Capillary Curves Research Articles

Investigation of pore structure and petrophysical property in tight sandstones

Laboratory measurements include porosity, permeability, high pressure mercury intrusion (HPMI), nuclear magnetic resonance (NMR) measurements and microscopic analysis of thin sections and scanning electron microscope (SEM) were used to gain insight into the nature of the pore throat structure including pore geometry, pore size distribution and pore connectivity of Bashijiqike tight gas sandstones in Keshen 5, Keshen 6, Keshen 8, Keshen 9 and Keshen 13 Wellblock of Kuqa depression. The relationships between microscopic pore structure parameters and macroscopic petrophysical behaviors were investigated by regression analysis. The results show that various types of pores with wide ranges of pore radius are observed. The pore throats are very small (commonly <1 μm), and large pores are generally connected by tiny pore throats. Pore throats larger than rapex (pore radius at the apex of the Pittman's hyperbola) accounts for a small fraction of the pore volume, but make a significant contribution to permeability. The porosity connected by large pore throats (>rapex) controls permeability in tight gas sandstones. The NMR pore size distribution is broader than the HPMI pore throat distribution. In the NMR analysis, only the pore systems connected by the relatively large pore throats should be accounted as movable, and some portion of large pores, which are not connected by effective large pore throats, are not effectively movable. The effective movable porosity is calculated by excluding those pores restricted by the tiny pore throats. The content of effective movable porosity from NMR measurements shows good correlation relationship with the porosity connected by large pore throats in HPMI analysis. Three typical types of pore structures are recognized through thin section, SEM analysis combined with the capillary curve and NMR T2 spectrum, and the microscopic and macroscopic characteristics of the three pore structures are investigated. The pore structure were comprehensively evaluated and characterized by linking NMR T2 spectrum with HPMI analysis.

Reflectance spectroscopy: to shed new light on the capillary refill test.

To use Bioengineering methodology is used to achieve, at five anatomical sites, a detailed, quantitative assessment of the return of blood content to the blanched area, during the Capillary Refill (CR) test. An observational, non-randomized, experimental study on 23 healthy subjects (14 females) was performed in our climate controlled skin physiology laboratory. Our main outcome measures were based on the chronological assessment and quantification of red blood cell concentration (RBC) after the release of blanching pressure in the CR test, using Tissue Viability Imaging (TiVi), a digital photographic technique based on polarisation spectroscopy. TiVi enabled collection of detailed data on skin RBC concentration during the CR test. The results were shown as curves with skin blood concentration (TiVi-value) on the y-axis and the time on the x-axis. Quantitative CR responses showed site and temperature variability. We also suggest possible objective endpoint values from the capillary refill curve. Detailed data on skin RBC concentration during the CR test is easily obtained and allows objective determination of end points not possible to achieve by naked eye assessment. These findings have the potential to place the utility of the CR test in a clinical setting in a new light. Picture: Regular photograph and TiVi Image showing CR test and corresponding graph for the CR response.

Evaluation of Transport Properties Effect on the Performance of Gas-Condensate Reservoirs Using Compositional Simulation

Gas-condensate productivity is highly dependent on the thermodynamic behavior of the fluids-in-place. The condensation attendant with the depletion of gas-condensate reservoirs leads to a deficiency in the flow of fluids moving toward the production channels. The impairment is a result of condensate accumulation near the production channels in an immobility state until reaching a critical saturation point. Considering the flow phenomenon of gas-condensate reservoirs, tight formations can be inevitably complex hosting environments in which to achieve economical production. This work is aimed to assess the productivity gas-condensate reservoirs in a naturally fractured setting against the effect of capillary pressure and relative permeability constraints. The severity of condensate coating and magnitude of impairment was evaluated in a system with a permeability of 0.001 mD using an in-house compositional simulator. Several composition combinations were considered to portray mixtures ascending in complexity from light to heavy. The examination showed that thicker walls of condensate and greater impairment are attained with mixture containing higher nonvolatile concentrations. In addition, the influence of different capillary curves was insignificant to the overall behavior of fluids-in-place and movement within the pores medium. A greater impact on the transport of fluids was owed to relative permeability curves, which showed dependency on the extent of condensate content. Activating diffusion was found to diminish flow constraints due to the capturing of additional extractions that were not accounted for under Darcy's law alone.

