OIL-FIELD-BRINE-INDUCED COLLOIDAL DISPERSION: A CASE STUDY FROM SOUTHEAST TEXAS

The improper disposal of oil-field brine is a wide spread problem in the Gulf Coast region of the United States. Oil-field brine contamination has scarred the landscape, damaged watersheds and compromised water supplies. An additional unrecognized threat of oil-field brine contamination is colloidal dispersion. Colloidal dispersion causes the disaggregation of colloids, such as clays, by the altering of fluid and surface chemistry to create a stable suspension. Colloidal dispersion has been shown to cause: piping erosion, slope failure, increased erosion, decreases in hydraulic conductivity, degradation of soil productivity, and increased potential for transport of adsorbed contaminants. At a site in southeast Texas piping erosion features are found in conjunction with oil-field brine contamination. Neural network analysis of data from the contaminated soil indicate that elevated sodium adsorption ratios and elevated pH levels increases colloidal dispersion when pore water electrical conductivity levels are low. These results suggest that the interaction of oil-field brines with colloid mineral surfaces causes dispersion when excessive pore fluid ions are flushed from the soil.