Remaining oil distribution and recovery performances with waterflooding and surfactant-polymer flooding: An experimental investigation

An oilfield has been developed with waterflooding for a long time, and the water cut has reached a high level. Surfactant-polymer (SP) flooding is considered as the following enhanced oil recovery (EOR) technique. To determine the feasibility of SP flooding in this oilfield, the microscopic oil displacement experiments are performed, and the distribution of remaining oil after waterflooding and SP flooding is observed. The recovery rates are measured by the producing liquid amount and nuclear magnetic resonance (NMR) technique. The two methods show similar measurement results, with deviations of about 10%. The contributions of different pore and throat diameters are analyzed with the NMR technique. The results show that SP flooding has a much lower contribution limit of pore and throat diameter than waterflooding, indicating that SP flooding can effectively improve sweep efficiency. The SP flooding can improve by about 30% EOR rate. The frozen slicing technique and ultraviolet fluorescence excitation are applied to observe the status and distribution of remaining oil. The results show that both waterflooding and SP flooding can effectively reduce all types of remaining oil. Comparing the remaining oil proportions in the high and low permeability cores, we can conclude that the high permeability contributes to the performance of waterflooding and SP flooding. This work proves the efficiency of SP flooding in this oilfield development and provides a microscopic explanation of remaining oil distribution after waterflooding and SP flooding.     

An investigation into surfactant flooding and alkaline-surfactant-polymer flooding for enhancing oil recovery from carbonate reservoirs: Experimental study and simulation

The main aim of the present work was to study history matching of surfactant flooding using CMG-STARS simulator and experimental results. In the experimental case, the critical micellar concentration of dodecyltrimethylammonium bromide solution is obtained, and the changes in the contact angle are investigated from 1 to 10% weight. Then, after water flooding, surfactant flooding is applied on the critical micellar concentration of dodecyltrimethylammonium bromide. In the simulation case, after history matching of production data, the performance of alkaline-surfactant-polymer flooding using sodium hydroxide, hydrolyzed polyacrylamide, and that surfactant was a prediction. The numerical simulation alkaline-surfactant-polymer flooding increased the oil recovery factor 26% more than surfactant flooding.     

Visualization and quantification of cathode channel flooding in PEM fuel cells

An understanding of two-phase flow mechanisms in micro-channels is critical to water management in fuel cell applications. In this work, an in situ visualization study of cathode flooding in an operating fuel cell is presented. Gas relative humidities of 26%, 42% and 66%, current densities of 0.2, 0.5 and 0.8 A cm⁻²and flow stoichiometries ranging from 2 to 4 are used in this study which represent typical operating conditions for automotive applications. Results are presented in the form of a flow map depicting various two-phase flow patterns. The impact of flooding is also presented in terms of measurable parameters like two-phase pressure drop coefficient and voltage loss. A new parameter called wetted area ratio is introduced to characterize channel flooding and liquid water coverage on a gas diffusion layer, and its repeatability with multiple tests is demonstrated.     

In situ detection of anode flooding of a PEM fuel cell

This paper proposes an early detection scheme of anode flooding in a PEM fuel cell. Through experimental testing of an eight-cell hydrogen-fueled polymer electrolyte stack it is shown that anode flooding can be detected prior to a rapid voltage decline. The proposed detection scheme requires no additional costly instrumentation and uses the existing voltage scan cards.     

Experimental study on mitigating the cathode flooding at low temperature by adding hydrogen to the cathode reactant gas in PEM fuel cell

Severe flooding can be critical in a fuel cell vehicle operating at a high current density, and in a fuel cell vehicle at the initial stage of start up. It is often difficult to remove the condensed water from the cathode gas diffusion layer (GDL) of the fuel cell because of the surface tension between the water and the GDL. In this research, in order to remove the condensed water from the cathode GDL, a small amount of hydrogen was injected into the cathode reactant gases. The results showed that the hydrogen addition method successfully removed the liquid water from the cathode GDL. Water removal was verified for various hydrogen flow rates and hydrogen addition durations. Furthermore, the dew point temperature of the outlet gas at the cathode was observed to determine the amount of water removed from the cathode GDL. In addition, the water droplet in the cathode gas flow channel was visualized by using a transparent cell. Furthermore, degradation tests are also performed. Considering the degradation test, the hydrogen addition method is expected to be effective in mitigating cathode flooding.     

