Predicting the dew point pressure for gas condensate reservoirs: empirical models and equations of state

This paper presents a new empirical model to estimate dew point pressure (DPP) for gas condensate reservoirs as a function of routinely measured gas analysis and reservoir temperature. The proposed model was developed using experimentally measured and collected data of 340 gas condensate samples covering a wide range of gas properties and reservoir temperatures. The new model has an average relative deviation (ARD) of 0.44% and average absolute deviation (AAD) of 7.68% or 346 psia (1 psia=6.894757E−3 mPa). The accuracy of the model has been compared to SRK-EOS, PR-EOS and other correlations. Gas condensate samples from this study as well as from literature have been used to check the validity of the proposed model against EOS simulation. These examples have shown that the model successfully captures the physical trend and that the model is reliable. This model is useful to provide an estimate of the DPP when experimentally measured ones are not available.The current study also shows that predicting the DPP for gas condensates depends on the EOS(s), the number of pseudo-components and the characterization of the plus fraction. For most of the gas condensates used in this study, a 10–12 pseudo-components of the heptane plus (C₇₊) fraction resulted in minimum error in calculation of DPP using PR-EOS with Pedersen et al. characterization of the plus fraction.     

Vapor deposited ethanol–H2O ice mixtures investigated by micro-Raman scattering

Solid deposits have been formed at 88 K and 10⁻¹ Torr from ethanol–water gas collected above aqueous solutions of ethanol (EtOH) (0.6, 2, 4.5, 9 and 17 mol%). The composition of different gas mixtures varying between 1:16 and 1:0.8 EtOH:H₂O are determined at 295 K using our experimental vapor–liquid equilibrium (VLE) data in combination with the Wilson model [28]. The Wilson constants derived at this temperature are Λ₁₂ = 0.37(4) and Λ₂₁ = 0.58(5). The concentration of EtOH in the ice mixture can be calculated using these data and a kinetic model of condensation. It is found to vary between 9 and 65 mol% EtOH. The ice mixtures are analyzed in situ in a modified cryostage by micro-Raman spectroscopy. The distinct vibrational signatures of pure EtOH, EtOH aqueous solutions and EtOH–ice mixtures are identified in the 400–3800 cm⁻¹ spectral range. Internal vibrational motions of EtOH molecules are affected by temperature and concentration. The presence of amorphous EtOH–ice phases at 88 K is demonstrated by the characteristic vibrational signatures of the ν_OH stretching modes. The crystallization of an EtOH hydrate is proposed during annealing at ∼140 K of a 65 mol% EtOH–ice mixture. According to our preliminary X-ray diffraction work, this phase has apparently a distinct structure from that of solid EtOH or from EtOH–clathtrate structures usually found in frozen aqueous solutions. For ice mixtures of lower EtOH content, a distinct hydrate phase crystallizes at ∼170 K. These results suggest that ice mixtures obtained by vapor deposition reflect the existence of EtOH clusters of a distinctive structural nature with respect to those encountered in frozen aqueous mixtures.     

Formation of formic and acetic acids by low-temperature condensation of a mixture of methane and water vapor dissociated in MW discharge

Formic and acetic acids are formed by the low-temperature (77 K) condensation of a mixture of methane and water vapor dissociated by MW discharge at a low pressure. The effect of experimental conditions on the yield of HCOOH and AcOH was studied under different experimental conditions. The yields of H, OH, and O₂ from MW discharge in the CH₄+H₂O mixture were determined by ESR in the gas phase under the experimental conditions used to synthesize HCOOH and AcOH. The kinetics of the gas phase reactions in the connecting channel was simulated. The mechanism of formation of HCOOH and AcOH through the interaction of active species from the gas phase on the condensate surface was suggested. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 379–382, February, 2000.     

