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1.
Phase equilibria and spectroscopic data are used to develop a simple model for the interaction of various oxide components and molten SiO 2. Network modifying oxides, M xO y produce nonbridging oxygens thereby depolymerizing the SiO 2 network. The energetics of nonbridging oxygen formation are least favorable when the field strength of the metal cation is high. This produces relatively strong M-O and Si-O-Si bridging bonds at the expense of weaker Si-O-M bonds (De Jong et al., 1980). This relationship is manifested by an increase in positive deviations from ideality with increasing cation field strength in M xO y-SiO 2 systems; the activity coefficient of SiO 2 is inversely correlated with Si-O-M bond strength. Network forming oxides (aluminates, phosphates, titanates. zirconates, etc.) may copolymerize with the SiO 2 network. Mixing on the same quasi-lattice produces solutions which approach ideality. Deviations from ideality in such solutions can be linked to distortions in the SiO 2 network. Discrete anion formers (phosphates, titanates, chromates, zirconates) complex with metal oxides other than SiO 2 to form discrete structural units which do not copolymerize with SiO 2. The SiO 2 network is essentially shielded from the high charge density cations in such systems and unmixing is common. As a result, the relative deviations from ideality in such melts are high. It is important to recognize that oxides such as P 2O 5, TiO 2 and ZrO 2 may act as either network-formers or discrete anion formers depending upon melt composition, and are probably distributed between these two “sites” in most geologically important liquids. The latter structural role is favored in more basic compositions. 相似文献
2.
The solubility of CO 2 in dacitic melts equilibrated with H 2O-CO 2 fluids was experimentally investigated at 1250°C and 100 to 500 MPa. CO 2 is dissolved in dacitic glasses as molecular CO 2 and carbonate. The quantification of total CO 2 in the glasses by mid-infrared (MIR) spectroscopy is difficult because the weak carbonate bands at 1430 and 1530 cm −1 can not be reliably separated from background features in the spectra. Furthermore, the ratio of CO 2,mol/carbonate in the quenched glasses strongly decreases with increasing water content. Due to the difficulties in quantifying CO 2 species concentrations from the MIR spectra we have measured total CO 2 contents of dacitic glasses by secondary ion mass spectrometry (SIMS).At all pressures, the dependence of CO 2 solubility in dacitic melts on xfluidCO2,total shows a strong positive deviation from linearity with almost constant CO 2 solubility at xCO2fluid > 0.8 (maximum CO 2 solubility of 795 ± 41, 1376 ± 73 and 2949 ± 166 ppm at 100, 200 and 500 MPa, respectively), indicating that dissolved water strongly enhances the solubility of CO 2. A similar nonlinear variation of CO 2 solubility with xCO2fluid has been observed for rhyolitic melts in which carbon dioxide is incorporated exclusively as molecular CO 2 (Tamic et al., 2001). We infer that water species in the melt do not only stabilize carbonate groups as has been suggested earlier but also CO 2 molecules.A thermodynamic model describing the dependence of the CO 2 solubility in hydrous rhyolitic and dacitic melts on T, P, fCO2 and the mol fraction of water in the melt ( xwater) has been developed. An exponential variation of the equilibrium constant K 1 with xwater is proposed to account for the nonlinear dependence of xCO2,totalmelt on xCO2fluid. The model reproduces the CO 2 solubility data for dacitic melts within ±14% relative and the data for rhyolitic melts within 10% relative in the pressure range 100-500 MPa (except for six outliers at low xCO2fluid). Data obtained for rhyolitic melts at 75 MPa and 850°C show a stronger deviation from the model, suggesting a change in the solubility behavior of CO 2 at low pressures (a Henrian behavior of the CO 2 solubility is observed at low pressure and low H 2O concentrations in the melt). We recommend to use our model only in the pressure range 100-500 MPa and in the xCO2fluid range 0.1-0.95. The thermodynamic modeling indicates that the partial molar volume of total CO 2 is much lower in rhyolitic melts (31.7 cm 3/mol) than in dacitic melts (46.6 cm 3/mol). The dissolution enthalpy for CO 2 in hydrous rhyolitic melts was found to be negligible. This result suggests that temperature is of minor importance for CO 2 solubility in silicic melts. 相似文献
3.