Effect of channel-to-channel cross-flow on local flooding in serpentine flow-fields

Serpentine flow-fields have long been used in polymer electrolyte membrane (PEM) fuel cells for effective transportation of reactants from the flow-field to the reaction sites. It has been observed in the literature that localized flooding near the U-bend region of serpentine flow-fields occurs at high current densities. This has been attributed to the boundary layer separation and recirculation of flow in the U-bend. In the present study, it is established, using computational fluid dynamics (CFD) simulations, that this is due to lower channel-to-channel cross-flow in the electrodes between consecutive serpentine channels rather than to the flow-field in the gas distribution channels.     

Macroscopic analysis of characteristic water transport phenomena in polymer electrolyte fuel cells

Comprehensive analytical and numerical analyses were performed, focusing on anode water loss, cathode flooding, and water equilibrium for polymer electrolyte fuel cells. General features of water transport as a function of membrane thickness and current density were presented to illustrate the net effect of back-diffusion of water from the cathode to anode over a polymer electrolyte fuel cell domain. First, two-dimensional numerical simulation were performed, showing that the difference in molar concentration of water at the channel outlet is widened as the operating current density increases with a thin membrane (Nafion^®${\mathrm{Nafion}}^{\circledR }$ 111), which was verified by Dong et al. [Distributed performance of polymer electrolyte fuel cells under low-humidity conditions. J Electrochem Soc 2005; 152: A2114–22]. Then, analytical solutions were compared with computational results in predicting those characteristics of water transport phenomena. It was theoretically estimated that the high pressure operation of fuel cells expedites water condensing and results in shorter anode water loss and cathode flooding locations. In this study, it was also found that a thin membrane (Nafion^®${\mathrm{Nafion}}^{\circledR }$ 111) facilitates water transport in the through-membrane direction and therefore water concentration at the anode and cathode channel outlets reaches an equilibrium state particularly at low operating current densities. Moreover, the difference in the anode water concentration between Nafion^®${\mathrm{Nafion}}^{\circledR }$ 111 and Nafion^®${\mathrm{Nafion}}^{\circledR }$ 115 membranes becomes intensified in the in-plane direction under the same water production condition, while the cathode water concentration profiles remains almost same.     

A hydrophobic blend binder for anti-water flooding of cathode catalyst layers in polymer electrolyte membrane fuel cells

We report polymer electrolyte membrane fuel cells (PEMFCs) in which poly(vinylidene fluoride-co-hexafluoropropylene) (P(VdF-co-HFP)) copolymer was added to the existing sPEEK binder in cathode catalyst layers (CCLs). Compared to a control case with no such copolymer, the cell with the copolymer exhibits improved performance, particularly in the oxygen mass transport. The improved mass transport behavior is attributed to the copolymer that makes CCLs more hydrophobic and thus suppresses water flooding significantly. Contact angle measurements and various electrochemical characterizations consistently support the copolymer effect for the improved oxygen mass transport. In addition, the introduction of P(VdF-co-HFP) lowers the glass transition temperature of the binder, which contributes to enhancing the adhesion properties between the CCLs and membranes.     

The polymer-enhanced foam injection process: An improved-oil- recovery technique for light oil reservoirs after polymer flooding

Using the methods of physical simulation and numerical simulation, the feasibility of polymer-enhanced foam injection after polymer flooding is studied. First, an experiment-based screening criteria for polymer-enhanced foams is presented, and the influence of polymer concentration on foam mobility is investigated. Thereafter, the parallel experiments of polymer-enhanced foam injection and conventional foam injection after polymer flooding are performed. A Lorentz–Monte-Carlo method is then proposed to establish the heterogeneous geological models with different interlayer and plane heterogeneity. Thus, the sensitivity of reservoir heterogeneities on oil recovery of enhanced foam injection is analyzed numerically, and the implementation plan is optimized.     

A review of water flooding issues in the proton exchange membrane fuel cell

We have reviewed more than 100 references that are related to water management in proton exchange membrane (PEM) fuel cells, with a particular focus on the issue of water flooding, its diagnosis and mitigation. It was found that extensive work has been carried out on the issues of flooding during the last two decades, including prediction through numerical modeling, detection by experimental measurements, and mitigation through the design of cell components and manipulating the operating conditions. Two classes of strategies to mitigate flooding have been developed. The first is based on system design and engineering, which is often accompanied by significant parasitic power loss. The second class is based on membrane electrode assembly (MEA) design and engineering, and involves modifying the material and structural properties of the gas diffusion layer (GDL), cathode catalyst layer (CCL) and membrane to function in the presence of liquid water. In this review, several insightful directions are also suggested for future investigation.     

