No abstract

Organic petrography has been proposed as a tool for characterizing the heterogeneous organic matter present in soil and sediment samples. A new simplified method is proposed as a quantitative means of interpreting observed sorption behavior for phenanthrene and different soils and sediments based on their organic petrographical characterization. This method is tested under singe solute conditions and at phenanthrene concentration of 1 microg/L. Since the opaque organic matter fraction dominates the sorption process, we propose that by quantifying this fraction one can interpret organic content normalized sorption distribution coefficient (Koc) values for a sample. While this method was developed and tested for various samples within the same aquifer, in the current study the method is validated for soil and sediment samples from different sites that cover a wide range of organic matter origin, age, and organic content. All 10 soil and sediment samples studied had log Koc values for the opaque particles between 5.6 and 6.8. This range of Koc values illustrates the heterogeneity of opaque particles between sites and geological formations and thus the need to characterize the opaque fraction of materials on a site-by-site basis.

Surfactant-enhanced washing of oil-based drill cuttings was evaluated as a technology of benefit to domestic oil producers. Laboratory studies showed the branched C14-C15 alcohol propoxylate sulfate to be a promising surfactant for liberating oils from these drill cuttings. Low concentrations (∼0.1% by weight) of this surfactant produced ultra-low oil-water interfacial tensions (IFTs), thereby allowing the rollup/snap-off mechanisms to liberate drilling oil (C16, C18 alpha olefins) from the cuttings. Surfactant-enhanced washing was compared between oil-based drill cuttings, Canadian River Alluvium (CRA), and silica, showing that the hydrophobic nature of the oil-based cuttings limited the amount of oil removed. The Ca++ content of the cuttings promoted surfactant abstraction by the cuttings, thereby increasing the hydrophobicity and oil retention by the cuttings. For this reason, three components were added to produce a robust system: (1) branched C14-C15 alcohol propoxylate sulfate, (2) octyl-sulfobetaine, and (3) builder (Na2SiO3). The Na2SiO3 builder was added to promote Ca++ sequestration, thereby decreasing the Ca++ available for precipitating the surfactant. The octyl-sulfobetaine helps mitigate high hardness and high hydrophobicity by acting as a lime soap dispersing agent (LSDA). Surfactant losses were minimized and oil removal was maximized by using all three components. When washing with this three-component formulation, oil removal was relatively independent of operating conditions such as bath-cuttings contact time and agitation energy; minimizing the contact time and agitation has the added benefit of reducing the fines production during washing operations. When washing with the three-component formulation, the oil was liberated from the cuttings as a free phase layer, sans surfactant and sans solids. The final (post washing) oil content of oil-based cuttings was in the range of 2% to 5%, which is below treatment standards for these cuttings. In addition, greater than 85% of the initial branched C14-C15 alcohol propoxylate sulfate remained in the bath after washing, which minimizes the need for make-up surfactant when the wash water is reused.

No abstract