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Increasing the share of renewable energy sources (RESs) in the energy mix of countries is one of the main objectives of the energy transition in national economies, which must be established on circular economy principles. In the natural gas storage in geological structures (UGSs), natural gas is stored in a gas reservoir at high reservoir pressure. During a withdrawal cycle, the energy of the stored pressurised gas is irreversibly lost at the reduction station chokes. At the same time, there is a huge amount of produced reservoir water, which is waste and requires energy for underground disposal. The manuscript explores harnessing the exergy of the conventional UGS reduction process to generate electricity and produce hydrogen via electrolysis using reservoir-produced water. Such a model, which utilises sustainable energy sources within a circular economy framework, is the optimal approach to achieve a clean energy transition. Using an innovative integrated mathematical model based on real UGS production data, the study evaluated the application of a turboexpander (TE) for electricity generation and hydrogen production during a single gas withdrawal cycle. The simulation results showed potential to produce 70 tonnes of hydrogen per UGS withdrawal cycle utilising 700 m3 of produced field water. The analysis showed that hydrogen production was sensitive to gas flow changes through the pressure reduction station, underscoring the need for process optimisation to maximise hydrogen production. Furthermore, the paper considered the categorisation of this hydrogen as "green" as it was produced from the energy of pressurised gas, a carbon-free process. [ABSTRACT FROM AUTHOR]

Extended-reach drilling represents an advanced way of drilling and accessing reservoirs that were previously economically not feasible to drain, impossible to reach or in an environmentally sensitive area. One of the main issues that appears while drilling such wells is caused by the high values of friction factor which cause high values of torque and drag. One of the suggested solutions is to use a protective sliding ring made from materials such as POM, Teflon and PA6 in combination with lubricants added to a polymer mud system. First, measurements were conducted on a lubricity tester to choose the best material and, after finishing, a mechanical wear test was conducted on a specially designed device to measure mechanical wear. Results showed that Teflon showed lower values of friction factor in comparison to steel and the mechanical wear was minimal. The lowest value of friction force was recorded for blocks made from Teflon in tested mud systems. It is also noticeable that, in polymer mud with weighting additives and lubricant, the value of the friction force is higher than in polymer mud with lubricant only. [ABSTRACT FROM AUTHOR]

The 1D moisture diffusivity of porous materials may strongly depend on the content of moisture in the materials, varying over an order of magnitude or more. In this paper we present a new model from which the diffusivity can be evaluated, using the pore size distribution and water absorption coefficient. We point out that this is a more efficient approach than the standard Boltzmann–Matano (BM) method, because measurements of pore curves and water absorption are much shorter and rather accurate compared to moisture profile experiments needed in the BM method. As an example, we apply our model to two samples of a ceramic brick for which experimental data on both pore curves and moisture profiles had been measured. A very good quantitative agreement in the diffusivity is obtained for early stage profiles. For later stages, however, the model predicts three to four times higher diffusivity than the BM method. The reasons for this discrepancy are discussed and further tasks to validate the effectiveness of the new model are proposed. We also compare our model with the pore models of Burdine and Mualem. [ABSTRACT FROM AUTHOR]

Development of cement based composites suitable for radionuclide immobilization is of great interest for secure containment of nuclear waste. This requires, in particular, detailed knowledge of how radionuclides are transported in such composites. In this paper we investigate the transport of gadolinium in a dry cement composite. Experimental data are obtained in a non-destructive way by neutron imaging. Their theoretical interpretation is based on a diffusion-advection model in which sorption is included.

Copyright of Rudarsko-Geolosko-Naftni Zbornik is the property of Faculty of Mining, Geology & Petroleum Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

With the development of different segments within the drilling technology in the last three decades, well drilling has become possible in harsh downhole conditions. The vertical well provides access to oil and gas reserves located at a certain depth directly below the wellsite, and a large number of vertical wells are required for the exploitation of hydrocarbons from spatially expanded deposits. However, the borehole can deviate from the vertical well, which means that the target zone can be reached by a horizontal directional well. With this type of well, especially in the case of drilling an extended-reach well (ERW), the length of the wellbore in contact with the reservoir and/or several separate reservoirs is significantly increased, therefore, it is a much better option for the later production phase. Unfortunately, the application of extended-reach drilling (ERD technology), with all of its advantages, can cause different drilling problems mostly related to the increased torque, drag, hole cleaning and equivalent circulation density (ECD), as well as to an increase in the well price. Overcoming these problems requires continuous operational change to enable operators to address downhole challenges. Today, the longest well reaches 15,240 m (50,000 ft), which raises the question of the technological and economic feasibility of this type of drilling project, especially with the lower oil price on the energy market. This paper provides a comprehensive overview of extended-reach drilling technology, discusses the main problems and analyzes current achievements. [ABSTRACT FROM AUTHOR]

