CO2 Emulsion Research Articles

Replacement of Methane from Hydrates in Porous Sediments with CO2-in-Water Emulsions

CO2-in-water emulsions formed from polyoxyethylene sorbitan monooleate (Tween 80) and sodium dodecyl sulfate (SDS) were evaluated in terms of stabilization time and emulsion droplet distribution. A CO2 emulsion with 0.5 wt % SDS + 5 wt % Tween 80 was found to be more stable than the other emulsions. With an increase in the stirring rate or pressure or a decrease in the temperature, the size of CO2 emulsion droplets tended to be smaller, and the stabilization time of the CO2 emulsion increased. With the optimized CO2 emulsion, the CH4–CO2 replacement reaction in a hydrate-bearing quartz sand sample was performed in a three-dimensional reactor. In the emulsions, the function of Tween 80 is to make the emulsion much more hydrophilic and reduce the flow resistance of the emulsion, whereas that of SDS is to make the newly formed hydrate particles/layers more granular and looser. The results indicate that, for hydrate reservoirs located in the stability fields of both CO2 hydrate and methane hydrate, the replacement efficiency of the CO2 emulsion can reach 47.8%, higher than those of liquid CO2 and gaseous CO2. The addition of 3.35 wt % salt to the emulsion can prevent the pore spaces of sediments from being blocked.

Gelled Emulsions of CO2, Water, and Nanoparticles

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 166072, ’Gelled Emulsions of CO2/Water/Nanoparticles,’ by Fawaz M. Al-Otaibi, Sunil L. Kokal, Yun C. Chang, Jassi F. Al-Qahtani, and Amin M. Al-Abdulwahab, Saudi Aramco, prepared for the 2013 SPE Annual Technical Conference and Exhibition, New Orleans, 30 September-2 October. The paper has not been peer reviewed. Enhanced oil recovery (EOR) by carbon dioxide (CO2) injection is an effective method for recovering additional oil beyond waterflooding. However, the CO2-EOR process is handicapped, especially in thick reservoirs, by CO2 gravity override. Because of density differences between the injected CO2 and resident fluids in the reservoir, the lighter CO2 tends to rise to the top of the reservoir, thereby bypassing some of the remaining oil. This paper investigates the use of gelling CO2/water emulsions, stabilized by silica nanoparticles, to control the mobility of CO2. Introduction The CO2-EOR process, while increasingly important, is handicapped by several challenges. The first challenge is the gravity override of the injected CO2 because of density differences between the injected CO2 and resident fluids in the reservoir. The second is viscous fingering caused by the lower viscosity of the injected CO2. Typical dense CO2 viscosity at reservoir conditions is in the range of 0.05–0.1 cp, which is much lower than the viscosity of resident oil and brine. The resulting unfavorable mobility ratio leads to viscous fingering, causing early CO2 breakthrough, high CO2-usage factors, poor sweep efficiency, and low overall oil recovery. The third challenge associated with CO2 EOR is reservoir geology and heterogeneities, including high-permeability streaks and fractures that can impact the sweep efficiency of a CO2-EOR flood. Most of these challenges have been countered by use of water-alternating-gas (WAG) processes. Although the WAG process improves the mobility of CO2, it loses its effectiveness in controlling CO2 mobility deep into the reservoir and beyond a certain distance from the wellbore. This paper discusses another technique that provides an excellent alternative to WAG to control CO2 mobility: the CO2/foam emulsion. The main purpose of using CO2 foams is to increase the viscosity of the CO2 and therefore reduce its mobility through the reservoir. This emulsion is generated with water-soluble surfactants, CO2-soluble surfactants, or nanoparticles. This paper investigates the use of gelling CO2/water emulsions, stabilized by silica nanoparticles, to control the mobility of CO2.

