Identification and Assessment of Alternative Disposal Options for
Radioactive Oilfield Wastes
Scales containing naturally occurring radioactive material are a
by-product of hydrocarbon extraction. In the Scottish area of the North
Sea the dominant nuclides in these scales are radium 226 and its
daughters and radium 228 and its daughters. Typically all the daughters
down to lead 210 are present in varying degrees of equilibrium. In the
southern sector of the North Sea the radioactivity is mainly due to the
presence of lead 210 and its daughters which are deposited by a
The scales are normally found on installations where injected water has
mixed with water present in the formation. Barium sulphate is formed
and precipitated as well fluids are brought to the surface. Some barium
is substituted by radium and the precipitate is therefore radioactive.
Naturally Occurring Radioactive Material (NORM) can be found as hard,
insoluble scales adhering to equipment or as contaminated sand and silt
Installations are authorised to dispose of NORM as solid or liquid
waste. Solid waste includes contaminated equipment sent to land for
decontamination. Liquid waste includes solids in suspension discharged
to sea. The UK Strategy for Radioactive Discharges 2001-2020 states
that these discharges will continue to be tightly controlled and
reduced wherever practicable. The Strategy also includes the statement
that [authorisation holders] will be expected to manage their wastes in
ways that minimise discharges to the environment.
Currently there is only one onshore facility which routinely disposes
of NORM waste is Scotoil Services in Aberdeen.
2. PROJECT AIMS
This research aimed to:
3. PROJECT OUTPUTS
- Investigate factors influencing the production of
- Determine the amount of NORM waste likely to be
installations operating in the UKCS during the operational and
- Assess the availability, potential for
utility of existing and novel waste minimisation techniques and
- Provide guidance to industry and regulators on
minimisation and disposal of NORM waste.
Four separate reports have been produced from this research:
4. KEY FINDINGS
- Technical Summary Report: provides a synthesis of the
Phases 1 and 2 plus a discussion of capacity issues. This is the main
project reference including the summary guidance.
- Phase I Technical Report: provides details on NORM origins,
occurrence in oil and gas processing and quantification (from a variety
of data sources).
- Phase II Technical Report: provides details on the
relevant to NORM disposal, NORM prevention and waste volume reduction,
NORM removal techniques, NORM disposal routes and risk ranking of the
- Summary Guidance: contains an overview of the issues
the three main project documents above. The intended users of this
document are likely to be: well informed in at least some of the issues
associated with oilfield NORM; and have access to Radiation Protection
Advisor (RPA) services and advice on current NORM disposal practice.
NORM origins and
Amounts of NORM waste produced on the United Kingdom Continental Shelf
(UKCS) were quantified and predictions made of potential arisings from
future production and during decommissioning. Data obtained from
operators, decontamination contractors, literature review, disposal
outlets and the regulators has been included in the estimates.
NORM contaminated deposits in oil and gas production occur in two main
The estimates of the current arisings have been prepared and are
summarised in section 4.4.6 of this report. The main findings are
summarised in the points below:
- As mineral scales, and sludges of particulate scale,
containing radium and its decay products;
- As thin coatings and “black sludges” in
condensate processing equipment, mainly containing decay products from
Radon-222, predominantly Lead-210 and Polonium-210.
The Phase II Report (SNIFFER 2004b) investigated NORM waste
minimisation and disposal options for the NORM from the UKCS and
produced a ranking of potential disposal options.
- The total activity discharged in produced water is
relatively high due to the volumes produced.
- The largest arising of solid NORM occurs through offshore
decontamination, either through routine cleanout and descaling
operations or from decommissioning. Terminal vessel sludges and pigging
waxes account for the bulk of NORM solids dealt with onshore.
- Onshore equipment decontamination accounts for a small
fraction of the total activity and volume of solids discharged to sea.
- The masses of solids from decommissioning are small in
to offshore decontamination. In all of the cases reviewed the actual
amount of NORM solids disposed of from decommissioning has been
significantly lower than original predictions.
- The general trend in solid NORM is a slight increase in
operational arisings in the next 2-3 years, as new facilities outpace
decommissioning, followed by a steady decline as decommissioning
increases in pace. Total arisings peak in about 2007 and are sustained
by decommissioning arisings until around 2012, after which there is a
sharp decline. By 2040, mass and activity via all disposals is
estimated to be between 5-10% of its current value.
- The total activity in produced water is also predicted to
in 2007 but falls steadily thereafter. By 2040, mass and activity via
all disposals is estimated to be between 5-10% of its current value.
Produced water discharged to sea is predicted to have already peaked
and is in decline.
NORM prevention, removal
methods and waste reduction
A review of methods is presented. Of the NORM prevention methods, the
only method widely used on the UKCS is chemical scale inhibition and to
a lesser extent sulphate removal from injection water. NORM removal
onshore and offshore is predominantly by mechanical means, mainly water
jetting (with and without abrasives).
Waste reduction of solid NORM arisings is not routinely carried out on
the UKCS as most NORM is discharged to sea. There is currently no
reliable method for reducing the overall amount of radioactivity
transferred from the subsurface in oil and gas production.
There are some chemical waste reduction methods at different stages on
development but none are currently in use on UKCS. There needs to be
financial backing and regulatory impetus for their development for use
on the UKCS. There are some novel methods at the pilot stage
particularly waste reduction by chemical concentration.
NORM disposal options
There is a wide variety of disposal options that are available in
principle and feasible options are discussed. Different options are
suited to different types of NORM waste and a mixture of options may be
the best solution.
From discussions with waste contractors it emerges that some degree of
financial security or guaranteed customer base is required for
development of new onshore disposal facilities along with an indication
of regulatory support. Even with such assurances, the relatively small
predicted amounts of NORM arisings for onshore disposal under the
current regulatory regime, even at the peak of decommissioning, suggest
that a multi-industry LLW disposal facility would be the viable option.
None of the disposal routes appears to present a significant
occupational or public radiation exposure risk apart from
landspreading. Consequently, factors other than dose may be equally
important in determining acceptability.
A generic risk ranking of disposal alternatives for the UKCS has been
Although the current disposal routes present no immediate capacity
problems, there is the potential for future pressure on existing
oilfield NORM disposal routes, for example OSPAR and EU targets to
reduce discharges of naturally occurring radionuclides to sea to
background levels by 2020. If this were to mean that offshore discharge
was discontinued and solid NORM waste had to be brought onshore for
disposal there would be insufficient capacity (currently none in
Scotland for some of the wastes).
If the UK continues to rely on a single site (Drigg) as the main
onshore disposal route for non-exempt NORM waste, some assurance will
need be sought by the regulators that oil and gas NORM waste will
continue to be accepted.
If nothing is done to provide alternative onshore disposal routes there
is the potential for stockpiling and consequent problems with public
relations, licensing and ultimate disposal. The UK oil and gas industry
is reliant on a single nearshore discharge to dispose of almost all
NORM from onshore decontamination and on a single disposal facility for
non-exempt wastes. Currently, the total amounts are low and appear to
be within existing capacities, but this assumes that the capacity is
available if required and this cannot be guaranteed at present. It also
assumes that there will not be regulatory changes which discontinue the
current practice of offshore disposal of most of the NORM waste.
Each report is available separately in electronic format at
£20.00 + VAT.
Hard copy available at the following prices:
Technical Summary Report (January 2005) £25.00
Phase 1 Technical Report (September 2004) £25.00
Phase 2 Technical Report (November 2004) £35.00
Summary Guidance(March 2005) £10.00
All prices less 20% to FWR members.
The report is available for download from the SNIFFER Website