Experimental investigation of solar-hydrogen energy system performance

Recently, the Solar-hydrogen energy system (SHES) becomes a reality thanks as well as a very common topic to energy research in Egypt as it is now being the key solution of different energy problems including global warming, poor air quality and dwindling reserves of liquid hydrocarbon fuels. Hydrogen is a flexible storage medium for energy and can be generated by the electrolysis of water. It is more particularly advantageous and efficient when the electrolyzer is simply coupled to a source of renewable electrical energy. This paper examines the operation of alkaline water electrolysis coupled with solar photovoltaic (PV) source for hydrogen generation with emphasis on the electrolyzer efficiency. PV generator is simulated using Matlab/Simulink to obtain its characteristics under different operating conditions with solar irradiance and temperature variations. The experimental alkaline water electrolysis system is built in the fluid mechanics laboratory of Menoufiya University and tested at certain input voltages and currents which are fed from the PV generator. The effects of voltage, solution concentration of electrolyte and the space between the pair of electrodes on the amount of hydrogen produced by water electrolysis as well as the electrolyzer efficiency are experimentally investigated. The water electrolysis of different potassium hydroxide aqueous solutions is conducted under atmospheric pressure using stainless steel electrodes. The experimental results showed that the performance of water electrolysis unit is highly affected by the voltage input and the gap between the electrodes. Higher rates of produced hydrogen can be obtained at smaller space between the electrodes and also at higher voltage input. The maximum electrolyzer efficiency is obtained at the smallest gap between electrodes, however, for a specified input voltage value within the range considered.     

Study on water transport in hydrophilic gas diffusion layers for improving the flooding performance of polymer electrolyte fuel cells

For hydrogen-based polymer electrolyte fuel cells (PEFCs), water transport control in gas diffusion layers (GDLs) by wettability distribution is useful to suppress the flooding problem. In this study, the water transport of a novel GDL with hydrophilic-hydrophobic patterns was investigated. First, we clarified that the water motion in the hydrophilic GDL with microstructures could be reproduced by the enlarged scale model. The scale model experiment also showed that the same water behavior in hydrophilic GDL can be obtained from Capillary numbers (Ca) in a range of Ca ~ 10^?5 to 10^?3. As the computational load is inversely proportional to Ca, the computational load could be reduced by 1/100th by using Ca ~ 10^?3, which is 100 times higher than PEFC operation (Ca ~ 10^?5). Finally, the simulation with Ca ~ 10^?3 was performed, and we showed that the GDL with straight region of contact angle 50° minimized the water accumulation.     

Experimental and theoretical investigation of dual purpose solar collector

Experimental data indicate that high temperature and high performance can be obtained using dual purpose solar collector (DPSC) compared to single water or air collector. A mathematical model based on effectiveness method has been developed for the investigation of thermal performance of DPSC. In the collector two fluids (water and air) flow simultaneously. Three different kinds of channels are used to enhance the performance of collector, such as: rectangular fin, triangular fin and without fin. Simulation results show that channels with rectangular fin have better performance compared with others. The effect of water inlet temperature and air flow rate on heat delivery by air and water has been investigated.     

Prevention of the water flooding by micronizing the pore structure of gas diffusion layer for polymer electrolyte fuel cell

In polymer electrolyte fuel cells, high humidity must be established to maintain high proton conductivity in the polymer electrolyte. However, the water that is produced electrochemically at the cathode catalyst layer can condense in the cell and cause an obstruction to the diffusion of reaction gas in the gas diffusion layer and the gas channel. This leads to a sudden decrease of the cell voltage. To combat this, strict water management techniques are required, which usually focus on the gas diffusion layer. In this study, the use of specially treated carbon paper as a flood-proof gas diffusion layer under extremely high humidity conditions was investigated experimentally. The results indicated that flooding originates at the interface between the gas diffusion layer and the catalyst layer, and that such flooding could be eliminated by control of the pore size in the gas diffusion layer at this interface.     

An overview of nanomaterials in fuel cells: Synthesis method and application

The emerging of fuel cell as one of the promising future energy sources is due to its vast advantages and applications. Despite many challenges to commercialize it, nanostructured materials have brought a new innovation and finding in order to overcome them. The utilization of nanomaterials in various components of fuel cell (catalyst, electrolyte/membrane, electrodes) can defeat many restrictions such as expensive materials and fuel crossover that hinder its commercialization. The distinct properties of nanomaterials including their high surface area and unique size effect can greatly increase overall efficiency as well as the performance of cell. This article provides an overview of the current breakthrough in the performance of fuel cell through the employment of nanomaterials in its major components. The development of nanomaterials can be categorized into four classes namely zero-dimensional (0D), one-dimensional (1D), two-dimensional (2D) and three-dimensional (3D) that synthesized by different methods and their current progress in fuel cell application are also addressed. Selecting a suitable synthesizing method for nanomaterials is the primary stage that determines the properties of the catalysts and the membrane fabricated. This article also discusses the parameters involved in the methods used that can affect the cell performance. The advantages and the drawbacks of each method are also reviewed.     