We have analysed the kinetics of Argon and CO 2 diffusion in simplified iron free rhyolitic to hawaiitic melts using the diffusion couple technique. The concentration distance profiles of Ar and CO 2 were measured with electron microprobe analysis and Fourier Transform Infrared Spectroscopy, respectively. Error functions were fitted to the symmetrical concentration distance profiles to extract the diffusion coefficients.In the temperature range 1373 to 1773 K the activation energies for Ar diffusion range from 169 ± 20 to 257 ± 62 kJ mol −1. Ar diffusivity increases exponentially with the degree of depolymerisation. In contrast, the mobility of total CO 2, that is identical to Ar mobility in rhyolitic melt, keeps constant with changing bulk composition from rhyolite to hawaiite. CO 2 speciation at 1623 K and 500 MPa was modeled for the range of compositions studied using the diffusion data of Ar and total CO 2 in combination with network former diffusion calculated from viscosity data. Within error this model is in excellent agreement with CO 2 speciation data extrapolated from temperatures near the glass transition temperature for dacitic melt composition. This model shows that even in highly depolymerised hawaiitic and tholeiitic melts molecular CO 2 is a stable species and contributes 70 to 80% to the total CO 2 diffusion, respectively. 相似文献
4.
To investigate the influence of temperature and composition on the diffusivities of dissolved carbon dioxide and argon in silicate melts, diffusion experiments were performed at magmatic pressure and temperature conditions in (a) albite melts with excess Na 2O (0-8.6 wt%) and a constant Si/Al ratio of 3, and (b) albite 70quartz 30 to jadeite melts with decreasing SiO 2 content and a constant Na/Al ratio of 1. We obtained diffusion coefficients at 500 MPa and 1323-1673 K. In the fully polymerized system Ab 70Qz 30 - Jd, the change in composition only has a weak effect on bulk CO 2 diffusivity, but Ar diffusivity increases clearly with decreasing SiO 2 content. In the system Ab + Na 2O, bulk CO 2 and Ar diffusivity increase significantly with gradual depolymerisation. The relatively small change in composition on molar basis in the depolymerized system leads to a significantly larger change in diffusivities compared to the fully polymerized Ab 70Qz 30-Jd join. Within error, activation energies for bulk CO 2 and Ar diffusion in both systems are identical with decreasing silica content (Ab + Na 2O: 159 ± 25 kJ mol −1 for bulk CO 2 and 130 ± 8 kJ mol −1 for Ar; Ab 70Qz 30-Jd: 163 ± 16 kJ mol −1 for bulk CO 2 and 148 ± 15 kJ mol −1 for Ar) even though this results in depolymerisation in one system and not the other.Although there is a variation in CO 2 speciation with changing composition as observed in quenched glasses, it has previously established that this is not a true representation of the species present in the melt, with the ratio of molecular CO 2 to carbonate decreasing during quenching. Thus, diffusion coefficients for the individual CO 2 species cannot be directly derived by measuring molecular CO 2 and CO 32- concentration-distance profiles in the glasses. To obtain diffusivities of individual CO 2 species, we have made two assumptions that (1) inert Ar can be used as a proxy for molecular CO 2 diffusion characteristics as shown by our previous work and (2) the diffusivity of CO 32− can be calculated assuming it is identical to network forming components (Si 4+ and Al 3+). This is derived from viscosity data (Eyring eqn.) and suggests that CO 32− diffusion would be several orders of magnitude slower than molecular CO 2 diffusion.The systematics of measured bulk CO 2 diffusivity rates and comparison with the Ar proxy all suggest that the faster molecular CO 2 species is much more dominant in melts than measurements on resulting quenched glasses would suggest. This study has confirmed an observation of surprisingly consistent bulk CO 2 diffusivity across a range of natural compositions were Ar diffusivity significantly increases. This is consistent with an actual increase in molecular CO 2 mobility (similar to Ar) that is combined with an increase in the proportion of the slower carbonate in the melt.These results demonstrate that the CO 2 diffusion and speciation model provides an insight into the transport processes in the melt and is promising and an alternative tool to in situ speciation measurements at magmatic conditions, which at the moment are technically extremely difficult. We present the first high pressure high temperature in situ MIR spectra of a CO 2 bearing albitic glass/melt suggesting that molecular CO 2 is a stable species at high temperature, which is qualitatively consistent with the modelled CO 2 speciation data. 相似文献
5.