The formation of formic acid upon low-temperature condensation of a methane-carbon dioxide mixture dissociated in a microwave discharge

Formic acid was found as the main product upon low-temperature (77 K) condensation of the CH₄+CO₂ mixture dissociated in the microwave discharge at a low pressure. The yield of HCOOH was studied as a function of the experimental conditions: flow rate of the initial gas mixture. CH₄ content in the initial mixture, pressure in the reactor, and output power of the microwave generator. The concentrations of H, O, OH, and O₂ in the gas phase were measured by ESR spectroscopy. Mathematical modeling of the kinetics of the gas phase chemical reactions in the connecting channel was performed. The mechanism of formic acid formation by the interaction of active species of the gas phase on the condensate surface was proposed. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 826–831, May, 2000.     

Measurement and calculation of gas compressibility factor for condensate gas and natural gas under pressure up to 116 MPa

The volumetric properties of two reservoir fluid samples collected from one condensate gas well and one natural gas well were measured under four groups of temperatures, respectively, with pressure up to 116 MPa. For the two samples examined, the experimental results show that the gas compressibility factor increases with the increase of pressure. But the influence of the temperature is related to the range of the experimental pressure. It approximately decreases with the increase of temperature when the pressure is larger than (45 to 50) MPa, while there is the opposite trend when the pressure is lower than (45 to 50) MPa. The dew point pressure was also determined for the condensate gas sample, which decreases with the increase of temperature. The capabilities of four empirical correlations and a thermodynamic model based on equation of state for describing gas compressibility factor of reservoir fluids under high pressure were investigated. The comparison results show that the thermodynamic model recommended is the most suitable for fluids whatever produced from high-pressure reservoirs or conventional mild-pressure reservoirs.     

K2CO3-catalyzed synthesis of 2-amino-3-cyano-4H-chromene derivatives with different substituents in water

The direct three-component condensation of resorcinol, 1-(2,4-dihydroxyphenyl)ethanone or 2,4-dihydroxybenzophenone with benzaldehydes and malononitrile to generate some novel 2-amino-3-cyano-4H-chromene derivatives has been carried out over K₂CO₃ (25 mol%) with high efficiency in water as a green solvent at 70 °C.     

On the retrograde condensation of one or two liquids

This contribution discusses the phenomena of retrograde condensation of one or two liquids. It w1 be shown that both phenomena can be well understood. Also the relation of retrograde condensation of one liquid phase with the condensation behavior of natural gas will be discussed. Similarly that of two liquid phases with multiple phase behavior occurring in low temperature reservoir fluids will be pointed out.     

The partition coefficients of ethylene between vapor and hydrate phase for methane + ethylene + THF + water systems

The vapor-hydrate equilibria were studied experimentally in detail for CH₄ + C₂H₄ + tetrahydrofuran (THF) + water systems in the temperature range of 273.15–282.15 K, pressure range of 2.0–4.5 MPa, the initial gas–liquid volume ratio range of 45–170 standard volumes of gas per volume of liquid and THF concentration range of 4–12 mol%. The results demonstrated that, because of the presence of THF, ethylene was remarkably enriched in vapor phase instead of being enriched in hydrate phase for CH₄ + C₂H₄ + water system. This conclusion is of industrial significance; it implies that it is feasible to enrich ethylene from gas mixture, e.g., various kinds of refinery gases or cracking gases in ethylene plant, by forming hydrate.     

The local structure of gadolinium vanadate–tellurate glasses and glass ceramics: Te2V2O9 crystalline phase

Glasses in the system xGd₂O₃ · (100 − x)[0.7TeO₂ · 0.3V₂O₅] with 0 ≤ x ≤20 mol% have been prepared from melt quenching method. Influence of gadolinium ions on structural behavior in vanadate–tellurate glasses has been investigated using FTIR spectroscopy, X-ray diffraction (XRD), and magnetic susceptibility measurements. The structural changes have been analyzed with increasing rare earth concentration. The structural changes, as recognized by analyzing band shapes of XRD and FTIR spectra, revealed that Gd₂O₃ causes a higher extent of network polymerization as far as 20 mol%. The structure of the heat-treated glasses was found to consist mainly of the Te₂V₂O₉ crystalline phase. These vitreous systems were investigated by magnetic susceptibility measurements. From the paramagnetic susceptibility χ was calculated at different temperature and from the 1/χ(T) graph, the Curie temperature of the glass has been evaluated. Magnetic susceptibility data show the presence of small antiferromagnetic interactions between the Gd⁺³ ions.     

