Water-soluble Solvents Research Articles

A Study of Dimethyl Ether-Steam Coinjection Using a Large-Scale Physical Model

Summary Dimethyl ether (DME) as a water-soluble solvent has been studied as a potential additive to steam for improving the energy efficiency of steam-assisted gravity drainage (SAGD). The main objective of this research was to study in-situ flow characteristics and energy efficiency of DME-SAGD using a large-scale physical model. Results from DME-SAGD were compared with the control experiment of SAGD with no solvent injection using the same experimental setup. The main novelty of this research lies in the experimental data that demonstrated enhanced bitumen drainage by DME-SAGD in comparison with SAGD. The experiment was conducted in a cylindrical pressure vessel with a diameter of 0.425 m and a length of 1.22 m, which contained a sandpack with a porosity of 0.34 and a permeability of 5.0 darcies. The DME-SAGD experiment used a DME concentration of 10 mol% and a steam coinjection rate of 27.6 cm3/min [cold-water equivalent (CWE)] at 3000 kPa. Temperature distributions within the sandpack, along with injection and production histories, were recorded during the experiment. Subsequently, numerical simulations were performed to history match the experimental data, and the calibrated simulation model was used to analyze the details of compositional flow characteristics. Results showed that the 10 mol% DME-SAGD experiment yielded a recovery factor (RF) of 92.7% in 4.2 days, and the SAGD experiment yielded an RF of 68.6% in 6.0 days; for both experiments, the first 2 days were the preheating and the steam-only injection (SAGD) stages. The peak rate of bitumen production was 43.8 mL/min in the DME-SAGD experiment, which was more than twice greater than the peak rates observed in the SAGD experiment. The substantially increased rate of bitumen production resulted in a cumulative steam/oil ratio in DME-SAGD that was less than half of that in SAGD. Analysis of experimental results indicated that the solubility of DME in the aqueous and oleic phases caused different flow characteristics between DME-SAGD and SAGD. For example, the oleic and aqueous phases were more uniformly distributed in the sandpack in the former. Simulations indicated that DME-SAGD had a greater distribution of grid-scale inverse mobility ratio and increased oleic-phase mobilities in comparison with SAGD.

Advanced machine learning-based modeling of interfacial tension in the crude oil-brine-diethyl ether system: Insights into the effects of temperature and salinity

Solvent injection, a well-established method for enhanced oil recovery (EOR), has demonstrated significant improvements in oil recovery when compared with conventional water flooding techniques. The interfacial tension (IFT) is pivotal in determining the displacement efficiency and overall performance of innovative techniques like dimethyl ether-enhanced waterflooding (DEW), which has gained substantial attention in recent years. In this study, following laboratory measurements of IFT, six advanced machine learning (ML) techniques were employed: Generalized Linear Model (GLM), Generalized Additive Model (GAM), Random Forest (RF), Support Vector Machine (SVM), Extreme Gradient Boosting (XGBoost), and Boosted Regression Tree (BRT) to model the IFT in both oil-brine and oil-brine-diethyl ether (DEE) systems. The analysis is based on an extensive dataset comprising 7,017 data points for oil-brine and 6,949 data points for oil-brine-DEE systems obtained from experimental studies. The findings indicate that the developed RF model excels in predicting IFT, boasting a remarkable coefficient of determination (R2 = 0.99) along with the lowest root mean squared error (RMSE = 0.2), mean squared error (MSE = 0.04), and mean absolute error (MAE = 0.13). The study underscores the significance of optimizing salinity levels to achieve the most substantial reduction in IFT. This reduction is attributed to the enhanced migration of polar components, such as asphaltene molecules, to the interface of the oil-brine system. Moreover, the research highlights a synergistic decrease in IFT when both DEE and soluble ions are present, resulting in the lowest IFT at around 2 mN/m in 40,000 ppm salinity (S2) at 70 °C (T3). This indicates that the adsorption of DEE at the water–oil interface forms a layer capable of adsorbing ions, thereby enhancing the layer's thickness. As a result, the oil–solvent-ion layer becomes thicker compared to the oil-ion layer, leading to the maximum decrease in IFT. Additionally, with increasing temperature up to 70 °C, the IFT of both systems demonstrated a downward trend, as evidenced by all experiments. The outcomes of this study have the potential to enhance our comprehension of the underlying mechanisms involved in water-soluble solvent EOR techniques.

