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LSA/NORM

LSA/NORM. Training and Awareness Pack. Why Oilfield Scale Occurs. Reservoir water is rich in calcium, barium and strontium ions. Injection water is rich in sulphate ions. When they mix, precipitation of calcium, barium and strontium sulphate occurs.

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LSA/NORM

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  1. LSA/NORM Training and Awareness Pack

  2. Why Oilfield Scale Occurs • Reservoir water is rich in calcium, barium and strontium ions. Injection water is rich in sulphate ions. When they mix, precipitation of calcium, barium and strontium sulphate occurs. • Pressure and temperature drops also promote precipitation. • This causes a layer of scale to form inside production tubing and process vessels.

  3. Why it Becomes LSA • Reservoir rock contains small amounts of natural uranium and thorium and daughters. One daughter, radium, is water soluble - dissolves in the reservoir water. • Radium precipitates with the barium and calcium ions to make the scale slightly radioactive. • This makes the scale a Naturally Occurring Radioactive Material (NORM) which is of Low Specific Activity (LSA).

  4. Where it Appears • LSA scale appears within the well fluid handling system - Tubing string (especially tailpipe) Liner, below the packer Subsurface Safety Valves Wellheads Manifolds Separators Oil coolers Produced water pipework • It can also appear in the service water system, in pig wax, in storage cells etc.

  5. How it Gets There • Incompatible waters mix as they pass through perforations - this starts scale depositing in the tailpipe and tubing, then throughout the plant. • Deposition is heaviest in areas of turbulence - bends, valves, restrictions. • Also where temperature or pressure changes occur - chokes, separators, coolers. • Separator deposits - clays may absorb radionuclides directly from water. • Service water systems probably due to concentrating natural radioactivity from seawater.

  6. How it Looks • Pure barium sulphate is hard dense white solid. Pure LSA scale can be like that (especially in tubulars). • More usually thin, eggshell-like, light or dark brown. • Can be stratified, like rings in a tree trunk. • Sometimes deep in the surface matrix, so not visible. • Separator sludges are granular suspensions. • Pig waxes are black tarry materials, often with chunks of rust and scale mixed in. • See Photo.

  7. An LSA Contaminated Tubular

  8. Structure of the Atom • All matter consists of atoms. • The atom consists of a nucleus, made up of protons and neutrons, and a cloud of electrons surrounding the nucleus. • Each sub-atomic particle has its own properties in terms of mass and charge- Proton Mass = 1 Charge = +1 Neutron Mass = 1 Charge = 0 Electron Mass = 0.0005 Charge = -1 • See picture

  9. Atomic Structure

  10. Types of Radiation • Some atomic structures are unstable because the ratio of protons to neutrons in the nucleus is wrong. • These naturally decay to a stable configuration by emitting radiation. • Three types of radiation are emitted - Alpha 2p+2n Mass = 4 Charge = +2 Beta electron Mass = 0.0005 Charge = -1 Gamma photon Mass = 0 Charge = 0

  11. Hazards of Each Type • Alphas - large and highly charged. Easily stopped and absorbed. Sheet of tissue, outer skin or centimetres of air will stop them. • Betas - smaller and less charged, so more penetrating. Sheet of cardboard, metal foil or metres of air will stop them. • Gammas - pure electromagnetic energy. Very penetrating. Require lead sheet, steel plate or many metres of air to stop them. • See penetration picture.

  12. Penetration of Each Radiation Type

  13. External and Internal Hazard • These properties determine effect on health. • Gammas can penetrate body from outside and damage deep internal cells. This penetration makes them an External Hazard. • Alphas/betas cannot penetrate far from outside. However if alpha emitting materials enter the body, particularly the lungs, the size and charge of the alphas makes them very damaging to the cells they hit. This alpha toxicity makes them an Internal Hazard.

  14. Uranium -238 and Thorium-232 Decay Series • Two decay series in LSA scale - U-238 and Th-232. • Uranium-238 emits alphas, betas and gammas to decay through protoactinium, thorium, radium, radon, polonium and bismuth to stable lead-206. • Thorium-232 emits alphas, betas and gammas to decay through radium, actinium, radon, bismuth, polonium and thallium to stable lead-208. • Each decay step takes an approximate length of time (half life). Because some half lives are long, ratio alphas/betas/gammas is fairly constant. • See decay series charts.

  15. Uranium -238 Decay Series

  16. Thorium -232 Decay Series

  17. Hazards of LSA Scale • Because LSA scale contains so little activity, the external field is generally low. However some old tubulars, separators, Wemcos may give measurable fields. • Because of the high alpha content, LSA scale is a significant internal hazard. • Therefore priority is to stop LSA scale particles being inhaled or ingested. • This alpha toxicity also makes safe disposal important.

