Bulletin on Management of Naturally Occurring Radioactive Materials (NORM) in Oil and Gas Production API BULLETIN E2 SECOND EDITION, APRIL 2006 Bulletin on Management of Naturally Occurring Radioactiv[.]
Introduction
Naturally occurring radioactive materials (NORM) can be found in oil and gas operations, potentially accumulating in well tubulars, surface piping, and processing equipment This document aims to inform operators about the presence of NORM and offers guidance on protecting workers, the public, and the environment It provides essential information to help users understand the radiation issues related to NORM management and highlights the importance of consulting with professional health physicists or industrial hygienists Operators are encouraged to engage closely with their state regulatory office regarding all NORM-related matters.
Radiation originates from both man-made and natural sources, such as dental x-rays and cosmic rays from the sun Naturally occurring materials in the earth's crust and living organisms also emit radiation Radioactive materials are unstable and decay over time, releasing ionizing radiation Excessive exposure to this radiation can lead to biological damage in individuals and their descendants, heightening the risk of cancer and birth defects Therefore, it is crucial to safeguard humans from unnecessary exposure to high levels of radiation.
NORM is prevalent in both natural environments and human-made materials, including building materials and fertilizers, and is associated with oil and gas production In oilfield operations, NORM originates from subsurface formations and is brought to the surface with produced water As this water rises and cools, it leads to the formation of precipitates in tubing and equipment, resulting in scales and sludges that may contain radium, its decay products, and other uranium and thorium progeny Additionally, radon can be present in produced natural gas, potentially creating thin radioactive lead films on the inner surfaces of gas processing equipment.
Measurements of equipment surfaces with Naturally Occurring Radioactive Material (NORM) typically show radiation levels that are not concerning However, during inspections or repairs, there is a risk of inhaling or ingesting NORM, which can expose workers to radioactivity To mitigate this risk, it is essential for personnel to take precautions to minimize dust generation and to use protective equipment Additionally, proper management and disposal of NORM waste and equipment are crucial to safeguard the public from unnecessary exposure.
History
In the early 1980s, radioactivity was detected in North Sea oil and gas operations, and in 1986, Naturally Occurring Radioactive Material (NORM) was identified in tubing from a Mississippi well during routine work Since then, numerous operators across the United States have conducted surveys, revealing the presence of NORM at various sites Typically, in oil and gas operations, NORM is found in small quantities, at widely scattered locations, and exhibits low levels of radioactivity.
After the discovery of NORM in Mississippi in 1986, the American Petroleum Institute:
• Gathered more than 36,000 nationwide measurements of external radioactivity
• Studied methods for measuring NORM in petroleum equipment
• Evaluated alternatives for disposing of NORM waste
API has continued to study the management of NORM issues API has prepared reports on the following topics:
• Surveys of NORM in petroleum production and gas processing facilities
• Methods for measuring NORM in petroleum production equipment
• Management and disposal alternatives for NORM in oil production and gas plant equipment
• Dose estimates and indoor radon concentrations attributed to remediated oilfield NORM
For access to reports on these studies, please contact the Coordinator of Upstream Environmental Affairs at the American Petroleum Institute, located at 1220 L Street Northwest, Washington DC 20005 These studies, along with similar research conducted by individual companies, form the foundation of the information presented in this document.
This document outlines the API's guidelines for effectively managing NORM as of the publication date Operators are advised to consult federal and state regulatory agencies to determine applicable legal requirements.
NORM in oil and gas production
NORM encompasses a variety of naturally radioactive materials, such as carbon-14 and potassium-40, which are found in the human body In the context of oil and gas production, radioactive elements like uranium, thorium, and their decay products are naturally present in the earth's crust and can be found in the formations from which these resources are extracted Key isotopes of concern include radium-226 (Ra-226), radium-228 (Ra-228), and their progeny.
Uranium is sometimes found in small quantities alongside oil and gas, as these radioactive elements occur in varying concentrations within oil and gas-bearing formations Many reservoirs, particularly those with shales, may have elevated levels of these elements Their solubility allows them to enter production fluids, influenced by the physical and chemical properties of the formations, which often enhance the solubility of these elements.
When radioactive elements are brought to the surface with production fluids, various changes can occur based on site characteristics Typically, these elements remain in the water phase and may either integrate into pipe scale, such as radium coprecipitated in barium sulfate, or form sludges The formation of Naturally Occurring Radioactive Material (NORM) scale happens when radium replaces barium in barite scale, resulting in a coprecipitated (Ba, Ra)SO4 scale Additionally, radium can substitute for calcium and strontium in a similar fashion.
Radium can substitute for barium due to similarities in ionic radius, molecular size, and valence, but the substitution is typically minimal because barium is more abundant in solution As a result, radioactive sludges and scales, including those containing radium, lead (Pb-210), and polonium (Po-210), can accumulate in process equipment such as pipes, heater treaters, separators, and salt water tanks This accumulation is often linked to the formation of sulfide precipitates.
Radon can dissolve in produced water and oil, often released during gas production, particularly in ethane and propane processing The highest concentrations of radon progeny, including lead-210 (Pb-210), bismuth-210 (Bi-210), and polonium-210 (Po-210), are typically found in pumps, tanks, and product lines These progeny may accumulate in gas processing equipment, such as inlet filters and reflux pumps, and can manifest as a thin black film (ferric sulfide), sludge (pipe rouge), or on clean metal surfaces It's crucial to understand that these accumulations do not always indicate increased radioactivity levels, and their removal can vary from easy (as with sludge) to requiring more intensive methods like grinding The formation of ferric sulfide in gas vessels results from hydrogen sulfide interacting with steel.
Surveys of Naturally Occurring Radioactive Material (NORM) have revealed that significant concentrations are found in a small percentage of oil and gas production operations, primarily in specific regions such as the Gulf Coast, northeast Texas, southeast Illinois, and southern Kansas This indicates that facilities in these areas are more likely to encounter notable NORM occurrences However, it is important to note that NORM may still be present in other locations To ensure that oil and gas operations are free from significant NORM levels, conducting a thorough site survey is essential, as outlined in Section 3.
