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Download Free PDFAn equation of state for the CH4-CO2-H2O system: I. Pure systems from 0 to 1000°C and 0 to 8000 barJohn Weare

1992, Geochimica et Cosmochimica Acta

https://doi.org/10.1016/0016-7037(92)90347-Lvisibility

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Abstract

An equation of state ( EOS ) for the CH4-C02-H20 system covering a wide T-P range has been developed. In this article the new EOS is presented and applied to the pure endmembers. The equation is similar to that of LEE and KESLER ( 1975) and contains fifteen parameters. It is used with a mixing rule in the following article to provide a thermodynamic model for the mixed system. Though the parameters are evaluated from the PVT data in the temperature range from 0 to 450°C for CH.,, from 0 to 1OOO'C for CO2 and H20, and for pressures from 0 to 3500 bar, comparison of this EOS with a large amount of experimental data in the pure systems indicates that predictions for temperatures and pressures from 0 to 1OOO'C and 0 to 8000 bar (or slightly above) are very nearly within experimental uncertainty. The EOS can describe both the gas and the liquid phases of the endmember systems with similar accuracy. Fugacity coefficients are derived and compiled. In this paper mixing is considered using ideal mixing based on the endmember fugacities ( Amagat's rule). It is shown that such an approach leads to quite accurate predictions for high temperatures and low pressures.

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Key takeaways

AI

1. The new EOS accurately predicts PVT and phase equilibria for CH4-CO2-H2O from 0 to 1000°C and 0 to 8000 bar.
2. Fugacity coefficients for CH4, CO2, and H2O are derived to enhance mixing model accuracy.
3. The EOS incorporates 15 parameters, evaluated from extensive PVT data, ensuring reliable extrapolation.
4. The model maintains accuracy within 0.1-0.5% for 3360 data points across the studied temperature and pressure ranges.
5. Ideal mixing provides accurate predictions at high temperatures and low pressures, despite nonideal endmember behavior.

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AI

What specific challenges does the CH4-CO2-H2O system present in modeling?add

The study finds that mixtures in this system show complex behavior across temperature and pressure ranges, complicating accurate predictions of phase equilibria.

How does the proposed EOS improve predictions over existing models?add

This EOS demonstrates superior accuracy, achieving predictions within experimental error across the entire range up to 8000 bar and 1000°C.

What methodology is used for parameterizing the new equation of state?add

The methodology involves extensive fitting of 3360 experimental data points, yielding an average error of just 0.466% in molar volume predictions.

Which existing EOS were compared to support the effectiveness of this new model?add

Comparisons were made with the RK, LK, and BWR equations, highlighting the proposed EOS’s accuracy, especially at pressures exceeding 700 bar.

What implications does the new EOS have for geological applications?add

The EOS allows for reliable predictions of two-phase behavior in geothermal systems, enhancing understanding of gas solubility and phase equilibrium.

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An equation of state for the CH4-CO2-H2O system: II. Mixtures from 50 to 1000°C and 0 to 1000 barJohn Weare

Geochimica et Cosmochimica Acta, 1992

system has been developed. The model is based on the highly accurate endmember EOS presented in the previous article and on an empirical mixing rule, The mixing rule is based on an analogy with high order contributions to the virial expansion for mixtures. Comparison with experimental data indicates that the mixed system EOS can predict both phase equilibria and volumetric properties for the binaries with accuracy close to that of the experimental data for a temperature range from 50 to 1000°C and a pressure range from 0 to 1000 bar (or to 3000 bar with less accuracy).

downloadDownload free PDFView PDFchevron_rightAccurate prediction of the thermodynamic properties of fluids in the system H2O–CO2–CH4–N2 up to 2000 K and 100 kbar from a corresponding states/one fluid equation of stateJohn Weare

Geochimica et Cosmochimica Acta, 2000

Previously, we reported an equation of state (EOS) modeling approach that successfully calculated the PVTX properties of supercritical fluid mixtures. The model is based on a corresponding states assumption applied to a highly accurate EOS for the reference CH 4 system. The CH 4 EOS was parameterized from 273 to 723 K and 1 to 3000 bar by using experimental PVT data. Molecular dynamics simulated PVT data were used to extend the parameterization in the CH 4 system to 2000 K and 20 kbar. Mixing in the H 2 O-CO 2-CH 4-N 2 system was successfully described by using a simple empirical mixing rule with only two temperature-and pressure-independent parameters for each binary mixture. Results indicated that PVTX properties in higher order systems could be reliably calculated without additional parameters. In this paper, by using experimental PVTX data in the H 2 O-CO 2-CH 4-N 2 system that were not used in the EOS parameterization, we show that the model predictions are accurate from just above the critical temperature for the least volatile component to 2000 K and from 0 to 100 kbar. We also show that our modeling approach can be extended to reliably calculate supercritical phase equilibria and other thermodynamic properties, such as fugacity and enthalpy, under high-temperature and-pressure conditions.

downloadDownload free PDFView PDFchevron_rightThermodynamics of the carbon dioxide plus nitrogen plus methane (Co2 + N2 + Ch4) system: Measurements of vapor-liquid equilibrium data at temperatures from 223 to 298 K and verification of Eos-Cg-2019 equation of stateAnders Austegard