  18. Units of Radiation • Unit of Activity - Becquerel (Bq) 1 Becquerel = 1 disintegration per second This is effectively the size of the source, or as Bq/g, the amount of radioactivity in a substance • Unit of Absorbed Dose - Gray (Gy) 1 Gray = 1 joule per kilo absorbed This is the amount of radiation energy absorbed • Unit of Corrected Absorbed Dose - Sievert (Sv) 1 Sievert = 1 Gray x Quality Factor This is the “harmfulness” of absorbed radiation

  19. Legislative Overview • Two main pieces of legislation. • Ionising Radiations Regulations - set standards for protection of workers, by requiring certain precautions. • Radioactive Substances Act - set standards for protection of public and the environment, by setting conditions for holding, using, storage and disposal. • Transport regulations are separate.

  20. Ionising Radiations Regulations • Set standards for protection of workers Risk Assessment Appointment of Radiation Protection Adviser (RPA) and Radiation Protection Supervisor (RPS) Local Rules Controlled and Supervised Areas Dose control Training and awareness • Regulated by HSE.

  21. Radioactive Substances Act • Set standards for protection of public and environment Registrations and Authorisations set detailed conditions Contaminated equipment to specified locations Offshore waste to sea only Ground to below 1mm Annual total discharge activity limit Record of all discharges No transfer between platforms • Regulated by SEPA.

  22. Definition of “Radioactive” • IRR brings a substance into its remit at 100 Bq/g. • RSA has a Schedule by radioelement - for radium the level is 0.37 Bq/g. • The large difference is due to the intent of the legislation - protection of the public and bioaccumulation require lower limits.

  23. Rare Earths Exemption Order • RSA is supported by Exemption Orders - allow some exemptions for certain radioelements under certain conditions. • Phosphatic Substances (Rare Earths) EO can be used for LSA scale. • Exempts material up to 14.8 Bq/g from RSA. • User must be able to prove EO applies.

  24. Radiation Protection Adviser • Every radiation employer must appoint a Radiation Protection Adviser (RPA) Professional radiation specialist Must be accredited by professional body Registered with HSE Must be consulted on radiation protection matters Carries out annual inspection of each location Shell RPA - Dr. Brian Heaton

  25. Radiation Protection Supervisor • At workplace level, every radiation employer must appoint Radiation Protection Supervisor(s) (RPS) Supervise radiation work directly Ensure Local Rules are met on the worksite Shell Expro 2 day course - Level 3 Train meter users and workforce - Level 2M, 2, 1 Appointed in writing - in APR and Local Rules Shell Competent Person is lead RPS

  26. Local Rules • Every radiation employer must make Local Rules Detailed and prescriptive rules Tailored to each location Written in cooperation with Business Units and RPSs Checked and approved by RPA In Document 3133-001 Also contains Source Register and LSA Record of Work

  27. Shell Expro LSA Local Rules • In Document 3133-001 01 - Preparation and Interfacing Prior to Work 08 - Working on LSA Contaminated Equipment 09 - Decontamination on the Installation 10 - Milling on LSA Scale 11 - Handling of LSA Contaminated Tubulars 12 - Handling of LSA Contaminated Well Control Equipment 13 - Handling of LSA Contaminated Pigs and Pig Debris 14 - Entry and Cleaning of LSA Contaminated Vessels 15 - Discharge of LSA Scale to Sea 16 - Dispatch of LSA Contaminated Items Onshore 17 - Instruction to Refurbishment Contractors 18 - Record Keeping, Reporting and Auditing 19 - Radiation Training and Competence

  28. Controlled and Supervised Areas • Every radiation employer must set up Controlled and Supervised Areas. • Controlled Area Where it is necessary to restrict significant exposure Where dose likely to exceed 6 millisievert/y • Supervised Area Where risk needs to be kept under review, or Where dose likely to exceed 1 millisievert/y • Shell Expro sets up an LSA Supervised Area around LSA work.

  29. Dose Controls • Every radiation employer must limit radiation exposure ALARP Engineering controls Systems of Work Personal protective equipment • Dose limits Workers - 20 millisievert/y Public/others - 1 millisievert/y At 6 millisievert/y, workers must be Classified. • Not really relevant to LSA scale work (external radiation limitation).

  30. Philosophy of LSA Management • Stop inhalation or ingestion of scale particles- Stop dust being created Stop dust becoming airborne Stop dust from entering the body Contain scale in one area and minimise contact • To achieve this we - Adhere to Local Rules Keep scale wet to stop dust rising Wear personal protective equipment Set up LSA Supervised Area and restrict contact

  31. LSA Workflow • General workflow is as follows - Identification of work with LSA potential Preparation for work with LSA potential Detection and identification of LSA contamination Working on LSA contaminated equipment LSA disposal to sea LSA contaminated equipment to onshore cleaner • The rest of this pack will cover each of these areas in detail.

  32. Identification of Work with LSA Potential • Assume all fluid bearing systems are LSA contaminated until proven clean. • Use Local Maps to identify areas of known LSA contamination. • External monitoring may identify very active LSA but not reliable. • Test all systems at first breach, and regularly as new surfaces are encountered. • Record zero readings.