Mechanical properties of Cu electroplated in supercritical CO2 emulsion evaluated by micro-compression test

This paper reports mechanical properties of Cu films fabricated by electroplating with supercritical CO2 emulsion (EP–SCE). Also, mechanical properties of Cu films fabricated by conventional electroplating (CONV) were evaluated to examine the effects of EP–SCE. The films were electroplated in an electrolyte composed of copper sulfate plating bath, supercritical CO2 and surfactant. Scanning ion microscopy images confirmed the supercritical CO2 emulsion refined microstructure of the plated Cu from about 1μm of grain size in CONV to about submicron order of grain size in EP–SCE. Non-tapered micro-sized Cu pillars were prepared by focused ion beam and used in the micro-compression test. Strengths of the Cu films fabricated by EP–SCE were 300MPa, which is higher than the CONV case. Impurity concentration in the films was evaluated by glow discharge optical emission spectroscopy, and no significant difference between EP–SCE and CONV was observed. The high strength in EP–SCE is believed to be mainly a result of grain refinement strengthening.

Porous nickel films plated in supercritical carbon dioxide emulsified electrolyte using a series of fluorinated nonionic surfactants

Thin porous Ni films were fabricated in supercritical CO2 (Sc-CO2) emulsion with a series of nonionic fluorinated surfactants, F(CF(CF3)CF2O)3CF(CF3)COO(CH2CH2O)nCH3 (denoted as PFP3-EOn where n=1, 2 and 5). The film morphology and size distribution of pores were studied as a function of number of ethylene oxide groups and different concentrations of surfactants. Surfactant PFPO3-EO1 from low to medium concentrations showed a narrow size distribution of shallow pores on the films, and at high concentration it showed shallow pores and some large size deep pores. Surfactant PFPO3-EO2 at low concentration showed a narrow size distribution of shallow and deep pores on the film, and from medium to high concentrations the size distribution of deep pores increased. Compared to other surfactants, for all concentrations, surfactant PFPO3-EO5 showed a broad size distribution of deep pores, and it showed shallow pores only up to medium range of concentration. The increase of ethylene oxide groups and concentration of surfactants increased the size distribution of pores and decreased the number of pores on the films. There was a significant decline in the number of pores by the surfactant PFPO3-EO5. Sc-CO2 emulsion assisted Ni deposition using a series of nonionic fluorinated surfactants and concentrations shows great promise as a method to control porous structure on the plated films.

Fabrication of through-silicon vias by supercritical CO2 emulsion-enabled nickel electroplating

Compared to the 2D plane, 3D integrated circuit (IC) structure could provide larger patterning areas by stacking the multi-planar chips, in which the electrical signals can be vertically conducted via through-silicon vias (TSVs). Thus, its advantages are lowered costs and reduced packaging space, size and weight. In this study, the TSVs used for 3D integration are fabricated and characterized. Four through holes with a diameter of 70μm on a silicon wafer are first etched by inductively coupled plasma reactive ion etch (ICP) and filled by nickel electroplating in supercritical CO2 emulsion. The chip is cut for observation and examination of the cross-sectional view of the TSVs. For hermeticity testing, a helium leaking detector was performed on all TSVs before and after the heat treatment process (heating up to 350°C). The average electrical resistance across the TSVs was measured to be 0.01Ω. Then the fabricated TSVs can be applied a maximum current of 10A continuously without burnout.

Control of Pore Structure in Porous Nickel Films Fabricated by Electroplating with Supercritical CO2 Emulsion

Control of Pore Structure in Porous Nickel Films Fabricated by Electroplating with Supercritical CO2 Emulsion

Quantitative study on removal of SU-8 photoresist patterns by supercritical CO2 emulsion

Supercritical CO2 emulsion (SCE) was found to be effective in removal of epoxy-type SU-8 photoresist. The ability to remove SU-8 was compared between a commercially available Remover PG (RPG) solution and SCE. Both RPG and SCE were effective in removing not-hard-baked SU-8 dots, with height of [email protected] and diameter ranged from 50 to [email protected] When the SU-8 dots were hard-baked at 150^oC for 10min, RPG could not remove any of the SU-8 dots. On the other hand, SCE could still remove 42.11% of the [email protected] SU-8 dots. When the SU-8 dots were hard baked at 200^oC for 10min, 5.75% of the [email protected] SU-8 dots could be removed by SCE.

