Pressure Volume Temperature Measurements Research Articles

Storage capacity of hydrogen in tetrahydrothiophene and furan clathrate hydrates

Abstract The storage capacity of hydrogen in the tetrahydrothiophene and furan hydrates was investigated by means of pressure–volume–temperature measurement. The hydrogen–absorption rate of tetrahydrothiophene and furan hydrates is much larger than that of tetrahydrofuran hydrate in spite of same crystal structure (structure-II). The storage amount of hydrogen at 275.1 K is about 1.2 mol (hydrogen)/mol (tetrahydrothiophene or furan hydrate) (∼0.6 mass%) at 41.5 MPa, which is coincident with that of tetrahydrofuran hydrate.

Effects of Branching on the Pressure−Volume−Temperature Behaviors of PP/CO2 Solutions

The pressure−volume−temperature (PVT) properties of polymer/gas solutions are characterized by determining their volume dilation at a known temperature and pressure. This paper presents the results of an experiment that measured the volume swelling of linear and branched polypropylene (PP) with CO2 using a new PVT measurement apparatus. The swellings and specific volumes for linear and branched PP/CO2 are compared. The swelling mechanism that occurred due to CO2 dissolution, and the effects of the branched structure on volume swelling are investigated and discussed. Due to its entangled branch structure, the branched PP underwent a lesser degree of volume swelling than did the linear PP.

A gas that sinks in a liquid—the first helium experiment published by Kamerlingh Onnes**Official Contribution of the National Institute of Standards and Technology; not subject tocopyright in the United States.

The year 1906 was a year of many remarkable achievements in the laboratory ofKamerlingh Onnes and his staff. They put into operation a hydrogen liquefier producing4 l h−1, followed by a liquid-hydrogen cryostat for work below 21 K. They prepared their firstsample of 2 l of helium gas. Pressure–volume–temperature measurements down to 54 K werein progress for hydrogen, and initiated for helium, in order to obtain an estimate for thecritical temperature of helium; this estimate was urgently needed for design of a heliumliquefier. Towards the end of 1906, Kamerlingh Onnes performed the first heliumexperiment at liquid-hydrogen temperature: a test of the phase behaviour of a mixture ofhydrogen and helium. In the process, he discovered what he termed the barotropic effect: atincreasing pressure, the helium-rich vapour phase sank to the bottom, having becomeheavier than the hydrogen-rich liquid phase. This paper describes the experiment andthe resulting flurry of activity by Van der Waals, Kamerlingh Onnes, Keesomand Van Laar, all trying to understand and model the curious phase behaviour,as well as earlier relevant work by Van der Waals, Korteweg, Kuenen and VanLaar.

A Combined Analysis of PVT and Rheological Measurements: Novel Results for Three Amorphous Polymers

AbstractThe fractional free volume f of polycarbonate (PC), polystyrene (PS) and poly(methyl methacrylate) (PMMA) is determined by pressure–volume–temperature (PVT) measurements using the Simha–Somcynsky equation of state. Results are compared with the free volume obtained by viscoelastic measurements. Temperature and pressure dependent viscosity and free volume results are correlated using the characteristic ratio C∞ and the parameter B of the monomeric friction factor ζ = ζexp B/f. This leads to obtain new results on the temperature and pressure dependence of C∞, as well as on the pressure dependence of B parameter.magnified image

Pressure–volume–temperature (PVT) measurements of ionic liquids ([bmim +][PF 6−], [bmim +][BF 4−], [bmim +][OcSO 4−]) and analysis with the Sanchez–Lacombe equation of state

Pressure–volume–temperature measurements of the pure ionic liquids 1-butyl-3-methyl-imidazolium hexafluorophosphate ([bmim +][PF 6 −]), 1-butyl-3-methyl-imidazolium tetrafluoroborate ([bmim +][BF 4 −]), 1-butyl-3-methyl-imidazolium octylsulfate ([bmim +][OcSO 4 −]) were performed with a metal bellows apparatus at temperatures from 313 to 473 K and at pressures up to 200 MPa. The pressure–volume–temperature data were used to determine parameters of the Sanchez–Lacombe equation of state, which was used to calculate the hard core volume and free volume of ionic liquids. It was found that the hard core volume of the ionic liquid was related with anion size and was slightly smaller than the van der Waals volume estimated with Bondi methods. The free volumes of [bmim +][PF 6 −] and [bmim +][BF 4 −] calculated with the Sanchez–Lacombe equation of state showed a similar pressure dependence and were close to each other (ca. 10–14 cm 3/mol) whereas the values for [bmim +][OcSO 4 −] were much higher (ca. 18–25 cm 3/mol) over the range of pressure.