NORM can be present in various locations, including downhole tubing, above-ground processing equipment, and saltwater disposal wells, as well as in soils affected by well workovers and leaks The highest levels of NORM activity are typically found in water-handling equipment at production facilities NORM activity in pipe scale can vary significantly, ranging from background levels to thousands of picocuries per gram (pCi/g), while oilfield sludges generally show NORM activity from background levels to several hundred pCi/g On average, NORM activity in both pipe scale and oilfield sludges is usually below 1000 pCi/g (37 Bq/g).
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Units of measurement
To comprehend NORM, it is essential to understand the different methods of radiation measurement NORM measurements assess the concentration of radioactive materials in various substances such as scale, sludge, and soil, as well as the potential exposure risk to individuals nearby In the United States, two measurement systems for radioactivity and radiation levels are currently in use: the traditional system and the international system (SI), with the latter indicated in parentheses throughout this document A summary of the units utilized in each system is provided in Table 1.1.
Table 1.1—Units of Radioactivity and Radiation Levels
Application SI units Traditional US units Conversion factors
Radioactivity becquerel (Bq) picocurie (pCi) 1 Bq = 27 pCi
Concentration becquerel/gram (Bq/g) picocurie/gram (pCi/g) 1 Bq/g = 27 pCi/g
Surface activity Bq/100 cm 2 disintegrations per minute/100 centimeters 2 (dpm/100 cm 2 )
Exposure Coulomb/kilogram (C/kg) Roentgen (R) 1 C/kg = 3876 R
Dose equivalent sievert (Sv) rem 1 Sv = 100 rem
Radioactive material quantity is measured by radioactivity level rather than weight or volume, with activity defined as the number of radioactive atoms disintegrating and emitting radiation per unit time The curie, equivalent to 2.2 trillion disintegrations per minute, is a large unit of measurement for activity In oil and gas production, the activity of radioactive materials is typically small, leading to the common use of the picocurie (pCi), which is one-trillionth of a curie In the International System of Units (SI), the becquerel (Bq) is the standard unit for measuring radioactivity.
The concentration of Naturally Occurring Radioactive Material (NORM) in various materials such as scale, sludge, soil, water, or air is assessed through laboratory analysis, typically reported in pCi/gm (Bq/g) for solids or pCi per liter (pCi/l) for liquids and gases Background soil levels of Ra-226 generally range from 0.5 to several pCi/g (under 1 Bq/g), while NORM-affected oilfield scales and sludges can vary significantly, ranging from 50 to several thousand pCi/g, or from a few Bq/g up to approximately 100 Bq/g On average, the NORM activity in pipe scale and oilfield sludges is usually below 1000 pCi/g (37 Bq/g).
Surface activity refers to radioactive material deposited on surfaces, which can be loosely or firmly attached through chemical or physical means This classification is crucial as it determines the ease of removal Surface activity is measured in disintegrations per minute per 100 centimeters squared (dpm/100 cm²) or Bq per 100 centimeters squared (Bq/100 cm²), with measurements aimed at assessing total and removable activity In oilfield NORM applications, for instance, Pb-210 and its progeny are measured when workers inspect and clean welds in pressure vessels at gas plants These measurements are initially collected in counts per minute (cpm) and then converted to dpm (Bq) using specific conversion factors based on the detector employed.
To detect the presence of Naturally Occurring Radioactive Material (NORM) in equipment or tubulars where scales and sludges cannot be sampled, external measurements can be performed using a calibrated scintillation detector This device measures gamma rays emitted by the scale that penetrate the equipment wall, with readings typically expressed in counts per minute (cpm) or microroentgens per hour (μR/hr) It is important to note that the rem unit has been replaced by the sievert, where 1 Sv equals 100 rem.
The use of scale inhibitors can significantly reduce the deposition of NORM-containing scale and the associated disposal costs By implementing a scale inhibition program, NORM can remain dissolved in the produced water However, a successful program necessitates a comprehensive understanding of the formation's water chemistry and a cost-benefit analysis Typically, NORM control alone does not justify the expenses of scale inhibition This section covers these critical topics.
• Implementation of a successful scale control program
Scale formation
NORM-containing scale is formed through the coprecipitation of radium sulfate with barium or strontium sulfate scale This phenomenon can arise from the mixing of incompatible formation waters with injection brines or workover fluids, as well as during the surface processing of produced water Additionally, fluctuations in temperature or pressure during fluid production can lead to scale formation.
Scale formation is a complex, multi-step process that can occur with or without NORM It begins when the concentration of a crystallizing mineral surpasses its solubility limit Next, the presence of small particles or rough surfaces is essential, as they provide sites for scale crystallization to initiate These sites may arise from spontaneous crystallization, corrosion products, or roughened production equipment surfaces Subsequently, mineral ions must adsorb onto these surfaces and integrate into the crystal structure Finally, scale deposits can form if conditions allow crystals to adhere to production equipment surfaces Disrupting any of these steps can be an effective strategy for controlling scale.
Control of scale deposition
Engineering controls serve as the primary defense against scale deposition, which often builds up in mechanical components due to excessive pressure drops and turbulence By modifying these components, scale formation can be minimized Additionally, preventing the mixing of incompatible waters can be achieved through the treatment of injection fluids or by designing surface facilities appropriately.
Scale inhibitors are essential in scenarios where engineering controls cannot prevent scaling These compounds, effective at low concentrations (1-50 ppm), disrupt the formation or growth of scale crystals, setting them apart from chemicals that dissolve existing scale or prevent formation through chelation, which require higher concentrations Commonly used scale inhibitors include phosphonates, polycarboxylates, and phosphate esters.
Screening tests that identify the minimum concentration of inhibitors necessary to prevent scaling are crucial for selecting the appropriate inhibitor Key factors influencing this selection include application temperature, brine pH, and brine composition Phosphate esters are cost-effective but are limited to temperatures below 212°F, while phosphonates can be used at temperatures up to 250-300°F Polycarboxylates are the most thermally stable, suitable for use up to 450°F The system pH significantly affects inhibitor performance, with all three types showing similar effectiveness at near-neutral pH However, as pH decreases, higher concentrations of inhibitors are required to prevent scaling Divalent ions in highly saline brines can lead to inhibitor precipitation, and polycarboxylates experience notable performance degradation in acidic conditions, particularly in saline environments The pH sensitivity of inhibitor performance varies based on the molecular structure of the inhibitor, leading to significant differences among inhibitors of the same type.