Phase equilibria data in the systems SiO 2-P 2O 5, P 2O 5-M xO y, and P 2O 5-M xO y-SiO 2 are employed in conjunction with Chromatographic and spectral data to investigate the role of P 2O 5 in silicate melts. Such data indicate that the behavior of P 2O 5 is complex. P 2O 5 depolymerizes pure SiO 2 melts by entering the network as a four-fold coordinated cation, but polymerizes melts in which an additional metal cation other than silicon is present. The effect of this polymerization is apparent in the widening of the granite-ferrobasalt two-liquid solvus. In this complex system P 2O 5 acts to increase phase separation by further enrichment of the high charge density cations Ti, Fe, Mg, Mn, Ca, in the ferrobasaltic liquid. P 2O 5 also produces an increase in the ferrobasalt-granite REE liquid distribution coefficients. These distribution coefficients are close to 4 in P 2O 5-free melts, but close to 15 in P 2O 5-bearing melts.The dual behavior of P 2O 5 is explained in a model which requires complexing of phosphate anions (analogous to silicate anions) and metal cations in the melt. This interaction destroys Si-O-M-O-Si bonds polymerizing the melt. The higher concentration of Si-O-M-O-Si bond complexes in immiscible ferrobasaltic liquids relative to their conjugate immiscible granite liquids explains the partitioning of P 2O 5 into the ferrobasaltic liquid. 相似文献
6.
Chemical diffusion profiles in molten CaO---Al 2O 3---SiO 2 have been measured over a large range of compositions at 1500°C and l GPa. The diffusion profiles have been inverted for effective binary diffusion coefficients (EBDCs) and for the chemical diffusion matrix. The EBDCs are shown to depend strongly on both composition and direction of diffusion in composition space. The dependence of EBDCs on direction in composition space, which for the system studied here can be as large as a factor of seven, severely limits the applicability of EBDCs to interdiffusion in any direction other than the one used to derive the EBDCs. The chemical diffusion matrix for molten CaO---Al2O3---SiO2 was determined using diffusion profiles from two or three mutually orthogonal diffusion couples in the ternary composition space. All features of the diffusion profiles shown in this work can be reproduced by representing the chemical fluxes in the three-component system as a linear combination of concentration gradients via a 2 × 2 diffusion matrix. Chemical diffusion in molten CaO---Al2O3---SiO2 shows clear evidence of strong diffusive coupling among the components. This can be seen in the uphill diffusion profiles of components that were initially uniform, in the fact that the apparent rate of diffusion of some components is a strong function of direction in composition space, and most quantitatively in the magnitude of off-diagonal elements of the diffusion matrix relative to the magnitude of the diagonal elements. SiO2 for example, is found to be strongly coupled with CaO in relatively silicic melts, whereas Al2O3 is strongly coupled with CaO in less silicic melts. Furthermore, the coupling of CaO with either Al2O3 or Si02 reverses sign between more and less polymerized compositions. Interdiffusion profiles in natural melts have numerous features that suggest similar coupling between Al2O3 and CaO and between SiO2 and CaO. 相似文献
7.
Traditionally, the application of stable isotopes in Carbon Capture and Storage (CCS) projects has focused on δ13C values of CO 2 to trace the migration of injected CO 2 in the subsurface. More recently the use of δ18O values of both CO 2 and reservoir fluids has been proposed as a method for quantifying in situ CO 2 reservoir saturations due to O isotope exchange between CO 2 and H 2O and subsequent changes in δ18O H2O values in the presence of high concentrations of CO 2. To verify that O isotope exchange between CO 2 and H 2O reaches equilibrium within days, and that δ18O H2O values indeed change predictably due to the presence of CO 2, a laboratory study was conducted during which the isotope composition of H 2O, CO 2, and dissolved inorganic C (DIC) was determined at representative reservoir conditions (50 °C and up to 19 MPa) and varying CO 2 pressures. Conditions typical for the Pembina Cardium CO 2 Monitoring Pilot in Alberta (Canada) were chosen for the experiments. Results obtained showed that δ18O values of CO 2 were on average 36.4 ± 2.2‰ (1 σ, n = 15) higher than those of water at all pressures up to and including reservoir pressure (19 MPa), in excellent agreement with the theoretically predicted isotope enrichment factor of 35.5‰ for the experimental temperatures of 50 °C. By using 18O enriched water for the experiments it was demonstrated that changes in the δ18O values of water were predictably related to the fraction of O in the system sourced from CO 2 in excellent agreement with theoretical predictions. Since the fraction of O sourced from CO 2 is related to the total volumetric saturation of CO 2 and water as a fraction of the total volume of the system, it is concluded that changes in δ18O values of reservoir fluids can be used to calculate reservoir saturations of CO 2 in CCS settings given that the δ18O values of CO 2 and water are sufficiently distinct. 相似文献
8.