Reservoir-Fluid Sampling and Characterization — Key to Efficient Reservoir Management

This paper, SPE 103501, is based on paper 101517 presented at the 2006 Abu Dhabi International Petroleum Exhibition & Conference, Abu Dhabi, 5-8 November. Distinguished Author Series articles are general, descriptive representations that summarize the state of the art in an area of technology by describing recent developments for readers who are not specialists in the topics discussed. Written by individuals recognized as experts in the area, these articles provide key references to more definitive work and present specific details only to illustrate the technology. Purpose: to inform the general readership of recent advances in various areas of petroleum engineering. Abstract Reservoir-fluid properties play a key role in the design and optimization of injection/production strategies and surface facilities for efficient reservoir management. Inaccurate fluid characterization often leads to high uncertainties in in-place-volume estimates and recovery predictions, and hence affects asset value. Reservoir-fluid pressure/volume/temperature (PVT) characterization begins with acquisition of adequate volumes of representative fluid samples followed by PVT-data measurement with strict quality-assurance/quality-control (QA/QC) protocols and phase-behavior modeling through best-practice methods. In this paper, key steps involved in accurate fluid characterization are discussed for a wide spectrum of fluid types ranging from extra-heavy oils to highly volatile near-critical fluids and lean gas condensates undergoing a wide range of production processes from simple depletion to complex tertiary recovery. Selection of appropriate sampling methods and tools, design of tool strings, and customizing procedures are demonstrated through these examples. Routine and special laboratory-fluid-analysis strategies for various fluid types and for different production strategies are highlighted. Fluid-modeling techniques including optimum-component selection, accurate C7+ characterization, robust Gibb's energy minimization, and gravity/chemical equilibrium calculations are demonstrated through appropriate field examples. Introduction Reservoir-fluid PVT properties are critical for efficient reservoir management throughout the life of the reservoir, from discovery to abandonment (See complementary paper by Honarpour et al. 2006.) Reliable PVT properties of in-situ fluids are essential for the determination of in-place volumes and recovery-factor calculations and are key input to reservoir simulations for technical evaluation of reservoir-development/-depletion plans. Fluid characterization and distribution within the reservoir help in defining reservoir continuity and communication among various zones. Interpretation of well-test data and the design of surface facilities and processing plants require accurate fluid information and its variation with time. In addition to initial reservoir-fluid samples, periodic sampling is necessary for reservoir surveillance. Reservoir-fluid characterization consists of several key steps:acquisition of representative samples,identification of reliable service laboratories to perform PVT measurements,implementation of QA/QC procedures to ensure data quality, anddevelopment of mathematical models to capture fluid-property changes accurately as functions of pressure, temperature, and composition. The fluid type and production processes dictate the type and the volume of required fluid data. This paper outlines recommended sampling techniques, PVT-data-acquisition strategies, and modeling methods and presents field examples covering a wide range of fluid types from heavy oils to lean gas condensates and production processes such as depletion, pressure maintenance, and miscible recovery.

