A Computational Study of Polymer Solutions Flow Regimes during Oil Recovery from a Fractured Model

The effect of ultrasound (US) on the shear viscosity of water-soluble polymers, polyvinyl alcohol, polyethylene glycol and polyacrylic acid, was studied in aqueous solutions with US exposure of 23, 43, 96 and 141 kHz for an 8.5–9 W US. The US exposure significantly decreased the shear viscosity of the solutions in this order: 43>23>96>141 kHz. When US exposure was stopped, the shear viscosities of the aqueous polymer solutions reverted to their original values. US stimulation during the decrease in viscosity was supported by the ultrasonic power transmitted through the aqueous polymer solution. In addition, Fourier-transform infrared spectra obtained during US exposure showed that hydrogen bonds in the aqueous polymer solution could be broken, especially at 43 kHz. We concluded that US exposure influenced hydrogen-bond interactions between the OH groups of the polymer and water molecules in the aqueous medium. This finding was supported by US absorption of the aqueous polymer solution in the transmittance model, which shows the US absorptivity, ɛUS, for each polymer system. The effect of US on the shear viscosity of water-soluble polymer solutions was studied. The 43 kHz US significantly decreased the shear viscosity of the solutions. FT-IR spectra obtained during the US exposure showed that hydrogen bonds in the aqueous polymer solution could be broken. US absorption model was proposed to explain US absorption and the breakage in the hydrogen bonds. US effect influenced the condition of water solvation to the water-soluble polymers.

Upscaling of CO2 injection in a fractured oil reservoir

Synthetic polymer single-chain nanoparticles (SCNPs) are an emerging new class of nanomaterials that possess similar folded structures as natural proteins. However, most SCNPs reported so far are p...

A slug containing 2 percent sulfonate, polymer for mobility control, and sodium tripolyphosphate for multivalent ion control - the entire system driven by a polymer solution - recovered 85 percent of the residual oil from a waterflooded Berea core. Because the surfactant adsorption is low, it appears that the process may be economically feasible for tertiary recovery of oil. Introduction In 1927, Uren and Fahmy concluded that an inverse relationship exists between oil-water interfacial tension and the percentage of oil recovered by waterflooding. In that same year a patent was issued to Atkinson that proposed the patent was issued to Atkinson that proposed the use of aqueous solutions of soap or other materials to decrease the "surface tension" between oil and the flooding medium and thereby increase the recovery of oil. During the next 25 years a major part of the reported research on the use of surfactants to recover oil was carried out by a group at Pennsylvania State U. This group recognized that interfacial tension. wetting conditions (contact angle), and surfactant adsorption were important factors. Preston and Calhoun discussed chromatographic transport of surfactants through porous rocks. Ojeda et al., and Paez et al., correlated residual oil saturation in Paez et al., correlated residual oil saturation in cores after a surfactant flood with sigma/Delta p and with a pore geometry parameter (k phi)1/2. These correlations pore geometry parameter (k phi)1/2. These correlations indicated that residual oil saturation could go to zero at values of sigma/Delta p approaching zero. Excluding patent literature, published research results for the last two decades have discussed the screening of surfactants for oil recovery "efficiency", changing wettability to improve oil recovery, adsorption and chromatographic transport of surfactants, and the role of major factors known to affect oil recovery by aqueous surfactant flooding. A comprehensive study directed primarily toward the influence of interfacial tension was reported by Reisberg and Doscher in 1956. Using a system that combined an aqueous alkali with a surfactant, they measured interfacial tensions less than 0.01 dynes/cm. With this same chemical system they recovered 100 percent of the oil from sand packs and more than 90 percent from Torpedo sandstone cores. Wagner and Leach showed that oil recovery increases when interfacial tension is reduced to about 0.07 dynes/cm and that further small decreases in interfacial tension result in large increases in oil recovery. In 1968, Taber presented theoretical and experimental results that presented theoretical and experimental results that further clarify the relation between residual oil saturation and Delta p/L sigma. He recognized that this correlation group should include the contact angle, but because of difficulties in systematically varying or indeed in even measuring the contact angle inside rocks, he examined the effects of the other parameters only. For Berea cores Taber found that a significant quantity of discontinuous oil (residual) was displaced when the ratio of Delta p/L sigma reached a value of about 5 (psi/ft)/(dynes/cm). He designated this as the critical value of the ratio and noted that further increases in the value of this ratio invariably produce more residual oil. He concluded that nearly 100 percent of the residual oil can be displaced if very high values of Delta p/L sigma, can be obtained. Gogarty and Tosch have recently discussed the principles of micellar surfactant systems. principles of micellar surfactant systems. JPT P. 186