Burr, B J., T M Howe, and J Goulding (1987) presented their research on a detectable polymer scale inhibitor designed to control sulfate scales through squeeze applications at the SPE International Symposium on Oilfield Chemistry in San Antonio, TX Their findings, documented in SPE 16261, highlight the development and practical application of this innovative solution in the oilfield industry.
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Carlberg, B L 1983 “Precipitation Squeeze Can Control Scale in High-Volume Wells.” Oil and Gas J 81/52:15254.
Carrell, K D 1987 “The Occurrence, Prevention and Treatment of Sulphate Scale in Shell EXPRO.” Presented at Offshore Europe '87, Aberdeen, Scotland 9/8-11/97, SPE 16538.
Chesnut, G D., Chappell, G D., and Emmons, D H presented their research on the development of scale inhibitors and evaluation techniques specifically for carbon dioxide enhanced oil recovery (EOR) floods at the 1987 SPE International Symposium on Oilfield Chemistry in San Antonio, TX Their findings, documented in SPE 16260, contribute valuable insights into improving oil recovery processes.
Essel A J., and B L Carlberg 1982 “Strontium Sulfate Scale Control by Inhibitor Squeeze Treatment in the Fateh Field.” J Petr Tech 34/1302-1306.
Hamouda, A A 1989 “Insight into Sulfate in High-Salinity Producers and Selection of Scale Inhibitor.” Presented at the 64th Ann Tech Conf of SPE, San Antonio TX, 10/8-11/90, SPE 19764.
Payne, G E 1987 “A History of Downhole Scale Inhibition by Squeeze Treatments on the Murchison Platform.” Presented at Offshore Europe '87, Aberdeen, Scotland, 9/8-11/87, SPE Paper 1653911.
Ramsey and Cenegy (1985) conducted a laboratory evaluation of barium sulfate scale inhibitors specifically designed for low pH conditions in the context of carbon dioxide enhanced oil recovery (EOR) Their findings were presented at the 60th Annual Technical Conference of the Society of Petroleum Engineers (SPE) in Las Vegas, NV, highlighting the effectiveness of these inhibitors in mitigating scale formation during EOR processes.
Rybacki, R L 1981 “Understanding Scale Inhibitors.” Well Serv 21/4:43-44, July-Aug.
In their 1989 presentation at the SPE Joint Rocky Mountain Regional/Low Permeability Reservoirs Symposium, Shuler, Freitas, and Bowker discussed the selection and application of barium sulfate scale inhibitors specifically for a carbon dioxide flood in the Rangely Weber Sand Unit located in Rangely, Colorado Their research, documented in SPE 18973, highlights the importance of effective scale management in enhancing reservoir performance.
Tanner, R N., and K P Wittingham 1986 “Scale Control During Waterflooding Operations: A Field Appraisal of Inhibitor Requirements and Performance.” Presented at the SPE Petr Eng Int Mtg Beijing China 3/17-20/86, Proc Vol 1/ 281-292, SPE 14127.
Yuan, M D., and A C Todd 1989 “Prediction of Sulfate Scaling Tendency in Oilfield Operations.” Presented at the 1989 SPE International Symposium on Oilfield Chemistry, Houston, TX 2/8-10/89, SPE 18484.
This section provides information describing radiation measurement and sampling techniques and appropriate applications in NORM surveys This section also gives information on instrument maintenance and calibration and associated records.
Survey measurement and sampling techniques
NORM surveys generally involve the following measurement and sampling techniques:
• Direct measurements for total and removable alpha or beta surface activity
• Radionuclide concentrations in media (e.g., soil, sediment, sludge, water, air)
• Personnel monitoring for external radiation exposure
• Personnel monitoring for internal radiation exposure
The following sections discuss each measurement or sampling technique and describe the application of the technique to monitor- ing for oilfield NORM.
Gamma surface scans are conducted using a ratemeter/scaler paired with a 1 or 2 inch sodium iodide scintillation detector These scans help identify areas with elevated direct radiation that may need further examination The surveyor carefully moves the detector over the surface, maintaining proximity to it, while monitoring the audible output for increases in the count rate, which indicate areas of concern for additional investigation.
A systematic survey of the area or item under investigation is essential, with particular focus on locations like pipe elbows where solids may accumulate The meter probe should be positioned no more than 1 centimeter from the equipment's external surface and moved slowly across it During the initial scanning, the survey instrument's response switch must be set to the “fast” position to reduce the risk of missing NORM deposits Once NORM deposits are detected, the response switch should be adjusted accordingly.
“slow” position in order to obtain more accurate readings.
It is essential to survey production equipment, especially water-handling equipment, for external gamma radiation Additionally, any equipment that is being taken out of service, undergoing maintenance, or designated for unrestricted use, such as sale or scrapping, must be assessed for Naturally Occurring Radioactive Material (NORM).
Gamma surface scans of soil should be performed on a defined grid, with spacing optimized based on the survey area size and the likelihood of detecting elevated readings Regulatory agencies often mandate a maximum grid spacing of 10 meters (30 feet) A highly effective method for surveying large areas involves using a gamma-sensitive detector paired with a global positioning system, enabling the simultaneous recording of detector responses and location data Areas with elevated readings must be flagged for further investigation, which may involve additional radiation measurements and soil sampling.
Exposure rate measurements utilize gamma-sensitive survey instruments, which can be either a single unit with a read-out device and detector, like a micro-R meter, or a combination of a rate meter/scaler connected to a sodium iodide detector To conduct the measurement, the surveyor positions the detector at the desired location and waits for the meter to stabilize before recording the average value observed.
Many states have established exposure rate guideline values for equipment and areas These guidelines specify the measurement location Exposure rate measurements are usually performed at contact or at 1 meter
Exposure rate measurements are usually performed on NORM-impacted soil areas, tubulars or equipment, and areas identified by gamma surface scans The following measurement locations are recommended:
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• Both ends of tubulars and pipes
• All openings in fittings (i.e Ts, elbows), manifolds, etc.