Phase behavior of 1,3,5-tri- tert-butylbenzene–carbon dioxide binary system

1,3,5-tri- tert-butylbenzene (TTBB) is solid at ambient conditions, and has substantial solubility in liquid and supercritical carbon dioxide. We present the phase behavior of TTBB–CO 2 binary system at temperatures between 298 and 328 K and at pressures up to 20 MPa. Phase diagrams showing the liquid–vapor, solid–liquid and solid–vapor equilibrium envelopes are constructed by pressure–volume–temperature measurements in a variable-volume sapphire cell. TTBB is highly soluble in CO 2 over a wide range of compositions. Single-phase states are achieved at moderate pressures, even with very high TTBB concentrations. For example, at 328 K, a binary system containing TTBB at a concentration of 95% by weight forms a single-phase above 2.04 MPa. TTBB exhibits a significant melting-point depression in the presence of CO 2, 45 K at 3.11 MPa, where the normal melting point of 343 K is reduced to 298 K. With its high solubility in carbon dioxide, TTBB has potential uses as a binder or template in materials forming processes using dense carbon dioxide.

Phase Behaviour and Compositional Changes Associated With Residual Oxygen in a Miscible CO/Light Oil Reservoir

Abstract Concern about the effects of global greenhouse gases has made people aware of the need to reduce the atmospheric concentration of industrial waste gas. Alberta, as the centre of Canada's petroleum industry, is strongly impacted by the politics of greenhouse gases. One way Alberta can achieve the goals of the Kyoto Protocol is to capture CO2 from stack gases and to inject it into oil reservoirs to enhance recovery while sequestering at least a portion of the CO2. This paper will concentrate on oil from the Swan Hills Formation reservoir operated by Devon Oil Corporation. The phase behaviour of different concentrations of CO2/O2 mixtures injected into the Swan Hills reservoir was investigated. Two PVT (Pressure-Volume-Temperature) apparatus were used to visually observe phases and to determine bubble points and swelling of the oil rich phase. The PVT measurements were performed to develop a basic understanding of the phase behaviour for the CO2 / O2 /oil system. The composition of oxidized oil was predicted using a previously developed low temperature oxidation model coupled with phase equilibrium calculations. Introduction Carbon dioxide flooding is a well established enhanced oil recovery process in regions where CO2 is available. Canada has been slow to implement CO2 floods due to the lack of natural sources. However, the public's concern with greenhouse gas emissions and Canada's support for the Kyoto Protocol provide sufficient environmental incentives to allow for the application of CO2 floodingas a combined EOR/sequestration process. Capturing the CO2 from stack gas is an expensive process and the actual cost will depend on the purity of the CO2 stream that is required. Oxygen is an important factor as its impurity can modify the native oil properties through low temperature oxidation reactions, promotion of corrosion in the injection and production piping and alter the phase behaviour of the reservoir fluids. The study described in this paper will examine how oxygen is consumed in the reservoir, and it will concentrate on the impact of oxidation reactions with regard to the composition and emulsification characteristics of the oil. Lee(1) studied the phase behaviour and displacement efficiency of a carbon dioxide-hydrocarbon system which consisted of various mixtures of n-pentane/n-hexane. The results demonstrated that multiple phase behaviour involving two liquids with and without a vapour phase occurred during carbon dioxide injection in low temperature reservoirs. A number of studies on the effectiveness of carbon dioxide displacement under miscible and immiscible conditions have been reported by Wilburn et al.(2), Dyer et al.(3), Srivastava and Huang(4, 5) and Srivastava et.al.(6). The results showed that CO2 /oil miscibility could be developed and that the swelling behaviour depended on the chemical composition of the oil. Wilburn et al.(2) also found that miscibility is strongly dependent on the volatility or boiling point distribution of the oil. Dyer et al.(3) investigated the phase behaviour of typical Saskatchewan heavy oils with carbon dioxide. Their study was divided into two categories: stock tank oil and reservoir oil, which were mixed with CO2 in different ratios. Parameters studied included viscosity, density, swelling factor and gas-oil ratio (GOR).

Interphase between nanoparticles and molten polymeric matrix: pressure–volume–temperature measurements

The pressure–volume–temperature (PVT) dependence of commercial polymers (viz. poly-ε-caprolactam, PA-6, polystyrene, PS, polypropylene, PP, and epoxy), and of nanocomposites based on these resins, was studied in the molten state. Incorporation of 2-wt% organoclay decreases the specific volume by about 1.0%. The Simha–Somcynsky (S–S) lattice-hole theory provided excellent description of the PVT behavior. Congruence between the theory and experiment yielded an explicit measure of the free volume. It has been found that in polymeric nanocomposites (PNC) the reduction of the free volume, Δh, correlated with the degree of clay dispersion (e.g. expressed as the interlayer spacing, d 001), or more precisely with total clay surface area accessible to macromolecules. The free volume reduction originates in adsorption and solidification of macromolecules on the high-energy clay surface – the phenomenon observed in the Surface Force Analyzer. The solidification offers consistent explanation for several reported puzzling behaviors of PNC.

