Resistivity index of fractional wettability porous media

The effects of fractional wettability on electrical resistivity index curves of porous media are investigated using pore network models. A bond percolation-and-fractal roughness model is used to simulate the oil/water drainage of the conventional porous plate method in pore networks composed of randomly distributed ‘strongly water-wet' and ‘strongly oil-wet' capillaries. Based on universal scaling laws of percolation quantities, effective medium approximation and fractal geometry, approximate analytic relationships are developed with respect to the dependence of the resistivity index, capillary pressure and saturation exponent on certain microstructural properties of the pore space and surface fractional wettability over the various water saturation regions. The simulated data are fitted to two-exponent power laws, which in turn are evaluated as macroscopic conceptual models of the resistivity index. At high water saturations, the saturation exponent becomes a strongly increasing function of the fraction of oil-wet pores when the value of this parameter exceeds the percolation threshold of the lattice network and oil percolates spontaneously through network joining clusters of oil-wet pores. At intermediate water saturations, the saturation exponent is a moderately increasing function of the fraction of oil-wet pores, whereas the slope of the capillary pressure curve remains almost unaltered to variations of wettability. At low water saturations, as the fraction of oil-wet pores becomes quite large, permanent trapping of water may occur with result that both the saturation exponent and the slope of the capillary pressure curve tend to infinity at the limit of irreducible water saturation. The exponents of the phenomenological models of the resistivity index change significantly with fractional wettability and are consistent with the values of the saturation exponent obtained with the approximate analytic relationships.     

Characteristics of Milk Powders Produced by Spray Freeze Drying

Skim and whole milk powders were manufactured at lab scale by spray freeze drying (SFD), using liquid nitrogen as the cryogen. The polydispersity of droplet/particle sizes was limited using an encapsulator nozzle to atomize the feed. Particle morphology was examined using a scanning electron microscope. Samples were compared with equivalent spray-dried powders in tests of wettability and dissolution in water. The spray freeze-dried powders were found to be highly porous, with a uniform structure of pores throughout the entire particles. When tested in water, SFD skim milk powders wetted roughly three times as fast as industrially spray-dried agglomerated skim milk powders and were observed to dissolve rapidly by breaking down into smaller particles.     

Surface Activation and Adhesion Properties of Wood-Fiber Reinforced Thermoplastic Composites

Four surface activation methods were evaluated on a series of wood-fiber reinforced thermoplastic composites (WPCs) as a means to improve the adhesion of a water-based acrylic coating. Treatments with chromic acid and oxygen plasma performed best, increasing the acrylic coating peel load to WPCs by 170 and 122%, respectively, and yielding adhesion levels equivalent to or higher than those obtained on wood. The benzophenone/ultraviolet and flame treatments also improved the coating adhesion by 100 and 64%, respectively, but did not reach the adhesion levels achieved on wood. For both the chromic acid and oxygen plasma treatments, the WPC formulation impacted the treatment efficacy. Profilometry and scanning electron microscopy (SEM) showed that the chromic acid treatment acted mainly by roughening WPC surfaces. While surface oxidation was not evident from attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), the improved wettability of WPCs with water suggested that the oxygen plasma treatment oxidized WPCs.     

Electroless oxidation of diamond surfaces in ceric and ferricyanide solutions: An easy way to produce “C-O” functional groups

Despite many works are devoted to oxidation of diamond surfaces, it is still a challenge, to successfully produce well defined “C-O” functions, particularly for functionalization purposes. In this paper we describe and compare, for the first time, the “electroless” oxidation of as-deposited polycrystalline boron-doped diamond (BDD) films in ceric and ferricyanide solutions at room temperature. Both reactions efficiently generate oxygen functionalities on BDD surface. While a higher amount of “C-O” moieties is produced with Ce⁴⁺ as oxidizing agent, the use of ferricyanide specie seems the most interesting to specifically generate hydroxyl groups. Additionally, this easy to perform oxidative method appears not damaging for diamond surfaces and adapted to conductive or non-conductive materials. The resulting surfaces were characterized using X-ray photoelectron spectroscopy, contact angle and capacitance-voltage analysis.     

Effect of Grain Boundary on the Wettability and Interfacial Morphology in the Molten Bi／Cu System

The wetting behavior of molten Bi on polycrystalline Cu substrate and single crystal Cu substrate was studied by the sessile drop method in the temperature range from 673 to 873K. At low temperature the wetting behaviors of molten Bi on both types of Cu substrate were similar. However, at high temperature, the equilibrium contact angle of polycrystalline Cu substrate was lower than that of single crystal Cu substrate, because the preferred dissolution of grain boundaries leads to a smaller liquid/solid interracial energy for polycrystalline Cu substrate. The formation mechanism of arrow-shaped Cu grains at the Bi/single crystal Cu interface is also discussed.     