• Both ends and the throats of valves
• Individual deposits or accumulations within vessels and tanks
Correlations can link gamma or exposure rate measurements to concentrations of NORM in scale or sludge, but operators must exercise caution due to various influencing factors such as NORM density, volume, thickness, nuclide composition, and detector efficiency Facility and equipment-specific correlations tend to provide more accurate results than generic ones, necessitating laboratory analysis of multiple samples collected at different exposure rates Similarly, a correlation for solid waste can be established by measuring samples of known concentrations in a consistent geometry, like a 1-liter open-mouth plastic jar Typically, the accuracy of these correlations is around ±50%.
Measurements of total and removable alpha and beta activity on equipment surfaces are conducted using appropriate detectors connected to a ratemeter-scaler Typically, a Geiger-Mueller (GM) tube is employed for beta measurements, while a zinc sulfide scintillator is used for alpha measurements The surveyor positions the detector against the surface at the measurement site and accumulates counts for a set duration, usually one minute, resulting in counts per minute (cpm) To obtain more useful units, such as disintegration per 100 cm² (dpm/100 cm²) or Bq per 100 cm² (Bq/100 cm²), conversion factors are applied to account for detector efficiency, count time, and geometry.
To assess removable activity levels, measurements are taken by applying moderate pressure to filter or smear paper and wiping a surface area of about 100 cm² The activity on the smear can be quantified either by counting the filter paper with survey instrumentation or by sending it to a radioanalytical laboratory for analysis Results are then reported in units of dpm/100 cm² or Bq/100 cm² after appropriate conversions.
Measurements of total and removable surface activity are typically conducted at gas plants While gas flows through process equipment, external surveys can detect areas where radon progeny accumulate However, if equipment has been inactive for over 4 hours or if the production stream lacks radon, these surveys may not identify internal radon progeny accumulations Such equipment may harbor significant amounts of Pb-210 and its progeny, necessitating internal surveys when the equipment is opened State radiation control regulations provide suitable limits for assessing radon progeny deposits, defined as surface activity or contamination limits.
Determining concentrations of Naturally Occurring Radioactive Materials (NORM) in air, soil, scale, and water often requires specialized collection techniques and equipment Environmental professionals or analytical laboratories can offer guidance on appropriate sampling methods It is crucial to maintain a documented history of the sample, known as chain of custody, to ensure integrity Samples are then sent to radioanalytical laboratories for radionuclide concentration analysis.
Soil sampling is essential at NORM-impacted sites for assessing radionuclide concentrations prior to land use changes or transactions It helps characterize surface activity and requires additional samples from non-NORM areas to establish background soil levels While external measurements can provide rough estimates of radionuclide concentrations, these should only inform follow-up analyses and not serve as the sole basis for remediation planning unless specific correlations for the area are established.
3.1.5 Personnel External Radiation Dose Assessment
Personnel radiation exposures can be assessed using thermoluminescent dosimeters or film badges, which need to be returned to the supplier for analysis Alternatively, radiation surveys can be conducted using a tissue-equivalent scintillation detector, a shielded energy compensated GM probe, or an ion chamber survey meter that provides readings in mrem/hour To accurately estimate radiation dose with the survey method, details about the work location and duration are essential.
State organizations, including the Occupational Safety and Health Administration (OSHA), set exposure limits for personnel, with an annual occupational limit of 5 rem (0.05 Sv) as specified in 29 CFR 1910.1096(b)(1) Additionally, the whole body dose must not exceed 3 rem (0.03 Sv) in any calendar quarter, according to 29 CFR 1910.1096(b)(2)(i) Monitoring typically occurs at a fraction of the limit, usually between 10% to 25% of the allowable exposure In the general industry segment, work area radiation levels are generally well below these regulatory limits, resulting in infrequent routine personnel radiation exposure surveys.
3.1.6 Personnel Internal Radiation Dose Assessment
Ambient airborne concentrations of Naturally Occurring Radioactive Materials (NORM) are typically assessed by filtering high-volume air samples for radiometric analysis While NORM deposits in equipment and piping do not pose airborne exposure risks during normal operations, maintenance or dismantling activities require precautions To minimize airborne NORM exposure, standard industrial hygiene practices, such as keeping deposits wet and using respiratory protective equipment, should be implemented However, activities like grinding, cutting, chipping, sanding, and removing NORM scale can lead to increased airborne activity, making it essential to evaluate employee exposure to ambient airborne NORM concentrations under these conditions.
Personnel exposures are assessed using similar sampling and laboratory methods, but personnel utilize lapel air samplers that function at a flow rate of 2 to 5 liters per minute, in contrast to the higher flow rate ambient air pumps For both methods, it is crucial to determine the volume of air sampled alongside the radiometric results to accurately calculate airborne Naturally Occurring Radioactive Material (NORM) concentrations.
Integration of survey techniques
Effective radiological measurement techniques require trained operators who understand the procedures involved It is crucial for the operator to identify the survey's purpose and the reference values for comparison The selection of the appropriate measurement technique hinges on this information For instance, if the goal is to assess the need for monitoring workers for occupational radiation exposure, the survey should focus on determining exposure rates and evaluating estimated internal doses, which may include measuring exposure rates and airborne concentrations of radioactive materials.
When a property is released from regulatory licensing, survey techniques such as gamma surface scans, exposure rate measurements, and soil NORM concentration assessments are typically employed The choice of these survey methods depends on the survey's objectives and the relevant guidelines for comparing the results.
Instrument care, maintenance, and calibration
Portable survey meters for NORM surveys are durable, but their detectors and probes require careful handling To prevent damage, avoid sharply bending connecting cables, as this can break the internal wires It's essential to keep battery contacts clean and free from corrosion In humid conditions or with infrequent use, remove batteries from the survey meters when not in use Additionally, ensure that survey instruments are kept clean, and that detectors are free from NORM residue.