Corrigendum: Capillary water retention curve and shear strength of unsaturated soils

<i>Corrigendum:</i> Capillary water retention curve and shear strength of unsaturated soils

A QUANTITATIVE EVALUATION METHOD OF LOW PERMEABLE SANDSTONE PORE STRUCTURE BASED ON NUCLEAR MAGNETIC RESONANCE (NMR) LOGGING: A CASE STUDY OF Es4 FORMATION IN THE SOUTH SLOPE OF DONGYING SAG

AbstractLow permeability sandstone has become an important target of exploration and development for increasing reserves and productions, while the complicated pore structure makes the reservoir and its effectiveness difficult to accurately identify. We used the physical property, mercury injection, and nuclear magnetic data to analyze the pore structure of low permeability sandstone of the Es4 in the south slope of Dongying sag, and divided the pore structure into three different types. Nuclear magnetic T2 spectrum and capillary pressure can reflect the distribution of pore throat to a certain extent. The pseudo capillary pressure curve reconstructed by T2 spectrum with the routine method can be used to invert for the pore radius distribution, but there is a large error between the pore radius distribution and capillary pressure pore‐throat radius distribution. The rock pore free fluid T2 and mercury intrusion pore throat size distribution have a better corresponding relationship. Therefore, this relationship is used to construct the formula for different pore structure types and on different pore scales (large scale: the linear relationship; small scale: power function in different scale). By identifying the pore structure types along the wellbore profile, we can further determine the pore radius distribution using NML data without building the pseudo capillary curve. And this method not only supply a direct evidence for efficiency evaluation of low permeability sandstone reservoir, but also play an important role in the exploration of quantitative inversion of the pore radius distribution on a micro‐scale.

Revisiting the applications of drainage capillary pressure curves in water-wet hydrocarbon systems

AbstractThe main focus of the paper is to introduce a new approach at studying and modelling the relationship of initial water saturation profile and capillarity in water-wet hydrocarbon reservoirs, and describe the available measurement methods and possible applications. As a side track it aims to highlight a set of derivable parameters of mercury capillary curves using the Thomeer-method. Since the widely used mercury capillary pressure curves themselves can lead to over-, or underestimations regarding in-place and technical volumes and misinterpreted reservoir behaviour, the need for a proper capillary curve is reasonable. Combining the results of mercury and centrifuge capillary curves could yield a capillary curve preserving the strengths of both methods, while overcoming their weaknesses. Mercury injection capillary curves were normalized by using the irreducible water saturations derived from centrifuge capillary pressure measurements of the same core plug, and this new, combined capillary curve was applied for engineering calculations in order to make comparisons with other approaches. The most significant benefit of this approach is, that all of the measured data needed for a valid drainage capillary pressure curve represents the very same sample piece.

A Laboratory Investigation of the Effects of Temperature, Hardness, Surfactants, and Alkaline on Oil Recovery from Carbonate Reservoirs Using Spontaneous Imbibition Tests

More than 50 % of the known petroleum reserves are stuck in carbonate reservoirs, which can be divided into limestone, chalk, and dolomite. On average, the oil recovery from carbonates is below 30 % due to low water wetness, natural fractures, low permeability, and inhomogeneous rock properties. Therefore, there is increasing interest to improve oil recovery from carbonate reservoirs, as we are challenged to make up depleted reserves. Although there is a great potential to improve oil recovery in carbonate reservoirs, the research in this area is very limited due to technical and economic challenges. Chemical enhanced oil recovery research in carbonate reservoirs has been focused on using such as surfactant and alkaline increase oil recovery or to change oil-wet to more water-wet to enhance water imbibition into matrix blocks. Wettability alteration results in spontaneous imbibition of water into oil containing matrix, thus driving oil out of the matrix. Wettability alteration has been formulated with surfactant adsorption, and relative permeability and capillary curves are modified based on the degree of wettability alteration. Many research has been investigated in a lab scale how a wettability of reservoir rocks affected in oil recovery and how wettability alteration can be controlled to maximize the oil recovery in limestone rocks. The objective of this study is to investigate the effects of temperature, hardness, surfactants, and alkaline on oil recovery from limestone rock. In order to investigate the effect of these parameters, the limestone rocks were placed in the oven in brine to simulate realistic reservoir conditions. Then, they were aged in crude oil in the oven. After that, the solution with various compositions of surfactant, alkaline, and hardness were tested by spontaneous imbibition test. The spontaneous imbibition test in this study was performed at 25 oC and 80 oC with different limestone rocks. The results show that, at high temperature, the oil recovery is higher than at low temperature. The hardness has various impacts on the wetting properties. and are important in changing wettability on limestone surface and were proved by increase in oil recovery. ion was demonstrated by the very small increase in oil recovery. The alkaline has increased oil recovery from limestone rocks.

