Phase behavior of condensate gas and CO2 / CH4 re-injection performance on its retrograde condensation

Wenchang A Depression in Pearl River Mouth Basin is the largest hydrocarbon generating depression in the west of the area. After more than 30 years of exploitation, a large amount of gas condensate has been produced near the wellbore, which will cause gas condensate damage to the reservoir. It is planned to reinject the self-produced gas from Well WC9-2-X and the gas transported from the WC14-3 gas field to relieve the condensate damage in the near-wellbore area by means of retrograde condensation. In this article, the phase state change process of condensate gas in Well WC9-2-X with temperature and pressure was firstly investigated, and then the retrograde condensation effect of two types of gas on condensate was investigated. The research shows that when the reservoir temperature is 158.80 °C, the dew point pressure of condensate gas is 20.71 MPa, and the maximum amount of condensate is 1.28% (P = 9.01 MPa). Although Wenchang 9–2 is a low condensate reservoir, in the process of depressurization and production over the years, gas condensate has gradually accumulated, resulting in a large amount of gas condensate near the wellbore. With the increase of the gas re-injection amount, the two types of gas have a significant effect on the retrograde condensation of the gas condensate. From the variation trend of the gas and oil density released by the retrograde condensation, it can be seen that the re-injection gas preferentially dissolves the light components in the condensate, and then gradually dissolves the heavy components. The self-produced gas (gas No. 1) of Well WC9-2-X is dominated by CH₄ (78.33 mol%), and the CO₂ / CH₄ contents in the input waste gas (gas No. 2) of the WC14-3 gas field are 42.50 mol% / 41.60 mol%, respectively. The retrograde condensation effect of gas No. 2 is better than gas No. 1, mainly because the content of CO₂ in gas No. 2 is high, and it is easier to achieve the effect of miscible dissolution of condensate when mixed with condensate.It is recommended that gas No.2 should be preferentially used in WC9-2-X well for reinjection of retrograde condensation to relieve condensate damage. This article provides theoretical support for gas re-injection to relieve condensate damage in Wenchang 9–2 gas field, and has important significance for long-term exploitation of condensate gas reservoir.     

Analysis of the gas states at a liquid/solid interface based on interactions at the microscopic level

The states of gas accumulated at the liquid/solid interface are analyzed on the basis of the continuum theory, in which the Hamaker constant is used to describe the long-range interaction at the microscopic scale. The Hamaker constant is always negative, whereas the "gas" spreading coefficient can be either negative or positive. Despite the complexity of gas, including that the density profile may not be uniform due to absorption on both solid and liquid surfaces, we predict three possible gas states at the liquid/solid interface, that is, complete "wetting", partial "wetting", and pseudopartial "wetting". These possible gas states correspond, respectively, to a gas pancake (or film) surrounded by a wet solid, a gas bubble with a finite contact angle, and a gas bubble(s) coexisting with a gas pancake. The typical thickness of the gas pancakes is at the nano scale within the force range of the long-range interaction, whereas the radius of the gas bubbles can be large. The state of a gas bubble(s) coexisting with a gas film is predicted theoretically for the first time. Our theoretical results can contribute to the development of a unified picture of gas nucleation at the liquid/solid interface.     

Determination of anabolic steroids with gas chromatography-ion trap mass spectrometry using hydrogen as carrier gas.

Helium is considered to be the ideal carrier gas for gas chromatography/mass spectrometry (GC/MS) in general, and for use with an ion trap in particular. Helium is an inert gas, can be used without special precautions for security and, moreover, it is needed as a damping gas in the trap. A disadvantage of helium is the high viscosity resulting in long GC run times. In this work hydrogen was tested as an alternative carrier gas for GC in performing GC/MS analyses. A hydrogen generator was used as a safe source of hydrogen gas. It is demonstrated that hydrogen can be used as a carrier gas for the gas chromatograph in combination with helium as make-up gas for the trap. The analysis time was thus shortened and the chromatographic performance was optimized. Although hydrogen has proven useful as a carrier gas in gas chromatography coupled to standard detectors such as ECD or FID, its use is not mentioned extensively in the literature concerning gas chromatography-ion trap mass spectrometry. However, it is worth considering as a possibility because of its chromatographic advantages and its advantageous price when using a hydrogen generator.     