Fluid Phase Equilibria, 2019

Vapor-liquid equilibria (VLE) data of the ternary mixture of CO 2 þ N 2 þ CH 4 were measured at the isotherms 223 K, 253 K, 273 K, 283 K, and 298 K and for pressures in the range of 0.8 MPae9.3 MPa. The 62 experimental dew or bubble point data points have been measured using an analytical technique. For each temperature, the ratio between N 2 and CH 4 mole fraction in the total composition has been close to constant, enabling the data to be visualized as quasi phase envelopes. Estimated standard measurement uncertainties (k ¼ 1) better than 14 mK in temperature, 1.5 kPa in pressure, and 0.06 mol% in composition are reported, yielding a total uncertainty in terms of composition better than 0.07 mol%. The experimental data were compared to the EOS-CG-2019 model, which is a state-of-the-art Helmholtz energybased equation of state for the mixture of CO 2 þ N 2 þ CH 4 . All deviations between model and experimental data points are below 0.5 mol% for liquid compositions and 1.0 mol% for vapor compositions. The deviations between model and experimental points in the ternary mixture of CO 2 þ N 2 þ CH 4 follow the same trends seen in earlier reports between model and experimental data for the binary mixtures of CO 2 þ N 2 and CO 2 þ CH 4 . In addition, the model was analysed with respect to other thermophysical properties available in the literature. To a large extent, the results presented in this work validate the assumption that the thermodynamic properties of the multicomponent system CO 2 þ N 2 þ CH 4 can be described purely based on the pure component and binary mixture contributions.

downloadDownload free PDFView PDFchevron_rightThe CO 2-H 2O system. II. calculated thermodynamic mixing properties for 400°C, 0–400 MPaLawrence Anovitz

Geochimica Et Cosmochimica Acta, 1999

An excess molar volume (V ex )-explicit virial equation, and two empirical V ex expressions developed from experimentally determined densities, were used to calculate excess Gibbs free energies (G ex ) and activity-composition (a-X) relations for CO 2 -H 2 O fluids at 400°C, 0 -400 MPa. Excess Gibbs free energies are continuously positive and asymmetric toward H 2 O at all pressures up to 400 MPa, rising to peak values of approximately 1300, 1800, 2000 and 2100 J ⅐ mol Ϫ1 at 50, 100, 200 and 400 MPa, respectively. Calculated activities for H 2 O and CO 2 vary correspondingly, increasing substantially from 0 to 100 MPa, moderately from 100 to 200 MPa, and slightly from 200 to 400 MPa. In addition, because G ex is asymmetric toward H 2 O, a-X relations for H 2 O are distinctly different from those for CO 2 . These results indicate that CO 2 -H 2 O fluids are strongly nonideal at 400°C and all pressures above ϳ30 MPa, despite the fact that peak values for V ex decrease from ϳ50 cm 3 ⅐ mol Ϫ1 at 30 MPa to ϳ1 cm 3 ⅐ mol Ϫ1 at 200 MPa, and remain small to pressures at least as high as 500 MPa. Excess Gibbs free energies and a-X relations for CO 2 -H 2 O fluids at 400°C and pressures to 400 MPa calculated from modified Redlich-Kwong and Lee-Kesler equations of state generally suggest significantly smaller positive deviations from ideality.

downloadDownload free PDFView PDFchevron_rightMeasurement and prediction of multi-property data of CO2-N2-O2-CH4 mixtures with the “Peng-Robinson + residual Helmholtz energy-based” modelSilvia Lasala

Fluid Phase Equilibria, 2017

The so-called "Peng-Robinson + residual Helmholtz energy-based mixing rules" equation of state is a promising thermodynamic model that enables the accurate representation of VLE properties of highly non-ideal binary mixtures including the Type-III phase behaviour, according to the classification of van Konynenburg and Scott. So far, the accuracy of this model has been assessed only considering data over which it has been optimized. This publication aims at presenting a multi-property validation of this model over vapour-liquid equilibrium data of the ternaries CO 2-N 2-O 2 and CO 2-CH 4-N 2 and experimental values of enthalpy changes due to mixing of binary mixtures CO 2-N 2 and CO 2-CH 4 found in the literature. To integrate the scarce amount of available multicomponent data, this paper also presents new experimental isothermal VLE data for the mixture CO 2-N 2-O 2 at 273 and 233 K, also used along the model validation process. Finally, modelling results obtained from the model "Peng-Robinson + residual Helmholtz energy-based mixing rules" are compared with calculations performed with the widely applied standard Peng-Robinson equation of state.

downloadDownload free PDFView PDFchevron_rightComparison of the GERG-2008 and Peng-Robinson Equations of State for Natural Gas MixturesQUEST JOURNALS

This work compares two equations of state applicable to natural gas mixtures, namely the GERG-2008 equation of state (EoS), which was proposed as a high-accuracy reference model, and the traditional Peng-Robinson (PR) EoS. This comparison is done in terms of the accuracy of calculated properties such as pressure and density with respect to experimental data from the literature, as well as in vapor-liquid equilibria (VLE) calculations. It was found that the GERG-2008 EoS gives better results in comparison with PR for the calculation of density and pressure, generating deviations in the range from 0.1 to 1%. For the VLE calculations, the accuracy of GERG-2008 was slightly better than PR. However, this accuracy is accompanied with increased mathematical complexity, resulting in increased computational time: 2 to 6 times higher. This is due to the fact that the calculation of molar density of GERG-2008 requires an iterative calculation step for the liquid and vapor phases, which makes the resolution of the VLE calculation slower.