Mechanical properties of nickel fabricated by electroplating with supercritical CO2 emulsion evaluated by micro-compression test using non-tapered micro-sized pillar

This paper reports mechanical properties of nickel films fabricated by high pressure electroplating (HPE) and electroplating with supercritical CO2 emulsion (ESCE). Structures and mechanical properties of the plated films were examined by TEM, electron backscattered diffraction analysis and micro-compression test using a non-tapered micro-sized pillar. The films were electroplated in an electrolyte composed of Watts bath, supercritical CO2 and surfactant. Agitation in ESCE leads to the formation of many CO2-in-water type micelles. The micelles would cause an effect called periodic plating characteristic, and this effect refined the microstructure of the plated nickel from 3@mm of columnar grained structure to 8nm diameter of equiaxial grained structure. Mechanical properties were also improved to 3.5GPa of compressive strength, which was five times higher than the HPE nickel. The high strength in ESCE is believed to be largely a result of grain refinement and carbon impurity.

S082017 CO2を利用するメタンハイドレートの増進回収法 : 生産対象層を模擬した実内実験の結果([S082]高効率火力発電およびCCS技術)

When CO2 is injecting into marine sediments, CO2 forms solid CO2 hydrate and it blocks voids of the sediments. So an injecting method is necessary for long term injection in order to use CO2 for methan hydrate recovery. We have been focused into the exothermic heat of CO2 hydrate. The heat can warm saturated Toyoura sands by about 9 degrees centigrade. This means that the layers are warmed to phase equilibrium. We have shown CO2 can flow at the phase equilibrium temperature. CO2/water emulsion can generate heat at the top of flow without blocking the voids. The emulsion flows through sands at the phase equilibrium temperature. This function of CO2 emulsion shows a possibity for enhanced recovery of methane hydrate using CO2.

Effects of pressure on electroplating of copper using supercritical carbon dioxide emulsified electrolyte

Electroplating of Cu with supercritical CO2 emulsion (SCE) is studied to clarify the effects of SCE in the electroplating reaction. Properties of the SCE can be adjusted by pressure. Size and size distribution of the dispersed phase are reduced by increasing pressure, which is expected to promote the transfer efficiency of Cu2+ into the diffusion layer and causes a decrease in on-time of the periodic-plating-characteristic in the electroplating with SCE (ESCE). A minimum value for both surface roughness and grain size was observed for the Cu films electroplated at 15MPa when pressure was increased from 9 to 21MPa. The most positive potential response was observed for ESCE also at 15MPa in chronopotentiometry. Therefore, we believed a critical size for the dispersed phase was reached at roughly 15MPa to cause the phenomena observed.

A Review on Research on Replacement of CH4 in Natural Gas Hydrates by Use of CO2

This paper introduces the research advances on replacement of CH4 in Natural Gas Hydrates (NGHs) by use of CO2 and discusses the advantages and disadvantages of the method on the natural gas production from such hydrates. Firstly, the feasibility of replacement is proven from the points of view of kinetics and thermodynamics, and confirmed by experiments. Then, the latest progress in CH4 replacement experiments with gaseous CO2, liquid CO2 and CO2 emulsion are presented Moreover, the superiority of CO2 emulsion for replacement of CH4 is emphasized. The latest experiment progress on preparation of CO2 emulsions are introduced. Finally, the advancements in simulation research on replacement is introduced, and the deficiencies of the simulations are pointed. The factors influencing on the replacement with different forms of CO2 are analyzed and the optimum conditions for the replacement of CH4 in hydrated with different forms of CO2 is suggested.