NORM survey instruments must be returned to manufacturers or qualified calibration agents for maintenance and calibration at least annually, or semi-annually in certain jurisdictions Each meter, detector, and connecting cable should be calibrated as individual units, as switching components between them voids their calibration It is crucial to ensure that instruments measuring exposure rates are properly calibrated and responsive to the existing radiation field.
Before using an instrument, it is essential to perform operational checks, especially after it has been dropped or struck against a hard surface, to confirm its proper functioning and accuracy in readings These checks are crucial for ensuring reliable performance.
To check the battery, set the meter dial to the “Battery” position and ensure the indicator stays within the accepted range, or press the “Battery” button on the meter to observe the dial's reading.
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To ensure accurate measurements, it is essential to expose the detector to a known source of radioactivity and verify that the meter displays the correct reading Simply confirming a positive response is insufficient, as a damaged detector may still indicate a positive result, albeit at a significantly lower level than expected.
Various types (and strengths) of radioactive check sources may be purchased from most survey instrument suppliers Operation checks of NORM survey instruments should be recorded on a form.
When connecting or disconnecting detector cables, or operating switches, there is a risk of sparking In areas where explosive atmospheres could be present, it is essential to conduct tests for flammable gas or vapor before performing a radiation survey.
Records
Accurate documentation and record-keeping of all data collected during a NORM survey are essential, as this information may be reviewed and evaluated many years later.
All NORM survey data must be documented on a comprehensive form for each survey conducted To assist in identifying surveyed equipment, refer to the equipment classification abbreviations listed in Table 3.1 It is essential to maintain accurate records of all survey results.
MANIFOLD Manifold/header piping, valves, etc.
SEP Separators, including production separators, gunbarrels, etc.
FLOAT Flotation cells, wemcos, etc.
SUMP Sumps, including pits, pigtraps, ponds, etc.
FLINE Flowlines, including all valves and elbows
GLINE Gathering lines before processing
PIG Production pig launcher/receiver
OTHER All other measurements of in service equipment
SOIL Soil readings at pipe yards, tank battery pads, etc.
TUBE Production tubulars at pipe yards, etc.
INLET LINE All inlet lines to facility
SCRUBBER Inlet scrubber, separators, etc.
SWEETENER All gas sweetening equipment, including amine systems, etc.
DEHYDRATOR Dehydration equipment: Glycol, EG and TEG systems, etc.
FRAC TOWER All process towers/columns
CYRO UNIT All equipment associated with cryogenic process except reflux pumps REFLUX PUMP All reflux pumps
BOTTOMS PUMP Pumps transferring liquid off the bottom of towers
METER All metering equipment: meters, meter runs, screens, strainers, filters, etc. GAS PIG Gas processing pig launcher/receiver
PRODUCT LINE All product pipelines
COMPRESSOR Compressors and associated equipment
REFRIG All equipment associated with propane refrigeration system
GOTHER All other gas processing equipment
Program needs determination
Under normal conditions at NORM-impacted sites, external radiation exposure is typically low, allowing standard work procedures to continue without modification However, during non-routine activities like well workovers and equipment maintenance, employees may come into direct contact with NORM-impacted materials It is essential for facilities to assess NORM levels and determine if monitoring of employee exposures is necessary According to OSHA regulations, radiation doses for classified workers must be kept as low as reasonably achievable (ALARA) and should not exceed 5 rem/yr (0.05 Sv) For those not classified as radiation workers, the public dose limit is set at 100 mrem/yr (1 mSv) Operators must work closely with regulators to identify current guideline values and include evaluations of estimated annual doses from both internal and external exposure pathways.
In facilities with minimal NORM presence, periodic spot checks are sufficient This program should encompass instrument calibration and maintenance procedures, a survey methodology, necessary documentation, and a records management system.
In facilities where employee radiation exposure is unlikely to exceed 500 mrem/year (5 mSv) but where Naturally Occurring Radioactive Material (NORM) is present, a more rigorous radiation protection program is required Implementing a monthly survey that encompasses general area gamma scans and/or exposure rate measurements is essential Key components of such a program may include specific monitoring and safety protocols to ensure employee safety and compliance with radiation standards.
2 Area monitoring and control a Radiological controls b Radiation monitoring c Instrument calibration and maintenance
3 Radiological controls a Posting and labeling b Sealed radioactive source accountability and control
Most NORM facilities possess adequate in-house health and safety capabilities to establish a robust program However, smaller organizations may choose to engage a health physics professional to aid in the development and implementation of such programs.
If exposure to NORM-impacted materials could lead to worker doses exceeding 10% to 25% of the applicable guideline (0.5 to 1.25 rem or 5 to 12.5 mSv), a comprehensive radiation protection program (RPP) is essential and should be developed with a health physics professional According to OSHA 1910.1096(d)(2)(i), a monitoring threshold of 25% of the guideline value is established While this document does not detail the program, it may include various critical elements.
5 Area monitoring and control a Radiological controls area radiation monitoring b Airborne radioactivity monitoring c Contamination monitoring and control d Instrument calibration and maintenance
6 Radiological controls a Radiological work planning b Entry and exit controls c Radiological work controls d Posting and labeling e Release of materials and equipment f Sealed radioactive source accountability and control
This list illustrates the intricacies of a complete Radiological Protection Program (RPP) Items will be chosen based on the existing radiological conditions, regulatory requirements from the state, and the facility's specific characteristics Such a comprehensive program is essential only for facilities where radiation exposure is expected to surpass 500 mrem/year (5 mSv).
Working with NORM-impacted material
To minimize internal exposure to Naturally Occurring Radioactive Material (NORM), it is essential to implement specific work practices Employees and contractors must be informed about the presence and risks associated with NORM, along with procedures to reduce exposure Prohibiting eating, drinking, smoking, and applying cosmetics in areas where NORM is handled is crucial Openings on NORM-impacted equipment should be sealed to limit dust generation Personnel radiation exposure should be regularly evaluated When handling NORM-impacted tubulars or equipment, protective clothing, including boots, gloves, and coveralls, is necessary Keeping NORM scale and sludge wet can help minimize dust For tasks that may produce airborne particulates, such as cutting or grinding, respirators approved for radionuclides should be worn, with P100 cartridges being the minimum requirement Temporary plastic ground covers should be utilized to contain displaced NORM material during work, and sealed concrete paving is recommended for areas requiring frequent cleaning Lastly, personnel must wash their hands and face before consuming food or applying cosmetics after working with NORM.