downloadDownload free PDFView PDFchevron_rightVapor - liquid equilibrium of the carbon dioxide/methane mixture at three isothermsJacob Stang

Fluid Phase Equilibria, 2018

Experimental vapor-liquid equilibrium data for the CO2/CH4 mixture have been measured at 293.13 K, 298.14 K and 303.15 K, with emphasis on the mixture critical area. The maximum estimated standard uncertainties are 3 mK in temperature, 2 kPa in pressure and 0.0008 in mole fraction. The scaling law of statistical thermodynamics has been fitted to the critical region data of each isotherm and very good estimation of the critical point is achieved with a maximum uncertainty of 10 kPa in critical pressure and 0.0009 in critical molar composition. The measurements have been validated against experimental data taken from the literature, where available, and against the prediction of the GERG-2008 model. The Soave-Redlich-Kwong (SRK) and Peng-Robinson (PR) Equations of State using the classic van der Waals one fluid mixing rules, the perturbed chain statistical association fluid theory (PC-SAFT) and the Universal Mixing Rule-Peng Robinson (UMR-PRU) model have been fitted to the data of each isotherm with very satisfactory results. UMR-PRU yields the lowest deviation, especially concerning the critical point area, with an overall absolute average deviation (AAD) of 0.18% in bubble point pressure and 0.43% in CO2 mole fraction of the vapor phase. In the critical points, UMR-PRU results in an average % AAD equal to 1.55 in critical pressure and 0.99 in the critical point composition.

downloadDownload free PDFView PDFchevron_rightWater Solubility at Saturation for CO2–CH4 Mixtures at 323.2 K and 9.000 MPaCatherine Yonkofski

Journal of Chemical & Engineering Data, 2017

downloadDownload free PDFView PDFchevron_rightVapor-liquid equilibria for binary systems carbon dioxide + 1,1,1,2,3,3-hexafluoro-3-(2,2,2-trifluoroethoxy)propane or 1-ethoxy-1,1,2,2,3,3,4,4,4-nonafluorobutane at 303.15–323.15 KAlyssa Nelson

Fluid Phase Equilibria, 2020

The phase behavior of binary mixtures of carbon dioxide (CO 2 ) and hydrofluoroethers (HFEs) has been studied. In particular, experimental vapor-liquid equilibrium (VLE) data for CO 2 + 1,1,1,2,3,3-hexafluoro-3-(2,2,2-trifluoroethoxy)propane (HFE-449mec-f) and 1-ethoxy-1,1,2,2,3,3,4,4,4-nonafluorobutane (HFE-7200) at temperatures of 303.15, 313.15, and 323.15 K are reported. The VLE data were measured using a static-type apparatus and then correlated using the Peng-Robinson equation of state with the van der Waals one fluid and Wong-Sandler-NRTL mixing rules. Reasonable correlation results were obtained from the Peng-Robinson equation of state with both the van der Waals one fluid and the Wong-Sandler-NRTL mixing rules. The GC-SAFT-VR equation also gave good predictions of the phase behavior. Additionally, the group contribution SAFT-VR (GC-SAFT-VR) equation was used to predict the experimental VLE in good agreement with the experimental data, as well as the full p,T phase diagram for both systems.

downloadDownload free PDFView PDFchevron_rightExperimental Determination of (p, ρ, T) Data for Three Mixtures of Carbon Dioxide with Methane for the Thermodynamic Characterization of Nonconventional Energy GasesFrédérique Haloua

Journal of Chemical & Engineering Data, 2012

Experimental characterization of the thermodynamic behavior of gas binary mixtures containing components of fuel gases is of great importance due to the proved lack of reliable data of thermodynamic properties of mixtures. These data are essential not only for the improvement and test of the current reference equation of state for natural gases and related mixtures, GERG-2008, but also for the indirect determination of other properties. In this work density measurements of mixtures of carbon dioxide with methane are presented as a contribution to the research project EMRP ENG01 of the European Metrology Research Program, in the field of characterization of energy gases. Accurate density measurements for three binary mixtures of carbon dioxide with methane (x CO 2 = 0.20, 0.40, and 0.60) were performed at temperatures between (250 and 400) K and pressures up to 20 MPa, using a single sinker densimeter with magnetic suspension coupling, which is one of the state of the art methods for density determination over wide ranges of temperature and pressure. Experimental densities were compared with the GERG-2008 equation of state and with the experimental data reported by other authors for similar mixtures. Relatively large deviations from the equation of state observed at low temperatures suggests the possibility of higher uncertainties of the GERG model in the low temperature range.

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Re-equilibration of fluid inclusions in diagenetic-anchizonal rocks of the Cinera-Matallana coal basin (NW Spain)Ronald Bakker

Geofluids, 2003

Thermally re-equilibrated fluid inclusions are reported in natural fissure quartz (qtz1) from polymineralic veins in the diagenetic-anchizonal clastic sedimentary rocks of the Ciñera-Matallana coal basin (Variscan, NW Spain). Euhedral quartz formed during early fissure opening from an immiscible fluid mixture composed of a low salinity aqueous solution and a CH4-rich vapour phase, at temperatures of about 110–120°C and pressures ranging from 15 to 56 MPa. Five textural types of re-equilibration are recognised in progressive order of inclusion modification: scalloped, hairy, annular-ring shaped, haloes and decrepitation clusters. These textures resulted from a combination of brittle fracturing and dissolution and re-precipitation of quartz, with preferential loss of water. The thermal peak was short-lived, but was high enough to induce extensive decrepitation of fluid inclusions in vein quartz throughout the entire basin. Enhanced temperatures can be related to the intrusion of diorites in the basin. Careful analysis of textural features in fluid inclusions from diagenetic and very low-grade metamorphism environments constitutes a useful tool for recording basin thermal history.