Melting and other first-order phase changes usually occur in phase change materials (PCMs) within a noticeable temperature range rather than at a unique phase change temperature ( T pc ). Then the enthalpy and heat capacity have rather wide jumps and peaks, respectively, spread over such ranges of temperatures. Surprisingly, wide jumps and peaks are observed even in plain and simple cases when PCMs are pure substances with negligible hysteresis and/or supercooling and the measurements are quasi-equilibrium using very slow heating/cooling rates, as in adiabatic scanning calorimetry (ASC). We show that in such cases a unique T pc can be identified and calculated from the measured heat capacity peaks. It suffices to take into account that PCM samples do not have an ideal microstructure but are rather composed of many micro- to nano-sized domains. The heat capacity peak is then an average of individual peaks that (a) come from all domains and (b) have different shifts from T pc for different domain sizes. Interpreting a heat capacity peak measured by ASC in this way, we present a procedure from which T pc can be evaluated. We apply the procedure to three examples of materials using available ASC data and point out the importance of the size distribution of domains. [ABSTRACT FROM AUTHOR]

Wellbore instability is one of the most serious problems that can occur during drilling, mainly during drilling oil or gas wells through rocks that contain a higher proportion of clay, such as shales. To prevent wellbore instability, oil companies apply different approaches to strengthen wellbore walls, and use different shale swelling inhibitors. The aim of this research was to apply a green approach and the concept of the circular economy in mud design, and to determine whether mandarin peel powder, which is a waste material, can be used as an inhibitor of shale swelling. For that purpose, pellets consisting of bentonite and quartz in a 50:50 ratio were prepared using a compactor, and bentonite-based drilling mud (BM) with and without mandarin peel powder in concentrations of 0.5, 1, 1.5 and 2% by volume of water. The swelling of quartz–bentonite pellets after 2 and 24 h in each drilling-mud sample was determined at room temperature and 90 °C using a linear swell meter. On the basis of laboratory research, we concluded that increasing the concentration of mandarin peel powder reduces pellet swelling. By adding mandarin peel powder particles between 0.1 and 0.16 mm to the base mud at a concentration of 2% by volume of water, the following was achieved: 44% reduction in API filtration, 61.54% reduction in PPT filtration, 45% reduction in pellet swelling after 24 h at room temperature, and 48.6% reduction of pellet swelling after 24 h at 90 °C. [ABSTRACT FROM AUTHOR]

Drilling fluid represents the most important fluid that must fulfill numerous important assignments during drilling operations. Many commercially available additives for water-based drilling fluid fall into the category of non-degradable and environmentally hazardous materials. Significant development in this area can be made by using biodegradable materials as additives in drilling fluids. The objective of this study was to determine whether mandarin peel powder particle size affects the properties of the drilling fluid. In this paper, mandarin peel was used in the form of a dry powder divided into particle sizes smaller than 0.1 mm, and between 0.1 mm and 0.16 mm. Mandarin peel powder was added to a water-based drilling fluid in four different concentrations (0.5, 1, 1.5, and 2% by volume of water). By increasing the mandarin peel powder concentration, the API filtration reduced up to 42%, PPT filtration significantly decreased up to 61.54%, while the rheological parameters generally increased but remained within acceptable limits. It is determined that the optimal concentration of mandarin peel powder is up to 1.5% by volume of water. [ABSTRACT FROM AUTHOR]

For years, drilling engineers have been faced with the challenge of drilling wells through naturally fractured reservoirs that are present around the world. During drilling, the pressure at the bottomhole of a well is frequently intentionally higher than formation pressure, which can result in the loss of mud in surrounding rocks. During well cementing, the bottomhole pressure is even higher than it is during drilling, because the cement slurry density is higher than the density of the mud. Therefore, if natural or induced fractures in the surrounding rocks are not plugged during drilling, the cement slurry can be lost to them, reducing their permeability which is undesirable in the case of a pay zone. To prevent the loss of circulation and the related consequences, it is necessary to apply good drilling and cementing practices and to use adequate methods and carefully selected materials for plugging the loss zones. The aim of this article is to give an overview of the preventive and corrective methods that can be applied in drilling and cementing through fractured zones as well as improvements in drilling and cementing technology to avoid lost circulation issues (e.g., aerated drilling fluid, casing while drilling, managed pressure drilling, expandable tubulars, lightweight cement slurries, etc.). [ABSTRACT FROM AUTHOR]