Vectorial detection of sub-microscale capillary curvature by laser beam profile

We demonstrate a simple and non-invasive optical technique to detect direction and magnitude of long-range, sub-microscale capillary curvature of fluid interfaces in various situations. By analyzing magnitude and direction of the distorted spatial profile of the laser beam, following its weak Fresnel's reflection from the air-water interface, ultra-low curvature of 0.1 μm−1 caused by dipped slides, glass tubes, and microscopic twisted silk fibers was measured up to six capillary lengths away from the object. The flexibility of this technique allows us to measure curvature of remotely placed fluid-fluid interfaces and interaction between capillary curves of multiple objects. The high sensitivity of our technique is demonstrated in measuring magnetic susceptibility of water and the full spatial profile of deformation under weak magnetic field. This technique might find applications in precision measurements in optofluidics and interface physics.

Porosity development in a thermo-hygral finite element model for cementitious materials

A numerical model for the thermo-hygral (TH) behaviour of cementitious materials is presented. The model includes a new approach to the evaluation of porosity during hydration in which a colloid model and stoichiometry are used to evaluate the volume of bound and unbound water forms. The advantage of the proposed porosity function is that it accounts for different cement types and concrete mixes and it gives a porosity evolution consistent with the moisture mass balance equation. Sink/source terms are introduced for the capillary water that account for the moisture entering/exiting the gel pores and the aggregate, whilst the standard capillary curve is modified to account for temperature and changing porosity with hydration. The numerical model considers as the primary variables the water degree of saturation of capillary pores and the temperature and is validated using several drying experiments. The results are generally in good agreement with experimental measurements.

Capillary Curves for Ex‐situ Washing of Oil‐Coated Particles

AbstractThe oil removal efficiency for the ex situ extraction of bitumen from oil sands, or ex situ washing of oil‐contaminated sand and related processes is determined by the balance of forces at the oil/water and solid/fluid interfaces. The objective of this work is to estimate the balance of forces at the interface using dimensionless numbers, and their use in evaluating and engineering ex situ soil washing processes. To this end, bitumen was removed from bitumen‐coated sand particles using a two‐step process. In the first step, the particles were mixed with a suitable solvent (toluene) used, primarily, to reduce the viscosity of bitumen. The particles were then mixed with water or an aqueous surfactant solution capable of producing low interfacial tensions with the solvent‐bitumen mixture. The fraction of oil retained after washing was evaluated as a function of interfacial tension, solvent/bitumen ratio, mixing time, mixing velocity, and particle size. These ex situ washing conditions were normalized using dimensionless film and particle‐based Weber and Capillary numbers. The fraction of oil retained by the particles was plotted against these dimensionless numbers to generate capillary curves similar to those used in enhanced oil recovery. These curves reveal the existence of a critical film‐based Weber number and a particle‐based Capillary number that can be used in the design or evaluation of soil washing processes. The film‐based Weber number also explained literature data that associates interfacial tension with the removal of oil from oil‐based drill cuttings, as well as field observations on the role that particle size plays on the removal of oil in soil washing operations.