Direct Observation of Nodule Growth on Electroless Ni-P Deposition in Supercritical CO2 Emulsion

We have proposed a novel electroless plating using supercritical carbon dioxide emulsion (ELP-SCE) to obtain uniform and void-free Ni-P films. This reaction was conducted in emulsion of carbon dioxide (CO2) in Ni-P electroless plating solution with surfactant, and it showed an effect of nodules growth suppression. In this paper, we examine a direct observation of selected nodule growth in electroless plating reaction using atomic force microscope (AFM) on a square sample substrate of 50×50 μm fabricated by focused ion beam (FIB). The Ni-P film was plated by ELP-SCE again on the Ni-P plated film with nodule, which was formed by the conventional method. Changes in fine nodules and other areas at a specific position in the surface morphology were compared before and after the re-plating. In conventional method, nodules grew dominantly, while the growth was suppressed in ELP-SCE and the nucleation dominantly occurred in the surrounding regions of the nodules.

Effects of CO2 on Ni–P Electroless Plating in an Emulsion of Supercritical CO2

This paper reports experiments to demonstrate the effects of carbon dioxide on a Ni–P film obtained in supercritical carbon dioxide emulsion. The Ni–P film obtained by electroless plating in emulsion was extremely uniform, conformal, and free from pinholes and nodules. Two features of the emulsion prevented defects: the stronger acidic solution attained via the dissolution of and the transport properties with the diffusive dense . The phosphorus concentration and film growth rate were compared between plating films fabricated by two electroless plating techniques, one in emulsion and one in Ni–P electroless solution alone. The phosphorus concentration of the film fabricated by electroless plating in emulsion (22.7 wt %) was far larger than that of the film fabricated by electroless plating in Ni–P solution alone at pH 4.0–5.3. The film growth rate was lower in the electroless plating technique carried out in emulsion than in that carried out in Ni–P solution alone at pH 5.3 and 4.0. On this basis, we conclude that the rate of film formation in electroless plating in the emulsion was strongly influenced by the high speed agitation and the decrease in the oxidation of the reducing agent due to the lower pH.

Biocompatible, Lactide-Based Surfactants for the CO2−Water Interface: High-Pressure Contact Angle Goniometry, Tensiometry, and Emulsion Formation

The unique properties of compressed CO2, including its low cost, nontoxicity, easily tunable solvent strength, and favorable transport properties, make it an environmentally attractive alternative to volatile organic solvents. Suitable surface-active species can be utilized to realize the full potential of clean, CO2-based technologies, by helping to overcome the low solubility typically associated with many solutes of interest in CO2. In this work we synthesize and investigate the interfacial activity of a series of nonionic amphiphiles with a biocompatible and biodegradable CO2-phile at both the CO2-water (C|W) and CO2-water-solid (C|W|S) interfaces. We developed a high-pressure pendant drop tensiometer and contact angle goniometer that allows us to measure both tension and contact angle in tandem. The tension of the C|W interface was measured in the presence of the lactide (LA)-based surface active agents with varying molecular weight and hydrophilic-to-CO2-philic ratios. Emulsion studies with an optimum balanced surfactant were performed. The contact angle of water droplets against a silane-modified (hydrophobic) substrate under CO2 atmosphere was also measured in presence of a selected LA-based amphiphile. The results demonstrate that the nonionic copolymers with the biodegradable and biocompatible LA-based group can significantly reduce the tension of the C|W interface. The LA-based surface active species are also capable of forming stable emulsions of water and CO2 and reducing the angle of the three-phase C|W|S contact line.

Stubby Surfactants for Stabilization of Water and CO2 Emulsions: Trisiloxanes

Amphiphiles of a new class, with very short and bulky CO2-philic headgroups, the trisiloxane surfactants of the form ((CH3)3SiO)2Si(CH3)(CH2)3EOnR, where EO stands for ethylene oxide, are shown to be very interfacially active at the CO2−water interface, as indicated by their effectiveness in forming and stabilizing both concentrated and dilute emulsions of water and CO2. A transition in morphology from water-in-CO2 (W/C) to CO2-in-water (C/W) emulsions is induced by manipulating the surfactant hydrophilic-to-CO2-philic balance (HCB) through variation of the number of EO groups. This inversion in morphology is in agreement with a minimum in interfacial tension at the water−CO2 interface. Microscopy and turbidimetry are used to follow the time evolution of the particle size and stability of dilute W/C emulsions. Dilute W/C emulsions formed with a trisiloxane surfactant containing seven EO groups show unparalleled stability against flocculation, indicating effective solvation of the trisiloxane group by CO2....

