Hydration Pressure Research Articles

Bimodal behavior of C-S-H interpreted from short-term length change and water vapor sorption isotherms of hardened cement paste

Short-term length change isotherms (SLCIs) and water vapor sorption isotherms are useful to eliminate the effects of the colloidal features of C-S-H. SLCIs of hardened cement pastes initially conditioned by drying to equilibrium at different relative humidities (RHs) were measured over a complete RH loop between 5% and 98%. Based on the correlation between incremental thickness of adsorption and incremental strain from 40% to 98% RH, the basal spacing of C-S-H above 40% RH appears to increase further with increasing water vapor sorption. However, no correlation of these values was found from 5% to 40% RH and the basal spacing is considered stable in this domain. These properties of C-S-H are directly related to its isothermal volume change as a function of RH. It can be concluded that the dominant shrinkage driver above 40% RH is disjoining or hydration pressure and that below 40% RH is change in surface energy.

Phase equilibrium modeling of semi-clathrate hydrates of seven commonly gases in the presence of TBAB ionic liquid promoter based on a low parameter connectionist technique

Several studies show that thermodynamic ionic liquid promoter, such as Tetra-n-butylammonium bromide (TBAB) can moderate the formation conditions of gas hydrates. In the current study, a Support Vector Machine (SVM) and coupling of SVM with Genetic Algorithm (GASVM) have been developed to predict semi-clathrate hydrate pressure of CO2, CH4, N2, H2, Ar, Xe and H2S in the presence of TBAB ionic liquid according to the critical temperature (Tc), critical pressure (Pc) and acentric factor (ω) of abovementioned gases over wide ranges of temperature, pressure and concentration of TBAB. For implementation of networks, 528 experimental data points collected from the published papers have been employed. Moreover, to verify both proposed models, regression analysis and statistical analysis such as mean square errors (MSEs), average relative deviations (ARDs), standard deviations (STDs) and root mean square errors (RMSEs) have been conducted on the experimental and predicted values of semi-clathrate hydrate pressure of gases in TBAB. While, the values of R2=0.97759 and ARD=0.25465132obtained for SVM model, coefficient of determination (R2) and Average Relative Deviation (ARD) of GASVM between the experimental and predicted values are 0.99944 and 0.07180737 respectively. Finally, according to the obtained results, in this contribution, ability and better performance of using GASVM as a correlation for prediction of semi-clathrate hydrate pressure and temperature in TBAB has been shown against SVM model.

Dehydration/hydration of MgO/H2O chemical thermal storage system

Thermal energy storage systems improve the inefficiency of industrial processes and renewable energy systems (supply versus demand). Chemical reaction is a promising way to store thermal energy because of its high energy storage density, long-term energy storage, etc. This study investigated an MgO/H2O chemical thermal storage system that stores thermal energy by decomposing Mg(OH)2 (endothermic reaction), and supplies thermal energy by combining water vapor with MgO (exothermic reaction). Heat supply is greatly influenced by MgO properties, particularly dehydration temperature. Therefore, the equilibrium hydration fractions of MgO prepared at various dehydration temperatures were measured. Then, the relation between dehydration temperature and the equilibrium hydration fractions of MgO was determined. The equilibrium hydration fractions of MgO at various hydration temperatures and pressures were also measured. The chemical thermal storage system was inefficient at dehydration temperatures lower than 350 °C or higher than 500 °C. The efficiency of this system can be improved by increasing the hydration temperature while keeping the relative vapor pressure unchanged.

Mesenchymal stem cell tracking in the intervertebral disc.