We determined total CO 2 solubilities in andesite melts with a range of compositions. Melts were equilibrated with excess C-O(-H) fluid at 1 GPa and 1300°C then quenched to glasses. Samples were analyzed using an electron microprobe for major elements, ion microprobe for C-O-H volatiles, and Fourier transform infrared spectroscopy for molecular H 2O, OH −, molecular CO 2, and CO 32−. CO 2 solubility was determined in hydrous andesite glasses and we found that H 2O content has a strong influence on C-O speciation and total CO 2 solubility. In anhydrous andesite melts with ∼60 wt.% SiO 2, total CO 2 solubility is ∼0.3 wt.% at 1300°C and 1 GPa and total CO 2 solubility increases by about 0.06 wt.% per wt.% of total H 2O. As total H 2O increases from ∼0 to ∼3.4 wt.%, molecular CO 2 decreases (from 0.07 ± 0.01 wt.% to ∼0.01 wt.%) and CO 32− increases (from 0.24 ± 0.04 wt.% to 0.57 ± 0.09 wt.%). Molecular CO 2 increases as the calculated mole fraction of CO 2 in the fluid increases, showing Henrian behavior. In contrast, CO 32− decreases as the calculated mole fraction of CO 2 in the fluid increases, indicating that CO 32− solubility is strongly dependent on the availability of reactive oxygens in the melt. These findings have implications for CO 2 degassing. If substantial H 2O is present, total CO 2 solubility is higher and CO 2 will degas at relatively shallow levels compared to a drier melt. Total CO 2 solubility was also examined in andesitic glasses with additional Ca, K, or Mg and low H 2O contents (<1 wt.%). We found that total CO 2 solubility is negatively correlated with (Si + Al) cation mole fraction and positively correlated with cations with large Gibbs free energy of decarbonation or high charge-to-radius ratios (e.g., Ca). Combining our andesite data with data from the literature, we find that molecular CO 2 is more abundant in highly polymerized melts with high ionic porosities (>∼48.3%), and low nonbridging oxygen/tetrahedral oxygen (<∼0.3). Carbonate dominates most silicate melts and is most abundant in depolymerized melts with low ionic porosities, high nonbridging oxygen/tetrahedral oxygen (>∼0.3), and abundant cations with large Gibbs free energy of decarbonation or high charge-to-radius ratio. In natural silicate melt, the oxygens in the carbonate are likely associated with tetrahedral and network-modifying cations (including Ca, H, or H-bonds) or a combinations of those cations. 相似文献
9.