Upgrading low-quality natural gas with H2S- and CO2-selective polymer membranes: Part II. Process design, economics, and sensitivity study of membrane stages with recycle streams

The cost of membrane separation processes for removing CO₂ and H₂S from low-quality natural gas can be reduced for some concentration ranges of CO₂ and H₂S by utilizing concurrently two different types of polymer membranes, one with a high CO₂/CH₄ selectivity and the other with a high H₂S/CH₄ selectivity. The polymers considered in this exploratory study were 6FDA-HAB polyimide for the removal of CO₂ and [poly(ether urethane urea)] (PEUU) for the removal of H₂S. It was required that the concentrations of CO₂ and H₂S in low-quality natural gas be reduced to US pipeline specifications (≤2 mol% CO₂ and ≤4 ppm H₂S). Low-quality natural gas was simulated in this study by CH₄/CO₂/H₂S mixtures containing up to 40 mol% CO₂ and 10 mol% H₂S. Twenty-seven membrane process configurations (PCs) were examined by computer simulations and optimized in order to determine the most economical configurations. Part I of this study considered only PCs without recycle streams [J. Hao, P.A. Rice, S.A. Stern, Upgrading low-quality natural gas with H₂S- and CO₂-selective polymer membranes. Part I. Process design and economics of membrane stages without recycle streams, J. Membr. Sci. 209 (2002) 177–206]. In Part II, reported below, the study was extended to two- and three-stage PCs with various recycle options. A sensitivity analysis was also made to determine the effects of variations in feed flow rate, feed pressure, membrane module cost, and wellhead price of natural gas on process economics. The economically optimal PCs were found to be either two membrane stages connected in series with or without recycle streams or single stages without recycle, depending on feed composition and selected operating conditions. The optimal two-stage PCs with recycle streams would utilize the H₂S/CH₄-selective membranes in the first stage and either the CO₂/CH₄ or the H₂S/CH₄-selective membranes, or both, in the second stage. Three-stage membrane PCs were not found to be economically competitive under the conditions assumed in this study.     

Performance of a bench-scale membrane pilot plant for the upgrading of biogas in a wastewater treatment plant

A bench-scale membrane pilot plant for upgrading biogas generated at a municipal wastewater treatment plant was constructed and operated for extended periods of time. The raw biogas was available at 45–60 psia (3.1–4.1 bar) and contained 62.6 mol% CH₄, the balance being mainly CO₂ and a large number of organic impurities. The operation of the pilot plant was tested with two identical hollow-fiber modules for periods of over 1000 h (41 days) with each module. One of the hollow-fiber modules was tested at an average pressure of about 525 psia (36 bar) and at stage-cuts of 0.34–0.41, and the other module at about 423 psia (29 bar) and at stage-cuts of 0.36–0.39. The flow rates of the biogas feed were 30–36 ft³/h (2.4×10⁻⁴–2.8×10⁻⁴ m³/s) and 21–24 ft³/h (1.7×10⁻⁴–1.9×10⁻⁴ m³/s), respectively. The CH₄ concentration in the retentate stream (the upgraded biogas) was raised in these tests to 92–95 mol% CH₄. The performance of the pilot plant was stable over the entire test periods. An even higher CH₄ concentration of 97 mol% was reached in short-term tests at a stage-cut of 0.46. The raw biogas had to be pretreated to prevent the condensation of organic impurities which tended to dissolve the hollow fibers. Upgraded biogas containing over 90 mol% CH₄ produced in a large-scale membrane separation plant could be used for the generation of electricity. At the same time, the permeate (waste) stream would contain over 15 mol% CH₄ and could be used for heating applications.     