downloadDownload free PDFView PDFchevron_rightImprovements in clathrate modelling: I. The H2O-CO2 system with various saltsMichel Cathelineau

Geochimica et Cosmochimica Acta, 1996

The formation of clathrates in fluid inclusions during microthermometric measurements is typical for most natural fluid systems which include a mixture of H2O, gases, and electrolytes. A general model is proposed which gives a complete description of the CO2 ...

downloadDownload free PDFView PDFchevron_rightUncertainties of geochemical modeling during CO2 sequestration applying batch equilibrium calculationsChristoph Haase, Frank Dethlefsen

Environmental Earth Sciences, 2011

One of the uncertainties in the field of carbon dioxide capture and storage (CCS) is caused by the parameterization of geochemical models. The application of geochemical models contributes significantly to calculate the fate of the CO2 after its injection. The choice of the thermodynamic database used, the selection of the secondary mineral assemblage as well as the option to calculate pressure dependent equilibrium constants influence the CO2 trapping potential and trapping mechanism. Scenario analyses were conducted applying a geochemical batch equilibrium model for a virtual CO2 injection into a saline Keuper aquifer. The amount of CO2 which could be trapped in the formation water and in the form of carbonates was calculated using the model code PHREEQC. Thereby, four thermodynamic datasets were used to calculate the thermodynamic equilibria. Furthermore, the equilibrium constants were re-calculated with the code SUPCRT92, which also applied a pressure correction to the equilibrium constants. Varying the thermodynamic database caused a range of 61% in the amount of trapped CO2 calculated. Simultaneously, the assemblage of secondary minerals was varied, and the potential secondary minerals dawsonite and K-mica were included in several scenarios. The selection of the secondary mineral assemblage caused a range of 74% in the calculated amount of trapped CO2. Correcting the equilibrium constants with respect to a pressure of 125 bars had an influence of 11% on the amount of trapped CO2. This illustrates the need for incorporating sensitivity analyses into reaction pathway modeling.

downloadDownload free PDFView PDFchevron_rightEquation of state for the NaClH2OCO2 system: prediction of phase equilibria and volumetric propertiesJohn Weare

Geochimica et Cosmochimica Acta, 1995

An equation of state (EOS) has been developed for the NaCI-HrO-CO2 system which consistently predicts various properties including PVTX, immiscibility or phase equilibria, solubilities, and activities with an accuracy close to that of experimental data from 300 to about IOCKPC r&d O-6000 bar with NaCl concentrations to about 30 wt% of NaCl (relative to NaCl + H20) or to about 50 wt% with less accuracy. The EOS predicts that excess volumes can be over 30% of the total volume under some T-P conditions. Adding NaCl to the HzO-CO2 system dramatically increases the T-P range of immiscibility. The immiscibility field is minimal around 400-500°C. Above or below this temperature, it expands for a constant pressure. A moderately saline brine can evolve into a very saline brine by phase separation at high temperatures. The presence of NaCl can substantially decrease the activity of Hz0 and increase that of CO*, thus affecting decarbonation and dehydration reactions. Compared to the EOS of , the EOS of this study is more reliable in the calculation of volumetric properties particularly in the low pressure range. In addition, BH EOS cannot predict phase equilibria. thank Drs. A. Anderko, K. S. Pitzer, and John Wheeler for valuable discussions.

downloadDownload free PDFView PDFchevron_rightThe prediction of methane solubility in natural waters to high ionic strength from 0 to 250°C and from 0 to 1600 barJohn Weare

Geochimica et Cosmochimica Acta, 1992

A model for the solubility of methane in brines (O-6 m) for temperatures from 0 to 250°C and for pressures from 0 to 1600 bar (or slightly above) is presented. The model is based on Pitzer phenomenology for the liquid phase and a highly accurate equation of state recently developed for the vapor phase. Comparison of model predictions with experimental data indicates that they are within experimental un~~ainty. Most experimental data sets are consistent within errors ofabout 7%. Although the parameters were evaluated from binary and ternary data, the model accurately predicts methane solubility in much more complicated systems like seawater and Salton geothermal brines. Application to fluid inclusion analysis is discussed. Minimum trapping pressures are calculated given the composition and homogeni~tion iemperature. INTRODUCIION

downloadDownload free PDFView PDFchevron_rightAcoustic monitoring of gas emissions from the seafloor. Part II: a case study from the Sea of MarmaraAndré Ogor, Laurent Berger

