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Treating the oil sand tailings ponds is a major challenge owing to the vast amounts of tailings and the need for a reliable treatment technique for releasing water and generating the highly consolidated material required for land reclamation. Treatment with chemicals such as lime (calcium (hydr)oxide) is a promising technology for tailings dewatering and consolidation, particularly at higher pH. Given that kaolinite and silica minerals are the main constituents of many oil sands, we have investigated the influence of lime and NaOH addition on the silica/water/kaolinite interface over the pH range 7-12.4 using vibrational sum frequency generation spectroscopy (SFG). With lime addition, we observe a complete disappearance of the vibrational features of the interfacial water molecules for planar silica in contact with an aqueous dispersion of kaolinite particles at pH 12 and above with a concurrent increase in the amount of adsorbed kaolinite based on the observed peak at 3694 cm-1. This suggests that the absence of water features in the SFG spectra is associated with conditions that facilitate dewatering. With NaOH addition, however, the interfacial water SF intensity is still significant even under highly alkaline conditions despite the increase in adsorbed kaolinite at high pH. To better understand the SFG observations, we perform -potential measurements on the planar silica aqueous interface and kaolinite aqueous suspensions under the same pH conditions with NaOH and lime addition.

Phosphorus (P) losses from agricultural fields through leaching are the main contributors to eutrophication of lakes and rivers in North America. Adoption of P-retaining strategies is essential to improve the environmental quality of water bodies. The main objective of this study is to evaluate lime as a soil amendment in reducing phosphorus concentration in the leachate from three common soil textures with neutral to alkaline pH. Phosphorus leaching from undisturbed soil columns (10 cm in diameter and 20 cm deep) as well as small repacked columns was investigated and compared in this study. Lime (high calcium hydrated lime) at the rate of 1% by air-dried soil mass was applied to the topsoil of the columns. Both sets of experiments followed a full factorial design with two factors of soil texture at three levels (sandy loam, loam, and clay loam) and treatment at two levels (control and limed) with three replicates. Scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy was performed on the control and limed soil samples to confirm the formation of calcium phosphate compounds. For both intact and repacked columns, dissolved reactive phosphorus (DRP) concentrations in the leachates from limed sandy loam and limed loam soil columns was significantly reduced, while DRP in the limed clay loam column leachates was not changed. Elemental mapping demonstrated that in limed sandy loam and loam soils, the calcium loadings on the soil surface were always linked with phosphorus. The formation of calcium phosphate compounds and the increased phosphate adsorption on the soil surface through Ca bridging could be the two main phosphorus-lime retention mechanisms. Total dissolved phosphorus (TDP) in the leachates of limed loam and limed clay loam indoor intact and repacked columns was reduced, while there was no change in that of the sandy loam soil. In finer textured soils, lime can increase TDP retention through the immobilization of organic phosphates. The impact of lime application on DRP and TDP varied with the soil texture. The lime-induced reduction in the DRP and TDP was variable between the intact and repacked columns demonstrating the importance of soil structure on phosphorus and lime interactions in the soil. Overall, lime application at the studied rate can be considered a promising soil amendment in mitigating phosphorus loss from non-calcareous neutral to alkaline soils.

Oil sands tailings have a limited ability to dewater and can also release toxic water, so finding a cost-effective tailings reclamation strategy has been challenging. End pit lakes (EPLs) are being examined as one potential approach to reduce fluid fine tailings (FFT) inventories for the oil sands industry. This study investigated the effect of adding lime (650 to 4000 ppm) on FFT dewatering and improving cap water quality under the simulated EPL scenario. The results illustrated that a high lime dose of 3500 ppm achieved the highest FFT water recovery, decreased the cap water alkalinity at the end of the experiment (after 90 d), and increased the possibility of cation exchange (at day 0). In contrast, the degradation of petroleum hydrocarbons was slightly enhanced at low lime dose of 650 ppm in comparison to high doses. In addition, the 650 ppm dose resulted in minimal change in the microbial cell counts at day 90, compared with high lime doses that resulted in a large reduction in the cell counts. Comparisons of toxicity of the FFT pore water after lime addition exhibited higher toxic effects for lime dosages >1600 ppm. Nevertheless, at all lime doses, low cap water toxicity (i.e.