Reaction between dissolved water and sulphide was experimentally investigated in soda-lime-silicate (NCS) and sodium trisilicate (NS3) melts at temperatures from 1000 to 1200 °C and pressures of 100 or 200 MPa in internally heated gas pressure vessels. Diffusion couple experiments were conducted at water-undersaturated conditions with one half of the couple being doped with sulphide (added as FeS or Na 2S; 1500-2000 ppm S by weight) and the other with H 2O (∼3.0 wt.%). Additionally, two experiments were performed using a dry NCS glass cylinder and a free H 2O fluid. Here, the melt was water-saturated at least at the melt/fluid interface. Profiling by electron microprobe (sulphur) and infrared microscopy (H 2O) demonstrate that H 2O diffusion in the melts is faster by 1.5-2.3 orders of magnitude than sulphur diffusion and, hence, H 2O can be considered as a rapidly diffusing oxidant while sulphur is quasi immobile in these experiments.In Raman spectra a band at 2576 cm −1 appears in the sulphide - H 2O transition zone which is attributed to fundamental S-H stretching vibrations. Formation of new IR absorption bands at 5025 cm −1 (on expense of the combination band of molecular H 2O at 5225 cm −1) and at 3400 cm −1 was observed at the front of the in-diffusing water in the sulphide bearing melt. The appearance and intensity of these two IR bands is correlated with systematic changes in S K-edge XANES spectra. A pre-edge excitation at 2466.5 eV grows with increasing H 2O concentration while the sulphide peak at 2474.0 eV decreases in intensity relative to the peak at 2477.0 eV and the feature at 2472.3 eV becomes more pronounced (all energies are relative to the sulphate excitation, calibrated to 2482.5 eV). The observations by Raman, IR and XANES spectroscopy indicate a well coordinated S 2− - H 2O complex which was probably formed in the glasses during cooling at the glass transition. No oxidation of sulphide was observed in any of the diffusion couple experiments. On the contrary, XANES spectra from experiments conducted with a free H 2O fluid show complete transformation of sulphide to sulphate near the melt surface and coexistence of sulphate and sulphide in the center of the melt. This can be explained by a lower H 2O activity in the diffusion couple experiments or by the need of a sink for hydrogen (e.g., a fluid which can dissolve high concentration of hydrogen) to promote oxidation of sulphide by H 2O via the reaction S 2− + 4H 2O = SO 42− + 4H 2. Sulphite could not be detected in any of the XANES spectra implying that this species, if it exists in the melt, it is a subordinate or transient species only. 相似文献
10.
The solubility behavior of H 2O in melts in the system Na 2O-SiO 2-H 2O was determined by locating the univariant phase boundary, melt = melt + vapor in the 0.8-2 GPa and 1000°-1300°C pressure and temperature range, respectively. The NBO/Si-range of the melts (0.25-1) was chosen to cover that of most natural magmatic liquids. The H 2O solubility in melts in the system Na 2O-SiO 2-H 2O (X H2O) ranges between 18 and 45 mol% (O = 1) with (∂X H2O/∂P) T∼14-18 mol% H 2O/GPa. The (∂X H2O/∂P) T is negatively correlated with NBO/Si (= Na/Si) of the melt. The (∂X H2O/∂T) P is in the −0.03 to +0.05 mol% H 2O/°C range, and is negatively correlated with NBO/Si. The [∂X H2O/∂(NBO/Si)] P,T is in the −3 to −8 mol% H 2O/(NBO/Si) range. Melts with NBO/Si similar to basaltic liquids (∼0.6-∼1.0) show (∂X H2O/∂T) P<0, whereas more polymerized melts exhibit (∂X H2O/∂T) P>0. Complete miscibility between hydrous melt and aqueous fluid occurs in the 0.8-2 GPa pressure range for melts with NBO/Si ≤0.5 at T >1100°C. Miscibility occurs at lower pressure the more polymerized the melt. 相似文献
11.
The sodium solubility in silicate melts in the CaO-MgO-SiO 2 (CMS) system at 1400 °C has been measured by using a closed thermochemical reactor designed to control alkali metal activity. In this reactor, Na (g) evaporation from a Na 2O- xSiO 2 melt imposes an alkali metal vapor pressure in equilibrium with the molten silicate samples. Because of equilibrium conditions in the reactor, the activity of sodium-metal oxide in the molten samples is the same as that of the source, i.e., aNa 2O (sample) = aNa 2O (source). This design also allows to determine the sodium oxide activity coefficient in the samples. Thirty-three different CMS compositions were studied. The results show that the amount of sodium entering from the gas phase (i.e., Na 2O solubility) is strongly sensitive to silica content of the melt and, to a lesser extent, the relative amounts of CaO and MgO. Despite the large range of tested melt compositions (0 < CaO and MgO < 40; 40 < SiO 2 < 100; in wt%), we found that Na 2O solubility is conveniently modeled as a linear function of the optical basicity ( Λ) calculated on a Na-free basis melt composition. In our experiments, γNa 2O (sample) ranges from 7 × 10 −7 to 5 × 10 −6, indicating a strongly non-ideal behavior of Na 2O solubility in the studied CMS melts (γNa 2O (sample) ? 1). In addition to showing the effect of sodium on phase relationships in the CMS system, this Na 2O solubility study brings valuable new constraints on how melt structure controls the solubility of Na in the CMS silicate melts. Our results suggest that Na 2O addition causes depolymerization of the melt by preferential breaking of Si-O-Si bonds of the most polymerized tetrahedral sites, mainly Q 4. 相似文献
12.