Marine Geophysical Research, 2014

A rotating, acoustic gas bubble detector, BOB (Bubble OBservatory) module was deployed during two surveys, conducted in 2009 and 2011 respectively, to study the temporal variations of gas emissions from the Marmara seafloor, along the North Anatolian Fault zone. The echosounder mounted on the instrument insonifies an angular sector of 7°during a given duration (of about 1 h). Then it rotates to the next, near-by angular sector and so forth. When the full angular domain is insonified, the ''pan and tilt system'' rotates back to its initial position, in order to start a new cycle (of about 1 day). The acoustic data reveal that gas emission is not a steady process, with observed temporal variations ranging between a few minutes and 24 h (from one cycle to the other). Echo-integration and inversion performed on the acoustic data as described in the companion paper of Leblond et al. (Mar Geophys Res, 2014), also indicate important variations in, respectively, the target strength and the volumetric flow rates of individual sources. However, the observed temporal variations may not be related to the properties of the gas source only, but reflect possible variations in sea-bottom currents, which could deviate the bubble train towards the neighboring sector. During the 2011 survey, a 4-component ocean bottom seismometer (OBS) was co-located at the seafloor, 59 m away from the BOB module. The acoustic data from our rotating, monitoring system support, but do not provide undisputable evidence to confirm, the hypothesis formulated by , that the short-duration, nonseismic micro-events recorded by the OBS are likely produced by gas-related processes within the near seabed sediments. Hence, the use of a multibeam echosounder, or of several split beam echosounders should be preferred to rotating systems, for future experiments.

downloadDownload free PDFView PDFchevron_rightPreferential embrittlement of graphitic schists during extensional unroofing in the Alps: the effect of fluid composition on rheology in low-permeability rocksJane Selverstone

Journal of Metamorphic Geology, 2005

Interlayered graphitic and non-graphitic schists from the Tauern Window, Eastern Alps, record contrasting mechanical behaviour during extensional exhumation. Graphitic schists contain mesoscale extension fractures, pervasive microcracks in garnet, and abundant secondary fluid inclusion planes; all three types of structures are oriented perpendicular to the stretching lineation. Crack spacings in garnet from graphitic samples are tightly clustered around a mean of 180 lm. Non-graphitic schists have fewer and more randomly oriented microcracks and fluid inclusion planes and maintained strain compatibility via crystal plasticity. The presence or absence of graphite appears to have exerted a fundamental control on rheology during unroofing. Calculations for a model graphitic rock at 500°C and f O 2 ¼ 10 )24 MPa show that the equilibrium metamorphic fluid evolves from X CO 2 ¼ 0.07 to 0.38 during decompression from 700 to 400 MPa, in agreement with microcrack fluid inclusion data that show a change from X CO 2 < 0.1 to 0.45 in graphitic samples over the same pressure interval. This compositional shift results in >60% expansion of the pore fluid during decompression. H 2 O-rich fluid in non-graphitic rocks expands <15% over the same pressure interval. The greater pore fluid expansion in low-permeability graphitic horizons likely promoted tensile failure during unroofing. These results suggest that microcracking should be an inevitable consequence of decompression in many graphitic schists, whereas rocks that lack graphite are less likely to undergo microcracking. Microseismicity is predicted to be more common in graphitic than non-graphitic rocks during unroofing of mountain belts.

downloadDownload free PDFView PDFchevron_rightAbundance of CO2-rich fluid inclusions in a sedimentary basin-hosted Cu deposit at Jinman, Yunnan, China: implications for mineralization environment and classification of the depositGuoxiang Chi

Mineralium Deposita, 2011

The Jinman Cu deposit is hosted in sandstones and slates of the Jurassic Huakaizuo Formation in the Mesozoic to Cenozoic Lanping basin in western Yunnan, China. Despite the fact that Cu mineralization occurs mainly in quartz-carbonate veins controlled by faults and fractures, the Jinman deposit was classified as a sedimenthosted stratiform Cu deposit, mainly because it is hosted in a sedimentary basin characterized by abundant red beds with many stratiform Cu deposits. A detailed petrographic and microthermometric study of fluid inclusions from the Jinman deposit reveals the presence of abundant CO 2 -rich fluid inclusions, together with aqueous inclusions. The CO 2 -rich inclusions have CO 2 melting temperatures mainly from −58.0°C to −56.6°C, homogenization temperatures of the carbonic phase (mostly into the liquid phase) mainly between 22°C and 30°C, clathrate melting temperatures from 1.8°C to 9.2°C, with corresponding salinities from 1.6 to 13.4 wt.% NaCl equivalent, and total homogenization temperatures from 226°C to 330°C. The aqueous inclusions have first melting temperatures from −60°C to −52°C, ice melting temperatures from −41.4°C to −2.3°C, with salinities from 3.9 to 29.0 wt.% NaCl equivalent, and total homogenization temperatures mainly from 140°C to 250°C. These fluid inclusion characteristics are comparable to those of orogenic or magmatic mineralization systems and are uncharacteristic of basinal mineralization systems, suggesting that it is inappropriate to classify the Jinman deposit as a sediment-hosted stratiform Cu deposit. The results of this study, together with geochemical data reported previously, suggest that the Jinman deposit formed in a hydrothermal system that involved both extra-basinal, deeply sourced CO 2 -rich fluid and basinal, aqueous fluid.

downloadDownload free PDFView PDFchevron_rightSubsurface characterization and geological monitoring of the CO2 injection operation at Weyburn, Saskatchewan, CanadaJames B Riding

