动态条件下超声储层水敏性去除实验研究*

利用自主研制的超声发生仪,选取不同渗透率的天然岩心,模拟实际地层的温度、压力进行室内驱替实验,评价了渗流过程中超声作用对储层水敏性伤害去除的影响。研究表明,对于去除储层水敏性,超声频率存在最佳范围,频率与功率存在一定的补偿关系;超声最佳处理时间与储层物性有一定联系;渗透率恢复率与储层物性呈现较复杂的关系。研究结果有助于进一步认识超声水敏性去除的作用机理。     

Effects of solvent in the casting of poly(1-trimethylsilyl-1-propyne) membranes

Poly(1-trimethylsilyl-1-propyne) (PTMSP) membranes were fabricated by solvent casting from solutions of toluene, cyclohexane and tetrahydrofuran. The effects of the casting solvent on the physical structure of PTMSP were investigated using wide angle X-ray diffraction and positron annihilation lifetime spectroscopy. The permeability of oxygen, nitrogen and carbon dioxide through the cast membranes was also measured. It was found that the nature of the casting solvent markedly influenced the conformation and the free volume of PTMSP, which in turn affected the gas permeability of the cast membranes.     

Carrier gas flow arrangement based photoacoustic detection method for measuring gas permeability of polymer membranes

This paper describes a membrane permeability measuring set-up based on photoacoustic spectroscopy using continuous carrier gas flow to transport the permeated analyte molecules into a photoacoustic detection cell. The permeability parameters of the sample were determined from the measured permeation curves by using a numerical curve fitting algorithm. The method was applied to different membrane samples for determining methane and carbon-dioxide permeability at various carrier gas flow rates (CFRs). For each sample, a characteristic threshold flow rate (TFR) value can be identified below which a strong dependency of the determined permeation parameters on the CFR was found. For those cases when the CFR value cannot be set to be sufficiently high (i.e. above the TFR value), an extrapolation method was presented giving an accurate estimation of the permeation parameters.     

黏性土渗透性温度效应实验研究

由于全球气候变暖、城市热岛效应加剧和核废料地质处置等原因,温度对黏性土工程性质的影响日益受到关注。本文在实验的基础上,采用直接测量法,对南京下蜀土、淤泥质土以及混合土3种试样,进行了5°～45°温度下的变水头渗透实验,分析了温度对黏性土渗透性的影响。实验结果表明：温度对3种试样的渗透性均有较大影响。温度越高,渗透性越大; 试样的密度越大,渗透系数随温度变化率越低; 在3种试样中,混合土的渗透系数高于淤泥质土和下蜀土的对应值,而淤泥质土的渗透系数又略大于下蜀土。最后对黏性土渗透性的温度效应机理进行了分析,认为水的动力黏滞性,黏粒的双电层厚度以及土的微结构三方面因素的共同作用引起了黏性土渗透性的温度效应。
黏性土,渗透系数,温度效应,机理     

Surfactant Effects on the Permeability of Photosynthetic Membrane from Rhodobacter sphaeroides 2.4.1 Probed by Electrochromic Shift of Endogenous Carotenoids

Four surfactants, sodium cholate(SC), n-dodecyl-β-D-maltopyranoside(DDM), lauryldimethylamine oxide(LDAO) and Triton X-100(TX), which are generally used in photosynthetic pigment-protein complexes preparation, were studied on their interaction with photosynthetic membrane from Rhodobacter sphaeroides 2.4.1 by electrochromic absorption band-shift of endogenous carotenoids and by vesicle size measurements as well. The surfactant critical micelle concentration(cmc) was found to be negatively correlated with the capability of enhancing the permeability of photosynthetic membranes to proton, and more elaborated model of surfactants interacting with membranes was obtained. The electrochromic absorption band-shift measurement might develop into a useful tool to evaluate the effects of surfactants on various membranes.     

Co-dopant affect on the structural,electrical and magnetic properties of zirconium and copper co-substituted Ni0.75Zn0.25Fe2O4 spinel ferrites synthesized by sol-gel method

The zirconium and copper co-substituted Ni_0.75Zn_0.25Zr_xCu_xFe_2-2xO₄ (where x?=?0.05, 0.1, 0.15, 0.2) ferrites have been prepared by sol-gel auto-combustion method. The XRD patterns provide the evidence of single phase cubic spinel structure. The theoretical and experimental lattice parameters have resemblance with increase dopant concentration. The sintered density and porosity show the opposite trend with dopant concentration. The FT-IR spectrum of prepared samples reveal cubic spinel with $Fd\overline{3}m$($O_h^7$) space group. The wave numbers of tetrahedral and octahedral sites show agnate trend. The dielectric constant and loss factors decreased with increasing dopant concentration. The saturation magnetization and net magnetic moment have the identical trend with increasing dopant concentration. The coercive field is decreased with increasing dopant concentration. The Y–K angles are increased with increasing dopant concentration. The Q-factor in prepared samples, exhibit narrower frequency bands with increasing frequency.     