Over 80% of Athabasca, Alberta, Canada oil sands deposits are suitable for in-situ bitumen recovery processes. Steam assisted gravity drainage and cyclic steam stimulation processes are commercially implemented with current bitumen production capacity of about 850,000 bbl/d, which is projected to exceed 5000,000 bbl/d in the next two decades. Efficiency of these processes would be improved by reducing the steam-to-bitumen ratio. For this purpose addition of light hydrocarbons into steam as a solvent to reduce bitumen viscosity has been studied for decades with a limited commercial success. As an alternate strategy to solvent co-injection with steam, reduction of bitumen–water interfacial tension by co-injection of a surfactant, such as biodiesel (fatty acid methyl esters), with steam was proposed ( Babadagli et al., 2009 . Use of biodiesel as an additive in thermal recovery of heavy-oil and bitumen. In: Paper 049 Presented at the Canadian International Petroleum Conference (CIPC), 16–18 June, Calgary, Alberta, Canada; Babadagli and Ozum, 2012 . Oil Gas Sci. Technol.: Rev. IFP Energies Nouvelles 67 (3), 413–421). The present study focuses on three issues: (i) viscosity of bitumen in the neighborhood of the edge of the steam chamber using heat conduction models, where bitumen mobility should be controlled by viscosity and bitumen–water interfacial tension; (ii) generate bitumen recovery data, operating the steam chamber as a pressure cooker; where bitumen mobility should be controlled mainly by viscosity rather than bitumen–water interfacial tension, since the influence of the creeping flow of water-condensed steam is marginally small; and, (iii) measure bitumen content at different heights of the pressure cooker test spent core samples to predict bitumen mobility and permeability. Pressure cooker tests were performed using steam, steam and pentane as a solvent at 5%, 10% and 15% of bitumen by mass, and steam and biodiesel as a surfactant additive at 0.2% and 0.3% of bitumen by mass dosages. Our test results showed that solvent, such as pentane, addition reduced bitumen recovery as the dosage of solvent addition increased from 5% to 15% of bitumen. This observation is interpreted that while solvent addition reduces bitumen viscosity it also increases bitumen–water interfacial tension; the overall effect of which results in reduction of bitumen recovery efficiency. When biodiesel was used as a surfactant additive at 0.2% and 0.3% of bitumen by mass dosage, a slightly increase in bitumen recovery efficiency was observed. Bitumen mobility and bitumen permeability values predicted in this study were one order of magnitude smaller than that of the values reported in the literature; probably resulting from reduced bitumen–water interfacial tension, by the activation of natural surfactants contained in bitumen, promoting bitumen mobility in the field operations. Result of the present study suggests that further tests and modeling studies are needed to understand effects of bitumen viscosity reduction by solvent co-injection and bitumen–water interfacial tension reduction by surfactant co-injection with steam on the efficiency of steam assisted bitumen recovery processes.

As an alternative to solvent addition to the steam-assisted gravity drainage process for bitumen recovery, coinjection of biodiesel with steam as a surfactant additive to reduce bitumen–water interfacial tension was considered. The density and viscosity of bitumen and bitumen–pentane mixtures up to 15 % pentane concentrations by mass were measured at a 1 MPa pressure and up to 448 K temperature. The interfacial tension between bitumen, bitumen–pentane mixtures up to 15 % pentane concentrations, bitumen–biodiesel mixtures up to 0.3 % and water, and process water was also measured at a 1 MPa pressure and up to 423 K temperature. Laboratory tests showed that the density of bitumen–pentane mixtures decreased linearly with an increase in pentane content, and their viscosity decreased exponentially with the increase in temperature. A decrease in bitumen viscosity with an increase in pentane content was dramatic at low temperatures and became less sensitive at temperatures above 373 K. Interfacial tension measur...

