ingestion of food contaminated by deposition of re-suspended particulates, and inhalation of 

radon gas.

Individuals working inside an office building inadvertently constructed on an abandoned 

NORM waste pile also face the threat of radiation exposure. Potential risks assessed for the 

onsite individual include exposures from direct gamma radiation, dust inhalation, and indoor 

radon inhalation. 

What you can do to protect yourself: U.S. Environmental Protection Agency 

At this site you will find information on how to reduce total on-site radiation exposure 

at oil and gas drilling facilities. 

What is Being Done About These Wastes

The problem of TENORM contamination is now known to be widespread, occurring in oil and 

gas production facilities throughout the world. It has become a subject of attention in the 

United States and in other countries. In response to this concern, facilities in the U.S. and 

Europe have been characterizing the nature and extent of TENORM in oil and gas pipe scale, 

evaluating the potential for exposure to workers and the public, and developing methods for 

properly managing these low specific-activity wastes. 

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Both the oil and gas industry and state regulatory agencies are currently examining and 

regulating TENORM in oil and gas production facilities. The API has sponsored studies to 

characterize accumulations of TENORM in oil field equipment and to evaluate methods for its 

disposal. The API has also formed an Ad Hoc Committee on Low Specific-Activity (LSA) Scale 

and has prepared a draft measurement protocol for identifying producing areas where NORM 

scale is known to exist. The Part N Subcommittee of the Conference of Radiation Control 

Program Directors has been working since 1983 to develop model state regulations (Part N of 

Suggested State Regulations for Control of Radiation) for the control of NORM. While these 

regulations are intended to apply generally to all NORM-containing materials, several parts 

would apply specifically to oil and gas industry pipe scale. 

Many states with oil and gas production facilities are currently creating their own NORM 

regulations. For example, the State of Louisiana has regulations for NORM in scales and 

sludges from oil and gas production that differ from the Part N model regulations, where the 

State of Texas has NORM regulations similar to Part N regulations. 

Resources

Sector Notebook Project – Oil and Gas Extraction (PDF) (41 pp, 444K [about pdf format] ) 2000. U.S. 

Environmental Protection Agency, Office of Enforcement and Compliance Assurance 

This document provides a description of the oil and gas extraction process, how to comply 

with EPA’s health and the environmental laws and techniques for pollution prevention. 

Who is Protecting you? U.S. Environmental Protection Agency 

This site lists a number of federal and state agencies responsible for regulating radioactive 

materials and workers safety.

Health Effects U.S. Environmental Protection Agency 

Site provides information on the health effects associated with a range of radiation 

exposures. 

Potential Health Hazards Associated with Handling Pipe Used in Oil and Gas Production 26 

January 1989. OSHA Hazard Information Bulletins. U.S. Department of Labor, 

Occupational Safety and Health Administration 

This document warns workers of possible inhalation or ingestion of radioactive material in 

cutting and welding oil and gas pipes.

The American Petroleum Institute 

Trade association that represents all aspects of America’s oil and natural gas industry.

Programs  Topics  References

http://www.epa.gov/radiation/tenorm/oilandgas.html

Last updated on Friday, July 08, 2011

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