Supplement and optimization of classical capillary number experimental curve for enhanced oil recovery by combination flooding

In the middle of the last century, American scientists put forward the concept of capillary number and obtained the relation curve between capillary number and residual oil through experiments. They revealed that the corresponding residual oil saturation decreased with increasing of capillary number; after capillary number reached up to a limit, residual oil saturation would become stable and did not decrease. These important achievements laid a theoretical base for enhanced oil recovery with chemical flooding. On the basis of the theory, scholars developed chemical flooding numerical simulation software UTCHEM. During the numerical simulation study of combination flooding, the authors found that as the capillary number is higher than the limit capillary number, the changes of the residual oil saturation along with the capillary number differ from the classical capillary number curve. Oil displacement experiments prove that there are defects in classic capillary number experimental curve and it is necessary to mend and improve. Capillary number ‘calculation’ curve is obtained with a method of numerical simulation calculation and a complete description of capillary number curve is provided; On this basis, combination flooding capillary number experimental curve QL is obtained through experiments, which is different from the classical capillary curve; and based on which, an expression of corresponding combination flooding relative permeability curve QL is given and the corresponding relative permeability parameters are determined with experiments. Further oil displacement experiment research recognizes the cause of the singular changes of the capillary number curve. “Combination flooding capillary number experimental curve QL” and “combination flooding relative permeability curve QL” are written in combination flooding software IMCFS, providing an effective technical support for the application of combination flooding technical research.

An overview of chemical straightening of human hair: technical aspects, potential risks to hair fibre and health and legal issues

Personal image, as it relates to external beauty, has attracted much attention from the cosmetic industry, and capillary aesthetics is a leader in consumption in this area. There is a great diversity of products targeting both the treatment and beautification of hair. Among them, hair straighteners stand out with a high demand by costumers aiming at beauty, social acceptance and ease of daily hair maintenance. However, this kind of treatment affects the chemical structure of keratin and of the hair fibre, bringing up some safety concerns. Moreover, the development of hair is a dynamic and cyclic process, where the duration of growth cycles depends not only on where hair grows, but also on issues such as the individual's age, dietary habits and hormonal factors. Thus, although hair fibres are composed of dead epidermal cells, when they emerge from the scalp, there is a huge variation in natural wave and the response to hair cosmetics. Although it is possible to give the hair a cosmetically favourable appearance through the use of cosmetic products, for good results in any hair treatment, it is essential to understand the mechanisms of the process. Important information, such as the composition and structure of the hair fibres, and the composition of products and techniques available for hair straightening, must be taken into account so that the straightening process can be designed appropriately, avoiding undesirable side effects for hair fibre and for health. This review aims to address the morphology, chemical composition and molecular structure of hair fibres, as well as the products and techniques used for chemical hair relaxing, their potential risk to hair fibre and to health and the legal aspects of their use.

Implications of pore microgeometry heterogeneity for the movement and chemical reactivity of CO2 in carbonates

We studied the heterogeneity of natural rocks with respect to their pore-size distribution, obtained from mercury-intrusion capillary pressure (MICP) tests, at a scale about one-fifth of the standard plug size (2.5 cm). We investigated two Fontainebleau sandstone and two limestone samples. We found that at the scale of the MICP tests, heterogeneities are practically nonexistent. Still, there are large differences in the capillary curves from one rock type to another. Also, carbonate rocks, unlike Fontainebleau sandstone, show heterogeneities at a scale smaller than the scale used in MICP tests, as seen by the complexity in the mercury saturation versus pressure curves. We used this diversity between the capillary curves and this complexity within a single capillary curve to obtain information about the movement and chemical reactivity of [Formula: see text] in carbonates. The method consists of three steps: first, subdividing the carbonate pore system into microstructural facies, each of them having a specific range of pore throat size (e.g., tight micrite, microporous rounded micrite, small vugs, …); second, getting a characteristic value of their petrophysical properties (namely porosity, effective surface area, and permeability) from the collected MICP data; and third, computing, for experimental conditions corresponding to a transport-controlled system, the dimensionless Péclet and Damköhler numbers, expressed as a function of the aforementioned permeability and effective surface area. These numbers allowed us to infer the dominant process (i.e., diffusion, advection, or kinetics) controlling the dissolution/precipitation reaction induced by the carbonic acid. Because of heterogeneities in the pore microstructure, we found that either diffusion or advection is locally the dominant mechanism, which renders some zones (e.g., vugs or, to a lesser extent, microporous rounded micrite) chemically more reactive than others (e.g., tight micrite or spar cement).