Low back pain is a common clinical problem, which leads to significant social, economic and public health costs. Intervertebral disc (IVD) degeneration is accepted as a common cause of low back pain. Initially, this is characterized by a loss of proteoglycans from the nucleus pulposus resulting in loss of tissue hydration and hydrostatic pressure. Conservative management, including analgesia and physiotherapy often fails and surgical treatment, such as spinal fusion, is required. Stem cells offer an exciting possible regenerative approach to IVD disease. Preclinical research has demonstrated promising biochemical, histological and radiological results in restoring degenerate IVDs. Cell tracking provides an opportunity to develop an in-depth understanding of stem cell survival, differentiation and migration, enabling optimization of stem cell treatment. Magnetic Resonance Imaging (MRI) is a non-invasive, non-ionizing imaging modality with high spatial resolution, ideally suited for stem cell tracking. Furthermore, novel MRI sequences have the potential to quantitatively assess IVD disease, providing an improved method to review response to biological treatment. Superparamagnetic iron oxide nanoparticles have been extensively researched for the purpose of cell tracking. These particles are biocompatible, non-toxic and act as excellent MRI contrast agents. This review will explore recent advances and issues in stem cell tracking and molecular imaging in relation to the IVD.

Hydration Forces Between Lipid Bilayers: A Theoretical Overview and a Look on Methods Exploring Dehydration.

Although, many biological systems fulfil their functions under the condition of excess hydration, the behaviour of bound water as well as the processes accompanying dehydration are nevertheless important to investigate. Dehydration can be a result of applied mechanical pressure, lowered humidity or cryogenic conditions. The effort required to dehydrate a lipid membrane at relatively low degree of hydration can be described by a disjoining pressure which is called hydration pressure or hydration force. This force is short-ranging (a few nm) and is usually considered to be independent of other surface forces, such as ionic or undulation forces. Different theories were developed to explain hydration forces that are usually not consistent with each other and which are also partially in conflict with experimental or numerical data.Over the last decades it has been more and more realised that one experimental method alone is not capable of providing much new insight into the world of such hydration forces. Therefore, research requires the comparison of results obtained from the different methods. This chapter thus deals with an overview on the theory of hydration forces, ranging from polarisation theory to protrusion forces, and presents a selection of experimental techniques appropriate for their characterisation, such as X-ray diffraction, atomic force microscopy and even calorimetry.

Hydrate phase equilibrium of binary guest-mixtures containing CO2 and N2 in various systems

For sequestration or separation of CO2 from flue gas, hydrate phase equilibrium of (CO2+N2) binary guest-mixtures (xCO2=0.101, 0.180, 0.251M fraction) was investigated using isochoric multi-step heating dissociation method in various systems, i.e., pure water, Tetrahydrofuran (THF, yTHF=0.004, 0.012, 0.042M fraction) aqueous solution, Tetrabutyl ammonium bromide (TBAB, yTBAB=0.004, 0.012, 0.042M fraction) aqueous solution, natural seawater, seasand and (seawater+seasand) mixture. All measurements were carried out in a temperature and pressure region of (271.5 to 289.6)K and (0.62 to 18.27)MPa, respectively. The results show that the formation pressure of (CO2+N2) hydrate is still too high in pure water, but it can be obviously decreased in TBAB and THF aqueous solution and the pressure drop caused by TBAB is greater than THF only at the lower concentration of solution (in the concentration ranges investigated in this work). In seawater, hydrate formation pressure is raised while the seasand sample has no impact on it. Besides, hydrate equilibrium is mainly influenced by the ions in the (seasand+seawater) mixture while the effect of seasand particles is not obvious.

Does any therapy really work for neurocardiogenic syncope?

Effectiveness of a treatment for neurocardiogenic syncope can be defined in terms of symptom response, quality-of-life, healthcare utilization, treatment side effects and cost-effectiveness. Most trials have focused on syncope recurrence or burden, without assessing quality-of-life formally. Drug and device interventions are characterized by a dearth of randomized controlled trials, with those few of robust design demonstrating little impact on recurrence of syncope. General advice includes hydration, trigger recognition and counter pressure maneuvers to attenuate episodes. Lifestyle recommendations have limited comparative effectiveness evidence, but are favored due to lack of side effects and low cost. The frequency of syncope improves in many patients regardless of the intervention, although ultimate recurrence of syncope remains high. In the minority of patients seeking treatment due to recurrence, midodrine has reasonable supporting evidence for effectiveness with some evidence for beta-blockers in older age patients. Emerging evidence favors pacing in patients with asystole during spontaneous (as opposed to provoked) syncope. Combining long-term implantable cardiac monitoring, tilt and adenosine triphosphate testing may yet accurately define the optimal minority who benefit from pacing. In the remaining majority, pharmacologic and device interventions should be used sparingly until clear benefits are established. Better understanding of patient fears, beliefs and behaviors may help develop cognitive therapies and improve quality-of-life alongside the focus on physical symptoms.

