Technology

 

NORM

 

OIL AND GAS PRODUCTION

Analysis of oil and gas from many different wells has shown that the long-lived uranium and thorium isotopes are not mobilized from the rock formations that contain them. However Ra-226, Ra-224, Ra-228 and Pb-210 are mobilized, and appear mainly in the water co-produced during oil and gas extraction. These isotopes and their radioactive progeny can then precipitate out of solution, along with sulphate and carbonate deposits as scale or sludge in pipes and related equipment. Radon-222 is the immediate decay product of radium-226 and preferentially follows gas lines. It decays (through several rapid steps) to Pb-210 which can therefore build up as a thin film in gas extraction equipment.The level of reported radioactivity varies significantly, depending on the radioactivity of the reservoir rock and the salinity of the water co-produced from the well. The higher the salinity the more NORM is likely to be mobilized. Since salinity often increase with the age of a well, old wells tend to exhibit higher NORM levels than younger ones. Table 4 gives the characteristics of NORM produced during oil and gas extraction and some indicative measurements of concentrations.

 

 

If the scale has an activity of 30,000 Bq/kg it is 'contaminated', according to Victorian regulations. This means that for Ra-226 scale (decay series of nine progeny) the level of Ra-226 itself is 3300 Bq/kg. For Pb-210 scale (decay series of three) the level is 10,000 Bq/kg. These figures refer to the scale, not the overall mass of pipes or other material (cf Recycling section below). A 2010 analytical report shows Pb-210 scale at 18.6 MBq/kg from a pipeline in Canada. For seawater injection systems a further NORM issue has more recently come to light: that of bio-film deposits fixing significant amounts of the seawater's uranium. Fracking (hydraulic fracturing) for gas production releases significant NORM in some geological environments, both in drill cuttings and water. In the US Marcellus shale in Pennsylvania, New York and West Virginia (a black shale) typically activity is about 370 Bq/kg including high levels of radium-226, giving up to 625 Bq/L in brine and up to 66 Bq/L in other water returned to the surface. US Geological Survey figures for brine are reported as 377 Bq/L Ra-226 and 46 Bq/L for Ra-228. Other reports related wastewater here to the drinking water standard (0.185 Bq/L) and said it was 300 times Nuclear Regulatory Commission limits for industrial wastewater discharge. NORM in the oil and gas industry poses a problem to workers particularly during maintenance, waste transport and processing, and decommissioning. In particular Pb-210 deposits and films, as a beta emitter, is only a concern when pipe internals become exposed. External exposure due to NORM in the oil and gas industry are generally low enough not to require protective measures to ensure that workers stay beneath their annual dose limits (such as set out by the IAEA basic safety standards). Internal exposures can be minimized by hygiene practices.

 

 

 

 

 

 

 

 

The Energy Information Administration, the Environmental Protection Agency ("E.P.A."), the Texas Commission on Environmental Quality ("T.C.E.Q.") and the Texas Railroad Commission agree that Salt Caverns are superior for oilfield waste as well as storage for oil, natural gas, propane, and other hydrocarbon based materials.

 

 

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