The objective of this work is to acquire phase behaviour and physical property data of carbon dioxide/heavy oil systems pertaining ta enhanced oil recovery by CO2 huff-n-puff and steam stimulation. Phase behaviour and physical property measurements were carried out on Lindbergh heavy oil CO2 mixtures at 21 °C and 140 °C, and at pressures ranging up to about 15 MPa. Furthermore, the oil samples were analyzed using gas chromatographic simulated distillation. The experimental measurements were also carried out on three of the oil's fractions that can serve as "pseudo components" during equation of state correlations Of the experimental data. The solubility of CO2 was less in the heavier hydrocarbons than in the lighter fractions and the solubility also decreased with increasing temperature. The densities of the saturated mixtures did not change significantly as the saturation pressure was increased. The extent of viscosity reduction with increasing CO2 content was larger for the heavier hydrocarbon fractions than for the lighter ones. In addition, the viscosity was sometimes seen to increase with pressure in the liquid-liquid equilibrium region of the phase diagrams. Analysis of the residual oils indicated that in some cases a small amount of their light ends had been extracted by CO2 and/or some of the heavy ends had been depleted (presumably precipitated). Introduction Gas (more commonly CO2) injection into heavy oil reservoirs is becoming a viable enhanced oil recovery method(l-5). Mathematical studies of this process have been presented in the literature(6–10), as have been laboratory displacement data(11–13) and phase behaviour measurements(l4–19). The main mechanism in this process is the dissolution of the injected gas into the crude oil, thereby swelling it, reducing its viscosity, and making it more mobile. Usually the process is an immiscible one, in contrast to the more common miscible gas flooding of conventional oil reservoirs. The correlation of the phase behaviour data of conventional crude oils is usually carried out with one of the Van-der-Waals type of equations of state. Examples of these equations are those by Soave-Redlich-Kwong(20) and Peng-Robinson(21). Ideally, these equations require certain parameters to characterize each component in the mixtures under consideration. The common practice has been to represent the crude oil with a limited number (four to six, typically) of pseudo components. Several Authors(22–27) have proposed various schemes for selecting these pseudo components and evaluating their properties based on those of the crude oil. Most of the methods that have been developed for the characterization of crude oils were derived from data of light oil systems and these are usually directly applied to heavy oil data. This may not be an optimum approach since heavy oils have a much larger proportion of heavy ends, asphaltenes, and resins, and a much lower content of C5-C30 hydrocarbons than light oils. In addition, heavy oil reservoirs are usually shallower than light oil reservoirs and, consequently, have lower pressures and temperatures. Alternatively, enhanced oil recovery of heavy oil reservoirs is often carried out using thermal methods, such as steam or fire flooding, in which very high temperatures (> 200 °C) are encountered.

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Resistance to antileishmanial drugs such as sodium stibogluconate (SSG), amphotericin B (Amp-B), and miltefosine is on the rise, and alternate strategies for effective treatment have gained importance in recent years. Although nanoparticle (NP)based composite drugs that have emerged recently have been found to be effective, the associated toxicity limits their usage. Bimetallic NPs produced through reduction with medicinal plant extracts are proposed to overcome the toxicity of the NPs. In the present study, three types of gold−silver bimetallic nanoparticles (Au−Ag BNPs) were synthesized through a single-step reduction process using fenugreek, coriander, and soybean leaf extracts. All of the three types of BNPs exhibited high antileishmanial effects against promastigotes with half-inhibitory concentration (IC 50 ) values in the range of 0.03−0.035 μg/mL. The IC 50 values of the BNPs are much lower compared to those of miltefosine (IC 50 = 10 μg/mL). The synthesized BNPs induced the reactive oxygen species (ROS)mediated apoptosis-like death in the promastigotes and could potentiate the antileishmanial activity of macrophages. The intracellular amastigotes were reduced by 31−46% in macrophages. The biogenic BNPs synthesized in this study and their potent antileishmanial activity provide further impetus to the ongoing quest for novel drugs to effectively manage leishmaniasis.

Laboratory waterflood and miscible flood data of three Alberta reservoir systems are compared with their respective field projections. Trends in laboratory waterflood and miscible flood recoveries were found to correspond closely with the expected ultimate recoveries in the respective fields and to correlate well with reservoir wettability. The wettability, as characterized by measuring water-oil relatie permeabilities, ranged from strongly water-wet to strongly oil-wet with one system of intermediate wet/ability and another of probable mixed wettability. Miscible flood oil recoveries were high in systems possessing other than strongly water-wet nature. In addition to the water-shielding phenomenon, interfacial adhesion is also considered to gain a better understanding of the wettability effects in miscible gas processes. The results of this study could be used to identify candidate reservoirs for carrying out miscible floods and to re-evaluate the need for secondary waterfloods in certain reservoirs. In some reservoirs where mixed wettability conditions exist extended waterfloods, within economic limits, may not adversely affect the potential for future miscible floods. This paper brings forth the significant role played by wettability in miscible processes and also offers insight into strategic alternatives for field applications. Introduction Reservoir wettability is an important factor among the many that affect the design of a miscible enhanced oil recovery process. Wettability influences the extent of access of oil by the injected miscible solvent through its effect on the relative location of oil and water. This, in turn, will influence miscible flood performance. The influence of wettability on waterflood performance has been studied for several decades(l) and the published literature supports widely differing conclusions leading to some uncertainty. These uncertainties did not seem important as long as there existed a belief that all petroleum reservoirs were strongly water-wet. Many researchers have contributed significant findings over the last few decades to dispel this belief. It is now generally accepted that reservoir wettabilities vary widely between the extremes of strongly water-wet and strongly oil-wet states, with many falling in the mid-band of neutral or intermediate wettability where the rock shows equal preference to both oil and water- None of these homogeneous wettability states could explain the high waterflood recoveries in the East Texas Woodbine core displacement tests. Efforts to explain these results culminated in the concept of "mixed wettability" which was introduced by Salathiel in 1973(2). This mixed wettability state has also been recently assigned to the Pembina Cardium field in Alberta(3). What is the influence of these widely differing wettability states of petroleum reservoirs on their waterflood and miscible flood behaviour? Despite such a wide variation in reservoir wettability, should we continue to adopt the same sequence of production strategies namely secondary waterfloods and tertiary miscible floods? Or could we optimize our production strategies for maximum benefit by a better understanding of the influence of wettability on secondary and tertiary oil recoveries? This study attempts to address these concerns. This paper begins with the role of wettability in miscible enhanced oil recovery (EOR) operations wherein the literature dealing with this subject is reviewed.

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