Vessel entry procedures
For NORM-impacted vessels, it is essential to ventilate the vessel for at least 4 hours to eliminate hydrocarbon vapors and allow radon gas to dissipate, ensuring that short-lived radon progeny decay to safe levels Additionally, radiation detection equipment must not be used in potentially explosive atmospheres without proper hot work procedures and testing for lower explosive limits (LEL) During the initial entry for cleaning or inspection, it is recommended to use a self-contained breathing apparatus or a supplied-air respirator with air cylinder cascades to ensure safety.
To ensure safety in oil and gas production involving Naturally Occurring Radioactive Materials (NORM), it is essential to use recommended personal protective equipment, including latex or neoprene gloves, rubber work boots, impermeable suits, and respirators Personnel radiation exposures during vessel entry must be assessed according to specified guidelines All equipment containing NORM should be cleaned in designated areas using soapy water, and if cleaning is not feasible, materials must be double-bagged and sealed for proper disposal It is crucial that no NORM-impacted items leave the site without appropriate sealing Additionally, employees should maintain good personal hygiene by washing hands and faces before eating, drinking, or applying cosmetics to avoid ingestion of NORM-impacted materials.
This section outlines effective methods for removing scale, sludge, and film from oil and gas production equipment, including NORM-impacted gas plant equipment It emphasizes the importance of conducting removal operations safely to protect workers and the environment Techniques range from manual cleaning to high-pressure water blasting, often performed by specialized third-party contractors licensed for NORM removal These operations can take place either on-site or at the contractor's facility, with scale removal contractors typically returning NORM-impacted scale to the operator for proper disposal.
Resources
A key factor in selecting a NORM removal procedure is the availability of adequate resources Cleaning facilities, removal equip- ment, protective clothing, and safety equipment should be included in a resource evaluation.
Effective waste handling facilities are crucial for preventing the spread of NORM material into the environment, as inadequate measures can significantly increase removal operation costs.
In certain states, contractors must possess appropriate facilities and be licensed by state regulatory agencies to conduct NORM removal It is advisable to conduct an external assessment of facilities and, if necessary, perform radionuclide analyses of vessel contents prior to hiring third-party services Additionally, if the facility holds a radioactive materials license, reviewing the current status of that license and any recorded deficiencies is recommended.
Personnel safety and environmental protection
NORM removal is most effective at specialized facilities, although on-site cleaning of tanks and equipment is necessary Prior to initiating any NORM-removal operations, it is crucial to take specific precautions Equipment owners or operators should adhere to established procedures, which can also guide the assessment of third-party contractors Consulting state regulators is essential to verify contractor eligibility and to obtain information on acceptable radiation and activity levels for the operations being conducted.
Proper training for employees involved in NORM-removal operations is essential, with training records maintained as per state and federal regulations Equipment is considered NORM impacted if external radiation levels exceed state-specified limits Permanent cleaning areas must be paved with concrete to prevent ground contamination, and plastic ground covers should be used in temporary cleaning areas to contain contaminants NORM-removal activities should occur in well-ventilated spaces, and all personnel must be familiar with personal protective equipment and confined space entry procedures Radiation exposures during NORM removal should be evaluated when levels approach regulated values, and access to cleaning areas should be restricted to authorized personnel with minimal occupancy Workers should maintain NORM-containing materials in a wet state to prevent dust inhalation, and dry removal processes must minimize dust release Radiation surveys should be conducted before and after cleaning operations, and removed materials must be stored in appropriate containers If radiation levels remain unacceptable post-cleaning, equipment should not be released for unrestricted use.
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Cleaning methods
The choice of the removal procedure should depend on its removal efficiency as well as the resources, cost, and safety consider- ations outlined earlier.
Manual cleaning, which relies solely on human effort without machinery, typically involves hand washing equipment using detergent and water The process of removing NORM-impacted tank sludges can be achieved through manual methods, such as shoveling the sludge into storage containers, or by employing washing and pumping techniques.
Mechanical cleaning methods vary widely and may include high-pressure water washing, drilling or reaming, and vacuuming.
Water blasting is an effective technique for removing Naturally Occurring Radioactive Material (NORM) from production equipment, including separators, tanks, tubing, and pipes This method involves high-pressure water jetting, typically defined as operations exceeding 750 psi, with NORM scale cleaning pressures ranging from 10,000 psi to 30,000 psi.
High pressure washing systems must operate as closed systems to prevent wash water from escaping into the environment It is essential to contain, recirculate, or filter the wash water to eliminate scale Any disposal of wash water should adhere to approved methods and comply with permit requirements.
Drilling or reaming is essential for cleaning production tubing and piping, where a reamer is inserted into one end of a tube placed on a cleaning rack While this method offers high removal efficiency, it can produce NORM-impacted dust if performed dry To mitigate dust generation, wet drilling processes are recommended Both wet and dry drilling should utilize closed systems, similar to high-pressure water blasting, to prevent the release of NORM materials.
Vacuum systems, whether wet or dry, are highly effective for removing loose materials and are commonly employed prior to manual cleaning of equipment To minimize the spread of contaminants and reduce airborne activity, it is crucial that these systems are equipped with proper filtration Additionally, precautions must be taken to prevent the accumulation of large quantities of Naturally Occurring Radioactive Material (NORM) within the vacuum system.
NORM material can form as thin, often invisible films in natural gas processing equipment, consisting of radioactive substances that adhere to the equipment's walls To effectively remove these NORM films, chemical treatments or grinding may be required Additionally, NORM can accumulate as a dusty black powder, primarily iron sulfide, on the internal surfaces of gas processing and storage equipment, which may contain elevated levels of Pb-210 It is crucial to recognize that radiation conditions may be present when these systems are opened for cleaning or refurbishment, even if they are not apparent when the systems are closed.
Equipment containing Naturally Occurring Radioactive Material (NORM) must be removed from production sites and stored centrally before any repair, sale, cleaning, or disposal Adhering to specific guidelines for managing the storage of NORM is essential to protect employees from excessive radiation exposure Operators of NORM storage sites should ensure that their practices comply with relevant state regulations.
