Adsorption of a nonionic surfactant onto a silica surface

Chemical flooding is technically feasible to increase oil recovery from depleted sandstone reservoirs with low pressure. Polymer-surfactant flooding is a potential process in the chemical flooding methods for enhanced oil recovery (EOR) in sandstone porous media. However, chemical additive cost and surfactant loss due to adsorption on the reservoir rock are the main concerns in this type of EOR processes. This paper presents adsorption equilibrium of a natural surfactant, Zyziphus spina-christi, onto a real sandstone reservoir. Batch adsorption experiments were carried out to figure out the impacts of adsorbent dose on adsorption performance. The equilibrium adsorption data were analyzed with two common adsorption models and it was found that the Freundlich model is a pretty good fit for adsorption equilibrium of Z. spina-christi based on the value of determination coefficient (R²). Results from this study are instructive for appropriate selection of surfactants in design of EOR processes and reservoir stimulation plans for sandstone reservoirs.     

河北献县东部雾迷山组碳酸盐岩热储酸化压裂试验研究

通过对河北献县东部雾迷山组碳酸盐岩进行大尺寸高地应力酸化压裂物理模拟试验与小尺寸温度应力耦合环境下酸化压裂试验,讨论地应力、温度、酸液排量以及压裂模式等因素与碳酸盐岩压裂效果之间的关系,找到碳酸盐岩储层压裂裂缝的生长规律。研究表明：将裂缝发育与裂缝不发育储层碳酸盐岩压裂曲线对比发现,储层岩石裂缝发育程度可明显降低破裂压力;压裂试验中储层岩石内裂缝激活对破裂压力具有显著影响,现场压裂过程中应当考虑到储层工程地质中裂缝发育程度的问题;酸液处理可显著降低破裂压力,更有利于形成复杂裂缝网络,破裂过程中诱发更多声发射事件,同时储层岩石裂缝发育程度直接影响到压裂效果。     

Wettability alteration of carbonate reservoir rock using amphoteric and cationic surfactants: Experimental investigation

The objective of this study is to prove that altering the wettability of reservoir rocks by two surfactants (hexadecyl amino benzene sulfonic acid [HABSA] and cationic hexa decyl trimethyl ammonum bromide [CTAB]). Changing the wettability to preferentially water-wet condition will reduce the residual oil saturation (S_or). Because of reducing S_or, the percentage of recovered oil is increased. All surfactants were tested for their ability to alter the wettability of reservoir rocks. This alteration was measured based on the contact angle methods. Results of this study show that both amphoteric HABSA and CTAB surfactants alter the wettability of carbonate rocks from oil-wet to water-wet, while CTAB alters the wettability from oil-wet to water-wet more than HABSA. Also, recovery factor in CTAB injection was more than HABSA injection. Ultimately, the results show that the CTAB surfactant is more effective than HABSA surfactant to alter the wettability and improve oil recovery from carbonate reservoirs.     

Salinity,temperature and pressure effect on hydrogen wettability of carbonate rocks

Hydrogen had been injected into the geologic formations, and the geologic formation wettability would influence the hydrogen storage. Hydrogen wettability of sandstone reservoirs (quartz), mica and other rocks have been explored in the previous study. However, the research on hydrogen wettability of carbonate rocks was lacked. In this study, we studied the carbonate rock wettability alteration when exposed to the hydrogen environments. Salinity, temperature and pressure effect on H₂/carbonate rock/brine wettability were explored. When the solutions ions concentration increased, the advancing/receding contact angle would increase, and divalent ions could make the contact angle higher than monovalent ion, which was because ions could compress the electric double layer. The carbonate rock powder in brine showed negative charge, and the zeta potential increased with higher ions concentration. When temperature increased and the pressure decreased, the contact angle would decrease, which was related to the H₂ gas density and molecular interactions.     

A mass transfer model for the adsorption of pesticide on coconut shell based activated carbon

The adsorption isotherms of HCH on coconut shell based activated carbon type NP-5 at constant temperature have been experimentally measured. The porous properties such as, the density, BET surface area, pore size, pore volume along with pore distribution of NP-5 have been determined. The Freundlich’s, Langmuir’s, Temkin, Jovanovic and BET’s adsorption isotherm models describe of experimental data within the acceptable error ranges. The Freundlich, Jovanovic and Langmuir models were fitting better the experimental data. The shape of these isotherms indicates that the HCH is adsorbed as a monolayer and that there is no strong competition between the pesticide molecules and water to occupy the adsorption surface sites.     