The effect of the processing and formulation parameters on the size of nanoparticles based on block copolymers of poly(ethylene glycol) and poly( N-isopropylacrylamide) with and without hydrolytically sensitive groups

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 109965, "Low- Salinity Waterflooding To Improve Oil Recovery - Historical Field Evidence," by Eric P. Robertson, SPE, Idaho National Laboratory, prepared for the 2007 SPE Annual Technical Conference and Exhibition, Anaheim, California, 11-14 November. The paper has not been peer reviewed. Crude-oil/water/rock interactions can lead to large variations in the displacement efficiency of waterfloods. Laboratory waterflood tests and single-well tracer tests in the field have shown that injection of low-salinity water can increase oil recovery, but testing on a multiwell-field scale has not yet been undertaken. Three Minnelusa-formation waterfloods in the Powder River basin of Wyoming were compared on the basis of salinity of the formation and injection water and of reservoir characteristics. Introduction Different wetting states of crude-oil, water, and rock ensembles can yield different oil recoveries from laboratory-waterflood tests. The wetting state, or wettability, of a rock/fluid system can be altered. In the laboratory, wettability can be altered by changing the crude-oil composition, changing the temperature while aging the rock and crude oil, or by changing the temperature during water displacement. Also, water composition can have a significant effect on wettability and on oil recovery. Therefore, cases may exist in which attention to injection-water composition could increase oil recovery, and, likely, increase the economic profitability of a waterflood. An optimal composition of dissolved solids in the injection water may exist that would yield the highest oil recovery. The composition could involve many variables with respect to ionic composition and concentration, but current knowledge of how and when water composition can be manipulated to increase oil recovery is limited. Several examples of improved recovery by injecting low-ionic-strength brine have been reported for both outcrop- and field-core samples. Fig. 1 shows the potential for increased oil recovery from low-salinity waterflooding. These corefloods were performed on two cores from the CS reservoir under identical conditions except for the composition of the injected water. The conditions necessary for improved recovery, such as the type of crude oil and rock, composition of the formation and injected waters, and initial water saturation, still are not understood fully. The crude-oil/water/rock interactions that determine displacement efficiency are highly complex. Nevertheless, laboratory observations were sufficiently encouraging to justify more studies aimed at field application. The Idaho National Laboratory (INL) through funding from the US Department of Energy searched historical waterflood records for anecdotal evidence of increased oil recovery resulting from the injection of lower-salinity water to displace oil in reservoirs with higher-salinity initial formation water. The objective was to research and compare historical field data and to compare waterflood responses from low-and high-salinity injection waters.

Recent laboratory and mechanistic modeling studies have demonstrated that CO2-foam has the potential to recover additional oil in fractured water flooded chalk rock with low matrix permeability. The CO2-foam processes were carried out in short core plugs by injecting pre-formed foam at 340 bar and 55°C. The fractured model was represented by core plug with a 0.3 cm diameter hole drilled though the centre, and packed with monodispersed glass beads. Calculated mobilities also indicated that CO2-foam is highly effective in decreasing the mobility of CO2 and increasing the apparent viscosity of CO2 in fractured chalk rock. In this work, mechanistic simulation studies based on history-matched foam models tuned to laboratory data are used to investigate the effect of the strength of pre-formed foam and the role of gravity forces on oil recovery in long fractured chalk models. Pre-formed foam was injected either horizontally or vertically (from the bottom) at 340 bar and 55°C. Pure CO2 injection was also injected in fractured chalk models and used as base cases. The foam qualities and water saturation were varied. Results indicate that decreasing the foam quality increases the rate of oil production with both horizontal and vertical injection of pre-formed foam. However, the oil recovery efficiency with horizontal injection of pre-foamed foam was higher than with vertical injection. The simulation results show that molecular diffusion is an important oil recovery mechanism in chalk fractured rock with low matrix permeability and should be taken into account, and that considerable gravity effect can affect the oil recovery in horizontal injection of pre-formed foam. The mechanistic models can be used to study CO2-foam processes in fractured chalk reservoirs with multiple fractures.