Pressure–volume–temperature of molten and glassy polymers

AbstractThe pressure–volume–temperature (PVT) dependencies of several amorphous polymers (PS, PC, PPE, and PPE/PS 1:1 blend) in the glassy and molten state were studied. The Simha–Somcynsky (S–S) lattice‐hole equation of state (EOS) was used. Fitting the PVT data in the molten state to the EOS yielded the free volume quantity, h = h(T, P), and the characteristic reducing parameters, P*, V*, and T*. The data within the glassy region were interpreted assuming that the latter parameters are valid in the molten and vitreous state, than calculating h = h(T, P) from the experimental values of V = V(T, P). Next, the frozen free volume fraction in the glass was computed as FF = FF(P). The FF values of polystyrene (PS) resins at ambient pressure showed little scattering (FFP=1 = 0.691 ± 0.008), while their P‐dependencies varied, reflecting the thermodynamic history of the glass formation as well as the PVT measurements protocol. The pressure gradient of Tg was compared with the Ehrenfest relation for the second‐order transition; here also agreement depended on the method of vitrification. The experimental values of FF at ambient pressure decreased with increasing values of the characteristic temperature reducing parameter, T*. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 270–285, 2007.

Relation between PVT measurements and linear viscosity in isotactic and syndiotactic polypropylenes

Pressure–Volume–Temperature ( PVT) data of an isotactic and a syndiotactic PP are fitted to a modification of the Simha–Somcynsky equation of state (S–S), to calculate characteristic parameters, such as V ∗, T ∗, P ∗ and the solubility parameter δ. The hole fraction of the S–S model and the free volume are deduced from these parameters. The application of a modified Doolittle equation and a modified Berry–Fox equation to estimate viscosity, leads to extract novel conclusions on the differences between both types of PPs. An equation which accounts for the effect of temperature on the characteristic ratio of syndiotactic PP is presented.

PVT gauging with liquid nitrogen

Experimental results are presented for pressure–volume–temperature (PVT) liquid quantity gauging of a 0.17 m 3 liquid nitrogen tank pressured with ambient temperature helium in the normal gravity environment. A previously reported PVT measurement procedure has been improved to include helium solubility in liquid nitrogen. Gauging data was collected at nominal tank fill levels of 80%, 50% and 20% and at nominal tank pressures of 0.3, 1.0, and 1.7 MPa. The test tank was equipped with a liquid pump and spray manifold to circulate and mix the fluid contents and therefore create near-isothermal conditions throughout the tank. Silicon diode sensors were distributed throughout the tank to monitor temperatures. Close-spaced arrays of silicon diode point sensors were utilized to precisely detect the liquid level at the nominal 80%, 50%, and 20% fill levels. The tests simulated the cryogenic tank-side conditions only; helium mass added to the tank was measured by gas flowmeters rather than using pressure and temperature measurements from a dedicated helium supply bottle. Equilibrium data for cryogenic nitrogen and helium mixtures from numerous sources was correlated to predict soluble helium mole fractions. Results show that solubility should be accounted for in the PVT gauging calculations. Mole fractions predicted by Dalton’s Law were found to be in good agreement with the compiled equilibrium data within the temperature–pressure range of interest. Therefore, Dalton’s Law was deemed suitable for calculating ullage composition. Gauging results from the PVT method agreed with the reference liquid level measurements to within 3%.