Hydrogen storage in gas reservoirs: A molecular modeling and experimental investigation

Hydrogen is one of the clean energy sources that can be used instead of fossil fuel sources to reduce greenhouse emissions. However, hydrogen supply intermittency significantly reduces the deployment and reliability of this energy resource. Therefore, this work investigates the underground storage of hydrogen in depleted gas reservoirs to avoid seasonal fluctuations in hydrogen supply and assure long-term energy security. The obtained results from molecular simulation (Density Functional Theory) revealed hydrogen is adsorbed physically on calcite (104) and silica (001) surfaces on different adsorption configurations. This conclusion is supported by low adsorption energies (?0.14 eV for calcite and ?0.09 for silica) and by Bader charge analysis, which showed no indication of charge transfer. The experimental results illustrated that hydrogen has a very low adsorption affinity toward carbonate and sandstone rocks in the temperature range of 50–100 °C and pressure up to 20 bar. These results show the potential of depleted gas reservoirs to store hydrogen for s is useful in hydrogen recovery as no hydrogen will be adsorbed to the rock surface of conventional gas reservoirs.     

中国烃源岩研究进展、挑战与展望

新中国油气工业发展60年历经两次大飞跃:第一次是在20世纪50年代初至80年代初,实现了陆相油气勘探重大发现并建立了陆相石油地质理论;第二次是在上世纪80年代初至今,实现了海相碳酸盐岩层油气勘探的重大突破并形成了中国特色海相石油地质理论。这些成果基于从中元古界到新近系均有发育的丰厚烃源岩基础,其中新生界陆相烃源岩和下古生界海相烃源岩生成了主要的石油储量,发现了大庆油田、渤海湾富油区和塔河等大油田;石炭—二叠系和侏罗系烃源岩构成了天然气储量主体,探明了苏里格、克拉2和普光等大气田。进入21世纪以来,中国油气勘探更呈现出"三海一陆"并进、石油稳定发展、天然气快速发展的良好态势,继上世纪60年代大庆和渤海湾油气大发现以后,全国年均新增探明石油地质储量再次突破10×108t大关,新增探明天然气储量也以年均5000×108m3的速度增长。该成果的取得与优质烃源岩、多元生烃的认识及陆相岩性地层油气藏、海相碳酸盐岩油气藏理论的提出等理论认识的重大突破,以及不断进步的钻探、物探和有机地球化学等勘探技术密不可分。目前,我国烃源岩研究仍面临着找到了大油气田主力烃源岩尚未明确、深层油气生成及其保存机制尚不清楚和资源潜力预测仍存在不确定性等亟待解决的众多挑战,其未来发展必须借助于油气勘探稳定发展的良好时机,把握生烃成藏的核心问题和勘探开发实际需求,切实将成烃与成盆、成藏作为一个含油气系统来动态研究烃源岩问题。     

Lithium electrodes with and without CO2 treatment: electrochemical behavior and effect on high rate lithium battery performance

The ionic resistivity and integrity of a solid-electrolyte interphase (SEI) film on a lithium electrode surface was investigated. The performed lithium carbonate film on the surface of the lithium electrode was found to improve the electrode behavior by maintaining a low ionic resistance. In lithium/silver vanadium oxide batteries, voltage delay can be eliminated with the use of a lithium anode pretreated with CO₂. An SEI consisting of lithium carbonate appears to be responsible. Unlike the surface film formed from lithium-electrolyte reactions, the lithium carbonate film is relatively strong and can withstand high current density pulses (∼ 20 mA/cm²) without significant damage. An ion exchange mechanism involving the carbonate anion is proposed.     