Storage site design
Containers and equipment containing Naturally Occurring Radioactive Material (NORM) must be stored in a secure, well-ventilated area with restricted access When located alongside conventional oilfield equipment, the NORM storage area should be clearly marked, allowing entry only to authorized personnel It is essential that the storage area is designed to ensure that radiation levels at its perimeter do not exceed 100 millirem/year (1 mSv/yr) To achieve this, materials with higher radiation levels should be positioned towards the center of the storage area Additionally, all containers and equipment containing NORM should be secured to prevent unauthorized removal.
Uncontained NORM
Uncontained NORM must be stored in sealed containers for long-term management prior to final disposal If needed, NORM scale or sludge can be temporarily placed on impermeable pads with secure covers to contain the material and prevent off-site contamination.
Contained NORM
Loose NORM, including scale from tubing, sludge, or vessel cleaning, must be stored in sealed and labeled containers on pallets or racks To prevent package degradation, liquids should not be stored for long durations It is essential to handle, move, and store containers and equipment in a manner that prevents the release of loose radioactive materials into the environment Regular inspections of containers and equipment are necessary, and any leaking items should be promptly repacked or resealed.
Sealed openings
All openings on stored equipment or tubing containing NORM should be capped, plugged, or wrapped in plastic to prevent the spread of radioactive materials.
Cleaning exterior surfaces
To effectively clean the exterior surfaces of containers, tubing, and equipment from external NORM material, follow the NORM removal guidelines outlined in Section 5 of this document Ensure that all process water containing NORM is contained, recirculated, or filtered to eliminate the material Dispose of wastewater using approved methods that comply with relevant permit requirements.
Preventing dispersal of NORM material
To safeguard soil and surface water in the NORM storage area, it is essential to use plastic ground covers when handling unsealed containers or equipment Any NORM waste that lands on the plastic cover must be collected and placed in sealed containers Additionally, any water that is discarded must adhere to relevant regulations, and the operator must ensure that all necessary discharge permits are obtained.
Notifying employees and contractors
Employees and contractors entering NORM storage areas must be made aware of the presence of radioactive materials and the associated safety risks It is essential to inform them about methods to minimize radiation exposure If these areas are classified as radiation zones, employers are required to retain a copy of OSHA regulations regarding ionizing radiation protection (29 CFR §1910.1096) along with their own guidelines for working in NORM storage areas Additionally, maintaining copies of relevant state regulations may also be necessary.
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Worker protection guidelines
Employees and contractors working in NORM storage areas should adhere to the guidelines given in Section 4, “Worker Protec- tion.”
Signs outside storage area
Storage areas for NORM must be clearly marked at all entrances with signs featuring the three-bladed radiation symbol (magenta blades on a yellow background) and the warning “Caution, Radioactive Material Storage Area.” If whole-body radiation exposure within the storage area exceeds 5 mrem (0.05 mSv) in one hour, the sign must also include the designation “Radiation Area.”
Labels on drums and equipment
Containers, tubing, or equipment containing NORM should be tagged or labeled The label should contain wording similar to the following:
WARNING: NATURALLY OCCURRING RADIOACTIVE MATERIAL AVOID BREATHING DUSTS
The label must feature an identification code that aligns with the material records If joints of casing, tubing, or pipe are stored collectively, individual labels for each joint may not be necessary.
Record keeping
Records must be maintained to document essential information, including an identification code, the storage location of the material, and the type of radioactive material (such as scale or sludge) Additionally, it is important to record the date the material or equipment entered storage, its original location and type of service, and measurement data reflecting the radioactivity of each container and piece of equipment Furthermore, results of radioactive surveys of the NORM storage area, radiation exposure data for individuals required by OSHA regulations to wear personnel monitoring equipment, and training documentation should also be included.
This section aims to provide essential information on the shipment of NORM-impacted materials The Department of Transportation (DOT) guidelines, revised in 2004, significantly affect the transportation of these materials It is crucial for readers to consult a waste management specialist when shipping NORM-impacted materials classified as radioactive waste Operators must also review relevant federal, state, and local regulations, along with guidance from waste management experts, to understand the specific regulations that apply and their interpretations.
Federal and state regulation
The Department of Transportation (DOT) oversees the transportation of hazardous materials that impact interstate commerce, as outlined in 49 CFR Parts 171-180 For intrastate transportation, state agencies typically regulate these materials, often adopting the federal guidelines The primary regulatory bodies at the state level are usually the Department of Public Safety, the Department of Transportation, or the Department of Motor Vehicles.
DOT definitions
DOT regulates the transportation of radioactive materials having a concentration greater than the following values:
Table 7.1—Exempt values for Ra-226 and Ra-228 as stated in 49 CFR §173.436
Isotope Activity concentration for exempt material Activity limit for exempt consignment
Ra-226 1 2.7E-10 Ci/g (10 Bq/g) 2.7E-7 Ci (1E4 Bq)
Ra-228 2 2.7E-10 Ci/g (10 Bq/g) 2.7E-6 Ci (1E5 Bq)
1 Ra-226 and progeny included in secular equilibrium: Rn-222, Po-218, Pb-214, Bi-214, Po-214, Pb-210, Bi-210, and Po-210.
2 Ra-228 and progeny included in secular equilibrium: Ac-228
According to 49 CFR 173.401(b)(4), a multiplier of 10 can be applied to the exemption values in Table 7.1 for natural materials and ores with naturally occurring radionuclides, as long as they are not intended for processing for these radionuclides and the activity concentration does not exceed 10 times the values specified in §173.436 This application results in adjusted values that reflect the permissible limits for such materials.