癸烷在二氧化硅表面的油膜形成与表面润湿性

用二氧化硅片作为模拟岩石，以椭圆偏振法测量癸烷在其表面形成的油膜厚度，通过长度测量法测定水在二氧化硅表面的接触角来判断润湿性及润湿性的变化。亲水的二氧化硅表面难以形成油膜，而疏水的二氧化硅表面能形成较厚而稳定的油膜。疏水或近中性的二氧化硅表面在经碱水作用或吸附表面活性剂后，在特定的条件下能变成弱亲水或亲水，从而将油膜破坏。     

Synergistic Effect on Wettability of Mixtures of Amine Oxides,Alkylpolyglucosides, and Ethoxylated Fatty Alcohols

The mixture proportions of three surfactants, i.e. an alkylpolyglucoside (APG), an ethoxylated fatty alcohol, and an amine oxide (AO), were optimized by applying Response Surface Methodology in order to achieve the surfactant ratio that produces the highest wetting power. The synergistic effect of the binary samples of AO with the other surfactants was firstly verified. An improvement in this synergistic effect on wettability was found in the ternary mixture. In the experimental range analyzed, the surfactant concentration ratio that produced the highest wettability was a composition with 19.3 % APG, 30.1 % ethoxylated alcohol, and 50.6 % lauramine oxide.     

Wettability Enhancement of SiCp in Cast A356/SiCp Composite Using Semisolid Process

The effects of SiCp treatment and magnesium addition on microstructural and mechanical properties of Al356/20 wt% SiCp semisolid composites were investigated. The results showed that cleaning and oxidizing of SiCp and addition of 1 wt% Mg resulted in improving wettability, incorporation, and uniform distribution of SiCp in A356 matrix. Consequently, the ultimate tensile strength (UTS) value increased by 19% and 32% when the SiC was treated and also when Mg was added, respectively, compared to as-received SiCp. In addition, hardness value increased from 69.7 HV in as-received SiCp to 94.8 HV after SiCp treatment and addition of Mg.     

Petroleum geochemical proxies for reservoir engineering parameters

The prediction of fluid flow behaviour in petroleum reservoirs is influenced by the physical and chemical processes active in interacting crude oil/brine/rock systems. It is usually not possible to assess these complex systems directly so proxies for molecular scale behaviour are needed. By their very nature, polar non-hydrocarbons are sensitive to fluid–rock interactions, and if properly exploited they may be utilised as proxies for describing reservoir engineering properties (e.g. wettability) that are also sensitive to fluid–rock interactions. We have identified a group of aromatic oxygen (alkylphenols and alkylfluorenones) and aromatic nitrogen (alkylcarbazoles) compounds present in petroleum that appear to respond to variations in fluid–rock properties. Here we describe the chemical and physical changes in a series of core samples obtained from North Sea reservoirs. A number of petrophysical parameters displayed strong correlations with polar non-hydrocarbon occurrence. For example, deflections in gamma ray logs in response to clay content in a coarsening upwards sandstone unit also showed similar deflections from a number of geochemical logs.A core-flood experiment was designed to monitor the chemical and physical changes during oil migration in a siltstone core. Following completion of the core-flood experiment, Environmental Scanning Electron Microscopy (ESEM) analysis of core samples indicated hydrophilic and hydrophobic surface tendencies grading throughout the core. The distributions of polar non-hydrocarbons (e.g. C₀–C₃–phenols) appear to correspond closely to the observed wettability alteration. The results confirm the potential for developing proxies for fluid–rock interactions through monitoring the surface active compounds present in the polar non-hydrocarbon fraction of petroleum.     

The effect of wettability heterogeneity on capillary pressure and relative permeability

The effect of wettability on fluid flow properties in porous media has been extensively studied, and is still a subject of highly active investigation. Most of the work has focused on cores of homogeneous wettability. Little attention has been paid to wettability heterogeneity effects at the core or pore scale. In a previous paper, we reported on a series of centrifuge experiments performed to study the effect of wettability heterogeneity on capillary pressure. An experimental technique, named cyclic aging, was developed to create regions of different wetting in the same core sample. In this paper, the work is extended to study the effect of wettability heterogeneity on both capillary pressure and relative permeability curves using centrifuge, continuous injection and steady state techniques.The experimental procedure consists of three steps: (1) the core plug is fully saturated with brine and subsequently a drainage experiment is performed targeting an initial oil saturation S_oi, (2) after aging, oil is displaced by water to residual oil saturation S_or, and (3) oil is injected targeting higher initial oil saturation. In the secondary drainage experiment (step 3), oil first displaces water from the pores exposed to crude oil in primary drainage (step 1) and then enters fresh pores not exposed to crude oil before.In our previous study, it was found that wettability heterogeneity caused a step change in capillary pressure which correlated very well with the saturation at which wettability contrast was expected. However, the height of the step could not be explained by wettability contrast and/or water trapping alone. An experimental artifact caused by the centrifuge technique made the step higher than expected. The experimental artifact was the result of the nonuniform saturation profile developed across the core at the end of the centrifuge experiment. In this study, new techniques were used which resulted in a uniform saturation profile along the core sample during the primary drainage experiment. It was found that in this case the step in the capillary pressure is determined by wettability contrast and water trapping. It was also found that the relative permeability curve changes its characteristics when oil accesses the pores not previously exposed to crude oil.The results of this study show that (1) only the part of the pore space exposed to crude oil undergoes wettability changes on both core scale and pore scale, and (2) ignoring wettability heterogeneity can lead to large errors in the estimated two phase flow functions with important consequences with respect to fluid flow in porous media.