L–Arabinose-based coordination polymers were synthesized by the oxidation of L–arabinose using warm HNO3 to form arabinaric acid and allowing the resulting arabinaric acid to react with the different metal ions such as zinc(II), lead(II), copper(II), iron(III), and chromium(III). Only zinc(II) and lead(II) ions produced crystalline coordination polymers suitable for analysis while copper(II) produced a gummy solid. Preliminary characterization of the coordination polymers was based on their solubility, melting points, UV–Visible spectra, and infrared spectra. The coordination polymers were insoluble in common organic solvents and in acidic aqueous solutions but soluble in moderately basic aqueous solutions (pH 12). The zinc(II) and lead(II) coordination polymers have melting points above 300°C while the copper(II) polymer melts from 218–225°C. UV–Visible spectra showed that these polymers have maximum absorption in the ultraviolet region. Zinc(II), lead(II), and copper(II) arabinarate coordination polymers had maximum absorbance at λmax = 217 nm, λmax = 240 nm, and λmax = 220 nm, respectively. The infrared spectra of the coordination polymers indicated the association of the arabinarate ligand with the metal ions. Introduction and incorporation of molecular species such as azobenzene and molecular iodine to the coordination polymers were also investigated. Infrared spectra obtained from the azobenzene inclusion experiments showed additional infrared absorption bands below 1000 cm –1 implying absorption of azobenzene within the polymers. Iodometric titrations also confirmed the inclusion of iodine in the coordination polymers. The potential of the coordination polymers to incorporate lead(II) ions in aqueous solutions was also investigated using column elution of different sample concentrations of lead(II). Atomic Absorption Spectrometric analysis illustrated significant lead reduction of up to 80.70 ppm of lead(II) on the eluted samples. Introduction Rapid industrialization in the modern world today causes severe pollution in the environment. This may be due to toxic, inorganic, or non-biodegradable materials released to the environment as waste products during industrial processes. Heavy metals, like lead, are among the most harmful of the environmental elemental pollutants. Lead contamination from excessive exposure has been found to cause several health hazards and long term detrimental effects. Prominent conventional processes for the removal of lead from aqueous mixtures, such as sludge separation, chemical precipitation, and electrochemical treatments are relatively expensive and can cause secondary pollutants (Manahan, 1993 as cited in Acabal et al., 2000). Due to the problems of pollution, “green” industrial productions of compounds and their derivatives based on renewable starting materials and biodegradable products are developed (Kiely, 2001). Carbohydrates are biodegradable, widely available, and generally economical. Hence, their study for chemical and industrial applications would be very sensible. Because of their ease in functionalization forming sugar derivatives, they could serve as valuable building blocks for potentially useful polymers (Abrahams et al., 2003). Heavy metal sequestering properties of certain types of these polymers provide an alternative and potentially economical treatment process for heavy metal removal and recovery.

Detailed understanding of the interaction between dyes and additives and the aggregation behaviour of the dye molecules in aqueous solutions is required to develop ink‐jet ink for textiles. In the present study, the aggregation behaviour of three acid dyes (CI Acid Red 88, CI Acid Red 13 and CI Acid Red 27) containing different number of sulphonate groups in aqueous solutions was investigated by means of visible absorption spectroscopy. As a result, the higher the solubility of the dyes in water (the larger the number of sulphonate groups in the dyes), the lower are the aggregation constants of the dyes. For all the dyes, the aggregation constants decreased with increasing temperature, indicating the exothermic process of the dye aggregation. The thermodynamic process for CI Acid Red 88 with one sulphonate group is less enthalpic and more entropic than that for CI Acid Red 13, which contains two sulphonate groups. CI Acid Red 27, which includes three sulphonate groups, hardly forms any aggregates. To elucidate the effects of the polymer additive, the binding constants of the dyes with the water‐soluble polymer, poly(vinylpyrrolidone) and the aggregation constants of the dyes in aqueous polymer solutions were also estimated. In addition, the binding constants were influenced by the number of sulphonate groups in the acid dyes: the larger number of sulphonate groups diminished the binding constants. The aggregation constants in the presence of poly(vinylpyrrolidone) were smaller than those in its absence at every temperature for all dyes. This suggests that poly(vinylpyrrolidone) has disaggregation effects. Furthermore, poly(vinylpyrrolidone) makes the aggregation process less enthalpic with a greater entropic change. Thus, the aggregation process of the dyes in the polymer solutions is thermodynamically different from that in water, reflecting the interactions between the dyes and the polymer.