Gravity drainage of bitumen under controlled thermodynamic conditions in DME-steam co-injection

Dimethyl ether (DME), a water-soluble solvent, has been studied as a potential additive to steam for improving the efficiency of steam-assisted gravity drainage (SAGD) for bitumen recovery. This paper presents an experimental study of bitumen gravity drainage in DME-SAGD in comparison to SAGD and butane-SAGD (C4-SAGD).Small-scale experiments were conducted using a sand pack with a diameter of 1.5 inches and a length of 15 inches, which was housed inside a 25-L cylindrical steel vessel. A DME-SAGD experiment with 10 mol% DME was conducted at 3500 kPa with a total in-situ injection rate of 3897 cm3/min. Temperature distributions inside and outside the sand pack, as well as injection and production histories, were recorded during the experiment. Results were compared with previous studies of SAGD and C4-SAGD (20 mol% C4) that used the same experimental program. Then, numerical simulations were performed to history-match the experimental data and investigate the bitumen recovery mechanisms.The peak bitumen rate was 16.8 cm3/min for 10 mol% DME-SAGD, 9.8 cm3/min for SAGD, and 14.6 cm3/min for 20 mol% C4-SAGD. That is, DME was more effective than C4 as a steam additive even at the concentration reduced by half. The observed enhancement in bitumen drainage was attributed partly to the combined thermal and dilution effects on bitumen viscosity reduction, in which DME-SAGD exhibited a higher chamber-edge temperature than C4-SAGD. Furthermore, the oleic (L) and aqueous (W) phases were more evenly distributed with less gravity segregation in the sand pack in DME-SAGD than in SAGD and C4-SAGD, which facilitated the overall bitumen flow in the sand pack. Results collectively show that the slight polarity of DME as a solvent additive to steam enhanced the bitumen flow not only by L-phase viscosity reduction, but also by more uniformly enhanced bitumen flow in the sand pack.

A review of the mechanics of heavy-oil recovery by steam injection with chemical additives

The efficiency improvement of steam injection (more oil, less steam) is a critical challenge in heavy oil recovery. Using chemical additives is one option to achieve this efficiency improvement, but many different mechanisms are involved in this process, and different considerations need to be taken depending on the existing conditions and chemical type. For example, many tested thermally stable chemicals—surfactants, nanofluids, and water-soluble solvents—were able to favorably alter the wettability. The underlying physics behind this favorable alteration and other mechanisms are not well comprehended yet, especially for new generation chemicals under thermodynamic conditions. The comprehensive review and discussion presented in this paper mainly focus on the improvements on heavy-oil and bitumen thermal recovery, particularly on the late-stage steam injection as well as the fundamentals of the residual oil development mechanism post-steam injection. More importantly, this paper presents the experimental result-based, and comparative analyses of potential chemical additives (alkali, ionic liquid, surfactants, hydrocarbon solvents, water-soluble solvents, and new generation chemicals) applied to improve heavy oil recovery. This analysis is necessary not only to further evaluate the chemical's performance on the recovery improvement—specifically at the late-stage steam injection—but also to investigate the underlying recovery mechanisms, such as viscosity reduction, wettability alteration, interfacial tension (IFT) reduction, foaming effect, and emulsification presented by the chemical additives. Based on the outputs obtained from different experimental methodologies, the underlying recovery mechanisms induced by the potential chemical additives were identified. The results revealed that synergy among the recovery mechanisms presented by chemical additives could potentially improve the heavy oil recovery by more than 80% during steam injection. A comprehensive analysis of the mechanics of the heavy oil recovery provides valuable substantiation and understanding, honoring the potential implications of utilizing chemical additives as potential steam additives to the heavy oil recovery process. The results present beneficial information and recommendations for oil fields operating under steam injection applications.