Effects of defect and pressure on the thermal expansivity of FexO

Pressure–volume–temperature measurements have been carried out using synchrotron X-ray diffraction for wustite at static pressures of 1.9, 2.6, and 5.4 GPa. Our results revealed that the composition change of wustite and, hence, rearrangements of defect structures are primarily caused by the magnetite (Fe3O4) exsolution at temperatures of 523–723 K. Based on the isobaric volume–temperature data collected during cooling, the contribution of compositional variations to the unit-cell volumes of wustite in the ranges of 300–673 K and 723–1073 K is negligibly small, within the experimental uncertainties. These observations suggest that the measured volume changes in the range of 300–673 K and 723–1,073 K can be attributed to the metal–oxygen bond expansion. Owing to the magnetite exsolution, thermal expansion data are obtained in each experiment at 1.9, 2.6, and 5.4 GPa for wustite of two different compositions, Fe0.987O and Fe0.942O. At all three pressures, Fe0.942O shows a thermal expansion that is about 30% larger than Fe0.987O. Such findings represent the first experimental evidence of a substantial effect of nonstoichiometry on thermal expansivity, and based on previous thermodynamic calculations of the defect formation and interaction, this effect is likely associated with the distinct defects arrangements in iron-rich and more iron-deficient wustite. This study also presents thermal equations of state for wustite of two different compositions. Such volume-related properties at high temperatures are experimentally difficult to obtain in wustite but important for thermodynamic studies in the binary Fe–O system.

Quantitative analysis of deuterium and tritium in erbium hydride films of neutron tube targets

An apparatus for measuring the deuterium and tritium in erbium hydride films on neutron tube targets has been designed, constructed, and tested at the Tritium Science and Fabrication Facility at Los Alamos National Laboratory. The apparatus consists of a pumped thermal desorption inlet system (TDIS) and a high-resolution mass spectrometer (HRMS). The pumped TDIS has a unique capability to perform complete and rapid thermal desorption of gases from the erbium hydride film and pressure–volume–temperature measurement for accurate quantification of the total moles of released gas. The HRMS measures the partial pressures of the hydrogen isotopes in the released gas. From these two measurements, we can determine the total moles of each hydrogen isotope in erbium hydride films accurately. The optimum desorption time is 2 to 3 minutes; the optimum desorption temperature is 900 °C. Under these conditions, 99.98% of the total moles of deuterium in the hydride films of deuterated erbium (ErD2) targets are released in a single desorption step. The molar atomic ratios of total hydrogen isotopes to erbium (HDT/Er), deuterium to erbium (D/Er), and tritium to erbium (T/Er) of deuterated and tritiated erbium (ErDxT2−x) targets are measured with better than 2% precision.

High-pressure adsorption measurements. A comparative study of the volumetric and gravimetric methods

In this paper, we propose a comparative study between a volumetric apparatus and a gravimetric one, which were developed for the acquisition of high-pressure adsorption isotherms. The volumetric apparatus is able to perform measurements in the temperature range 278–323 K and in the pressure range 0–4000 kPa. We provide a complete report on the experimental errors due to the mass balance calculation based on pressure–volume–temperature measurements. The same analytical study has been achieved for a gravimetric apparatus (temperature range: 223–393 K, pressure range: 0–10 000 kPa). The comparison comments are based on experimental data obtained for the system: activated carbon (CENTAUR Chemviron Carbon)–nitrogen. It appears that for such a system exhibiting quite low adsorbed quantities, important discrepancies may appear if the measurements are not properly achieved. Minimizing the experimental errors for the two experimental techniques leads to an average observed deviation (relative error) between the two methods equal to 3% in the whole measurement range.

Pressure‐dependent glass‐transition temperatures of poly(methyl methacrylate)/poly(styrene‐co‐acrylonitrile) blends

AbstractThe pressure‐dependent glass‐transition temperatures (Tg's) of poly(methyl methacrylate) (PMMA)/poly(styrene‐co‐acrylonitrile) (SAN) blends were determined by pressure–volume–temperature (PVT) dilatometry via an isobaric cooling procedure. The Gordon–Taylor and Fox equations were used to evaluate the relationships between the Tg's and compositions of the PMMA/SAN system at different pressures. The relationships were well fitted by the Gordon–Taylor equation, and the experimental data for Tg positively deviated from the values calculated with the Fox equation. Also, the influence of the cooling rate (during the PVT measurements) on Tg was examined. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 959–962, 2003