Uniform Model for Moisture Transport in Porous Materials and Its Application to Concrete at Selected Chinese Regions

The present study investigates the mechanisms of moisture transport in porous materials. For partially saturated porous materials, moisture transport relies on both the Darcian flow by capillary pressure gradient and the Fickian flow by gas concentration gradient. Taking into account the capillary curves that are associated intimately with the pore structure and play crucial roles on both drying and wetting processes, a uniform model that only depends on one variable, the saturation degree, is established. The isothermal adsorption/desorption method and the Kelvin equation are used to evaluate the capillary curve that obeys the van Genuchten form equation. The established model is applied to characterize the moisture distribution in four (near) coastal regions of China (Guangzhou, Hangzhou, Jinan, and Shenyan). Wetting time is shown to be a dominant factor influencing the stable saturation degree and the influence depth.

Geological controls on matrix permeability of Devonian Gas Shales in the Horn River and Liard basins, northeastern British Columbia, Canada

Abstract Controls of matrix permeability are investigated for Devonian Gas Shales from the Horn River and Liard basins in northeastern British Columbia, Canada. Mineralogy is varied with high carbonate, high quartz and moderate quartz, carbonate and clay rich strata. Quartz content varies between 2 and 73%, carbonate varies between 1 and 93% and clay varies between 3 and 33%. The TOC content ranges between 0.3 and 6 wt.% and porosity varies between about 1 and 7%. For Horn River basin samples, quartz is mainly biogenic in origin derived from radiolarians. TOC content increases with the quartz content suggesting the TOC and quartz both are derived from siliceous phytoplankton. A positive relationship between porosity and quartz content is due to the positive relationship between quartz and TOC. Matrix permeability parallel to bedding varies between 7.5E− 02 and 7.1E− 07 mD at an effective stress of 15 MPa. Variation in permeability is due to a complex combination of factors that includes origin and distribution of minerals, pore‐size distribution and fabric. Mercury intrusion capillary curves indicate that the higher matrix permeability values (> 2E− 03 mD) occurs in samples that contain interconnected pore apertures greater than 16 μm even when these samples may contain less macropores than low permeability samples. The fabric of high permeability samples can be either isotropic or anisotropic; however permeability of anisotropic samples is more sensitive to changes in effective stress than isotropic samples. More highly anisotropic samples contain moderate amounts of quartz, carbonate and in some, clay. High permeability samples that contain a more balanced ratio between micro-, meso- and macroporosity would not only have faster flow rates but also greater access to sorbed gas within the microporosity compared to samples that lack mesopores. Several Muskwa samples compared to Evie and Besa River samples contain higher quartz, moderate clay and high TOC content coupled with high permeability, less sensitivity to effective stress and balanced ratios between micro-, meso- and macroporosity would be a lower exploration risk due a greater propensity to fracture, the ability to produce and store hydrocarbons due to higher TOC contents and greater communication between macropores and micropores in the organic and clay fractions.

Quantitative Evaluation of Micro Pore Throat Characteristics in Extra Low Permeability Sandstone Oil Reservoir of Yanchang Group in Ordos Basin Using Constant Rate Mercury Penetration Technique

Micro pore throat characteristics of extra low permeability sandstone oil reservoir of Yangchang group in Ordos basin are analyzed using constant rate mercury penetration technique. The results show that pore radius distributes similarly, in 100～200μm, peak values are about 140μm in extra low permeability sandstone oil reservoir. The lower the permeability is, the narrower the distribution ranges of throat are, content of smaller throats become high and variation is more sensitive to permeability, distribution ranges of pore throat radius ratio are wide and permeability has bigger influence on input mercury saturation of throat in extra low permeability sandstone oil reservoir. The difference of pore throat characteristics mainly depends on throat in extra low permeability sandstone oil reservoir. The impacts of pore and throat on total capillary curve are various to different permeability cores, Throat development should be paid more attention in middle or later stage of oil development to extra low permeability sandstone oil reservoir.