Pore capillary pressure and saturation of methane hydrate bearing sediments

To better understand the relationship between the pore capillary pressure and hydrate saturation in sediments, a new method was proposed. First, the phase equilibria of methane hydrate in fine-grained silica sands were measured. As to the equilibrium data, the pore capillary pressure and saturation of methane hydrate were calculated. The results showed that the phase equilibria of methane hydrates in fine-grained silica sands changed due to the depressed activity of pore water caused by the surface group and negatively charged characteristic of silica particles as well as the capillary pressure in small pores together. The capillary pressure increased with the increase of methane hydrate saturation due to the decrease of the available pore space. However, the capillary-saturation relationship could not yet be described quantitatively because of the stochastic habit of hydrate growth.

DEVELOPMENT OF THE METHOD FOR PREDICTING FIELD DOSAGE OF KINETIC HYDRATE INHIBITOR

The increased application of low dosage hydrate inhibitors in oil and gas production has made it necessary to develop a method for determining the consumption rates of kinetic hydrate inhibitors, as no techniques are currently available for that purpose. The method was developed in the experiments with the kinetic hydrate inhibitor SONHYD-1801A, representing a stereoregular copolymer of N-vinylpyrrolidone and caprolactam. The currently used technology for application of kinetic hydrate inhibitor SONHYD-1801A has been improved, allowing effective prevention of hydrate formation in pipelines. It is stated that the chemical can be used for continuous injection in the oil, oil-gas and oil/gas-condensate fields to prevent hydrate formation during the production and transportation of associated gas within the limited temperature and pressure range. For the experiment, a model gas hydrate-forming mixture was prepared, consisting of methane and propane in the ratio of 60/40 respectively, and with a 99.98% purity of the components. This gas mixture simulates the composition of both associated gas and gas produced from oil-gas-condensate fields. Based on the investigations performed, it is established that the kinetic hydrate inhibitor SONHYD-1801A is able to reduce the hydrate equilibrium temperature within the range of 14˚C against the equilibrium temperature. The operating pressure range is up to 15 MPa, and the inhibiting capacity is not reduced considerably as in the case with low temperatures. An empirical equation has been obtained that shows kinetic hydrate inhibitor consumption vs. pressure, temperature and water content of the gas mixture. Based on the equation, a method has been developed for optimal consumption of kinetic hydrate inhibitor under various gas flow regimes.

Experimental measurement of the induction time of natural gas Hydrate and its prediction with polymeric kinetic inhibitor

It is assumed that the heterogeneous nucleation of hydrates in the upstream oil and gas industry occurs, which would block the fluid flow transportation, when produced fluids (oil/gas/water) in a multiphase pipeline enter the hydrate stability temperature and pressure conditions. This has led to the development of flow assurance strategies to operate outside the hydrate stability region. The past flow loop data on oil and gas systems suggest that hydrates usually require some sub-cooling (on the order of 3K or so) to be formed and it takes a while. Thus, there are two different ways to transport the fluid; firstly by staying outside of the hydrate-stable region or secondly transport the fluid in the hydrate stable region before hydrate formation started. Thus it would be also possible to transport the fluid in hydrate stability region before hydrate formation started. To achieve this goal, three different kinds of inhibitors are used: (1) thermodynamic inhibitors, (2) kinetic inhibitors, and (3) anti-agglomerants. Thermodynamic inhibitors would change the equilibrium condition of gas hydrates, while kinetic inhibitors would change the induction time and anti-agglomerants inhibit the crystal agglomeration. In this work, two kinetic inhibitors (poly N-vinylpyrrolidone, PVP and poly N-vinylcaprolactam, PVCap) were tested and a kinetic model to predict the induction time with an inhibitor was developed using the Freundlich adsorption isotherm. Currently, the model can be used in limited conditions such as specific gas composition, temperature range and polymeric inhibitors. However, this model has a good potential to predict the minimum concentration of inhibitor to prevent hydrate plugging at various temperatures and pressure conditions.