Thermal studies of the state of water in proton conducting fuel cell membranes

The thermodynamics of acid group hydration was studied for different membranes (including Nafion^® and sulfonated poly(arylene ether sulfone) (BPSH)) and model systems (including an organic/inorganic composite (I/O) and a multiblock polymer (MB-150)). Experiments were carried out with the membranes exposed to different activities of water corresponding to different levels of membrane hydration. Isopiestic sorption shows a significantly greater uptake in water for the multiblock polymer as compared to the others. Differential scanning calorimetry (DSC) was used to study thermal properties to elucidate the state of water in the membranes. A comparison is made of various modes of collecting data using DSC. Based on these data, we discuss the overall understanding of water interactions with these membranes as well as the limitations of thermodynamic data in describing microenvironments within the membrane.     

Vapor/gas separation through carbon molecular sieve membranes: Experimental and theoretical investigation

The separation of H₂O vapor from (hydrogen-rich) gaseous streams is a topic of increasing interest in the context of CO₂ valorisation, where the in situ water removal increases product yield and catalyst stability. In this work, composite alumina carbon molecular sieve membranes (Al-CMSM) were prepared from phenolic resin solutions loaded with hydrophilic boehmite (γ-AlO(OH)) nanosheets (0.4–1.4 wt. % in solution) which partially transform to γ-Al₂O₃ nanosheets upon thermal decomposition of the resin, improving the hydrophilicity and thus the adsorption-diffusion contribution of the H₂O permeation. The γ-Al₂O₃ nanosheets showed no influence on the pore size distribution of the membranes in the range of micropores, but they increased the membrane hydrophilicity. In addition, the use of boehmite in the resin solution causes an increase in the viscosity and thus an increase in the carbon layers thickness deposited on the porous α-Al₂O₃ support (from 1 to 3.3 μm). Furthermore, the alumina sheets introduce defects in the carbon matrix, increasing the tortuosity of the active layer, as concluded via phenomenological modelling and parametric fitting of the experimental results. As a consequence, the water permeability exhibits a maximum (1.3?10^?6 mol?s^?1 Pa^?1 m^?1 at 150 °C) with boehmite/alumina content of ca. 0.8 wt. %, as the combined effects of increasing hydrophilicity (which favour H₂O permeability) and increasing thickness and tortuosity (which hamper permeability) upon increasing boehmite loading. Similarly, the H₂O/gas perm-selectivity is optimum at 1.2 wt. % boehmite loading. We further investigated the H₂O permeation mechanism by modelling the mono- and multi-layer adsorption and capillary condensation of water in microporous media, which result as the main transport mechanisms in the explored conditions.     

Bunsen reaction and hydriodic phase purification in the sulfur-iodine process: An experimental investigation

This paper reports an investigation on the Bunsen reaction. An experimental campaign was conducted by means of a stirred reactor. Runs were carried out at a constant temperature in the 30-120 °C range, following a semi-batch procedure by feeding gaseous sulfur dioxide in an iodine/hydriodic acid/water solution. A specific analytical procedure to measure the hydriodic phase composition was implemented. It was observed that both the amount of absorbed SO₂ and its conversion lowered as the temperature increased. Secondary reactions were beyond the detection limit in the reactor, even at low temperature and low iodine content. The purification of the produced hydriodic phase was also investigated. It was possible to satisfactorily reduce the impurities content without the occurrence of secondary reactions only when high temperature and high iodine content were applied.     

Experimental investigation of producer gas burner for thermal application

This paper deals with the performance evaluation of a premixed-type burner with producer gas, in terms of emission, axial and radial flame temperature. In this study, a burner of 150 kWth capacity was tested on an open core downdraft-type gasifier. The developed burner is a concentric tube-type where the air is supplied through a central tube, which is surrounded by another one. The burner consists of a swirl vane for mixing the air and producer gas, mixing tube and bluff body for flame stabilization. Swirl angle and bluff body diameter were kept constant throughout the study. The burner was evaluated with an open core downdraft-type gasifier. The temperature evaluation and emission testing was done for three flow rates and air–fuel ratio. The study shows low NO _x and CO emission at 125 Nm³ h^?1 when compared with that of 75 and 100 Nm³ h^?1. Maximum flame temperature (753 °C) was recorded at 10 cm axial and 10 mm radial distance.