Characterization Of The Humic-Clay Complex And Its Influence On Bitumen Displacement From Athabasca Oil Sand

Abstract

Abstract The objective o/this research is to develop a better understanding of the role played by humic matter and associated clay on the displacement of bitumen from compacted samples of reconstituted oil sand. Athabasca oil sand was first extracted with toluene to remove bitumen and water. The remaining sand was then treated with 0.1 M NaOH to liberate humic-clay material. This material was collected and analyzed. It was determined from elemental analysis that while this material was primarilyinorganic, it contained significant quantities of carbon hydrogen and oxygen. From thermogravimetric analysis and Fourier transform infrared analysis it was observed that both carbonaceous matter and waters of hydration were removed by heating to 775 °C. Reconstituted oil sand samples used in the displacement experiments were prepared by first mixing sand, water and a bituminous phase in desired proportions and then compacting the mixture under high pressure. The humic content of the sandwas controlled by its pre-treatment temperature. It was observed that in oil sands which contained humic matter, the recovery by alkaline displacement was significantly greater than the recovery by water displacement. No such incremental recovery reappeared when humic matter was specifically added during the reconstitution process. These effects are attributed to a reaction between sodium hydroxide and humic acids resulting in the formation of surfactants which lower interfacial tension between bitumen and the displacing phase. This conclusion is supported by interfacial tension measurements. Introduction It is well known that heavy organic species can be adsorbed on the surfaces of clay mineral types commonly found in oil sands(1–4). The formation of such organic-clay complexes undoubtedly affects the interfacial forces within the oil sand matrix and, ultimately, the bitumen displacement process. In situ recovery of bitumen is a very complex process which is difficult to generalize, largely because of the variability and complexity of oil sand composition. Improved understanding of this process at a mechanistic level is dependent upon betterknowledge of the interactions between the displacing phase and oil sand components. Oil sand reconstitution provides a convenient method whereby such interactions can be investigated. Humic material is a generic term used to describe large molecules of biological origin containing polar functionalities, notably carboxylic groups. The material is insoluble in most organic solvents and remains associated with the inorganic fraction after extraction of bitumen and water from oil sand. Montgomery(5) reported that the organic chemical types found in humic matter are not observed in bitumen. Kotlyar et al.(6) described work in which it was hypothesized that the solvent-insoluble humic material was affiliated primarily with the clay particles in oil sand via an iron complex linkage. Similar findings were reported by Kessick(7). Ignasiuk et al.(8) presented an extraction sequence which was used to obtain concentrated samples of humic material. Elemental and infrared analyses were performed on the concentrated samples of humic acids. It was observed that these species were rich in oxygen and nitrogen. The presence of carboxylic acid functional groups was suggested. Iron is again mentioned as a probable link in the clay-organic complex.