The influence of individual clay minerals on formation damage of reservoir sandstones: a critical review with some new insights

AbstractThe influence of individual clay minerals on formation damage of reservoir sandstones is reviewed, mainly through the mechanism of fine particle dispersion and migration leading to the accumulation and blockage of pore throats and significant reduction of permeability. The minerals discussed belong to the smectite, kaolinite, illite and chlorite groups respectively. These minerals usually occur in an aggregate form in reservoir sandstones and the physicochemical properties of these aggregates are reviewed in order to reach a better understanding of the factors that lead to their dispersion in aqueous pore fluids. Particularly significant properties include the surface charge on both basal and edge faces of the clay minerals and how this varies with pH, external surface area of both swelling and non-swelling clays, porosity and pore size distribution in the micro- and meso-pore size range and overall aggregate morphology. For non-swelling clays, and perhaps even for swelling clays, dispersion is thought to be initiated at the micro- or meso-pore level, where the interaction between the pore solution and the charged clay surfaces exposed on adjacent sides of slit- or wedge-shaped pores brings about expansion of the diffuse double electric layer (DDL) and an increase in hydration pressure. Such expansion occurs only in dilute electrolyte solutions in contrast to the effect of concentrated solutions which would shrink the thickness of the DDL and so inhibit dispersion. Stable dispersions are formed, particularly where the solution pH exceeds the isoelectric pH of the mineral, which is often at alkali pH values, so that both basal face and edge surfaces are negatively charged and the particles repel each other. The osmotic swelling of smectitic clays to a gel-like form, so effectively blocking pores in situ, is often invoked as an explanation of formation damage in reservoir sandstones. Such swelling certainly occurs in dilute aqueous solutions under earth surface conditions but it is uncertain that stable smectitic gels could form at the temperatures and pressures associated with deeply buried reservoir sandstones.

Clay mineralogy and shale instability: an alternative conceptual analysis

AbstractThe instability of shales in drilled formations leads to serious operational problems with major economic consequences for petroleum exploration and production. It is generally agreed that the nature of the clay minerals in shale formations is a primary causative factor leading to their instability, although the exact mechanism involved is more debateable. Currently, the principal cause of shale instability is considered to be volume expansion following the osmotic swelling of Nasmectite. However, illitic and kaolinitic shales may also be unstable, so that interlayer expansion cannot therefore be considered as a universal causative mechanism of shale instability. This review considers alternative scenarios of shale instability where the major clay minerals are smectite, illite, mixed-layer illite-smectite (I/S) and kaolinite respectively. The influence of interacting factors that relate to shale clay mineralogy such as texture, structure and fabric are discussed, as are the pore size distribution and the nature of water in clays and shales and how these change with increasing depth of burial. It is found from the literature that the thickness of the diffuse double layer (DDL) of the aqueous solutions associated with the charged external surfaces of clay minerals is probably of the same order or even thicker than the sizes of a significant proportion of the pores found in shales. In these circumstances, overlap of the DDLs associated with exposed outer surfaces of clay minerals on opposing sides of micropores (<2 nm in diameter) and mesopores (2–50 nm in diameter) in a lithostatically compressed shale would bring about electrostatic repulsion and lead to increased pore/ hydration pressure in smectitic, illitic and even kaolinitic shales. This pressure would be inhibited by the use of more concentrated K-based fluids which effectively shrink the thickness of the DDL towards the clay mineral surfaces in the pore walls. The use of soluble polymers would also encapsulate these clay mineral surfaces and so inhibit their hydration. In this scenario, the locus of action with respect to shale instability and its inhibition is moved from the interlamellar space of the smectitic clays to the charged external surfaces of the various clay minerals bounding the walls of the shale pores.