Analytical and numerical study of thermal and solvent-based gravity drainage for heavy oil recovery

With the increasing demand for energy, an initial screening for heavy oil recovery options is important. However, the calculation of the gravity drainage recovery of heavy oil is complex and involves coupled fields and changes in the properties of heavy oil or its mixtures. There is currently no general analytical treatment for heavy oil gravity drainage processes, such as steam-assisted gravity drainage (SAGD), vapor extraction (VAPEX) and warm VAPEX, with the simplest possible assumptions but with the necessary mechanisms. In this study, a novel discrete hypothetical model has been proposed to simplify the calculation of gravity drainage flow in porous media. Then, a validated equation with a reasonable mixing rule is used to describe the property changes of heavy oil or its mixtures under decoupled temperature and concentration variables. Finally, internal velocity distributions for different gravity drainage processes are validated with numerical modeling results. Our results agree with previous work on the importance of mass transfer coefficients. Moreover, different from the previous work, the effect of slightly water-soluble solvents (dimethyl ether) has been investigated on diffusion in both the oil phase and the water phase. For solvent-based heavy oil recovery, a slightly water-soluble solvent shows great advantages with promising application potentials. The results of this study can guide the initial screening for a gravity drainage process and the analysis of its key mechanisms.

Oxygen-evolving hollow polydopamine alleviates tumour hypoxia for enhancing photodynamic therapy in cancer treatment.

Hypoxia, a characteristic hallmark of solid tumours, restricts the therapeutic effect of photodynamic therapy (PDT) for cancer treatment. To address this issue, a facile and nanosized oxygen (O2) bubble template is established by mixing oxygenated water and water-soluble solvents for guiding hollow polydopamine (HPDA) synthesis, and O2 is encapsulated in the cavity of HPDA. HPDA with abundant catechol is designed as a carrier for zinc phthalocyanine (ZnPc, a boronic acid modified photosensitizer) via borate ester bonds to fabricate nanomedicine (denoted as HZNPs). The in vitro and in vivo results indicate that O2-evolving HZNPs could alleviate tumour hypoxia and enhance PDT-anticancer efficiency. Melanin-like HPDA with a photothermal conversion rate (η) of 38.2% shows excellent synergistic photothermal therapy (PTT) efficiency in cancer treatment.

Polymer grafted gibbsite nanoplatelets via direct initiator tethering and surface-initiated atom transfer radical polymerization

An efficient method for the preparation of polymer grafted gibbsite nanoplatelets (NPs) was proposed by direct preparation of initiator-tethered gibbsite (gibbsite-Br) NPs followed by surface-initiated atom transfer radical polymerization (SI-ATRP) to obtain gibbsite particle brushes. By adding portion of water-soluble solvent (e.g., alcohol), individual ATRP initiator-tethered gibbsite NPs were fabricated using 2-bromo-2-methylpropionic acid as a tetherable initiator avoiding the aggregation of gibbsite NPs which are ready for polymer grafting process. To verify the efficiency of the tethered initiator, various polymers grafted gibbsite NPs were fabricated by SI-ATRP. The results indicated that initiator anchored gibbsite NPs and various gibbsite-g-polymers (e.g., gibbsite-g-poly2-(dimethylamino) ethyl methacrylate, gibbsite-g-polyacrylonitrile, gibbsite-g-polymethyl methacrylate) were synthesized successfully. The thermal stabilities of gibbsite-g-polymer hybrid materials have been enhanced significantly. Compared with PMMA matrix, the fire-retardant behavior of gibbsite-g-polymethyl methacrylate was strengthened due to the incorporation of gibbsite NPs. This work proposed a versatile and convenient method for producing initiator-immobilized solid NPs and polymer grafts, which thereby enables promised properties of polymer hybrid materials depending on the orientation and interactions of particle brushes.

Experimental Measurement of Molecular Diffusion and Evaporation Rate of Battery Organic Electrolytes in Ambient Air

In this paper, we measured the molecular diffusivity and evaporation rate of organic solvents—1,2-dimethoxyethane (DME), dimethyl carbonate (DMC), diethyl carbonate (DEC), and propylene carbonate (PC)—in ambient air, which are commonly used in light metal batteries, such as Li-ion, Li-air, and Na-O2 batteries. The measurement was conducted through the evolution of the evaporation rate of a liquid solvent in a glass tube, which was designed based on a one-dimensional (1-D) mass transfer model. The experiment successfully measured the diffusion coefficients of DME (0.0925 cm2 s−1), DMC (0.2116 cm2 s−1), and DEC (0.0569 cm2 s−1) in dry air, but failed for that of PC. The PC testing showed a liquid loss smaller than the measurement uncertainty due to its slow evaporation rate under the experimental condition. In the ambient air with the relative humidity (RH) of 50 ± 5%, higher water-soluble solvents showed more decrease in diffusivity calculation compared to that under the dry condition, which is likely due to uncertainty arising from water dissolving to the testing liquid. In addition, we also investigated the time constant for experimental measurement. For the organic liquids, the effective running time can be up to 10 days under room temperature.