Geological Society, London, Special Publications, 2009

The IEA Weyburn Carbon Dioxide (CO 2 ) Monitoring and Storage Project analysed the effects of a miscible CO 2 flood into a Lower Carboniferous carbonate reservoir rock at an onshore Canadian oilfield. Anthropogenic CO 2 is being injected as part of a commercial enhanced oil recovery operation. Much of the research performed in Europe as part of an international monitoring project was aimed at analysing the long-term migration pathways of CO 2 and the effects of CO 2 on the hydrochemical and mineralogical properties of the reservoir rock. The pre-CO 2 injection hydrochemical, hydrogeological and petrographical conditions in the reservoir were investigated in order to recognise changes caused by the CO 2 flood and to assess the long-term fate of the injected CO 2 . The Lower Carboniferous (Mississippian) aquifer has a salinity gradient in the Weyburn area, where flows are oriented southwest-northeast. Hydrogeological modelling indicates that dissolved CO 2 would migrate from Weyburn in an east-northeast direction at a rate of about 0.2 m/year under the influence of regional groundwater flow. The baseline gas fluxes and CO 2 concentrations in groundwater were also investigated. The gas dissolved in the reservoir waters allowed potential transport pathways to be identified. Analysis of reservoir fluids proved that dissolved CO 2 and methane (CH 4 ) increased significantly in the injection area between 2002 and 2003. Most of the injected CO 2 exists in a supercritical state, lesser amounts are trapped in solution and there is little apparent mineral trapping. The CO 2 has already reacted with the reservoir rock sufficiently to mask some of the strontium isotope signature caused by 40 years of water flooding. Experimental studies of CO 2 -porewater-rock interactions in the Midale Marly Unit indicated slight dissolution of carbonate and silicate minerals, followed by relatively rapid saturation with respect to carbonate minerals. Carbon dioxide flooding experiments on similar samples demonstrated that porosity and gas permeability increased significantly through dissolution of calcite and dolomite. Several microseismic events were recorded over a six-month period and these are provisionally interpreted as being related to small fractures formed by injection-driven fluid migration within the reservoir, as well as other oilfield operations. Experimental studies on the overlying and underlying units show similar reaction processes, however secondary gypsum precipitation was also observed. Reaction experiments were conducted with CO 2 and borehole cements. The size and tensile strength of the cement blocks were unaffected, however their densities increased. A multidisciplinary study of the till deposits in the Weyburn area indicates that a single, heterogeneous till sheet is present. Pre-and post-injection soil gas data are consistent with a shallow biological origin for the measured CO 2 in soil gases. Isotopic (δ 13 C) data values are higher than in the injected CO 2 , and confirm this interpretation. No evidence for leakage of the injected CO 2 to ground level has been detected. The long-term safety and performance of CO 2 storage was assessed by the construction of a features, events and processes (FEP) database that provides a comprehensive knowledge base for the geological storage of CO 2 .

downloadDownload free PDFView PDFchevron_rightCarbon dioxide dynamics in Kelud volcanic lakeCorentin Caudron

Journal of Geophysical Research, 2012

downloadDownload free PDFView PDFchevron_rightA Computationally Efficient Approach to Applying the SAFT Equation for CO2 + H2O Phase Equilibrium CalculationsKamy Sepehrnoori

Journal of Solution Chemistry, 2014

The statistical associating fluid theory equation of state (EoS) is employed in a time efficient way for the correlation and prediction of vapor-liquid equilibrium of the CO 2 ? H 2 O binary system for the temperature (10-100°C) and pressure (1-600 bar) ranges suitable for simulation of CO 2 geologic sequestration. The effective number of segments and energy parameter are correlated with the reduced temperature. Simple mixing rules are applied to obtain binary interaction parameters. Assigning a fixed H 2 O composition in the mixing rule makes the phase equilibrium calculations relatively fast compared to other EoS's. The results obtained by the model used were found to be in satisfactory agreement with the literature data.

downloadDownload free PDFView PDFchevron_rightDeposition of highly crystalline graphite from moderate-temperature fluidsJan Marten Huizenga

Geology, 2009

ABSTRACT Recognized large occurrences of fluid-deposited graphite displaying high crystallinity were previously restricted to high-temperature environments (mainly granulite facies terranes). However, in the extensively mined Borrowdale deposit (UK), the mineralogical assemblage, notably the graphite-epidote intergrowths, shows that fully ordered graphite precipitated during the propylitic hydrothermal alteration of the volcanic host rocks. Fluids responsible for graphite deposition had an average XCO2/(XCO2 + XCH4) ratio of 0.69, thus indicating temperatures of ∼500 °C at the fayalite-magnetite-quartz buffered conditions. Therefore, this is the first reported evidence indicating that huge concentrations of highly crystalline graphite can precipitate from moderate-temperature fluids.

downloadDownload free PDFView PDFchevron_rightOptimal process design for the polygeneration of SNG, power and heat by hydrothermal gasification of waste biomass: Process optimisation for selected substratesFrancois Marechal

Energy & Environmental Science, 2011

Based on a previously developed thermo-economic process model, this paper presents a detailed design study for the polygeneration of Synthetic Natural Gas (SNG), power and heat by catalytic hydrothermal gasification of biomass and biomass wastes in supercritical water. Using multi-objective optimisation techniques, the thermodynamic and thermo-economic performances of all candidate configurations from a general process superstructure are optimised with respect to SNG and electricity cogeneration and its associated investment cost, production cost and plant profitability. The paper demonstrates how both the optimal system configuration, its operating conditions and performances depend on the available technology, catalyst lifetime, process scale and the characteristics of the processed substrate.

downloadDownload free PDFView PDFchevron_rightEstimating Pore Space Hydrate Saturation Using Dissociation Gas Evolution Measurements: In Relevance to Laboratory Testing of Natural or Artificially Synthesised Hydrate-Bearing Soil SpecimensAnuruddhika G Jayasinghe