Table 7.2—Exempt values for Ra-226 and Ra-228 as stated in 49 CFR §173.436 and as modified based on §173.401
Isotope 10x activity concentration for exempt material 10x activity limit for exempt consignment
Ra-226 1 2.7E-9 Ci/g (100 Bq/g) 2.7E-6 Ci (1E5 Bq)
Ra-228 2 2.7E-9 Ci/g (100 Bq/g) 2.7E-5 Ci (1E6 Bq)
1 Ra-226 and progeny included in secular equilibrium: Rn-222, Po-218, Pb-214, Bi-214, Po-214, Pb-
2 Ra-228 and progeny included in secular equilibrium: Ac-228
NORM-impacted materials that fall within the limits specified in Table 7.2 are not classified as radioactive by the DOT and are therefore exempt from the regulations governing the shipment of radioactive materials Consequently, most NORM-impacted materials are treated as non-radioactive shipments.
Transportation guidelines for NORM
If the operator classifies the NORM-impacted material as radioactive, it is essential to consult a waste management organization for transportation guidance The waste transportation contractor is responsible for ensuring compliance with all relevant regulations and safe handling of the material.
• Packaging all NORM materials and soil in appropriate containers for shipment
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• Surveying the packaged material using a gamma rate meter
• Collecting samples and analyzing to determine the correct manifest, shipping labels, and placards that are appropriate
• Identifying waste acceptance criteria for the waste disposal site selected
• Verifying that the waste meets the site waste acceptance criteria
The management of NORM-impacted property and equipment must adhere to all relevant laws and regulations It is crucial for decision-makers to define the objectives for transferring NORM-impacted assets This process is challenging due to the absence of established guidelines for transferring such property or equipment, particularly in oil-field production activities, and for the unrestricted release of NORM-impacted items.
This article outlines general methods for transferring NORM-impacted property and equipment for ongoing production activities, followed by a discussion on the unrestricted release of such property and equipment.
Regulations—property transfer
Currently, no state has regulations limiting the transfer of oil and gas properties and equipment containing Naturally Occurring Radioactive Material (NORM) based on radiological levels A review of state regulations shows that the results of the latest radiation surveys must be provided to the new owner or producer before the property transfer, and the relevant state authorities should be informed of the transfer.
Review/assessment—property transfer
Before transferring property, it is essential to identify and document potential environmental issues through site reviews, audits, or assessments This information aids in evaluating the radiological levels associated with the property or equipment Although specific guidance is lacking, API recommends that sellers conduct comprehensive surveys to characterize the radiological conditions and prepare documentation for the buyer The assessment should establish a baseline of data regarding the nature, volume, and location of Naturally Occurring Radioactive Material (NORM) present at the time of transfer Consideration should be given to various survey activities during this process.
Gamma surface scans are essential for comprehensive transfer surveys across the entire property, including structures and equipment These surveys can be organized into grids, allowing surface scan results to be linked to specific grid locations Alternatively, a global positioning system (GPS) can be utilized to combine positioning data with instrument responses The final report produced from this system can feature clear visuals, displaying surface scan results overlaid on the property's characteristics.
Direct measurements for total and removable activity Direct measurements for total and removable activity should be made at representative locations on equipment
Exposure rate measurements should be conducted at key contact points on equipment and at a height of 1 meter across various locations on the property These direct measurement sites must be clearly indicated in figures, and the findings should be incorporated into the report.
To assess NORM content, it is essential to collect and analyze soil and scale samples These samples must be sent to a radioanalytical laboratory for thorough analysis The findings should be documented in the report, and the locations of the samples should be clearly indicated in accompanying figures.
The report should include a comprehensive site history detailing both past and current operations, a thorough description of the site that highlights its features and equipment, as well as any other relevant information.
Disclosure—property transfer
If environmental site reviews reveal the presence of NORM, the transferor can disclose the results to the transferee through various methods.
• Placing a general disclosure statement in the sales agreement or deed covering, among other items, NORM
• Transferring company files to the transferee
• Making specific reference to the presence of NORM in the sales agreement or deed
• Providing the transferee with copies of site review reports
• Providing access to the property and or equipment
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Regulations—property release
Several states have integrated NORM-impacted property and equipment into their general radiation protection regulations, while others have established specific rules Currently, around 13 states have regulations governing the management of NORM-impacted property and equipment, with varying standards for the unrestricted release of such items The criteria used to assess these standards differ from state to state.
• Concentrations of NORM in surface and subsurface soil
• Exposure rates at 1 m from the surface
• Exposure rates at contact with the ground surface or equipment
• Dose to individual using pathway analysis/dose assessment
• Total and removable surface activity levels
The varying numerical values for different criteria, coupled with the complexity and evolving nature of current regulations, create challenges for property owners To navigate these issues and address potential future liability, API advises consulting a health physics professional for guidance on surveying and releasing property or equipment that may be impacted by NORM.
The disparity between state regulations for the unrestricted release of equipment and the acceptance criteria of scrap metal facilities poses a significant challenge As radiation monitors become more prevalent, scrap metal that complies with state guidelines is increasingly being rejected This means that equipment not classified as NORM under state rules may still face rejection from scrap dealers, necessitating cleaning before it can be recycled.
Currently, there are no federal regulations and limited state regulations governing the disposal of oilfield NORM, as the federal exemption shifts the regulatory responsibility to individual states Some states are developing regulations for NORM disposal, while others have imposed prohibitions until such regulations are established Texas and Louisiana have implemented specific regulatory programs for these wastes In states with NORM regulations, there may be options for both on-site and commercial disposal Given the constantly evolving nature of waste disposal regulations, it is crucial for operators to consult relevant state and local regulatory agencies, waste management specialists, and consider lease or landowner obligations before disposing of NORM-impacted materials.
The choice of waste disposal methods is influenced by various factors such as waste forms, characteristics, radiation levels, volumes, costs, and land management considerations On-site options typically involve injection, encapsulation, or landspreading, while off-site alternatives may include transferring waste to NORM disposal facilities, commercial low-level radioactive waste sites, hazardous waste landfills, or smelting facilities for equipment containing NORM Additionally, some waste may require transportation to a treatment facility before final disposal Commercial facilities offer disposal methods that include treatment, injection, and burial.
Numerous organizations have developed documents that tackle the challenges related to the disposal of NORM-impacted materials A summary of findings from two key reports can be found in Appendix E, specifically in Sections E.1 and E.2 It is important to emphasize that this information has not received approval from state or federal agencies and should not be relied upon for disposal decisions without securing the necessary agency authorization.