Study of Molecular interaction in Binary Mixtures containing N, N-Dimethylformamide and n-Butanol

The acoustic studies of the interactions between alcohol molecules and water soluble polar solvent DMF are significant for understanding the relationships between structure and function of polar molecule like DMF, and for explaining the mechanisms of interaction of alcoholic OH group with an electronegative moiety. In this piece of work Ultrasonic velocity, density and viscosity have been measured at 298 K, 308 K, 318 K and 328 K for mixture of N,N-dimethylformamide (DMF) and n-butanol, the frequency being maintained at a constant value. The experimental data have been used to calculate the acoustical and thermodynamical parameters like adiabatic compressibility, free length, free volume, internal pressure, acoustic impedance, Gibbs free energy

Tertiary-Recovery Improvement of Steam Injection Using Chemical Additives: Pore-Scale Understanding of Challenges and Solutions Through Visual Experiments

Summary Our previous research, honoring interfacial properties, revealed that the wettability state is predominantly caused by phase change—transforming liquid phase to steam phase—with the potential to affect the recovery performance of heavy oil. Mainly, the system was able to maintain its water-wetness in the liquid (hot-water) phase but attained a completely and irrevocably oil-wet state after the steam-injection process. Although a more favorable water-wetness was presented at the hot-water condition, the heavy-oil-recovery process was challenging because of the mobility contrast between heavy oil and water. Correspondingly, we substantiated that the use of thermally stable chemicals, including alkalis, ionic liquids, solvents, and nanofluids, could propitiously restore the wettability. Two types of heavy oil (450 and 111,600 cp at 25°C) were used in a glass-bead-pack model at steam temperatures up to 200°C. Initially, the glass-bead-pack model was saturated with synthesized formation water and then displaced by heavy oils. The process was then followed by steam injection generated by escalating the temperature to steam temperature and maintaining a pressure lower than saturation pressure. Subsequently, the previously selected chemical additives were injected into the glass-bead-pack model as a tertiary-recovery application to further evaluate their performance. We observed that phase change (in addition to the capillary forces) was substantial in affecting both the phase distribution/residual oil in the porous media and wettability state. A more oil-wet state was evidenced in the steam case rather than in the liquid (hot-water) case. Despite the conditions, auspicious wettability alteration was achievable with thermally stable surfactants, nanofluids, water-soluble solvent [dimethyl ether (DME)], and switchable-hydrophilicity tertiary amines (SHTAs), improving the capillary number. The residual oil in the porous media yielded after injections could be favorably diminished post-chemical injection (for example, in the case of DME). In addition, more than 80% of the remaining oil was recovered after adding this chemical to steam. Analyses of wettability alteration and phase distribution/residual oil in the porous media through glass-bead-pack-model visualization on thermal applications present valuable perspectives in the phase-entrapment mechanism and the performance of heavy-oil recovery. This research also provides evidence and validations for tertiary recovery beneficial to mature fields under steam applications.

Enzyme-Coated Micro-Crystals: An Almost Forgotten but Very Simple and Elegant Immobilization Strategy

The immobilization of enzymes using protein coated micro-crystals (PCMCs) was reported for the first time in 2001 by Kreiner and coworkers. The strategy is very simple. First, an enzyme solution must be prepared in a concentrated solution of one compound (salt, sugar, amino acid) very soluble in water and poorly soluble in a water-soluble solvent. Then, the enzyme solution is added dropwise to the water soluble solvent under rapid stirring. The components accompanying the enzyme are called the crystal growing agents, the solvent being the dehydrating agent. This strategy permits the rapid dehydration of the enzyme solution drops, resulting in a crystallization of the crystal formation agent, and the enzyme is deposited on this crystal surface. The reaction medium where these biocatalysts can be used is marked by the solubility of the PCMC components, and usually these biocatalysts may be employed in water soluble organic solvents with a maximum of 20% water. The evolution of these PCMC was to chemically crosslink them and further improve their stabilities. Moreover, the PCMC strategy has been used to coimmobilize enzymes or enzymes and cofactors. The immobilization may permit the use of buffers as crystal growth agents, enabling control of the reaction pH in the enzyme environments. Usually, the PCMC biocatalysts are very stable and more active than other biocatalysts of the same enzyme. However, this simple (at least at laboratory scale) immobilization strategy is underutilized even when the publications using it systematically presented a better performance of them in organic solvents than that of many other immobilized biocatalysts. In fact, many possibilities and studies using this technique are lacking. This review tried to outline the possibilities of this useful immobilization strategy.

