Effects of petroleum hydrocarbon concentration and bulk density on the hydraulic properties of lean oil sand overburden

Abstract

In the Alberta oil sands, sand containing less than 8% petroleum hydrocarbon (PHC) is referred to as lean oil sand (LOS) and is used as subsoil in reclamation. The objective of this study was to determine how bulk density and PHC concentration affect the hydraulic properties of LOS. The LOS was packed in soil cores at varying bulk densities and PHC concentrations, representing the range in these parameters that occur in the reclamation setting. The cores were placed on a tension table and pressure plates to measure water retention. The constant head method was used to measure the saturated hydraulic conductivity (Ks) of the LOS. Results show that increasing PHC concentration reduced the water retention of LOS due to the presence of PHCs in soil micropores. PHC concentration also had a significant effect on the van Genuchten curve fitting parameters for the water retention curve, although the shape of the curves remained similar regardless of PHC content. Furthermore, there is a significant reduction in Ks at the high bulk density and high PHC concentrations (3.25%-7.48%), compared with low PHC concentrations (0%-1.63%). Due to the reduced Ks with increased PHCs and bulk density, LOS used as the base material in reclamation will reduce percolation and increase water storage in the reclamation soil cover.