Formation of Carbon Dioxide in Water Miniemulsions Using the Phase Inversion Temperature Method

The curvature of an emulsion of CO2 and brine stabilized with a triblock copolymer of poly(dimethylsiloxane) (PDMS) and poly(ethylene oxide) (PEO), PEO-b-PDMS-b-PEO, was inverted from H2O-in-CO2 to CO2-in-H2O (C/W) by reducing the temperature. A “v-shaped” trough was observed in the interfacial tension between the aqueous and CO2 phases versus temperature at constant CO2 density. The minimum in the interfacial tension coincided with the phase inversion temperature (PIT) where the curvature of the emulsion inverts. Novel C/W miniemulsions consisting of 200 nm droplets, measured by multiwavelength turbidimetry, were formed by low-shear stirring in the low interfacial tension PIT region and then cooling to 25 °C. These droplets were 3 times smaller than those produced isothermally by high shear at a temperature below the PIT region.

Mapping the Stability and Curvature of Emulsions of H2O and Supercritical CO2 with Interfacial Tension Measurements

ABSTRACT The stability and curvature of emulsions of H2O and CO2 are reported and analyzed in terms of measurements of interfacial tension versus formulation variables, including salinity, CO2 density, temperature and pH. Among the surfactants studied are, quaternary ammonium cationic ones with perfluoropolyether tails, block copolymer ionomers and a poly (hydroxyethyl methacrylate) with polydimethylsiloxane tails, and a nonionic ethylene oxide surfactant with a fluoroalkane tail. The interfacial tension measurements were made at surfactant concentrations from 0.05 to 1.0 wt% with a variable-volume pendant drop tensiometer up to 345 bar and 363°K. As a formulation variable was varied, the system reached a balanced state characterized by a minimum in interfacial tension, a loss in emulsion stability and in some cases an inversion from a W/C to C/W emulsion. Here the Marangoni-Gibbs stabilization weakens, and also it becomes easy to bend and rupture the surfactant monolayer, causing coalescence. Except in the case of the nonionic fluorinated surfactant C8F17—SO2NEt-(CH2CH2O)12–14CH3, the crossover from the CO2-continuous (W/C) to the H2O-continuous (C/W) emulsion occurred abruptly due to clouding of the surfactant out of the CO2 phase. For PFPE-TMAA, the plot of γ versus surfactant concentration revealed both pre-micellar aggregates and a critical micro emulsion, each of which was dependent on salinity.

Mapping the Stability and Curvature of Emulsions of H2O and Supercritical CO2 with Interfacial Tension Measurements

Mapping the Stability and Curvature of Emulsions of H2O and Supercritical CO2 with Interfacial Tension Measurements

Carbon dioxide flooding for enhanced oil recovery: Promise and problems

AbstractOf the enhanced oil recovery methods currently being considered for application to many of the nation’s older oil fields, carbon dioxide flooding may offer the largest potential for additional oil recovery. The physical mechanisms by which CO2 contacts and mobilizes crude oil are reviewed. Influence on the displacement process of factors such as the phase behavior of CO2‐crude oil mixtures, swelling of oil by dissolved CO2, and reduction of oil viscosity are considered. Adverse effects of the viscous instability which occurs when very low viscosity CO2 displaces the more viscous oil and water are dicussed. Advantages and disadvantages of three potential methods for controlling the mobility of CO2 are reviewed: thickening CO2 with polymeric additives, reduction of CO2 mobility by high water saturations, and use of surfactants to generate foam‐like emulsions of water and CO2. Field experience to date and the recent surge in field activity are discussed. Finally, a brief assessment of the future of CO2 flooding research and practice is offered.