A facile acid induced water-based solvent by improving hydrophobicity for simultaneous remediating total petroleum hydrocarbon, heavy metals and benzo(a) pyrene contaminated soil: Laboratory- and pilot-scale studies

Herein, the partially water-soluble solvent (ethyl-acetate/ethanol/water, designated as EAEW) was applied to remediate complexly contaminated soils by total petroleum hydrocarbons (TPH), heavy metals (HMs) and benzo(a)pyrene (BaP). The hydrochloric acid (HCl) modified EAEW solvent had 95% of TPH and 80% of HMs removal efficiencies at room temperature, making suitable feature for energy saving. The laboratory tests revealed that the optimized condition of washing process was pH 3, soil (g) to solvent (mL) ratio (8:25) and 3 h washing time. Further, the EAEW solvent was regenerated and reused for 3 cycles using a distillation system and high removal efficiencies were kept for TPH (avg. 97.5%) and HMs (avg. 83.6%). As the highlighted finding, the addition of HCl for the EAEW solvent is crucial for highly removing multi-pollutants because HCl can leach HMs and enhance the TPH extraction through suppressing the hydrolysis of EA that can promote higher hydrophobicity. In the pilot-scale system, a sequential washing process by the use of HCl modified EAEW solvent followed by 0.1 M HCl removed 74.2–91% HMs and 96% BaP, satisfying all Korean standard (KS) guidelines. More importantly, 95.5% of EA/ethanol was recovered by the distillation system operated at 60 °C and 500 mm Hg pressure for 15 min. Not only proven effectiveness of EAEW solvent, but also its high recovery and environmental-friendly property could give a high potential for feasible on-site application for multi-polluted soil remediation.

Solvent mixing generating air bubbles as a template for polydopamine nanobowl fabrication: Underlying mechanism, nanomotor assembly and application in cancer treatment

Fabrication of hollow or bowl-like materials using gas bubbles as templates is an attractive technique. However, it is challenging to develop simple and mild methods that produce nanosized and homogeneous gas bubble templates. Herein, excess air could outgas in the form of bubbles by mixing water and water-soluble solvents in the proper proportion. And polydopamine (PDA) nanobowls are fabricated using these bubble templates. Furthermore, Mn(CO)5Br (COMn, gas fuel generator) is loaded on PDA nanobowls to form a nanomotor to carry zinc phthalocyanine (ZnPc, photosensitive drug) (denoted PCZN), which can migrate efficiently in cancer cells. Singlet oxygen (1O2), the primary cytotoxic reactive oxygen species (ROS) in photodynamic therapy (PDT), has an extremely short lifetime (<0.04 µs) and action radius (<20 nm), which limits its influence range to strictly around its production site. The movement of PCZNs can enlarge the ZnPc diffusion range, expand the 1O2 reach, and improve the PDT activity. In addition, PCZNs have multiple functions, including tumor vasodilatation to promote nanomedicine accumulation, tumor hypoxia relief to supply O2 for PDT, photothermal therapy (PTT) for synergistic treatment and multimodal imaging to ensure the theranostic outcome.

Underwater superoleophobic APTES-SiO2/PVA organohydrogel for low-temperature tolerant, self-healing, recoverable oil/water separation mesh

Hydrogel is attracting more and more interest in the field of oil-water separation because of its hydrophilicity and underwater oleophobicity. However, most traditional hydrogel composites have poor recycling performance, can not achieve self-repairing effect in the case of external mechanical damage, and inevitably freeze and at subzero temperatures because of a lot of water-soluble solvents in the gel network. These properties limit its application in the oil-water separation field. Therefore, it is still a challenge to prepare self-repairing and recyclable gel-based materials for oil/water separation in multiple environments. Here, superhydrophilic/underwater superoleophobic anti-freezing (3-aminopropyl) triethoxysilane-functionalized silica/polyvinyl alcohol (APTES-SiO2/PVA) organohydrogel and the related gel-coated mesh were successfully synthesized through a low-cost and simple process. The gel-coated mesh can separate oil-water mixtures in various water environments (including deionized water, HCl solution (1 M), NaOH solution (1 M), saturated NaCl solution, artificial seawater and saturated NaCl solution (−20 °C)) with a separation efficiency of above 99%. Impressively, they can achieve self-repairing and the recycling of raw materials through the excellent remoldability of organohydrogel (sol-gel transformation). The low-cost and easy fabrication, harsh-environment tolerance, self-repairing and recyclable features make the organohydrogel-based mesh promising toward oil/water separation under practical conditions.