A New Model for the Genesis of Natural Gases——Multi-source Overlap, Multi-stage Continuity, TypeControlled by Main Source and Nomenclature by Main Stage (Ⅱ)——Multi-stage Continuity and Nomenclature by Main Stage

The generation of natural gases involves several stages and the various stages are of continuous transition. This is another feature of natural gas generation. The term "multi-stage" is relative mainly to oil-generating threshold value and liquid window. The evolution of organic matter is affected by different epigene agencies and natural gases differing in geochemical properties such as biogenic gas (bacterial gas), thermocatalytic gas and pyrolytic gas could be produced at different stages of the evolution of organic matter. The proposal of bio-thermocatalytic transitional-zone gas presents a pattern of mutual linking and continuous transition of natural gases originated at different stages.In the genetic classification of natural gases, the nomenclature of a certain gas is based mainly on the epigene agency which is responsible for its formation, for example, biogenic gas, pyrolytic gas. That is the "nomenclature by the main stage" described in this study. On account of the continuity of gas generati     

Stabilization of methane hydrate by pressurization with He or N2 gas

The behavior of methane hydrate was investigated after it was pressurized with helium or nitrogen gas in a test system by monitoring the gas compositions. The results obtained indicate that even when the partial pressure of methane gas in such a system is lower than the equilibrium pressure at a certain temperature, the dissociation rate of methane hydrate is greatly depressed by pressurization with helium or nitrogen gas. This phenomenon is only observed when the total pressure of methane and helium (or nitrogen) gas in the system is greater than the equilibrium pressure required to stabilize methane hydrate with just methane gas. The following model has been proposed to explain the observed phenomenon: (1) Gas bubbles develop at the hydrate surface during hydrate dissociation, and there is a pressure balance between the methane gas inside the gas bubbles and the external pressurizing gas (methane and helium or nitrogen), as transmitted through the water film; as a result the methane gas in the gas bubbles stabilizes the hydrate surface covered with bubbles when the total gas pressure is greater than the equilibrium pressure of the methane hydrate at that temperature; this situation persists until the gas in the bubbles becomes sufficiently dilute in methane or until the surface becomes bubble-free. (2) In case of direct contact of methane hydrate with water, the water surrounding the hydrate is supersaturated with methane released upon hydrate dissociation; consequently, methane hydrate is stabilized when the hydrostatic pressure is above the equilibrium pressure of methane hydrate at a certain temperature, again until the dissolved gas at the surface becomes sufficiently dilute in methane. In essence, the phenomenon is due to the presence of a nonequilibrium state where there is a chemical potential gradient from the solid hydrate particles to the bulk solution that exists as long as solid hydrate remains.     

Energy of vented gases as a means for improving product purity during swing adsorption

The equilibrium swing adsorption model is used to show that the purity of the product gas linearly increases with decreasing the ratio of the gas pressure during the recovery stage to the gas pressure during the adsorption step. We propose to use the energy of the vented gas for decreasing this ratio through ejecting the vented gas flow. A fundamentally new swing adsorption flowsheet with a gas ejector is proposed.     

Influence of Gas Supply Changes on the Formation Process of Complex Mixed Gas Hydrates

Natural gas hydrate occurrences contain predominantly methane; however, there are increasing reports of complex mixed gas hydrates and coexisting hydrate phases. Changes in the feed gas composition due to the preferred incorporation of certain components into the hydrate phase and an inadequate gas supply is often assumed to be the cause of coexisting hydrate phases. This could also be the case for the gas hydrate system in Qilian Mountain permafrost (QMP), which is mainly controlled by pores and fractures with complex gas compositions. This study is dedicated to the experimental investigations on the formation process of mixed gas hydrates based on the reservoir conditions in QMP. Hydrates were synthesized from water and a gas mixture under different gas supply conditions to study the effects on the hydrate formation process. In situ Raman spectroscopic measurements and microscopic observations were applied to record changes in both gas and hydrate phase over the whole formation process. The results demonstrated the effects of gas flow on the composition of the resulting hydrate phase, indicating a competitive enclathration of guest molecules into the hydrate lattice depending on their properties. Another observation was that despite significant changes in the gas composition, no coexisting hydrate phases were formed.     

Parallel temperatures in supersonic beams: ultracooling of light atoms seeded in a heavier carrier gas

Supersonic expansion is a very powerful tool to produce an atomic beam with a well defined velocity and, by seeding a test gas in such an expansion, the energy of the test gas can be transferred, at least partially, to the very-low-temperature carrier gas. The case usually studied is the one of a heavy gas seeded in a light carrier gas and, in this case, the parallel temperature of the seeded gas is always larger than the one of the carrier gas. In the present paper, we study the opposite case which has received less attention: when a light gas is seeded in a heavier carrier gas, the parallel temperature can be substantially lower for the seeded gas than for the carrier gas. This effect has been first observed by Campargue and co-workers in 2000, in the case of atomic oxygen seeded in argon. In the present paper, we develop a theoretical analysis of this effect, in the high dilution limit, and we compare our theoretical results to several experimental observations, including a set of measurements we have made on a beam of lithium seeded in argon. The agreement between theory and experiments is good.     