应力和侵蚀性溶液渗透耦合作用下碳酸盐岩渗透特性试验研究

为研究不同应力及溶液组合下碳酸盐岩渗流特性演化规律,选择H2SO4溶液、蒸馏水作为渗透流体,使用岩石耦合渗透试验装置对碳酸盐岩试样分别进行较长时间的渗透试验,得到三种不同工况下岩石试样渗透率和渗出液中矿物离子浓度随时间变化的曲线,分析了试验中围岩、渗透压、溶液等影响因素与渗透率、岩石内部矿物质溶解规律之间的内在联系。结果表明,试验初期阶段,围压对岩样渗透率有较大影响,恒定围压施加后使得岩样孔隙受到压缩从而影响渗透率。试验过程中,渗透压的增大会导致岩样渗透率产生短时间的上升,随后岩样渗透率逐渐回落。不同渗透溶液则有不同的影响,H2SO4溶液对岩样内部的侵蚀性较强,在岩样上游段产生较强溶解,当溶解的矿物离子浓度达到过饱和后,可能在下游段产生沉淀,使得岩样整体渗透率不断降低;而蒸馏水对岩样的侵蚀作用较弱,沿程产生均匀溶解,不能对孔隙结构造成较大改变,整体渗透率保持稳定。岩样整体渗透率的变化是应力、渗透溶液的溶蚀作用和矿物沉淀共同作用的结果。研究成果可用于指导工程实践。     

Dynamic Interfacial Tension Between Crude Oil and Octylmethylnaphthalene Sulfonate Solution

The surface tension of surfactant aqueous solutions and dynamic interfacial tensions (DIT) between Shengli Oilfield crude oil and solution of octyl methylnaphthalene sulfonate surfactants (OMNS) have been measured. The effects of various parameters such as surfactant concentration, salinity and sodium carbonate concentration on the interfacial behavior of crude oil-water were investigated. It was found that the prepared surfactants can reduce the interfacial tension to ultra-low only at certain surfactant concentration, salinity and alkaline concentration ranges. It was also found that there exist optimum values with respect to all of surfactant concentration, salinity and alkaline concentration. The DIT can low to 10^?6 mN.m^?1 under the optimum conditions. Moreover, the DIT behavior of OMNS flooding without alkaline has also been investigated. It was found that the DIT also reaches ultra-low value under the optimum sodium chloride concentration without alkaline. The results show that the OMNS is more effective on lowering surface tension of aqueous solutions and dynamic interfacial tensions (DIT) between crude oil and water. OMNS possesses a great potential to be used in EOR with low costs and high efficiency.     

Investigation of adsorption properties of geological materials for CO2 storage

The assessment for realistic CO₂‐adsorption capacities of different rocks is important for understanding the processes associated with CO₂ storage. This paper investigates the adsorption characteristics of rocks for CO₂ (limestone, sandstone, marl, claystone, clay, siltstone and metamorphic rock) by using a gravimetric method. The measurements were performed at 21°C with pressures from 1 up to 4 MPa. Sandstone (and clay with sand/sandstone) showed the largest adsorption capacity at 21°C. The highest amount of in situ CO₂ contents in measured samples was 21.4 kg/t. The CO₂‐adsorption capacities were lower than past results in different coal samples. The results indicate that adsorption of CO₂ into rocks may play an important role in storing CO₂ in subsurface rock. Copyright © 2012 John Wiley & Sons, Ltd.     

An ionic liquid-present hydrothermal method for preparing hawthorn sherry ball shaped palladium (Pd)-based composite catalysts for ethanol oxidation reaction (EOR)