我室采用MIR-10型CO2激光器,在一种富BrF5的氛围中使激光对硅酸盐和氧化物矿物样品加热形成O2,经多次纯化后用5A的分子筛吸收,再直接送至气体质谱仪进行氧同位素比值测定.这个实验流程与传统方法相比的改进不仅在使用激光加热技术及样品的放置上,而且在直接采用O2而不是CO2进行质谱测定.采用O2进行直接分析的优点不仅避免了向CO2转化过程中的潜在同位素分馏,而且能够得到样品的δ17O值,因此为宇宙样品分析提供了可能.CO2激光氟化技术的优点是所需样品量小(可低达1~2
mg),因此能够分析微小岩石区域或单矿物晶体内的氧同位素分布.同时,激光可以达到非常高的温度(>4000K),因此能够对某些难熔矿物(如锆石、蓝晶石、橄榄石等)进行氧同位素分析. 相似文献
13.
Thermodynamic properties of PbO-SiO 2 melts, obtained from published data and calculated from freezing point depressions, reflect the gradual polymerization of silicate anions in the melt as the ratio is increased. The free energy of mixing curve at 1000°C has a minimum at 40 mole % SiO 2 and is convex-upward between 72 and 98 mole % SiO 2. The latter is an indication of metastable liquid immiscibility. The free energy minimum is correlated with the maximum in the distribution of nonbridging oxygens in the melt. In SiO 2-poor melts, the activities of PbO and SiO 2 (pure liquid standard states) show sharp negative deviations from ideality. The PbO activity reflects the paucity of free oxygen species in the melt whereas the SiO 2 activity reflects the depolymerized state of the silicate anions. In more SiO 2-rich melts, the activity of SiO 2 shows a positive deviation from ideality which is qualitatively correlated to a polymerization parameter. The heat of mixing term has a minimum of ?2000 cal at 35 mole % SiO 2 and a maximum of +200 cal at 90 mole % SiO 2. The minimum is associated with the exothermic heat effect obtained during the reaction ( O0) + ( O2?) = 2( O?), whereas the maximum corresponds to the endothermic heat effect obtained when coordination polyhedra of oxygens form around the Pb cation. The entropy of mixing curve has the same form but is systematically smaller than a theoretical curve calculated on the assumption of random mixing of oxygen species. The discrepancy is due to the entropy loss obtained by the clustering of oxygen species to form complex silicate species. 相似文献
14.
Crushed rock from two caprock samples, a carbonate-rich shale and a clay-rich shale, were reacted with a mixture of brine and supercritical CO 2 (CO 2–brine) in a laboratory batch reactor, at different temperature and pressure conditions. The samples were cored from a proposed underground CO 2 storage site near the town of Longyearbyen in Svalbard. The reacting fluid was a mixture of 1 M NaCl solution and CO 2 (110 bar) and the water/rock ratio was 20:1. Carbon dioxide was injected into the reactors after the solution had been bubbled with N 2, in order to mimic O 2-depleted natural storage conditions. A control reaction was also run on the clay-rich shale sample, where the crushed rock was reacted with brine (CO 2-free brine) at the same experimental conditions. A total of 8 batch reaction experiments were run at temperatures ranging from 80 to 250 °C and total pressures of 110 bar (∼40 bar for the control experiment). The experiments lasted 1–5 weeks.Fluid analysis showed that the aqueous concentration of major elements (i.e. Ca, Mg, Fe, K, Al) and SiO 2 increased in all experiments. Release rates of Fe and SiO 2 were more pronounced in solutions reacted with CO 2–brine as compared to those reacted with CO 2-free brine. For samples reacted with the CO 2–brine, lower temperature reactions (80 °C) released much more Fe and SiO 2 than higher temperature reactions (150–250 °C). Analysis by SEM and XRD of reacted solids also revealed changes in mineralogical compositions. The carbonate-rich shale was more reactive at 250 °C, as revealed by the dissolution of plagioclase and clay minerals (illite and chlorite), dissolution and re-precipitation of carbonates, and the formation of smectite. Carbon dioxide was also permanently sequestered as calcite in the same sample. The clay-rich shale reacted with CO 2–brine did not show major mineralogical alteration. However, a significant amount of analcime was formed in the clay-rich shale reacted with CO 2-free brine; while no trace of analcime was observed in either of the samples reacted with CO 2–brine. 相似文献
15.