Experimental study on the influence of low-frequency and low-intensity ultrasound on the permeability of the Mycobacterium smegmatis cytoderm and potentiation with levofloxacin

Tuberculosis is an infectious disease caused by the bacterium M. tuberculosis. The aim of this study was to investigate the bactericidal effect and underlying mechanisms of low-frequency and low-intensity ultrasound combined with levofloxacin treatment against M. smegmatis (a surrogate of M. tuberculosis). As part of this study, M. smegmatis was continuously irradiated with low frequency ultrasound (42 kHz) using several different doses whereby both intensity (0.138, 0.190 and 0.329 W/cm²) and exposure time (5, 15 and 20 min) were varied. Flow cytometric analyses revealed that the permeability of M. smegmatis increased following ultrasound exposure. The survival rate, structure and morphology of bacteria in the lower-dose (I_SATA = 0.138 W/cm² for 5 min) ultrasound group displayed no significant differences upon comparison with the untreated group. However, the survival rate of bacteria was significantly reduced and the bacterial structure was damaged in the higher-dose (I_SATA = 0.329 W/cm² for 20 min) ultrasound group. Ultrasound irradiation (0.138 W/cm²) was subsequently applied to M. smegmatis in combination with levofloxacin treatment for 5 min. The results demonstrated that the bactericidal effect of ultrasonic irradiation combined with levofloxacin is higher compared to ultrasound alone or levofloxacin alone.     

CO<Subscript>2</Subscript> injection into saline carbonate aquifer formations I: laboratory investigation

Although there are a number of mathematical modeling studies for carbon dioxide (CO₂) injection into aquifer formations, experimental studies are limited and most studies focus on injection into sandstone reservoirs as opposed to carbonate ones. This study presents the results of computerized tomography (CT) monitored laboratory experiments to analyze permeability and porosity changes as well as to characterize relevant chemical reactions associated with injection and storage of CO₂ in carbonate formations. CT monitored experiments are designed to model fast near well bore flow and slow reservoir flows. Highly heterogeneous cores drilled from a carbonate aquifer formation located in South East Turkey were used during the experiments. Porosity changes along the core plugs and the corresponding permeability changes are reported for different CO₂ injection rates and different salt concentrations of formation water. It was observed that either a permeability increase or a permeability reduction can be obtained. The trend of change in rock properties is very case dependent because it is related to distribution of pores, brine composition and thermodynamic conditions. As the salt concentration decreases, porosity and the permeability decreases are less pronounced. Calcite deposition is mainly influenced by orientation, with horizontal flow resulting in larger calcite deposition compared to vertical flow.     

Pressure drop and friction factor of steady and oscillating flows in open-cell porous media

Open-cell metal foams are often used in heat exchangers and absorption equipment because they exhibit large specific surface area and present tortuous coolant flow paths. However, published research works on the characteristics of fluid flow in metal foams are relatively scarce, especially for the flow oscillation condition. The present experimental investigation attempts to uncover the behavior of steady and oscillating flows through metal foams with a tetrakaidecahedron structure. In the experiments, steady flow was supplied by an auto-balance compressor and flow oscillation was provided by an oscillating flow generator. The pressure drop and velocity were measured by the differential pressure transducer and hot-wire sensor, respectively. The friction factor of steady flow in metal foam channel was analyzed through the permeability and inertia coefficient of the porous medium. The results show that flow resistance in the metal foams increases with increasing form coefficient and decreasing permeability. The empirical equation obtained by the present study indicates that the maximum friction factor of oscillating flow through the tested aluminum foams with specific structure is governed by the hydraulic ligament diameter-based kinetic Reynolds number and the dimensionless flow amplitude.     

Investigation of the porous drag and permeability at the porous-fluid interface: Influence of the filtering parameters on Darcy closure

The porous-fluid interface encompasses a region bridging the flow inside a porous medium and a free-flowing fluid. In the context of volume-averaged simulations, it can be described by a set of gradually changing parameters defining the porous medium, mainly porosity and permeability. In this paper, both the permeability and the porous-induced drag force are evaluated a-priori, by explicitly filtering a set of Particle-Resolved Simulations (PRS) of the flow in the channel partially occupied by the porous medium. Different porous matrices are considered and the influence of the geometry and filtering parameters on the macroscopic quantities is studied. Especially, the focus is placed on the requirements for the kernel type and size to perform filtering accurately, and their impact on the distribution of permeability at the interface. The performance of the typically used models for the permeability is compared to the explicitly filtered results. Lastly, a new model for permeability and the drag force is introduced, taking into account the information about the filtering size and non-uniformity of the velocity field. The model greatly improves the prediction of velocity at the porous-fluid interface and serves as a proof of concept that a successful porous drag model should strive to include information about both parameters.