Solvation properties of raft-like model membranes

Dimethyl sulfoxide (DMSO) is a universal water-soluble solvent widely used in many biotechnological and medical applications, such as cells cryopreservation, and for the treatment of different human diseases (e.g. amyloidosis). Despite the great number of reported studies, the effects of DMSO on the physico-chemical properties of biological membranes are poorly understood. Often, these studies are limited to model membranes composed of phosphatidylcholines (PCs) and cholesterol (Chol). In this work, we explored the effect of DMSO on liposomes composed of the natural egg sphingomyelin (ESM) and Chol as raft-like model membranes.With a multi-technique approach we probe the structure and the thermal stability of ESM/Chol bilayer at different Chol mole fractions. In particular, we investigate the ESM-solvent interactions to clarify the role of DMSO in perturbing the solvating conditions of lipid vesicles and show that the addition of DMSO increases the thermal stability of vesicles. An increase of transition temperature, a decrease of both enthalpy and entropy as well as a decrease of the cooperativity of the gel to liquid phase transition are observed at 0.1 DMSO mole fraction. Fluorescence experiments with the probe Laurdan and FTIR spectra strongly indicate that DMSO exerts a dehydration effect on the membrane. Besides, FTIR measurements with tungsten hexacarbonyl, in combination with fluorescence data of the probe NBD-PE, indicate that DMSO promotes the formation of a highly packed membrane by reducing the thickness of the membrane.

A solvatochromic AIE tetrahydro[5]helicene derivative as fluorescent probes for water in organic solvents and highly sensitive sensors for glyceryl monostearate

In this paper, a tetrahydro[5]helicene-based imide dye with thienyl group (THID) was studied on its solvatochromism and aggregation-induced emission (AIE) properties by dissolved in various organic solvents. The linear relationship between Stokes shift and aprotic solvent polarity parameter was well fitted with Lippert-Mataga model. Furthermore, Stokes shift also were positively correlated with the normalized molar electronic transition energy, suggested that THID exceptionally depends on solvent polarity for twisted intramolecular charge transfer. In addition, THID demonstrated typical AIE features when adding large amounts of water into good solvent. Meanwhile, it can function as intensity and wavelength-based fluorescence sensor for detecting low-level water content in water soluble solvents, even the low of detection was 0.014 vol% in ACN. Therefore, a simple and highly selective fluorescence analysis for glyceryl monostearate has been established on basis of its AIE property.

Microfluidic block copolymer membrane arrays for nanopore DNA sequencing

Nanopore DNA sequencing has the potential to provide significant improvements to DNA sequencing: it may decrease cost while increasing speed and portability. Due to fundamental limits on the speed of reading DNA as it moves through a nanopore, an array of nanopores is necessary to parallelize measurements for high speeds. Additionally, a practical nanopore sequencing device would benefit from the use of block copolymer membranes to house the nanopore proteins; block copolymers are more structurally and chemically stable than phospholipids. We have previously tailored membranes composed of a block copolymer to house the nanopore protein MspA for this purpose. In this work, we extend the use of this polymer to a membrane array. We find that when switching from our previous manual system to this microfluidic system, the nanopore protein MspA exhibits variable behavior despite the use of the same block copolymer solution as before. We establish a metric for quantifying this variability and investigate its cause. We find that the cause is likely the use of volatile and water-soluble solvents in a small channel volume. Finally, we demonstrate that MspA in these block copolymer membranes is able to translocate DNA similar to MspA behavior in lipid membranes. These results illustrate the viability of polymer membranes for nanopore-based sensors while highlighting the challenges inherent in the development of a practical nanopore DNA sequencing device.

