Evaluations of Radionuclides of Uranium, Thorium, and Radium Associated With Produced Fluids, Precipitates, and Sludges From Oil, Gas, and Oilfield Brine Injection Wells in Mississippi

Abstract

Naturally occurring radioactive materials (NORM) are known to be produced as a byproduct of hydrocarbon production in Mississippi. The presence of NORM has resulted in financial losses to the industry and continues to be a liability as the NORM-enriched scales and scale encrusted equipment is typically stored rather than disposed of. Although the NORM problem is well known, there is little publically available data characterizing the hazard. This investigation has produced base line data to fill this informational gap.A total of 329 NORM-related samples were collected with 275 of these samples consisting of brine samples. The samples were derived from 37 oil and gas reservoirs from all major producing areas of the state. The analyses of these data indicate that two isotopes of radium ( 226 Ra and 228 Ra) are the ultimate source of the radiation. The radium contained in these co-produced brines is low and so the radiation hazard posed by the brines is also low. Existing regulations dictate the manner in which these salt-enriched brines may be disposed of and proper implementation of the rules will also protect the environment from the brine radiation hazard. Ra content, and relationships exist between total dissolved solids, BaSO 4 saturation and concentration of the Cl ion. Principal component analysis points to geological controls on brine chemistry, but the nature of the geologic controls could not be determined.The NORM-enriched barite (BaSO 4 ) scales are significantly more radioactive than the brines. Leaching studies suggest that the barite scales, which were thought to be nearly insoluble in the natural environment, can be acted on by soil microorganisms and the enclosed radium can become bioavailable. This result suggests that the landspreading means of scale disposal should be reviewed. This investigation also suggests 23 specific components of best practice which are designed to provide a guide to safe handling of NORM in the hydrocarbon industry. The components of best practice include both worker safety and suggestions to maintain waste isolation from the environment.