For the first time, a hawthorn sherry ball shaped Pd-based composite catalyst for EOR was prepared via an ionic liquid-present two-step hydrothermal method in this work. In the first hydrothermal step, micron-scale solid carbon spheres (MSCS) were fabricated in the presence of glucose, an ionic liquid of 1-butyl-3-methyl tetrafluoroboric acid and one kind of surfactant. And in the second hydrothermal process, sesame like Pd particles were immobilized on the surface of MSCS forming a hawthorn sherry ball shaped Pd-based composite catalyst (denoted as Pd/MSCS) using PdO as the source of Pd. In the course of preparing MSCS, four kinds of surfactants were respectively employed desiring to study the influence of surfactant type on the physicochemical properties of the produced samples. The prepared MSCS and Pd/MSCS were examined majorly by X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). It was addressed by SEM images that in the presence of SDS and EDTA, hawthorn sherry ball shaped Pd-based composite catalysts were successfully prepared. XRD and XPS analysis substantially documented that metallic palladium was the main component of the synthesized Pd/MSCS catalysts. The electrocatalytic abilities of the Pd/MSCS catalysts for EOR were examined in 1 M C₂H₅OH alkaline solution mainly utilizing cyclic voltammetry (CV) and chronoamperometry (CA), illustrating that all produced Pd/MSCS catalysts had an electrocatalytic activity towards EOR, and the forward peak current density of EOR on the catalyst of Pd/MSCS (prepared in the presence of SDS) was 7 times larger, along with 60 mV decrease in the onset potential of EOR, than that on the Pd/MSCS (prepared with CATB) catalyst. Summarily, a very cost-effective and facile method for fabricating hawthorn sherry ball shaped Pd-based composite catalysts towards EOR was created in this work, which was very meaningful not only to the further development of EOR catalysts but also to the exploration of micron-devices.     

Surface reactivity of graphite materials and their surface passivation during the first electrochemical lithium insertion

The surface passivation of TIMREX^® SLX50 graphite powder was studied as received and after heat treatment at 2500 °C in an inert gas atmosphere by differential electrochemical mass spectrometry in electrochemical lithium half-cells. 1 M LiPF₆ in ethylene carbonate and either a dimethyl carbonate, propylene carbonate or 1-fluoro ethylene carbonate co-solvent was used as electrolyte systems in these half-cells. The SEI-film formation properties of both graphite materials were correlated with their active surface area (ASA), being responsible for the interactions between the carbon and the electrolyte system. The active surface area was determined from the amount of CO and CO₂ gas desorbed at temperatures up to 950 °C from the graphite material surface after chemisorption of oxygen at 300 °C. The structural ordering at the graphite surface increased significantly during the heat treatment of the SLX50 graphite material as indicated by the significant decrease of the ASA value. The increased surface crystallinity was confirmed by krypton gas adsorption, Raman spectroscopy as well as temperature-programmed desorption. This increased structural ordering seemed to be the parameter being responsible for a hindered passivation of the heat-treated SLX50 causing partial exfoliation of the graphite structure during the first electrochemical lithium insertion in the ethylene carbonate/dimethyl carbonate electrolyte. In the case of the ethylene carbonate/1-fluoro ethylene carbonate electrolyte system, primarily the fluoro compound is responsible for the graphite passivation. In this electrolyte system, pristine SLX50 and the less reactive, heat-treated SLX50 graphite showed significantly different SEI-film formation mechanisms. In contrast, no difference in the passivation mechanism could be identified for different graphite surfaces in the ethylene carbonate electrolyte system with propylene carbonate as co-solvent.     

Effect of deashing rice straws on their derived activated carbons produced by phosphoric acid activation

We studied the effect of physically and/or chemically deashing rice straw (RS) on the adsorption capacity of their derived activated carbons (ACs) produced by chemical activation with H₃PO₄. Surface area and pore volumes were determined by nitrogen adsorption at 77 K. Methylene blue adsorption isotherms onto ACs were carried out, and we applied Langmuir and Freundlich models to fit the adsorption data. We showed that preliminary deashing does not bring significant improvement to the resultant ACs’ properties. ACs prepared by H₃PO₄ activation of raw and deashed RS have intermediate performances between those of ACs prepared by 1- and 2-step KOH activation, but are much cheaper to produce.     

Study on Adsorption of Water in MCM41 Containing Metal Ions by Molecular Dynamic Simulations

To clarify whether the adsorption of water in MCM41 can be promoted by introducing some metal ions onto its surface, molecular dynamics simulations were carried out to investigate the behavior of some water molecules confined in mesoporous MCM41 whose pore size was tailored to 2.5 nm. Pure silica MCM41 as well as those containing some metal ions such as Al3 , Cu2 , and La3 was simulated, and by observing the local average density distribution of particles, we found that both the MCM41 containing Al3 and that of La3 performed higher adsorption and lower desorption temperature. It is concluded that the adsorption is improved mainly owing to the diversities of polarity, active sites, and structure imported by these metal ions.     