A droplet impinging on a solid substrate can result in liquid spreading, recoil, column formation/breakup, partial or complete rebound, or splash. These outcomes are governed by liquid density, viscosity, and surface tension along with surface wettability and roughness. This chapter discusses the recent developments in modeling Newtonian drop spread-recoil dynamics on a solid surface and provides a review of post-impact drop–surface interactions for aqueous surfactant and polymeric solutions. In aqueous solutions, surfactant molecules diffuse toward interfaces and are adsorbed there. As a result, the liquid–gas interfacial tension changes with surface age and the equilibrium tension is a function of surfactant concentration. The timescale of droplet deformation is often comparable to the timescale of surface tension relaxation of surfactant solutions which affects the surface deformation, spread-recoil oscillations, and column breakup. Furthermore, physisorption of surfactant molecules on the substrate alters its wettability and affects the spread-recoil phenomena. Aqueous polymeric solutions exhibit non-Newtonian viscous behavior, where their apparent viscosity is a function of the shear rate. The complex interplay between dynamic changes in interfacial properties and liquid deformation produces drop spread-recoil dynamics that is vastly different from their pure, Newtonian counterparts. Over last two decades, high-speed videography, computational simulations, and analytical modeling have provided useful understanding of droplet impact phenomena that unfolds over timescales of milliseconds or less for these complex fluids. Current understanding of the effect of dynamic changes in interfacial properties on the outcomes of droplet impact is presented in this chapter.

ABSTRACTIn recent years, polymer flood of heavy oil has been extensively studied in laboratories and successfully applied in several fields. Polymer flooding is the most successful chemical enhanced oil recovery method. However, still, the need for a large amount of polymer, leading to high operational costs, presents a big challenge in technologies. This challenge can be addressed by considering the newly emerging nanomaterials. In this work, the author focuses on roles of TiO2 nanoparticles on polymer viscosity and improve recovery in heavy oil recovery. He present the results obtained from a coreflood experiment with polymer injection in heavy oil at 1320 mPa.sec viscosity. Nanopolymer exhibits an outstanding flow behavior and enhanced oil recovery performance in coreflood displacement tests compared to base polymers. The results indicate that polymer flooding with higher viscosity can significantly improve oil recovery. Flooding test showed about 4% increase in oil recovery for nanopolymer solution in comparison with polymer solution after one pore volume fluid injection.

An experimental study was conducted on the flow of aqueous solutions of detergent through mesh screens to mimic cloth washing. Pressure losses across the mesh screens were measured for water, dilute polymer and several aqueous detergent solutions. A reduction of pressure losses was observed for the flow of aqueous solutions of low molecular weight surfactants such as Laurylether (AE), Laurylbenzene-sulfonic acid-sodiumsalt (LAS), Benzalkonium-chloride (BC) Sodium-dodecyl-sulfate (SDS), and Hexadecyltrimetyl-ammonium-bromide (CTAB), but not for the high molecular weight polymers like Polyethylene-oxide (PEO18) and Polyacrylamide (PAA), through mesh screens. A flow visualization experiment was carried out to observe the flow pattern upstream and downstream of the mesh screen. Photographic images revealed that, instead of an expected large converging flow from the upstream section into the screen opening as in orifice flow, the bulk of the liquid entering the screen aperture took the form of a liquid column of similar diameter as the inlet tube. Based on this observation, a flow model, which led to a new set of definitions of Reynolds number and drag coefficient, was proposed. Good correlations of drag coefficient and Reynolds number were obtained for all test solutions, and the drag reduction phenomenon was manifested for detergent aqueous solutions.

Enhanced oil recovery (EOR) in shale reservoirs has been recently shown to increase oil recovery significantly from this unconventional oil and gas source. One of the most studied EOR methods in shale reservoirs is gas injection, with a focus on carbon Dioxide (CO2) mainly due to the ability to both enhance oil recovery and store the CO2 in the formation. Even though several shale plays have reported an increase in oil recovery using CO2 injection, in some cases this method failed severely. This research attempts to investigate the ability of the CO2 to mobilize crude oil from the three most prominent features in the shale reservoirs, including shale matrix, natural fractures, and hydraulically induced fracture. Shale cores with dimensions of 1 inch in diameter and approximately 1.5 inch in length were used in all experiments. The impact of CO2 soaking time and soaking pressure on the oil recovery were studied. The cores were analyzed to understand how and where the CO2 flowed inside the cores and which prominent feature resulted in the increase in oil recovery. Also, a pre-fractured core was used to run an experiment in order to understand the oil recovery potential from fractured reservoirs. Results showed that oil recovery occurred from the shale matrix, stimulation of natural fractures by the CO2, and from the hydraulic fractures with a large volume coming from the stimulated natural fractures. By understanding where the CO2 will most likely be most productive, proper design of the CO2 EOR in shale can be done in order to maximize recovery and avoid complications during injection and production which may lead to severe operational problems.