Journal of Geological Research, 2013

Physical properties of gas hydrate-bearing soils are known to be greatly affected by the pore space hydrate saturation. The accuracy of most saturation estimation methods is affected by hydrate growth habit and pore space distribution. We highlight the usefulness of dissociation gas evolution measurement (DGEM) method as a reference laboratory method to calibrate most other methods. The DGEM method is based on the concept of mass balance and properties of volume compatibility between two distinct states of a closed system. The accuracy of the estimation depends on (1) the precision with which the laboratory measurements of temperature, pressure, and volumetric properties are obtained (2) and the ability of theoretical models used in the calculation to closely represent the true nature of the system. We perform an analysis to evaluate the sensitivity of the estimation (1) to various laboratory measurements and (2) to the use of different theoretical models to generate a feel for the appropriateness of various assumptions associated with DGEM. The comprehensive guide to available resources useful in the hydrate saturation estimation also serves as one of the major contributions of the work presented.

downloadDownload free PDFView PDFchevron_rightNumerical analysis of wave-induced fluid flow effects on seismic data: Application to monitoring of CO 2 storage at the Sleipner fieldDanilo Velis

Journal of Geophysical Research, 2011

In this work we analyze how patchy distributions of CO 2 and brine within sand reservoirs may lead to significant attenuation and velocity dispersion effects, which in turn may have a profound impact on surface seismic data. The ultimate goal of this paper is to contribute to the understanding of these processes within the framework of the seismic monitoring of CO 2 sequestration, a key strategy to mitigate global warming. We first carry out a Monte Carlo analysis to study the statistical behavior of attenuation and velocity dispersion of compressional waves traveling through rocks with properties similar to those at the Utsira Sand, Sleipner field, containing quasi-fractal patchy distributions of CO 2 and brine. These results show that the mean patch size and CO 2 saturation play key roles in the observed wave-induced fluid flow effects. The latter can be remarkably important when CO 2 concentrations are low and mean patch sizes are relatively large. To analyze these effects on the corresponding surface seismic data, we perform numerical simulations of wave propagation considering reservoir models and CO 2 accumulation patterns similar to the CO 2 injection site in the Sleipner field. These numerical experiments suggest that wave-induced fluid flow effects may produce changes in the reservoir's seismic response, modifying significantly the main seismic attributes usually employed in the characterization of these environments. Consequently, the determination of the nature of the fluid distributions as well as the proper modeling of the seismic data constitute important aspects that should not be ignored in the seismic monitoring of CO 2 sequestration problems.

downloadDownload free PDFView PDFchevron_rightAn Electrochemical Study of the Effect of High Salt Concentration on Uniform Corrosion of Carbon Steel in Aqueous CO2 Solutionsfazlollah madani sani

Journal of The Electrochemical Society

Uniform CO 2 corrosion of carbon steel facilities is often a major problem when handling produced water in the oil and gas fields. High amounts of dissolved salts are often present in produced water. A limited number of research studies has been conducted on the effect of salt concentration on uniform CO 2 corrosion. In this study, the effect of NaCl concentration on uniform CO 2 corrosion of X65 carbon steel was investigated in CO 2 saturated aqueous solutions using a rotating cylinder system at 30°C, autogenous pH, and 1 bar total pressure in an NaCl concentration range of 0-4.27 molality (m) (0-20 wt.%). With increasing NaCl concentration, the corrosion rate increased sharply and reached its maximum value at ∼0.17 m (1 wt.%) NaCl and then decreased with further increase in NaCl concentration. The observed trend in the corrosion rate with increasing NaCl concentration was primarily a consequence of the change in the cathodic limiting current density, which was the main factor controlling the rate of the overall corrosion process. The additional factor was the change in the rate of the anodic reaction with salt concentration.

downloadDownload free PDFView PDFchevron_rightHigh temperatures and high pressures Brillouin scattering studies of liquid H[sub 2]O+CO[sub 2] mixturesJun Li

The Journal of Chemical Physics, 2010

The Brillouin scattering spectroscopy studies have been conducted in a diamond anvil cell for a liquid mixtures composed of 95 mol % H 2 O and 5 mol % CO 2 under high temperatures and pressures. The sound velocity, refractive index, density, and adiabatic bulk modulus of the H 2 O +CO 2 mixtures were determined under pressures up to the freezing point at 293, 453, and 575 K. It is found from the experiment that sound velocities of the liquid mixture are substantially lower than those of pure water at 575 K, but not at lower temperatures. We presented an empirical relation of the density in terms of pressure and temperature. Our results show that liquid H 2 O+CO 2 mixtures are more compressible than water obtained from an existing equation of state of at 453 and 575 K.

downloadDownload free PDFView PDFchevron_rightOrigin of Spinel + Quartz Assemblage in a Si-undersaturated Ultrahigh-temperature Aluminous Granulite and its Implication for the P–T–fluid History of the Phulbani Domain, Eastern Ghats Belt, IndiaPROLOY GANGULY