A novel polymer encapsulated silica nanoparticles for water control in development of fossil hydrogen energy—tight carbonate oil reservoir by acid fracturing

This paper introduces and evaluates performance of a novel polymer encapsulated silica nanoparticles (CM-NPs) as RPM on reducing water-cut in tight carbonate oil formations with multistage hydraulic fractures. CM-NPs as RPM were prepared by graft-polymerization and quaternization and then identified by FT-IR method. Changes in the core surface properties and oil/water relative permeability were identified by SEM, XPS, wettability measurements and core flooding experiments. Certain changes occur, as confirmed by SEM and XPS, in the element compositions and microstructure of the core surface after introducing CM-NPs on the reservoir rock surface. Such changes irreversibly alter its wettability from the hydrophobicity to hydrophilicity. During the displacement experiments, there exists a disproportionate permeability reduction on relative permeability of the oil-water systems. Because of microstructure change of core surface, water relative permeability is reduced up to 60% and water flow restricted by hydrophilic polymer chains on the surface of CM-NPs while oil relative permeability decreases by less than 15% at different stages of water saturation. In addition, the rheological measurements and water drive tests shows the CM-NP solution has good acid resistance and strong adsorption on the core surface, keeping a long-term period of water control after acid fracturing in tight carbonate oil reservoir.     

贵州省岩溶地区年径流系数受下垫面影响的分析

为研究岩溶地区年径流系数受特殊地貌、地质条件的影响程度,利用贵州省境内23个岩溶流域1961~2000年的径流资料和气象资料,采用Budyko方程拟合表征流域下垫面特征的参数值,并通过Mann-Kendall方法与相关分析,分析年径流系数变化趋势及其与流域下垫面特征的关系。结果表明,贵州省多年平均径流系数的空间分布与流域坡度呈正相关,与碳酸盐岩所占比例呈负相关;1961~2000年年径流系数呈增大趋势,与下垫面特征参数变化趋势一致,可见相对于气候变化,下垫面变化是影响贵州省年径流系数变化的主要因素。     

Anodic behavior of Al current collector in 1-alkyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl] amide ionic liquid electrolytes

The anodic behaviors of aluminum current collector for lithium ion batteries were investigated in a series of 1-alkyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl] amide room temperature ionic liquids (RTILs) and EC + DMC electrolytes. It was found that the aluminum corrosion, which occurred in EC + DMC electrolytes containing LiTFSI, was not observed in the RTIL electrolytes. Further research showed that a passive film with amide compounds as main components formed firmly on aluminum surface during the anodic polarization in the RTIL electrolytes, which inhabited the aluminum corrosion. In addition, the additives generally used in the batteries, such as ethylene carbonate, ethylene sulfite and vinyl carbonate, as well as temperature did not obviously affect the aluminum passive film, the oxidation of the RTILs increased at the elevated temperature, which only resulted in the corrosion potential of aluminum in the RTIL electrolytes shifted to more negative potential, a passive film still firmly formed on the aluminum surface to surpassed the further oxidation of the aluminum current collector. Those results lead to a potential for the practical use of LiTFSI salt in the room temperature ionic liquid electrolytes for lithium ion batteries.     

Dye sensitized photovoltaic cells: Attaching conjugated polymers to zwitterionic ruthenium dyes

The synthesis of a zwitterionic ruthenium dye that binds to anatase surfaces and has a built-in functionality that allows for the attachment of a conjugated polymer chain is presented. The system was found to adsorb on the surface of anatase anchored by the ruthenium dye. Two types of devices were prepared: standard photoelectrochemical (PEC) solar cells and polymer solar cells. The PEC solar cells employed a sandwich geometry between TiO₂ nanoporous photoanodes and Pt counter electrodes using LiI/I₂ in CH₃CN as an electrolyte. The polymer solar cells employed planar anatase electrodes and the complex was adsorbed onto the surface before evaporation of gold electrodes. Alternative devices were obtained by spincoating of the polymer solution onto PEDOT:PSS covered indium-doped tin oxide substrates. PEC solar cells gave the best results and the main finding was that the polymer chain served as a light harvesting antenna for the ruthenium dye.