Reinvestigation of the Fe-rich part of the pseudo-binary system SrO–Fe2O3

The phase relations in the Fe-rich part of the pseudo-binary system SrO–Fe₂O₃ (>33 mol% Fe₂O₃) were reinvestigated between 800 and 1500 °C in air. A combination of microscopy, electron probe micro-analysis, powder X-ray diffraction and thermal analysis was used to determine phase relations, crystal structure parameters and phase transition temperatures. M-type hexagonal ferrite SrFe₁₂O₁₉ (85.71 mol% Fe₂O₃) is stable up to 1410 °C. No indication of a significant phase width was found; Sr₄Fe₆O_13±δ appears as a second phase in compositions with <85.71±0.2 mol% Fe₂O₃. Sr₄Fe₆O_13±δ itself is stable between 800 and 1250 °C. Two other hexagonal ferrites were found to exist at high temperatures only: W-type SrFe²⁺₂Fe³⁺₁₆O₂₇ is stable between 1350 and 1440 °C and X-type ferrite Sr₂Fe²⁺₂Fe³⁺₂₈O₄₆ between 1350 and 1420 °C, respectively, which is shown here for the first time. These findings in combination with previously published data were used to derive a corrected phase diagram of the Fe-rich part of the pseudo-binary system SrO–Fe₂O₃.     

Determination of Low Interfacial Tension with a Laser Light Scattering Technique and a Comparative Analysis with Drop Shape Methods

A comparative analysis of laser light scattering and drop shape techniques for measuring low interfacial tension is provided with particular reference to the gas condensate systems in petroleum reservoirs. Measurements of interfacial tensions for two real reservoir gas condensate samples were undertaken at elevated pressure and temperature reservoir conditions with the laser light scattering technique. The purposes of this study are (a) to clarify some existing confusion on the usefulness of three major interfacial tension measurement methods, pendant drop, spinning drop, and laser light scattering; and (b) to show the applicability of the laser light scattering technique to real reservoir gas condensate interfaces at low interfacial tensions. The laser light scattering technique has appeared to be the most suitable approach for the determination of low gas condensate interfacial tensions at reservoir conditions in terms of precision and operation. Copyright 2001 Academic Press.     

Synthesis of bis-indolylmethanes catalyzed by oxone

Oxone (3.5 mol%) was found to be an effective catalyst for the condensation reactions of indoles with aldehydes to afford bis-indolylmethanes in good to excellent yields within 10–30 min. The method is simple and economic. The catalyst is found to be recyclable.     

Aqueous germanate solution,alternative sol–gel precursor for preparation of Mn<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Ge<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript> diluted magnetic semiconductors

The solids content and gelation time of aqueous germanate solution were examined in this work. Samples of 5, 10 and 20 mol% Mn doped Ge were prepared by using the aqueous germanate solution as a liquid Ge precursor. No second phase such as Mn₅Ge₃ was detected in the 5 and 10 mol% Mn doped samples, implying that Mn ions were uniformly diluted into the Ge host matrix. The 5 and 10 mol% Mn-doped Ge samples exhibit room-temperature ferromagnetic behaviors that are likely originated from the RKKY (Ruderman–Kittel–Kasuya–Yosida)-like interaction between the localized Mn ions in the Ge matrix. Therefore, the aqueous germanate solution can be an alternative sol–gel precursor for preparation of the Mn _x Ge_1−x diluted magnetic semiconductors (DMSs).     

Intense white light luminescent Dy3+ doped lithium borate glasses for W-LED: A correlation between physical,thermal, structural and optical properties

In this article the physical, thermal structural and optical properties of Dy³⁺ doped lithium borate glasses have been studied for white LED application. The emission spectra shows two intense emission bands at around 483 nm and 574 nm corresponds to the ⁴F_9/2 → ⁶H_15/2 and ⁴F_9/2 → ⁶H_13/2 transitions along with one feeble band at 663 nm corresponds to ⁴F_9/2 → ⁶H_11/2 transition. The average lifetime <τ> of Dy³⁺ were found to be about 2.95 and 4.94 ns for blue and yellow emission bands respectively. CIE chromaticity diagram shows glass LBD-4 containing 0.5 mol% Dy₂O₃ with colour co-ordinates x = 0.33 and y = 0.37 have highest emission intensity. These glasses having emission in the white region and thus can be used for bright white LED's and modern white LED bulbs.     