Heavy oils with about 500 cp to 50,000 cP viscosity in unconsolidated sand reservoirs are commercially produced without heat injection, by a production method known as the Cold Heavy Oil Production with Sand (CHOPS). CHOPS reservoirs are generally about a kilometer wide and may range from 3 to 5 m thick sand blankets to 35 m thick sand channels which are between 0.5 to 5 Darcy permeability, 28 to 32% porosity, and have about 88% oil and 12% water saturations. CHOPS production is always coupled with the production of the dissolved gas, mostly CH4 and minor amounts of H2S and CO2, and sand production which causes formation of wormholes in the reservoir. Formation of wormholes in the initial phase of the reservoir life promotes oil migration and thus increases oil production; however, continued wormhole formation in long term operations reduces the oil production rate and harms the sweeping efficiency of the original oil in place, typically to less than 10%. Because of low sweeping efficiency, several Post-CHOPS process concepts have been investigated to recover the remaining oil in the reservoir. The objective of the present study is to increase the production and sweeping efficiencies of CHOPS and Post-CHOPS processes by altering the wettability of oil and reservoir sand as well as the wettability of oil and connate water and/or water injected into the reservoir. In this study, an oil-water emulsion sample produced by CHOPS process was centrifuged to separate the oil and water phases to avoid using chemical demulsifiers. The separated oil and water phases were physically and chemically characterized and the oil-water interfacial tension was determined using pendant drop method at a temperature range between 20 to 50 oC. The effects of solvent, surfactant, and pH on oil-water interfacial tension were independently investigated by either diluting the oil with pentane as a solvent additive (5% to 15% by mass of oil dosages), emulsifying biodiesel (fatty acids methyl esters, chemical formula: CnHm-COOCH3; m Results of these studies suggest that bitumen mobility and sweeping efficiency of CHOPS and Post-CHOPS processes could be improved by reducing the oil-water interfacial tension. The present experimental research demonstrates that oil-water interfacial tension could be reduced by either a basic or a nonionic surfactant additive. Implementation of these findings to CHOPS and Post CHOPS processes needs further understanding of the CHOPS reservoir characteristics. Laboratory test results are encouraging enough for further laboratory and field trials to increase the production and oil sweeping efficiencies of the CHOPS reservoirs.

In Alberta, Canada, bitumen production by surface mining followed by ore-water slurry based extraction processes is approaching 2,000,000 bbl/d capacity. The Clark Hot Water Extraction process developed in the 1930s is used at all commercial plants which use caustic NaOH as an additive to boost bitumen recovery efficiency. Use of NaOH as an extraction process additive increases process water salinity, specifically Na+ concentration, promotes dispersion of silt and clay size particles which results in greater production of toxic mature fine tailings. Increase in process water Na+ concentration detrimentally affects the performance of both bitumen extraction and tailings disposal processes. Existing mature fine tailings inventory stored in tailings ponds is exceeding 900x106 m3 and is predicted to grow alarmingly faster by the completion of new plants and by an increase in the production capacity of the existing plants. The Energy Resources Conservation Board of Alberta issued Directive 074 in February, 2009 urging oil sands plants to comply with a 50% reduction in mature fine tailings production. Proposed policies by the oil industry in response to Directive 074 have shown short fallings; which suggests that development of novel bitumen extraction and tailings management processes are needed. To reduce the mature fine tailings inventory, we studied production of nonsegregating tailings by treating a blend of cyclone underflow and thickened cyclone overflow with CaO additive. These tests were made using Albian Sands Muskeg River Mine tailings when the plant was operating at nonadditive and sodium citrate additive extraction modes and using Syncrude Canada Ltd.'s Aurora Mine tailings. Also, we studied the use of CaO as a bitumen extraction process additive replacing NaOH in the Clark Hot Water Extraction process; by which silt-clay size particles dispersion in the extraction process slurry is reduced and accumulation of Na+ in the process water is eliminated. Use of CaO as an extraction additive is considered as a fundamental and a new process alteration by the oil sands operators. Recently, to evaluate this new process the Canadian Oil Sands Innovation Alliance (COSIA) has requested NAIT-NARCOSS, an independent academic and industrial research laboratory, to perform a third party verification study for the use of CaO as a bitumen extraction process additive. The NAIT-NARCOSS test results are completed and are highly encouraging, confirming that use of CaO as an extraction process additive reduces dispersion of silt and clay size particles in the extraction process slurry without harming bitumen recovery efficiency. It also improves process water chemistry by eliminating accumulation of Na+ in the process water. It is concluded that a paradigm change is offered to the oil sands industry to reduce the adverse environmental impacts of oil sands plants in simple, cost effective and environmentally friendly manners; which is the simultaneous implementation of the use of CaO as additives in bitumen extraction and nonsegregating tailings production processes.