A recently developed microfluidic device, the optimized shape cross-slot extensional rheometer or OSCER [S. J. Haward, M. S. N. Oliveira, M. A. Alves, and G. H. McKinley, “Optimized cross-slot flow geometry for microfluidic extensional rheometry,” Phys. Rev. Lett. 109, 128301 (2012)10.1103/PhysRevLett.109.128301], is used to investigate the stability of viscoelastic polymer solutions in an idealized planar stagnation point flow. Aqueous polymer solutions, consisting of poly(ethylene oxide) and of hyaluronic acid with various molecular weights and concentrations, are formulated in order to provide fluids with a wide range of rheological properties. Semi-dilute solutions of high molecular weight polymers provide highly viscoelastic fluids with long relaxation times, which achieve a high Weissenberg number (Wi) at flow rates for which the Reynolds number (Re) remains low; hence the elasticity number El = Wi/Re is high. Lower concentration solutions of moderate molecular weight polymers provide only weakly viscoelastic fluids in which inertia remains important and El is relatively low. Flow birefringence observations are used to visualize the nature of flow instabilities in the fluids as the volumetric flow rate through the OSCER device is steadily incremented. At low Wi and Re, all of the fluids display a steady, symmetric, and uniform “birefringent strand” of highly oriented polymer molecules aligned along the outflowing symmetry axis of the test geometry, indicating the stability of the flow field under such conditions. In fluids of El > 1, we observe steady elastic flow asymmetries beyond a critical Weissenberg number,Wicrit, that are similar in character to those already reported in standard cross-slot geometries [e.g., P. E. Arratia, C. C. Thomas, J. Diorio, and J. P. Gollub, “Elastic instabilities of polymer solutions in cross-channel flow,” Phys. Rev. Lett. 96, 144502 (2006)10.1103/PhysRevLett.96.144502]. However, in fluids with El < 1 we observe a sequence of time-dependent inertio-elastic instabilities beyond a critical Reynolds number, Re crit, characterized by high frequency spatiotemporal oscillations of the birefringent strand. By plotting the critical limits of stability for the various fluids in the Wi-Re operating space, we are able to construct a stability diagram delineating the distinct steady symmetric, steady asymmetric and inertio-elastic flow regimes in this idealized planar elongational flow device.

A recently developed microfluidic device, the optimized shape cross-slot extensional rheometer or OSCER [S. J. Haward, M. S. N. Oliveira, M. A. Alves, and G. H. McKinley, “Optimized cross-slot flow geometry for microfluidic extensional rheometry,” Phys. Rev. Lett. 109, 128301 (2012)10.1103/PhysRevLett.109.128301], is used to investigate the stability of viscoelastic polymer solutions in an idealized planar stagnation point flow. Aqueous polymer solutions, consisting of poly(ethylene oxide) and of hyaluronic acid with various molecular weights and concentrations, are formulated in order to provide fluids with a wide range of rheological properties. Semi-dilute solutions of high molecular weight polymers provide highly viscoelastic fluids with long relaxation times, which achieve a high Weissenberg number (Wi) at flow rates for which the Reynolds number (Re) remains low; hence the elasticity number El = Wi/Re is high. Lower concentration solutions of moderate molecular weight polymers provide only weakly viscoelastic fluids in which inertia remains important and El is relatively low. Flow birefringence observations are used to visualize the nature of flow instabilities in the fluids as the volumetric flow rate through the OSCER device is steadily incremented. At low Wi and Re, all of the fluids display a steady, symmetric, and uniform “birefringent strand” of highly oriented polymer molecules aligned along the outflowing symmetry axis of the test geometry, indicating the stability of the flow field under such conditions. In fluids of El &amp;gt; 1, we observe steady elastic flow asymmetries beyond a critical Weissenberg number,Wicrit, that are similar in character to those already reported in standard cross-slot geometries [e.g., P. E. Arratia, C. C. Thomas, J. Diorio, and J. P. Gollub, “Elastic instabilities of polymer solutions in cross-channel flow,” Phys. Rev. Lett. 96, 144502 (2006)10.1103/PhysRevLett.96.144502]. However, in fluids with El &amp;lt; 1 we observe a sequence of time-dependent inertio-elastic instabilities beyond a critical Reynolds number, ${\mathop{\rm Re}\nolimits} _{crit} $ Re crit, characterized by high frequency spatiotemporal oscillations of the birefringent strand. By plotting the critical limits of stability for the various fluids in the Wi-Re operating space, we are able to construct a stability diagram delineating the distinct steady symmetric, steady asymmetric and inertio-elastic flow regimes in this idealized planar elongational flow device.