Crystallization kinetics of polypropylene under high pressure and steady shear flow

We investigate the simultaneous effect of pressure P and shear flow on the crystallization process of polypropylene using a modified pressure–volume–temperature measurement system that has been developed in our laboratory. We focus on the inverse of half-conversion time 1/t1/2 that is defined by the inverse of the time when the relative crystallinity of system reaches to one half. It is found that the pressure dependence of the quantity 1/t1/2 can be expressed by a shifted degree of super-cooling ΔT(P) by pressure. We also find that 1/t1/2(T,P,γ̇) under both pressure and shear flow can be described by a sum of 1/t1/2(T,P,γ̇=0) under no shear and a linearly increasing term with shear rate γ̇.

Pressure and temperature dependence of structural relaxation in diglycidylether of bisphenol A

The structural (α-) relaxation in diglycidylether of bisphenol A (DGEBA) has been examined using three spectroscopic methods: dielectric spectroscopy (DS), dynamic light scattering–photon correlation spectroscopy (LS), and mechanical spectroscopy. The DS and LS measurements were carried out as a function of both temperature and pressure. Moreover, pressure-volumetemperature measurements were obtained for the DGEBA. These data allow an assessment of the relative contributions of thermal energy and free volume to structural relaxation in DGEBA. The results clearly show a substantial role for both thermal and free volume fluctuations in the dramatic slowing down of the dynamics. The combined temperature- and pressure-dependences of the dielectric and light scattering relaxation times were analyzed using the Avramov equation, implying that the fragility (normalized temperature dependence) is pressure independent over the studied range of pressures. The pressure dependence was the same as measured by the different spectroscopies. Conformance to the time-temperature-pressure superposition principle was also observed for all measurement techniques.

Volume effects on the molecular mobility close to glass transition in supercooled phenylphthalein-dimethylether. II

Pressure–volume–temperature measurements in phenylphthalein-dimethylether (PDE) are reported, in combination with recently published dynamic light scattering data obtained under high pressure. We discuss the role that volume and thermal effects play in controlling the dynamics in the vicinity of the glass transition. Although volume is not the unique thermodynamical parameter characterizing the relaxation dynamics in PDE, its contribution to the super-Arrhenius behavior of the relaxation times in the vicinity of the glass transition is remarkable. The contribution of volume to the temperature dependence of the relaxation times has been characterized by means of the ratio of the activation energy at constant volume to the enthalpy of activation at constant pressure, EV/HP. We point out that this quantity is correlated with the temperature behavior of the nonexponentiallity parameter, βKWW. Moreover, the τ(T,P) values were analyzed in terms of an extension of the Adam–Gibbs model. It was shown that this model gives a satisfactory interpretation of the pressure sensitivity of the dynamics (d log10(τ)/dP)|T in terms of thermodynamic properties of the material.

A Pseudo Equation-of-State Approach for the Estimation of Solubility Parameters of Polyethylene by Inverse Gas Chromatography

Hildebrand solubility parameters (δ) of a series of linear low-density polyethylenes (LLDPE) were measured at several elevated temperatures by the inverse gas chromatography (IGC) method of DiPaola-Baranyi and Guillet [Macromolecules 1978, 11, 228−235] with the incorporation of a compressible regular solution model, recently proposed by Ruzette and Mayes [Macromolecules 2001, 34, 1894−1907], for data analysis. It was found that, with the inclusion of the pressure−volume−temperature (PVT) properties of the pure components in the data analysis, the measured δ agreed well with those obtained from PVT measurements on similar systems. This suggests that the model of Ruzette and Mayes, even though it is mathematically less sophisticated than the conventional equation-of-state (EOS) theories, it is useful for deriving solubility properties of polymers. The results were consistent with the prediction of conventional EOS theories that, in addition to the type and strength of intermolecular interaction, PVT properties of the individual components comprising polymer solutions and blends also play a significant role in determining their phase behavior, especially at elevated temperatures.