Journal of Petrology

A suite of high-grade rocks including felsic gneiss, aluminous granulite, charnockite and calcsilicate granulite is exposed at Phulbani, which belongs to a petrologically little understood crustal domain (Phulbani domain) of the Eastern Ghats Belt. The aluminous granulite is constituted of corundum þ spinel þ ilmenite þ garnet þ sillimanite þ quartz 6 K-feldspar 6 plagioclase 6 biotite. Textural analysis indicates that corundum, spinel, garnet and/or K-feldspar were formed as a result of biotite dehydration melting of a Si-poor protolith during prograde metamorphism. Although corundum and quartz coexist in micro-scale domains, phase diagram modelling suggests that garnet þ corundum þ spinel þ ilmenite þ sillimanite (up to 800 C at 8 kbar) and garnet þ spinel þ sillimanite þ ilmenite þ quartz (above 950 C at 8 kbar) assemblages were stabilized in two different temperature intervals while attaining the ultrahigh-temperature metamorphic peak. The transformation from corundum-to quartz-bearing assemblages was principally governed by chemical reactions. Quartz, formed at the peak stage, produced complex reaction textures involving spinel, corundum, garnet and sillimanite during near-isobaric cooling. Intersection of the same mineral reactions during the prograde and the retrograde paths implies the near-closed-system behaviour of the lower crust, at least at microdomain-scale, possibly achieved after large-scale melt loss along the prograde-to-peak stage of evolution. The pressure-temperature path remained near-isobaric during the prograde and the retrograde evolution of the assemblages. High-density (up to 1Á03 g cm-3) CO 2-rich fluid inclusions in aluminous granulite, coarse-grained charnockite and felsic gneiss indicate that peak metamorphism and subsequent evolution occurred under a CO 2-dominated fluid regime. The pressure-temperature-fluid evolutionary history of the Phulbani domain shows similarity to that of the adjacent Visakhapatnam domain of the Eastern Ghats Belt and poses questions on the status of the boundary separating these two domains.

downloadDownload free PDFView PDFchevron_rightFluid properties and dynamics along the seismogenic plate interfaceVincent Famin

Geosphere

Fossil structures, such as exhumed accretionary prisms, are the only direct recorders of the fluids wetting the plate interface near the base of the seismo genic zone. By studying exhumed accretionary prisms, it is thus possible to determine the physicochemical properties of fluids and the geometry and dynamics of their circulation. We considered here two transects encompass ing the brittleplastic transition (BPT) zone, in the FrancoItalian Alps and the Shimanto Belt in Japan, and compared our data with a broader set of exam ples from the literature. On quartz that grew synkinematically at peak burial conditions, we inferred fluid properties indirectly from quartz traceelement concentrations (using cathodoluminescence [CL] imaging) and directly from fluidinclusion composition and PρT properties (using Raman and micro thermometry). At ~250 °C, quartz grew principally through fracturing and two types of quartz, a CLbrown and a CLblue, precipitated alternately. At ~350 °C, where plastic deformation and recrystallization is pervasive, only a single, ho mogeneously CLbrown quartz is present. The salinity of the fluid in the inclu sions shallower than the BPT is consistently of the order or lower than sea water, while salinities are very scattered deeper than the BPT and often exceed seawater salinity. The gas dissolved in the fluid is predominantly CH 4 shal lower than the BPT, and either CH 4 or CO 2 deeper than the BPT, depending on the nature of the host rock and in particular on the proportion of carbonates. Cathodoluminescence properties, salinity, and nature of the gas all point to a closedsystem behavior in rocks deeper than the BPT. In contrast, shallower than the BPT (i.e., at seismogenic depths), textures revealed by CLimaging evidence the episodic influx of an external fluid, leading to the crystallization of CLblue quartz. The scale of the circulation leading to the generation of the CLblue quartz, or its relationship with the seismic cycle, is still unclear. Be sides, the fluid pressure recorded in the abundant waterrich fluid inclusions is systematically much lower than the corresponding lithostatic pressure, ir respective of the depth domain considered. For inclusions trapped at large depth, the low fluid pressure recorded in the inclusions reflects postentrap ment reequilibration. For inclusions trapped at shallower conditions, typically at seismogenic depths, the low fluid pressure may as well be the result of large fluid pressure drop after earthquakes.

downloadDownload free PDFView PDFchevron_rightEvolution of fluid expulsion and concentrated hydrate zones across the southern Hikurangi subduction margin, New Zealand: An analysis from depth migrated seismic dataandreia plaza

Identification of methane sources controlling hydrate distribution and concentrations in continental margins remains a major challenge in gas hydrate research. Lack of deep fluid samples and high quality regional scale seismic reflection data may lead to underestimation of the significance of fluid escape from subducting and compacting sediments in the global inventory of methane reaching the hydrate zone, the water column and the atmosphere. The distribution of concentrated hydrate zones in relation to focused fluid flow across the southern Hikurangi subduction margin was investigated using high quality, long offset (10 km streamer), pre-stack depth migrated multichannel seismic data. Analysis of low P wave velocity zones, bright-reverse polarity reflections and dim-amplitude anomalies reveals pathways for gas escape and zones of gas accumulation. The study shows the structural and stratigraphic settings of three main areas of concentrated hydrates: (1) the Opouawe Bank, dominated by focused periodic fluid input along thrust faults sustaining dynamic hydrate concentrations and gas chimneys development; (2) the frontal anticline, with a basal set of protothrusts controlling permeability for fluids from deeply buried and subducted sediments sustaining hydrate concentrations at the crest of the anticline; and (3) the Hikurangi Channel, with buried sand dominated channels hosting significant amounts of gas beneath the base of the hydrate zone. In sand dominated channels gas injection into the hydrate zone favors highly concentrated hydrate accumulations. The evolution of fluid expulsion controlling hydrate formation offshore southern Hikurangi is described in stages during which different methane sources (in situ, buried and thermogenic) have been dominant.

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