Phase equilibrium conditions of semi-calthrate hydrates of (tetra-n-butyl ammonium chloride + carbon dioxide)

In the present work, hydrate equilibrium conditions for (tetra-n-butyl ammonium chloride (TBAC)+carbon dioxide+water) mixtures were investigated. Tetra-n-butyl ammonium chloride was reported to form a semi-clathrate hydrate. The experiments were carried out within the TBAC mass fraction range of (0.05 to 0.3). The experimental results showed that the presence of TBAC decreased the formation pressure of carbon dioxide double hydrate within the experimental temperature range. Moreover, pressure reduction was dependent on the TBAC concentration.

Stimulus-Responsive Au@(MeO2MAx-co-OEGMAy) Nanoparticles Stabilized by Non-DLVO Interactions: Implications of Ionic Strength and Copolymer (x:y) Fraction on Aggregation Kinetics

Functionalized nanoparticles can assist in stabilizing fluid-fluid interfaces; however, developing and applying the appropriate surface modification presents a challenge because successful application of these nanomaterials for biotechnological, food processing, and environmental applications requires their long-term stability in elevated ionic strength media. This work studies stimulus responsive polymeric materials based on random copolymers of di(ethylene glycol) methyl ether methacrylate (x = MeO2MA) and oligo(ethylene glycol) methyl ether methacrylate (y= OEGMA) which, when grafted to gold nanoparticles, show significant, tunable, colloidal stability. The nanoparticles Au@(MeO2MAx-co-OEGMAy) display tunable, reversible aggregation that is highly dependent on the (x:y) ratio and ionic strength. Effects of these parameters on the initial rate constant of aggregation (k11) are studied by time-resolved dynamic light scattering (TR-DLS) experiments. At the same nanoparticle concentration, a strong sensitivity to salt concentration is observed. Over less than 300 mM increase in NaCl concentration, we observed a two-order of magnitude increase in aggregation rate constants, 4.2 × 10(-20) < k11 < 1.8 × 10(-18) m(3)s(-1). Additionally, for the same gold nanoparticles, a higher fraction of OEGMA requires a higher salt concentration to induce aggregation. A linear relationship between the critical NaCl coagulation concentration (CCC) and the copolymer composition is observed. Analysis of the experimental data with an extended Derjaguin-Landau-Verwey-Overbeek (xDLVO) theory that includes hydration and osmotic forces is used to explain the stability of these systems. We find the hydration pressure, 2.4 < P(h,0) < 7.2 MPa, scales linearly both with the osmotic pressure and the OEGMA monomer concentration (5 < y < 20%). Specific knowledge of P(h,0)(y, C(NaCl)) enables design of both aggregation kinetics and stability as a function of the copolymer ratio and external stimuli.

Clathrate Hydrate Equilibrium Data for the Gas Mixture of Carbon Dioxide and Nitrogen in the Presence of an Emulsion of Cyclopentane in Water

Carbon dioxide and nitrogen gas separation is achieved through clathrate hydrate formation in the presence of cyclopentane. A phase diagram is presented in which the mole fraction of CO2 in the gas phase is plotted against the mole fraction of CO2 in the carbon dioxide + nitrogen + cyclopentane mixed hydrate phase, both defined with respect to total amount of CO2 and N2 in the respective phase. The curve is plotted for temperatures ranging from 283.5 K to 287.5 K and pressures from 0.76 MPa to 2.23 MPa. The results show that the carbon dioxide selectivity is moderately enhanced when cyclopentane is present in the mixed hydrate phase. Carbon dioxide could be enriched in the hydrate phase by attaining a mole fraction of up to 0.937 when the corresponding mole fraction in the gas mixture amounts to 0.507. When compared to the three phase hydrate–aqueous liquid–vapor equilibrium in the ternary system {water + carbon dioxide + nitrogen}, the equilibrium pressure of the mixed hydrate is reduced by 0.95 up to 0....