Numerical modeling of water-soluble solvents for enhancing oil recovery in heterogeneous chalk reservoirs

Dimethyl Ether Waterflooding (DEW) is a promising water-soluble solvent-based EOR technique. Here, we study DEW mechanisms by developing a mathematical model taking into account the swelling and viscosity reduction of oil. Our analyses show that the swelling and viscosity reduction of oil cannot explain the observed increased recovery of DEW in the published core flooding data. Therefore, we define the residual oil saturation as a linear function of DME concentration in the oil phase to fit the model to the experimental data.After model validation against a 1D core flooding experiment, we utilize the model to study the effect of permeability heterogeneity and the injected DME slug size on the recovery of oil from a water-flooded chalk reservoir. We observe a sharp increase in the ultimate recovery when the DME slug size increases from 0.2 to 1.8 pore volume with a DME concentration of 10 wt%. Since DME is an expensive agent, the optimal slug size requires an integrated economic evaluation. We calculate the increased Net Present Value (NPV) of DEW flooding in the heterogeneous chalk reservoirs compared to the conventional water flooding for two scenarios of well completions. By comparing the water breakthrough and DME induced recovery, we conclude that the most economical scenario for the DEW flooding is observed in the reservoirs with the lowest heterogeneity.

Microencapsulation of caffeic acid and its release using a w/o/w double emulsion method: Assessment of formulation parameters

Caffeic acid (CAF)has numerous health benefits mainly due to its antioxidant, antibacterial and fungicide properties. However, its incorporation in skin care products as anti-aging and the photoprotective agent is still limited due to its solubility and stability in oily matrices or solutions balanced with the skin pH. In this research, CAF–ethyl cellulose (EC) microparticles were produced by water-in-oil-water double emulsion solvent evaporation encapsulation technique using a biocompatible polymer, EC, as a coating material and a surfactant, polyvinyl alcohol, as a stabilizer of the double emulsion. The study assessed the influence of formulation parameters as the solubility of the polymer in organic solvents and the polymer concentration on microparticles final characteristics. CAF–EC microparticles were characterized by product yield, encapsulation efficiency, mean particle size, particle size distribution and polydispersity and imaged by scanning light microscopy. In vitro release profiles were obtained in water and octanol to mimic oily based and water-based matrices balanced with the skin pH. In vitro release kinetics studies were carried out to investigate the release pattern of CAF in simulated cosmetic formulations. Both the product yield and the encapsulation efficiency were found to be dependent on the solubility of the polymer in the organic phase. The product yield was mainly affected by operational factors such as the sticking and the agglomeration of the polymer to the walls and the magnet stirring during microparticles hardening and results from the encapsulation efficiency revealed that an increase of the polymer concentration led to an increase of the encapsulation efficiency. The usage of a water-soluble solvent contributed to a decrease in the mean particle size and reduction of polydispersity with higher polymer concentrations. The polymer concentration, the polymer solubility in the organic phase and the amount of CAF entrapped shown to affect the release in water, whereas the release in octanol was mainly independent of the amount of CAF entrapped in EC microparticles. The double emulsion solvent evaporation technique and the assessment of the selected formulation conditions have given significant and innovative insights on the microencapsulation of bioactive ingredients for cosmetics formulations.

A phase inversion polymer coating to prevent swelling and spalling of clay fines in coal seam gas wells

We report a phase inversion polymer coating as a novel concept with potential to prevent clay swelling and fines generation in coal seam gas, or other petroleum, wellbores. Our approach uses polyethersulfone (PES) with N-methyl-2-pyrrolidone (NMP) as a water-soluble solvent to form a dense, low-porosity film across the clay-rich interburden layers, but a porous and permeable membrane on coal seams. This contrasting behaviour occurs because the coal contains much more free water than the clay-rich interburden layers. We demonstrate the efficacy of the method to prevent clay spalling in immersion tests and under a flow of fresh water in a visual swell test apparatus. The clay-rich rocks studied were mudstone and siltstone, and these were dip coated in the PES/NMP solution. The uncoated mudstone swelled and broke apart quickly in the immersion test and visual flow test, but the PES coated rock samples were stable for 30 days. The coated rock and coal samples were characterised by X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy. The morphology of coated mudstone and coated coal samples showed that the polymer formed a dense layer across the low-permeability mudstone, but an open porous structure on the coal surface. The effect of the coating on the permeability of KCl brine through coal was measured in a core-flood apparatus. Although the permeability of the coal showed some deterioration after coating, from (0.58 ± 0.12) mD to (0.3 ± 0.03) mD, these results demonstrate the potential of a smart polymer coating to prevent clay swelling while remaining permeable to gas and water on coal layers.