Structures buckling under tensile dead load

Some 250 years after the systematic experiments by Musschenbroek and their rationalization by Euler, for the first time we show that it is possible to design structures (i.e. mechanical systems whose elements are governed by the equation of the elastica) exhibiting bifurcation and instability (‘buckling’) under tensile load of constant direction and point of application (‘dead’). We show both theoretically and experimentally that the behaviour is possible in elementary structures with a single degree of freedom and in more complex mechanical systems, as related to the presence of a structural junction, called ‘slider’, allowing only relative transversal displacement between the connected elements. In continuous systems where the slider connects two elastic thin rods, bifurcation occurs both in tension and in compression, and is governed by the equation of the elastica, employed here for tensile loading, so that the deformed rods take the form of the capillary curve in a liquid, which is in fact governed by the equation of the elastica under tension. Since axial load in structural elements deeply influences dynamics, our results may provide application to innovative actuators for mechanical wave control; moreover, they open a new perspective in the understanding of failure within structural elements.

Post-prandial capillary triacylglycerol responses to moderate exercise in centrally obese middle-aged men

In this study, we wished to determine whether 30 min of moderate-intensity exercise, corresponding to minimal recommended guidelines, attenuates post-prandial capillary triacylglycerol concentrations in obese men. Ten middle-aged, centrally obese men (age 46 ± 2 years, body mass index 31.6 ± 1.0 kg · m−2, waist circumference 104.6 ± 2.2 cm) completed two 2-day trials (exercise and control) at least one week apart in a randomized, repeated-measures design. On day 1, participants either cycled for 30 min at approximately 60% of maximal heart rate in the afternoon or rested (no exercise). On day 2 of both trials, after a 10-h overnight fast, participants consumed a test meal of moderate fat content (35%) for breakfast. Capillary blood samples were collected in the fasted state (0 h) and at 2, 4, and 6 h post-prandially on day 2. Total area under the capillary triacylglycerol concentration versus time curve was significantly lower on the exercise than control trial (P = 0.023). One 30-min session of moderate-intensity cycling is effective in lowering post-prandial capillary triacylglycerol concentration in obese middle-aged men. These findings may have important implications for exercise recommendations as a means to reduce the risk of cardiovascular disease if such exercise is performed for an extended period.

On the triple line in infiltration of liquid metals into porous preforms

Two questions of current interest are addressed in this paper: (i) Are contact angles measured by means of the sessile drop technique of any help to understand liquid metal infiltration into solid porous preforms? (ii) To what extent are contact angles derived from either the capillary law or drainage curves valid? These questions have neither simple nor unique answers, as infiltration may occur under very different scenarios, i.e., non-reactive and reactive infiltration, both spontaneous and forced. However, while the use of the simplest version of the capillary law relies upon the questionable slug-flow hypothesis, analysing drainage curves by means of the Brooks and Corey model seems justified only for particular distributions of pore sizes such as a power law. However, experimental studies indicate that threshold pressures, and therefore contact angles, derived from those two methods are not very different.

Modeling the Effects of the Microporous Layer on the Net Water Transport Rate Across the Membrane in a PEM Fuel Cell

In this study, a model was developed to evaluate the effects of the microporous layer (MPL) on the net liquid water transport rate across the membrane. The results support the hypothesis that the improvement in fuel cell performance observed when an MPL is used in the cathode side is related to its effect on the water transport process in the electrode and membrane. Due to its high hydrophobicity, the MPL increases the liquid water pressure in the cathode to levels much higher than that in the anode, resulting in an increased back-transport rate of liquid water from the cathode to the anode. This reduces the amount of water that is transported out of the cathode through the gas diffusion layer (GDL) to the cathode flow channels resulting in a lower saturation level in the GDL, and consequently, faster oxygen transport to the catalyst sites. This model showed that the state of zero-net-water-transport-across-the-membrane could be achieved with the appropriate capillary properties of the porous media. Two capillary properties of the MPL identified to have the greatest impact on the proton-exchange-membrane (PEM) fuel cell performance are the liquid water saturation level at and the slope of the capillary curve in the hydrophobic region.