The palladium/silver membrane focusing injector — A new inlet system for thermal desorption capillary gas chromatography

Summary A new sample focusing technique for capillary gas chromatography is described. The system is designed as a focusing inlet for thermally desorbed gas samples. A solid-sorbent trapped sample is thermally released from the sample tube, transferred to a palladium/silver membrane chamber by a hydrogen carrier gas stream and retained there by the gas separation membrane, which is highly permeable to the carrier gas. After focusing in the membrane chamber the sample is injected onto the separation column. This technique allows focusing and injection of highly volatile compounds in capillary gas chromatography without using any coolant. The injection performance for n-alkanes is shown to be comparable to the cryofocusing technique.     

Influence of the Shroud Gas Injection Configuration on the Characteristics of a DC Non-transferred Arc Plasma Torch

The characteristics of the plasma jet emanating from a dc non-transferred plasma torch is affected by many factors including arc current, type of gas, gas flow rate, gas injection configuration and torch geometry. The present work focuses on experimental investigation of the influence of shroud gas injection configuration on the I–V characteristics and electro-thermal efficiency of a dc non-transferred plasma torch operated in nitrogen at atmospheric pressure. The plasma gas is injected into the torch axially and shroud gas is injected through three different nozzles such as normal, sheath and twisted nozzles. The effects of flow rates of plasma/axial gas and arc current on I–V characteristics and electro-thermal efficiency of the torch holding different nozzles are investigated. The I–V characteristics and electro-thermal efficiency of the torch are found to be strongly influenced by the shroud gas injection configuration. The effect of arc current on arc voltage decreases with increasing the axial gas flow rate. At higher axial gas flow rate (>?45 lpm), the I–V characteristics of the plasma torch are similar irrespective of the nozzle used. The variation of electro-thermal efficiency with arc current is almost similar to that of arc voltage with arc current. As expected, the electro-thermal efficiency is increased when the axial gas flow rate is increased and at higher axial gas flow rate, it is not influenced by the arc current and shroud gas configuration. The plasma torch with normal nozzle may be better in the range of operating conditions used in this study.     

天然气密度计算结果的不确定度分析比较

天然气的密度通常采用气相色谱分析方法得到。分析了这种方法计算密度结果的不确定度,并与SY/T6143《天然气流量的标准孔板计量方法》中经验公式计算的密度不确定度进行比较。结果表明:按照SY/T 6143标准计算的密度不确定度与天然气压力和温度有关,而采用气相色谱分析方法计算的密度结果的不确定度仅与天然气组分含量有关;SY/T 6143标准所计算的密度不确定度结果更可靠些。     

天然气焦炭的嵌锂特性研究

锂离子电池的研究与开发具有诱人的商业前景．以金属锂为负极的锂二次电池存在着充放电循环寿命短和使用安全性能差等诸多问题，解决的途径之一是采用嵌锂化合物替代金属锂作为负极材料．其中，以具有贮锂功能的碳素材料作为负极的锂离子电池，不仅具有较高的电容量和较长...     

STUDY ON COAL-BED GAS COMPOSITIONS AND ITS GEOCHEMICAL CHARACTERISTICS IN CHINA

This paper considers, through a lot of measured data of coal-bed gas, that the coal-bed gas is a kind of mixed gas of complex composition with some heavy hydrocarbons. In general, it is not a dry gas. The coal-bed hydrocarbon gases can obviously be divided into three stages of gas-storage: "poor hydrocarbon-storing stage", "rich hydrocarbon-storing stage" and "declining hydrocarbon stage". Authors point out that the normal gas geochemical indexes can relatively well show the geochemical chatacteristics of coal-bed gas. But, "the Benzene Index (B)" is a good indicator to identify the gas original types, and "the Hexane Index(H)" can show the gas evolution law and the organic matter maturity.     

基于半导体纳米SnO_2构建的气敏传感器的应用研究进展

SnO2是传统的气敏材料,由于其具有间隙锡离子和氧空位的特性,使得气体更容易吸附在材料表面,从而显示出更好的气敏性质.通过把SnO2进行贵金属附载掺杂和多种气敏性半导体氧化物的复合,探讨了一系列性能良好的气敏传感器,阐述了SnO2气敏传感的最新进展.     