The aim was to investigate: changes of inflammatory, stress and cardiac response in patients undergoing open heart surgeries up to five days after the procedure; the association between inflammatory, stress and cardiac response and whether changes in a certain marker can predict short-term patient outcome. Ninety patients were divided into three groups, 30 participants each (on-pump, off-pump revascularization and valve replacement group). The following markers were measured: complete blood count, CRP, IL-6, IL-10, leptin, resistin, monocyte chemoattractant protein-1 (MCP-1), cortisol, CK and hsTnT in 5 points. Resistin increased in all three groups. Lower IL-10 levels were found after the surgery and higher levels of leptin and MCP- 1 in the off-pump than in the on-pump group. Off-pump group had higher values of IL-6, IL-10, leptin, resistin and MCP-1 and lower levels of CK and hsTnT 24 after surgery than the on-pump group. We found significant correlation between MCP-1 and resistin. The difference between resistin at time points 2 and 3 significantly predicted transfusion needs; while the difference between CRP and resistin before and at the end of the surgery together with the difference between leukocytes at the end and 24 hours after the surgery predicted the use of inotropic agents/vasopressors. Cardiac surgeries cause an increase of inflammatory, stress and cardiac markers. Only resistin correlated with MCP-1 which confirms the link between resistin secreted form infiltrated macrophages and enhanced release of MCP-1. [ABSTRACT FROM AUTHOR]

We determine the ordered low temperature phases of the Andelman–de Gennes model of chiral discrimination, using rigorous statistical mechanical methods. The system is considered in the close-packed regime, equivalent to placing the molecules at every site of a honeycomb lattice. If the system contains an equimolar mixture of each of a pair of enantiomers, we prove in general that a heterochiral phase (disfavoring enantiomeric segregation) as well as a homochiral phase (favoring the segregation) is possible, depending on the types of intermolecular interactions. We apply our general results to the specific examples of the interactions considered by Andelman and de Gennes and provide a comparison with their conjectures that were based on two-molecule partition functions. [ABSTRACT FROM AUTHOR]

We study and explain shapes of voltammogram spikes, observed during underpotential deposition (UPD) on electrode surfaces, as averaged envelopes of mutually shifted spikes associated with first-order phase transitions that occur in crystalline domains of various sizes that are formed on the electrode surface. This concept, already used in our previous work for two-phase systems and symmetric voltammogram spike shapes, is here substantially generalized to systems with multiple-phase coexistence and asymmetric spike shapes, using the rigorous statistical mechanical techniques of Borgs and Kotecký. Rather than mere numerical plots, we extract explicit functions that accurately describe the spike shapes. For the sake of clarity, we present our analysis and apply our results to fit the voltammogram of the UPD of Cu on Au(111) in sulfuric acid medium. This voltammogram shows two distinct spikes with a broad foot region near the spike at higher potentials. As was done in earlier treatments, we explain each of the two spikes as a result of a first-order transition. Here, though, the spikes are obtained as envelopes of closely spaced spikes resulting from crystals of various sizes. In contrast to earlier studies, however, we also explain the foot region in the same way. The foot's shape, despite its large width and small height, can be equally well obtained as an envelope of shifted crystal spikes that are broader and smaller than those giving rise to the two distinct spikes. We achieve very good agreement with experiment. [ABSTRACT FROM AUTHOR]

We study the voltammogram spikes of the underpotential deposition at electrode surfaces that correspond to first-order phase transitions. The shape of symmetric spikes is approximated by the function cosh[sup -2]. In order to explain this spike shape microscopically, which is our main concern, we observe that an electrode surface consists of many small crystals. A voltammogram spike is then interpreted as an averaged result of the finite-size effects occurring in each of these crystals. This view also allows us to comment on asymmetry in the voltammogram spikes. Our analysis is based on the rigorous statistical mechanical techniques of the Pirogov-Sinai theory. For the sake of simplicity, we model the deposition process by the one-component lattice gas. We apply the results to the underpotential deposition of Cu on Pt(111) in a sulfuric acid medium, and find very good agreement with experiment. [ABSTRACT FROM AUTHOR]