Activated carbon fiber cloth and CaCl2 composite sorbents for a water vapor sorption cooling system

In this work, we investigated activated carbon fiber cloth (ACFC) and CaCl2 composite sorbent (CS) prepared using impregnation method. Formation mechanism of the composite was investigated. During the impregnation process, a solution of CaCl2 is concentrated inside the pores of the ACFC. The solution concentration process is described using the Polanyi potential theory and the Dubinin–Radushkevich equation while ignoring Ca2+ adsorption by the surface functional groups. If the CaCl2 content of the CS is less than 38.2%, all the CaCl2 locates inside the pores of the ACFC. The water sorption performances of the CS of different CaCl2 contents were measured using an ASAP2020M Accelerated Surface Area and Porosimetry analyzer. The CSs with a CaCl2 content of 15.2 and 22.8% exhibit a greater amount of absorbed water than the equivalent CaCl2. This is because the CaCl2 dispersed inside within pores exhibits a lower hydration pressure than the bulk CaCl2, and the ACFC contributes to the amount of water that is absorbed. However, it is likely that the hydration pressure of the dispersed CaCl2 in the CS containing the maximum possible amount of CaCl2 does not change. Water sorption in this kind of CS can reach as high as 90% of the equilibrium water sorption amount within 2 min. The coefficient of performance for the air conditioning cycles calculated from the isosters of the CS containing the maximum CaCl2 content may reach 0.7, which is considered promising for sorption cooling.

CO2하이드레이트의 film형 결정성장 거동에 관한 연구

지구 온난화의 대표적인 주범인 <TEX>$CO_2$</TEX>를 저감하기 위하여 많은 연구가 진행되고 있다. 특히 가스 하이드레이트 형성원리를 이용한 <TEX>$CO_2$</TEX> 분리 및 저장 공정이 주목을 받고 있다. 본 연구는 필름형 <TEX>$CO_2$</TEX> 하이드레이트의 결정성장 거동에 관하여 성장 메커니즘을 규명하였다. 다양한 압력조건에서 반회분식 교반 반응기를 이용하여 <TEX>$CO_2$</TEX> 하이드레이트를 형성시켰으며 객체가스의 용해도 차이를 최소화하기 위하여 모든 실험에서 온도는 고정하였다. 공급된 가스는 순도 99.999 %의 <TEX>$CO_2$</TEX> 가스를 사용하였고, CCD 카메라(Nikon DS-5M/Fi1/2M-U2)가 장착된 광학현미경을 사용하여 관찰 결과를 실시간 기록하였다. 실험에 적용되는 압력에 따라서 하이드레이트 성장형태와 성장속도는 매우 큰 차이를 보였다. 특히 2.0 MPa 이상의 압력에서 가장 큰 변화를 관찰하였으며, 이것은 <TEX>$CO_2$</TEX>의 농도 차이와 모세관 힘에 의한 것으로 사료된다. Many researches have been carried out to reduce and/or to capture the major global warming gases. Especially, the hydrate formation mechanisms were intensively investigated for carbon dioxide sequestration and storage process applications. In this study, the characteristics of film-type crystal growth mechanism of carbon dioxide hydrate were comprehensively examined. Carbon dioxide hydrate crystal was formed in semi-batch type stir reactor at various pressure conditions while the temperature was fixed to be constant to reduce and minimize the guest gas solubility effects. A supply gas composition was 99.999 % of Carbon dioxide, the observation data was collected by optical microscope adopted CCD camera (Nikon DS-5M/Fi1/2M-U2). This study revealed that the guest gas pressure changes significantly altered the crystal growth mechanism and film growth rate of carbon dioxide hydrate crystal. The critical pressure of the carbon dioxide hydrate of crystal growth mechanism change was found to be 2.0 MPa. The capillary force and gas concentration gradient also significantly changed the film-type crystal growth mechanism of carbon dioxide hydrate crystal.