Solvation studies of electrospray ions—method and early results

Experiments are described in which bare (completely desolvated) ions are separated from their source gas and mixed with a bath gas of any desired temperature and precisely controlled composition. The resulting mixture of ions and bath gas is transported by free jet expansion into a vacuum system for mass analysis to reveal the extent to which the ions have formed adducts with other species in the bath gas. Because the ions are separated from their source gas or vapor before they are mixed with the bath gas, the compositions of the bath gas and source gas are completely independent. Thus, one can examine solvation or adduction by any desired species contained in the bath gas without any interference from other species that might be present in the source gas. Reported here are results obtained on the solvation of electrospray ions of a small peptide, leucine-enkephalin, by water and several alkanols. One provocative finding is that a substantial fraction of ions thought to be singly charged monomers turned out to be doubly charged dimers.     

Influence of Electrode Energy Balance on Gas Convective Pattern of a High-Pressure Xenon Short Arc Lamp

The transport of tungsten vapour evaporated from the electrode surfaces of a high-pressure xenon short-arc lamp, which is dominated by the gas convection in the lamp, determines the location and extent of the blackened area on the inner bulb wall. We have investigated factors affecting the vapour transport and other important phenomena related to the gas convection using a unified numerical model. The influence of the lamp operating parameters and also the thermodynamic and transport properties of the gas is discussed. The predicted lamp characteristics and phenomena agree well with experimental results. The gas velocity in the lamp is strongly affected by the Lorentz force and the gas density, which respectively depend on the current and the filling pressure. The viscosity and density of the gas adjacent to the anode surface were found to depend on the anode energy balance and to affect the resistance of the gas flow, which in turn affects the separation point of the gas flow from the anode surface. This indicates that the anode surface temperature, which is determined by the energy balance between the gas and the anode, also affects the blackening location.

     

气体放电对SO_2和SO_3~(2-)氧化的影响

研究气体放电对SO2和亚硫酸盐氧化的影响,采用了直流电源和交直流叠加电源进行气体放电.结果表明,气体放电对于SO2氧化促进作用很少;但对溶液中的SO2-3的氧化则有明显促进作用.通过对两个反应过程的机理分析,认为亚硫酸盐溶液氧化快是因为气体放电产生的OH等自由基和液相里的亚硫酸根起作用,引发链反应,促进了溶液中四价硫被空气中的O2氧化为六价硫的过程.而气相中的SO2与OH等自由基作用不能形成链反应,所以影响不明显.实验表明,选择交直流叠加电源进行气体放电比用纯粹直流电源放电效果更好.     

Global oil and gas resources and their development

Global recoverable HC resources are estimated at 554.7 bln ton oil and 634.3 trln m³ gas. Reserves to resources ratio as of the beginning of 2008 is 62% for oil and 45%, for gas. Oil reserves to resources ratios are the highest in the Near and Middle East and the lowest in FSU countries. Remaining proved reserves are 188.6 bln ton oil and 179.4 trln m³ gas. Reserves to production ratios are 46 years for oil and 52 years for gas. Recently performed oil and gas production forecast is based on initial total oil and gas resource estimates, reserves to resources and resource depletion ratios, and remaining reserves and unexplored resource estimates. 2030 production is estimated at 5300 MMt oil and 4390 Bm³ gas.     

‘Intelligent’ alarm detector of gas leaks

Three types of tin oxide gas sensors have been developed and a gas-detecting apparatus using the developed sensors has been manufactured. This apparatus has the ability to identify the type of leaking gas out of isobutane, ethanol, hydrogen and carbon monoxide. It can also be used for accumulating data as the terminal unit of a microcomputer. When city gas or carbon monoxide gas is leaking, a pulse is output from the apparatus to an electromagnetic valve which cuts off the path of the gas. The use of the apparatus and microcomputer composes a countermeasure system against gas leak accidents.     

The gas temperature in and the gas expulsion from a graphite furnace used for atomic absorption spectrometry

A simplified model for heat transfer based on thermal conduction is used to calculate the radial gas temperature distribution inside a semi-enclosed, commercial graphite tube furnace used for atomic absorption spectrometry. In the absence of a forced convective flow of a purge gas, the gas temperature inside the graphite furnace during its heating is lower than the wall temperature. After the wall temperature has attained a steady-state value, the gas temperature approaches the wall temperature and the radial temperature gradient in the gas decreases. The difference between the wall temperature and the gas temperature depends on the temperature program used, the thermal properties of the purge gas, and the atomizer geometry. The residence time of relatively volatile analyte elements is largely controlled by expulsion when wall atomization at high heating rates and high atomization temperatures are used. Analytical sensitivities are often enhanced by vaporizing the analyte into a gas having an approximately constant temperature.