Glass transition behaviour of the quaternary ammonium type ionic liquid, {[DEME][I] + H2O} mixtures

By a simple DTA system, the glass transition temperatures of the quaternary ammonium type ionic liquid, {N,N-diethyl-N-methyl-N-(2-methoxyethyl) ammonium iodide, [DEME][I] + H₂O} mixtures after quick pre-cooling were measured as a function of water concentration (x mol% H₂O). Results were compared with the previous results of {[DEME][BF₄] + H₂O} mixtures in which double glass transitions were observed in the water concentration region of (16.5 to 30.0) mol% H₂O. Remarkably, we observed the double glass transition phenomenon in {[DEME][I] + H₂O} mixtures too, but the two-T_gs regions lie towards the water-rich side of (77.5 to 85.0) mol% H₂O. These clearly reflect the difference in the anionic effect between ${\text{BF}}_4^{-}$ and I^? on the water structure. The end of the glass-formation region of {[DEME][I] + H₂O} mixtures is around x = 95.0 mol% H₂O, and this is comparable to that of {[DEME][BF₄] + H₂O} mixtures (x = 96.0 mol% H₂O).     

Optimization of Cellulase and Xylanase Productions by Streptomyces thermocoprophilus Strain TC13W Using Oil Palm Empty Fruit Bunch and Tuna Condensate as Substrates

The modified medium composed of the alkaline-pretreated oil palm empty fruit bunch (APEFB) and tuna condensate powder was used for cellulase and xylanase productions by Streptomyces thermocoprophilus strain TC13W. The APEFB contained 74.46% (w/w) cellulose, 15.72% (w/w) hemicellulose, and 6.40% (w/w) lignin. The tuna condensate powder contained 55.49% (w/w) protein and 11.05% (w/w) salt. In the modified medium with only 6.75 g/l tuna condensate powder, 10 g/l APEFB, and 0.5 g/l Tween 80, S. thermocoprophilus strain TC13W produced cellulase 4.9 U/ml and xylanase 9.0 U/ml. The enzyme productions in the modified medium were lower than cellulase (6.0 U/ml) and xylanase (12.0 U/ml) productions in the complex medium (CaCl₂ 0.1, MgSO₄·7H₂O 0.1, KH₂PO₄ 0.5, K₂HPO₄ 1.0, NaCl 0.2, yeast extract 5.0, NH₄NO₃ 1.0, Tween 80 0.5). When tuna condensate powder in the modified medium was reduced to 5.0 g/l and Tween 80 was increased to 1.5 g/l, S. thermocoprophilus strain TC13W produced cellulase and xylanase activities of 9.1 and 12.1 U/ml, respectively. This study shows that the cost of enzyme production could be reduced by using pretreated EFB and tuna condensate as a carbon and a nitrogen source, respectively.

     

Study of gas generation in real L/ILW containers

To obtain reliable estimates of the quantities and rates of the gas production in L/ILW a series of measurements was carried in the last 7 years in Hungary. The typical gas production rates were 0.05–0.2 STP litre gas/day for CO₂ and CH₄ generation, and less for H₂. No explosive gas mixture was indicated in the L/ILW drums during the investigated storage period. Compositions of headspace gases in closed L/ILW vaults were in agreement with gas generation processes observed in L/ILW drums. The stable carbon isotope measurements show that the main source of the CO₂ gas is the degradation of organic matter and indicates microbial degradation processes as the main sources of CH₄. Typical tritium activity concentrations were <10 Bq/l gas in the drums and <1,000 Bq/l gas in the vaults. Typical ¹⁴C activity values of the headspace gases were <2.0 Bq/l gas in the drums and <1,000 Bq/l gas in the vaults.     

Glass formation study within the TeO2–TlF and Tl2Te3O7–TlF systems

Large glassy domains have been observed at 800 °C within the TeO₂–TlF (from 7 to 65 mol% of TlF) and Tl₂Te₃O₇–TlF (from 0 to 75 mol% of TlF content) systems. The density, glass transition and crystallisation temperatures of glassy samples have been determined. The main features of a structural evolution within the TlF–TeO₂ glasses have been interpreted by analysing the relevant Raman spectra, and comparing them with those previously observed for the Tl₂O-TeO₂ system.