- Copyright ©2006. The American Association of Petroleum Geologists/Division of Environmental Geosciences. All rights reserved.
Large quantities of brines are coproduced with hydrocarbons from oil and gas wells. Dissolved solutes from these brines precipitate, forming scale in and on production equipment and sludge in storage tanks. The most abundant component of these scales and sludges is barite. Radium is one of the solutes that may be incorporated into these precipitates, rendering them radioactive. One method for the disposal of scale and sludge is land spreading, in which the material is mixed into the top few centimeters of the soil and then covered with a layer of clean soil, such that the radioactivity is below governmental action levels. An assumption associated with this disposal method is that the inorganic components are highly insoluble, relatively immobile in the environment, and low in biological availability. To test this assumption, (1) radioactive scale and sludge samples were evaluated for leachability; then (2) leachability was evaluated after mixing scale and sludge samples with top soils and incubating them under moist conditions similar to what may be expected using land spreading; (3) soil-scale mixtures were also incubated wet or dry, followed by differential density separation of the scale and soil.
Incubating the samples under moist conditions with top soils increased the Ra that was extractable from them by several fold. This finding is remarkable in that soil retains most of the soluble Ra added to it and soils mixed with scale or sludge retain even greater proportions of the soluble Ra added to them. The implication is that although the retained, solubilized Ra is difficult to extract from the soil, it will be much more biologically available and mobile in the environment than in its original, highly insoluble form. This conclusion is of particular concern in warm and humid climates such as those typical of Mississippi and the southeastern United States.
John C. Matthews is a professor of pharmacology at the University of Mississippi, School of Pharmacy. His areas of research interest include environmental toxicology and the function of toxicants in aging-related neurodegenerative diseases.Shuanglian Li was a master's degree student in Matthews' laboratory when she worked on this project in partial fulfillment of the requirements for her master's degree. She is presently employed as a research scientist in the area of gene toxicity by Pfizer Pharmaceuticals, San Diego, California. She will reenter graduate school in the near future to pursue her Ph.D. in pharmaceutical science.
Charles T. Swann is a staff geologist with the Mississippi Mineral Resources Institute based on the campus of the University of Mississippi. His research interests include environmental aspects of hydrocarbon-production geology, tertiary stratigraphy, geotechnical characteristics of clays, and molluskan paleontology.
Rick L. Ericksen is the executive director of the Mississippi State Board of Registered Professional Geologists based in Jackson, Mississippi. Formerly a geologist with the Mississippi Department of Environmental Quality, he has a long-standing interest in research and regulatory issues associated with NORM from hydrocarbon production.