In Alberta, Canada, over 80% of oil sand reserves are suitable for thermal in-situ processes such as the steam assisted gravity drainage (SAGD) process. SAGD recovery is contingent on reducing the viscosity of bitumen, which is immobile at reservoir temperature, to increase its mobility, thus increasing recovery efficiency. Processes based on the co-injection of solvent and steam targeting further reduction of bitumen viscosity have been extensively investigated. These studies generally ignore the potential role of bitumen-water interfacial tension on bitumen mobility and bitumen recovery. In this study, we propose a new analytical model approach to analyze flow characteristics of injected steam in a bitumen containing reservoir and to clarify the physics of the displacement process during SAGD. The thickness of the chamber front where viscosity reduction occurs is defined for different injection and reservoir conditions and flow patterns are created for different fluid (viscosity and interfacial tension) and reservoir properties (thickness). This model shows how bitumen-water interfacial tension affects bitumen mobility and thereby influences both SAGD displacement efficiency and ultimate bitumen recovery. A composite set of models including the effects of interfacial tension between the bitumen and water in addition to viscosity reduction are developed. Finally, the observations obtained through analytical model studies are compared against SAGD field observations accumulated over the last two decades. The focus of this comparison is on the advancement rate of the chamber front and its growth characteristics. By understanding the bitumen to water interfacial tension effects, it will be possible to make a better prediction of the relative benefits of solvent or surfactant to accelerate the recovery rate and improve ultimate recovery.

In Alberta, Canada bitumen is commercially produced by in-situ processes at about 830,000 bbl/d capacity, production capacity is projected to exceed 5,000,000 bbl/d in the next two decades. Steam assisted gravity drainage (SAGD) process is one of the in-situ bitumen recovery processes; the economics and efficiency of which would be improved by reducing the steam to bitumen ratio. For this purpose, the addition of light hydrocarbon solvents into steam as a solvent to reduce bitumen viscosity has been studied; however, several decades of research efforts has resulted in only limited commercial success. More recently, as an alternative to solvent addition, the use of biodiesel (fatty acid methyl esters) with steam as a surfactant additive reducing bitumen-water interfacial tension was proposed and studied experimentally (Babadagli et al, 2009; Babadagli and Ozum, 2010). In the present study, experiments were performed at typical reservoir pressure conditions to evaluate the performance of solvent (pentane) addition with steam to reduce viscosity and biodiesel addition with steam to reduce bitumen-water interfacial tension to improve bitumen recovery efficiency. The results showed that bitumen recovery efficiency may decrease with the addition of hydrocarbon solvent if the solvent is added after a certain period of steam injection. Solvent addition to the steam was tested at 5% and 15% of bitumen mass dosages. Steam assisted bitumen recovery tests with biodiesel addition under 2-g/kg-bitumen dosage showed an increase in bitumen recovery efficiency. To further investigate the reasons behind the lowered recovery with solvent addition, an analytical model was developed to predict heat transfer and pressure fields in the reservoir causing Darcy flow, and therefore, bitumen mobility. The distribution of the aqueous and solvent phases injected in time and space considering the phase change (steam and solvent condensation) effect with respect to steam chamber were clarified for different injection conditions and scenarios. The results and observation will be useful in defining the appropriate application conditions for both solvent as a viscosity reducer and biodiesel as an interfacial tension reducer additive in SAGD operations.