A model for the combined long-term cycles of carbon and sulfur has been constructed which combines all the factors modifying weathering and degassing of the GEOCARB III model [Berner R.A., Kothavala Z., 2001. GEOCARB III: a revised model of atmospheric CO 2 over Phanerozoic time. Am. J. Sci. 301, 182-204] for CO 2 with rapid recycling and oxygen dependent carbon and sulfur isotope fractionation of an isotope mass balance model for O 2 [Berner R.A., 2001. Modeling atmospheric O 2 over Phanerozoic time. Geochim. Cosmochim. Acta65, 685-694]. New isotopic data for both carbon and sulfur are used and new feedbacks are created by combining the models. Sensitivity analysis is done by determining (1) the effect on weathering rates of using rapid recycling (rapid recycling treats carbon and sulfur weathering in terms of young rapidly weathering rocks and older more slowly weathering rocks); (2) the effect on O 2 of using different initial starting conditions; (3) the effect on O 2 of using different data for carbon isotope fractionation during photosynthesis and alternative values of oceanic δ13C for the past 200 million years; (4) the effect on sulfur isotope fractionation and on O 2 of varying the size of O 2 feedback during sedimentary pyrite formation; (5) the effect on O 2 of varying the dependence of organic matter and pyrite weathering on tectonic uplift plus erosion, and the degree of exposure of coastal lands by sea level change; (6) the effect on CO 2 of adding the variability of volcanic rock weathering over time [Berner, R.A., 2006. Inclusion of the weathering of volcanic rocks in the GEOCARBSULF model. Am. J. Sci.306 (in press)]. Results show a similar trend of atmospheric CO 2 over the Phanerozoic to the results of GEOCARB III, but with some differences during the early Paleozoic and, for variable volcanic rock weathering, lower CO 2 values during the Mesozoic. Atmospheric oxygen shows a major broad late Paleozoic peak with a maximum value of about 30% O 2 in the Permian, a secondary less-broad peak centered near the Silurian/Devonian boundary, variation between 15% and 20% O 2 during the Cambrian and Ordovician, a very sharp drop from 30% to 15% O 2 at the Permo-Triassic boundary, and a more-or less continuous rise in O 2 from the late Triassic to the present. 相似文献
16.
The melting temperatures of calcite and magnesite in the presence of excess CO 2 have been measured using Ag 2C 2O 4 in sealed capsules m a piston-cylinder apparatus. At 27 kbar, 11.5 wt % CO 2 dissolves in molten CaCO 2, depressing the freezing temperature from 1610 to 1505°C; and 6.5 wt % CO 2 dissolves in molten MgCO 3, depressing the freezing temperature from 1590 to 1510°C. The eutectic between calcite and lime was located at 1385°C at 27 kbar. These and other new results, combined with previously published data, permit completion of PT diagrams for the systems CaO-CO 2 and MgO-CO 2 from 1 bar to 35 kbar. The dissociation curve for each carbonate terminates at an invariant point where melting begins, at 40 bars and 1230°C for CaO-CO 2 and 23 kbar and 1550°C for MgO-CO 2 The differences between the two systems are explained by the different solubilities of CO 2 in the invariant liquids consequent upon the large pressure difference between the locations of these two invariant points. The results show that the temperatures for the beginning of melting of carbonates in the asthenosphere are lowered by about 100°C in the presence of CO 2. 相似文献
17.
