A nonaqueous process was developed using ionic liquids (ILs) to extract bitumen from Alberta oil sands at room temperature. Based on an IL design platform of balancing lipophilic/hydrophilic properties with possible interfacial interactions, trialkylamine/fatty acid-based ILs were studied and down-selected considering performance, cost, composition, and interaction with water. The use of protic ILs also allowed modifying the amine/acid composition to increase the bitumen extracted and decrease the solid content in extracted bitumen. Using the IL trioctylammonium oleate ([HN888]­[Oleate]) at a 1:3 IL/oil sand mass ratio, we were able to achieve bitumen extraction from high-grade Alberta oil sands of ca. 100% with low solids content (<1%) in a fast, low-energy process. Our results demonstrate that the proper design of the IL can lead to efficient oil extraction without conventional solvents, without generating aqueous tailings, and with minimum energy consumption, that is, a production process with environmental impacts comparable to those associated with production of other hydrocarbon resources.

Summary Steam injection is widely used for bitumen recovery. However, steam is not efficient for shallow or thin reservoirs because of heat loss in the wellbore or to surrounding formations. Numerous alternatives have been proposed, including the addition of solvents and replacement of steam with volatile solvents. Here, we describe a new technology that combines nonvolatile ionic liquids (ILs) and waterflooding for bitumen recovery that can deliver high recovery at ambient temperature. Different ILs were designed for complete dispersal/dissolution of bitumen at ambient temperature. The designed ILs were tested in coreflood experiments with high–grade oil–sand ore from Alberta. Two different scenarios were tested: continuous injection of ILs at different injection rates and injection of a slug of ILs followed by water injection. Different slug volumes were tested at a constant injection rate. After ILs injection, the oil sand was removed from the column, and the remaining bitumen was quantified using a modified Dean–Stark method. Viscosity and solid–content measurements of the recovered samples at breakthrough were conducted. Bitumen recovery by the designed ILs can be thought of as a solution mining process. Tuning the physical and chemical properties of the ILs is the most important aspect of achieving the desired interaction with the oil–sand system. Properties of the designed IL depend on the selected cation and anion, and the strength of their intermolecular interaction. Primary amines mixed with the oleic acid chosen for IL1 form a viscous IL that can recover bitumen, leaving a slight amount of bitumen behind, but a large pressure gradient. Changing the cation to tertiary amines produces significantly less–viscous ILs, which completely recover the bitumen in the oil–sand column. Moreover, the cation can be tailored to significantly minimize the fines (clay) migration and viscosity of the recovered bitumen and to provide compatibility with an aqueous phase. In all cases, these recoveries are significant, compared with the currently used technologies. This work proves that bitumen recovery from oil sand is possible at low temperatures by means of a process analogous to solution mining with the design of the proper ILs, in contrast to viscosity–reduction processes achieved by thermal methods. The properties of these ILs can be tuned for different recovery mechanisms. Thus, this work establishes the basis for developing a new class of in–situ recovery processes with high recovery efficiencies and low environmental impact.

Nanoparticles are usually small enough that they can pass through the porous media without mechanically plugging the pore throats. However, physicochemical interaction between the nanoparticles and the pore walls can cause significant retention of nanoparticles. The objective of this paper is to provide theoretical equations based on DLVO theory to calculate the rate of deposition and release at different temperatures, ionic strengths, and pH values. DLVO theory is used to understand the interaction between nanoparticles and rock minerals. Electrostatic interaction depends on the zeta potential of nanoparticles and pore surface. In this paper, an equation is developed to calculate zeta potential at different temperatures, ionic strengths, and pH values. The rate of deposition and release of Silica nanoparticles in a sandstone formation, where interaction energy profile has energy barrier, has been derived. To validate the theoretically calculated rates, a numerical model is developed to compare the theoretical calculations with experimental data. Increasing ionic strength and temperature decreases the energy barrier height and hence increases the rate of deposition. The effect of pH on the rate of deposition depends on the location of environment pH with respect to the isoelectric point of nanoparticles and rock surface. For extreme values of pH, energy barrier exists and rate of deposition is low. However, when the pH of the solution is between the isoelectric points of nanoparticles and rock surface, the energy barrier decreases and the rate of deposition increases. The rate of deposition is time dependent with the rate decreasing as more rock surface is covered by nanoparticles. These theoretically calculated rate values are used in a numerical model of the advection-dispersion equation with source/sink term. Several experimental data have been perfectly matched with the model that validates the theoretical calculations of the rate of deposition. The new mechanistic model for nanoparticles can be used to determine the fate of nanoparticles in porous media under different conditions of nanoparticle size, temperature, ionic strength, and pH. This model can help to understand the nanoparticles transport in porous media and effectively design nanoparticles fluid for injection into oil and gas reservoirs.

Acid stimulation is used in carbonate reservoirs to bypass formation damage. Carbonate reservoirs are highly heterogeneous with layers of large permeability variation. For even distribution of acid between layers, we have developed a new acid diversion system using nanoparticles. Nanoparticles aggregate size distribution evolves with time, and once it spans pore space, gel structure is formed. The objective of this present a new acid diversion system with nanoparticles based acid system along with model that can predict the gelation kinetics. Experimental inversitgation has been conducted to study the gelation kinetics of nanoparticles at different salts, ionic strength, pH, and temperature. Phase behavior study was first conducted. The best system was then tested in parallel coreflood. Then Population Balance equation (PBE) is used to model the growth of aggregates and the interaction between aggregates and porous media. Quadrature method of moments (QMOM) is used to convert the PBE with continuous distribution of nanoparticle size into moment transport equations for efficient computation. Finite volume method is used for discretization of moment transport equation, acid transport equation, continuity equation and Darcy law. Acid diversion in carbonates using nanoparticle-based in situ gelled acid is proven to be more efficient than convectional diversion systems especially for harsh reservoir conditions. The effect of different salts, ionic strength, pH and temperature was studied experimentally. Coreflooding shows that Nanoparticle-based system can create several complete wormholes in both low and high permeability cores. Nanoparticles plugging small pore throats can divert acid into larger pores and reduce acid leakoff. Model presented in this paper gives insight into the aggregation and gelation kinetics. Model displayed the influence of nanoparticle concentration on gelation time. Once the gel forms, shear thinning behavior is used to model the viscosity of the gel. Shear rate could highly reduce the viscosity of the gel and hence affect the efficiency of acid diversion. The model developed in this work accurately simulate aggregation, initiation of gelation of fumed silica and acid diversion in carbonates. The new acid diversion system is highly effective in even distribution of acid between layers of different permeability. The model developed in this study can help in optimization of new nanoparticles-based acid diversion system.

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