We introduce an explicit theoretical formula for the heat capacity peaks that occur in materials during phase changes. Such materials are of importance in many applications where thermal energy storage is needed, including solar systems, buildings, electronic devices, or radionuclide encasements. We show how theoretical parameters that appear in the formula can be adjusted in order to fit experimentally measured peaks. Two of these parameters are interesting in applications: the specific latent heat and phase change temperature. We illustrate this procedure for four peaks associated with phase changes in four different materials for which the heat capacity peaks had been measured at slow heating rates. [ABSTRACT FROM AUTHOR]

During the drilling of a well, differential pressure causes filtration of the mud liquid phase into the surrounding rocks. To reduce the filtrate invasion in the rock, it is necessary to maintain the density of the mud. Also, Wellbore Strengthening Materials (WSM) can be preventively added to the mud to increase the fracture initiation pressure of the drilled formation. The solid particles from the mud create a mud cake on the wellbore wall, which, for conventional drilling, implies the use of bentonite and barite whose particle dimensions range from 0.1 to 100 µm. While drilling shales, rocks which contain pores that have an average pore size of 10 to 30 nm, it is not possible to create a high-quality mud cake, so water passes into the shale and creates wellbore instability problems. To stabilize the shale, the petroleum industry uses oil-based muds, but due to their environmental impact, it is not always possible to implement them. Nanoparticles, because of their small dimensions, can enter into the nanopores and fill this space and strengthen the rock, resulting in decreased filtration. In this paper, a review of previous laboratory research of adding nanoparticles on filtration is shown. Also, the impact of adding nanoparticles on API and HTHP filtration is examined by adding TiO2 and SiO2 nanoparticles in concentrations of 0.5 wt% and 1 wt% to the five water-based muds. The best result was obtained with TiO2 nanoparticles at a concentration of 0.5 wt%. [ABSTRACT FROM AUTHOR]

When medication management or percutaneous coronary intervention is not successful in patients with advanced ischemic heart disease, surgical revascularisation-predominantly coronary artery bypass grafting (CABG)-is considered the gold standard. However, CABG surgery can lead to ischemia/reperfusion injury, which is characterized by a strong inflammatory response. Interleukin (IL)-18, is a strong inflammatory mediator, that is released from cardiomyocytes and can be found in the systemic circulation of patients during and immediately after CABG surgery. The existing damage of endothelial glycocalyx in patients with ischemic heart disease is further impaired concurrently during the surgery due to the anaesthesia-surgical technique used and intravascular fluid loading. This results in the increased incidence of adverse events, including myocardial infarction. IL-18 leads to the activation of lymphocyte cytotoxicity via cytotoxic mediators (Fas ligand, Tumour necrosis factor (TNF)-related apoptosis-inducing ligand, perforin, and granulysin). We hypothesize that IL-18 is released locally in the heart and the systemic circulation in patients undergoing CABG surgery and may be correlated with the level of activity of circulating lymphocytes. In turn, this may lead to lymphocyte-mediated cytotoxicity directed toward damaged and activated endothelial cells. Shear stress glycocalyx, as well as damaged and activated endothelial cells then become the main the source of pro-inflammatory cytokines, chemokines, and adhesion molecules. These attract activated lymphocytes to adhere to the endothelium or enter the subintimal layer, increasing existing or initiating the formation of new plaques, which leads to the development of myocardial infarction during or shortly after surgery. To evaluate our hypothesis, we will measure the local concentration of IL-18 in the sinus coronarius and systemic circulation. These values will then be correlated with immunological and biochemical parameters, predominantly with the concentration of degradation products of glycocalyx and cytotoxic mediators in activated lymphocytes. If our hypothesis is correct, measuring the IL-18 concentration that is responsible for glycocalyx deterioration, may become a useful tool for predicting myocardial infarction occurrence in patients undergoing CABG surgery. [ABSTRACT FROM AUTHOR]