CO 2 injection in unmineable coal seams could be one interesting option for both storage and methane recovery processes. The objective of this study is to compare and model pure gas sorption isotherms (CO 2 and CH 4) for well-characterised coals of different maturities to determine the most suitable coal for CO 2 storage. Carbon dioxide and methane adsorption on several coals have been investigated using a gravimetric adsorption method. The experiments were carried out using both CO 2 and CH 4 pure gases at 25 °C from 0.1 to 5 MPa (1 to 50 bar). The experimental results were fitted using Temkin's approach but also with the corrected Langmuir's and the corrected Tóth's equations. The two last approaches are more accurate from a thermodynamical point of view, and have the advantage of taking into account the fact that experimental data (isotherms) correspond to excess adsorption capacities. These approaches allow better quantification of the adsorbed gas. Determined CO 2 adsorption capacities are from 0.5 to 2 mmol/g of dry coal. Modelling provides also the affinity parameters of the two gases for the different coals. We have shown these parameters determined with adsorption models could be used for classification and first selection of coals for CO 2 storage. The affinity ratio ranges from a value close to 1 for immature coals to 41 for high rank coals like anthracites. This ratio allows selecting coals having high CO 2 adsorption capacities. In our case, the modelling study of a significant number of coals from various ranks shows that anthracites seem to have the highest CO 2 storage capacities. Our study provides high quality affinity parameters and values of CO 2 and CH 4 adsorption capacities on various coals for the future modelling of CO 2 injection in coal seams. 相似文献
18.
地下深部封存CO2已经被公认是人类削减温室气体排放的一条有效而又科学的途径。深部咸含水层CO2地质封存因封存潜力巨大,技术可行,且已有实际的工程运行,因而备受关注。松辽盆地是中国潜在的CO2储存场地之一,选择松辽盆地为大尺度模拟研究对象,选取姚家组砂岩层为储层,选取嫩江组泥岩为盖层,运用TOUGH-MP并行计算代码建立了覆盖整个松辽盆地的三维地质模型,在中央凹陷区开展大尺度CO2注入模拟研究,包括CO2运移、储存、地层压力提升以及储存安全性等问题。模拟结果表明:持续注入100a后形成的CO2羽远小于产生的压力积聚区影响范围。注入产生的压力抬升将在注入停止后迅速消散,不会对区域地层压力和浅层地下水系统产生显著影响。在千年之内注入的CO2将随着时间持续,逐渐溶解于水中,而不会因盖层微弱的渗透性而逃逸。 相似文献
19.
火山岩的脱气实验和对昌德东CO2气藏气源的分析结果表明加热火山岩到250℃时,脱出挥发分总量为0.0299~0.0790mL/g,其中CO2脱出量为0.0218~0.0706mL/g(0.429~1.387wt%);挥发组分以CO2为主,还含有H2、CO、CH4等还原性气体,以及少量低碳烷烃,CO2含量和总烃呈现反比关系;基性岩的CO2脱出量、脱出率高于中、酸性岩;CO2脱出量与岩石碱质含量正相关.松辽盆地北部昌德东CO2气藏成藏模式为"自生自储",成藏CO2气主要来自深部被火山岩吸附的气.随岩浆上升,在岩浆冷凝成火山岩的过程中被吸附于火山岩的节理、劈理和晶体位错之中的CO2气,连同火山岩包体中的残留气,成为高纯CO2气藏的主要补给源,并非地幔气体沿大断裂上来直接充注成藏. 相似文献
20.
CO 2 injected in the reservoir of McElroy Field, TX, for a CO 2 flood was in the supercritical state. Supercritical CO 2 fluid is capable of extracting light and intermediate hydrocarbons from rocks but is unable to extract heavy hydrocarbons and asphaltics. Therefore, plugging of asphaltics in reservoir rocks and a consequent reduction in injectivity and recovery may result when CO 2 only is used in enhanced oil recovery. By adding common solvents as chemical modifiers, the flooding fluid shows marked improvement in solvency for heavy components of crudes due to its increased density and polarity. Numerous supercritical CO 2 fluid extractions of dolomite rock from the Grayburg Formation containing known amount of spiked McElroy crude oil have been carried out to evaluate extraction efficiencies of CO 2 and CO 2 with chemical modifiers at various temperatures and pressures. All experiments show that extraction efficiency increases with increasing CO 2 pressure but decreases with increasing temperature. Addition of chemical modifiers to CO 2 also shows improved extraction efficiency and reduced asphaltic deposits. Under the pressure and temperature similar to McElroy reservoir conditions; chemically modified CO 2 yielded almost 3 times as much oil extracts as those in extractions with CO 2 only. It also reduced the asphaltics content in extracted rocks to nearly one half; indicating its potential for mitigating asphaltics plugging of formation rocks 相似文献
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