  33. Preparation for Work with LSA Potential • Local Rule 01 (onshore), 08 (offshore). • Onshore planning of work - coordination between Shell and contractor(s). • LSA Procedures/Local Rules in Workpacks. • All parties must know/understand Shell and own Local Rules. • Equipment - muncher, tape, labels, tags, polythene, PPE etc. • Training and awareness. Tool Box Talks etc. • Permit to Work.

  34. Detection and Measurement of LSA Scale - 1 • Shell standard LSA meter - Mini 900 with 44A probe Scintillation counter - detects high energy betas and gammas Readout in counts per second (cps) Fairly robust probe Not intrinsically safe • See Picture.

  35. Mini 900 with 44A Probe

  36. Detection and Identification of LSA Scale - 2 • Special meter for confirming external contamination on tubulars - Mini 900 with EP15 probe Geiger tube - detects alphas and low energy betas Readout in counts per second (cps) Fragile probe Not intrinsically safe Used by some operators and contractors as their standard LSA meter - Shell prefers 44A probe • See Picture.

  37. Mini 900 with EP15 Probe

  38. Detection and Identification of LSA Scale - 3 • Dosemeter - ICI Gammatrol PRI 90 and 90s Measures external radiation field at a point PRI 90 readout is in millirads per hour (mrad/h) Converts to microsieverts per hour (μSv/h) by multiplying by 10 (1 mrad = 10 μSv) PRI 90s readout is in microsieverts per hour (μSv/h) Both have three ranges - 100, 1000, 10000 μSv/h Use 100 μSv/h range for LSA scale fields Intrinsically safe • See Picture.

  39. ICI Gammatrol PRI 90

  40. Selection and Use of Meters • The Mini 900 with 44A probe is Shell’s standard meter for LSA identification. Measuring gammas is more reliable than alphas/betas in the field situation, as they are not attenuated by water, mud, wax etc. • The Mini 900 with EP15 probe can be used to confirm external contamination on tubing. • However the Mini 900 with EP15 probe is not always reliable for LSA identification in the field situation. Alphas/betas may be attenuated in dirty material

  41. Meter Reading to Declare LSA • Using the Mini 900 with 44A probe, a reading of 3 cps above background is LSA. 3 cpsabg is the lowest statistically reliable reading with the meter Does not convert directly to Bq/g, but 3 cpsabg is in the range of 0.37 Bq/g (depending on thickness etc) Note - it is not possible to convert from cpsabg to Bq/g as you do not know the thickness and thus the mass of scale that the counts come from. • We identify contamination, we do not measure scale activity.

  42. Use and Care of the Meter • Local Rule 08. • Turn on, battery check (green), read. • With or without speaker. • Function test - use test source before use. • Probe and meter are matched - do not mix. • Remove cap, replace with thin plastic bag. • Take background, bring to surface, back away - look for rise and fall. • Test all new exposed surfaces. • Calibrate annually - Aberdeen University.

  43. Work Precautions - LSA Contaminated Equipment • Local Rule 08. • Record the whole job on Form F/4507 as you go. • Regular monitoring of surfaces. • LSA Supervised Area. • Personal protective equipment. • Personal hygiene - shower after work. • PA announcement before work. • Keep scale wet during work. • Minimise wire brushing, grinding, burning. • If Mini 900/44A >200 cps, check with Gammatrol PRI 90. If >7.5 μSv/h, contact BU HS&E team. • Label and tag everything.

  44. Work Precautions - LSA Supervised Area • Local Rule 08. • Barriered off and labelled as “LSA Supervised Area”. • Deck lined with polythene to collect any loose scale. • Entry controlled and logged. • PPE donned on entry, removed at exit. • Contamination check on exit. • Minimise entry - need only. • Eyewashes and showers where appropriate. • PA announcement on setup. • All LSA to be contained in the area. • When work completed, area thoroughly cleaned and monitored.

  45. Work Precautions - Personal Protective Equipment • Local Rule 08. • One piece slicker suit or Tyvek disposable suit. • Impermeable gloves. • Impermeable boots. • Facepiece respirator to EN146FFP3 - 3M 8835 or Moldex 3405. • Eye protection - safety goggles. • All PPE to be cleaned after job and monitored as free from contamination. Must be reused or returned as normal waste. • Contaminated PPE cannot be sent to shore.

  46. Work Precautions - Personal Hygiene • Local Rule 08. • No eating, drinking, chewing gum, sweets, tobacco. • No application of barrier cream. • All cuts and abrasions effectively dressed. • Wash hands and face before eating, drinking or smoking. • Shower after work.

  47. Work Precautions - Labelling and Tagging • Local Rule 08. • Tape and tag immediately after testing. • Positive reading - yellow/black LSA Contaminated tape + tag. • Negative reading - green LSA Externally Clear tape + tag. • Mark tags with cps, Date, Name of Tester, Platform. • Tubulars - tape ends + 2 tubular tags • See pictures.

  48. Labelling and Tagging - LSA Contaminated

  49. Labelling and Tagging - LSA Externally Clear

  50. Labelling and Tagging - Tubulars

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