Copyright of Cardiologia Croatica is the property of Croatian Cardiac Society and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We study thermal expansion, mass changes, heat capacity, and thermal diffusivity and conductivity for a ceramic body with 20 mass% and without fly ash content, using the thermodilatometric analysis, thermogravimetric analysis, differential thermal analysis, differential scanning calorimetry, and flash method. The measurements were performed: (a) for green samples either isothermally or by a linear heating up to a temperature 600 °C, 1050 °C, or 1100 °C, depending on the measurement method; (b) at the room temperature for samples preheated at 100 °C, 200 °C, ..., 1100 °C. In case (a) addition of fly ash changes the final contraction only above ~900 °C, while the thermal properties remain almost unchanged. In case (b) the final contraction of samples at 1100 °C is the same. The thermal diffusivity is nearly identical up to 700 °C, and fly ash causes the diffusivity to stay almost constant up to 1000 °C. [ABSTRACT FROM AUTHOR]

The transport of salt, necessarily coupled with the transport of water, through porous building materials may heavily limit their durability due to possible deterioration and structural damage. Usually, the binding of salt to the pore walls is assumed to occur instantly, as soon as the salt is transported by water to a given position. We consider the advection-diffusion model of the transport and generalize it to include possible delays in the binding. Applying the Boltzmann-Matano method, we calculate the diffusion coefficient of the salt in dependence on the salt concentration and show that it increases with the rate of binding. We apply our results to an example of the chloride transport in a lime plaster. [ABSTRACT FROM AUTHOR]

Copyright of Collegium Antropologicum is the property of Croatian Anthropological Society and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A direct method for an accurate and rapid evaluation of a varying salt diffusion coefficient, $$D$$ , from experimental data is proposed for a coupled water and salt transport in porous materials. The evaluation uses data on the moisture and salt concentration profiles and is based on a formula obtained from the Boltzmann-Matano method. The coupled transport is described by the diffusion-advection model of Bear and Bachmat. A simple expression for $$D$$ in the center of the concentration interval is deduced from the formula to provide a rapid estimate on $$D$$ . Possible extensions of this analytical approach are pointed out, suggesting that it can serve as a convenient general tool in engineering calculations. The theoretical results are applied to a laboratory experiment in which a coupled moisture and chloride transport had been investigated in a lime plaster, and the chloride diffusion coefficient had been obtained numerically in dependence on the chloride concentration. The agreement with the numerical results is shown to be rather good, except at low concentrations where our analytical results should be more reliable. It is also shown that the unusually high value of the calculated chloride diffusion coefficient-about three orders of magnitude higher than for free chloride ions in water-cannot be explained by possible inaccuracies in the measurements and/or numerical calculations. The reason is that changes in the measured profiles' data could cause a change in $$D$$ of just the same order of magnitude. This shows that, besides diffusion and advection, additional mechanisms take part in the considered chloride transport. [ABSTRACT FROM AUTHOR]

We present a microscopic statistical-mechanical approach from which the chemical surface diffusion coefficient can be obtained in the local equilibrium limit, assuming that the system of a finite size undergoes a first-order phase transition between two phases. We also show the behavior of the jump diffusion coefficient and thermodynamic factor near such a transition. Explicit formulas for the dependences of these quantities on the chemical potential, coverage, and size of the system are presented. The general results are applied to a simple two-dimensional lattice model on a regular triangular lattice. [ABSTRACT FROM AUTHOR]

We analyze the chemical and jump surface diffusion coefficients, DC and DJ, near a first-order phase transition at which two phases coexist and the surface coverage, θ, jumps between single-phase values θ-* and θ+*. Contrary to other studies, we consider temperatures that are sufficiently subcritical. Using the local equilibrium approximation, we obtain approximate analytical formulas for the dependences of DC and DJ on the coverage and system size, N, near such a transition. In the two-phase regime, when θ ranges between θ-* and θ+*, the diffusion coefficients behave as the sums of two hyperbolas, Dc ≈ A-/N∣θ - θ-*∣ + A+/N∣θ - θ+*∣ and DJ ≈ A-∣θ - θ+*∣θ + A+∣θ - θ-*∣/θ. This behavior rapidly changes as the system goes from the two-phase regime to either of the single-phase regimes (when θ goes below θ-* or above θ+*.). The crossover behavior of DC(θ) and DJ(θ) between the two-phase and single-phase regimes is described by rather complex formulas involving the Lambert function. We consider a lattice-gas model on a triangular lattice to illustrate these general results, applying them to four specific examples of transitions exhibited by the model. [ABSTRACT FROM AUTHOR]