FTIR spectroscopy study of the pressure-dependent behaviour of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and 1-palmitoyl-2-oleolyl-sn-glycero-3-phosphocholine (POPC) at low degrees of hydration

High-pressure investigations of phospholipids at low degrees of hydration are highly important due to the continuous interest in hydration related phenomena. This is for instance the case when discussing differences between the molecular behaviour under hydrostatic or hydration pressure, e.g. to characterise the structural and thermodynamic conditions that hold for the different theoretical approaches proposed in the literature.The stability of phospholipid aggregates in aqueous solutions is determined by a balance of attractive end repulsive forces as well as entropic and energetic interactions. The pressure-dependent variation of the frequency of molecular vibrations determined by FTIR spectroscopy might be an appropriate tool to study the nature of these interactions as well as of conformational changes for various degrees of hydrations. The paper reports preliminary results for the stretching and bending vibration of the CH2 groups that are mainly situated in the hydrocarbon chains. In a hydration range of about 2 water molecules per lipid in the case of DOPC and 6 water molecules for POPC, the pressure-dependent vibrations in the liquid crystalline phase change between red shift and blue shift. A further interesting parameter is the onset pressure for the correlation field splitting. It increases with dehydration, and it is assumed that the correlation field splitting does not only depend on the disorder related to the gauche conformer population in the hydrocarbon chains but also on the chain tilt in the gel phase.

The sensitivity analysis of scaling criteria in gas hydrate reservoir physical simulation

A numerical approach of sensitivity analysis of dimensionless parameters in gas hydrate reservoir physical simulation is proposed by analyzing the sensitivity factor defined as the relative variation ration of a target function with respect to the relative variation of dimensionless parameter. With this approach, the dominance degree of all the dimensionless parameters can be quantitatively evaluated and the dominant ones can be singled out conveniently. Taking a 1-D experiment of gas production from hydrate reservoir by depressurization as an example, we find that the order of sensitivity factors ranges from 10−5 to 100. The most dominant dimensionless parameter is the dimensionless initial temperature of hydrate reservoir and the dimensionless phase equilibrium pressure of gas hydrate, which just reflects that the consumed energy for hydrate dissociation comes from the energy contained in formation and the driving force for hydrate dissociation is very important in hydrate dissociation by depressurization.

Thermodynamic modeling of ternary CH4[sbnd]H2O[sbnd]NaCl fluid inclusions

This paper reports the application of thermodynamic models, including equations of state, to ternary CH4H2ONaCl fluid inclusions. A simple equation describing pressure–temperature–salinity relations on the CH4 hydrate-liquid-vapor surface has been developed to calculate the NaCl contents (salinities) of inclusions, where the dissociation pressure of CH4 hydrate coexisting with vapor and liquid at a given temperature is calculated with a pressure equation of pure CH4. The pressure equation is a function of temperature and CH4 Raman peak position shift corrected by Ne lamp. With these relations and the latest CH4 solubility and PVTx models, a new iterative approach is presented to calculate the CH4 contents of CH4H2ONaCl inclusions on the assumption that the bulk molar volume of an inclusion at the melting temperature of CH4 hydrate and at the vapor bubble disappearance (homogenization) temperature are identical. A prominent merit of this method is that the compositions, molar volumes and homogenization pressures of CH4H2ONaCl inclusions can be simultaneously obtained without having to use volume fractions of vapor bubbles at the dissociation temperatures of CH4 hydrates determined based on optical observations or measurements. The homogenization pressures and isochores of CH4H2ONaCl fluid inclusions from updated models are briefly discussed. The code to estimate PVTx properties of inclusions in the ternary system CH4H2ONaCl, based on microthermometric and Raman data, can be obtained from Chemical Geology or the corresponding author (maoshide@163.com).