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1.

In the processes of discrimination between oil-cracked gases and kerogen-cracked gases, Behar and Pinzgofer et al.’s results were adopted in the former researches, in which the ratio of C2/C3 is basically a constant while the ratio of C1/C2 gradually increases in the course of primary cracking of kerogen. Otherwise in the course of secondary cracking of oil, the ratio of C2/C3 increases rapidly while C1/C2 keeps relatively stable. Our study on analogue experiment shows that, whether it is oil or kerogen, in its process of gas generating by cracking, the ratios of C2/C3, C1/C2 or C1/C3 will all be increased with the growth of thermal conditions. In comparison, the ratio of C2/C3, which is affected by genetic type to some comparatively less extent, mainly responds to the maturity of gases, while the value of C2/C3 is about 2, and that of C2/iC4 is about 10, and the corresponding value of R o is about 1.5%–1.6%. The influence of gas source on C2/C3 is less than that of gas maturity, otherwise C1/C2 (or C1/C3) is obviously affected by cracking matrices. The ratios of C1/C2, C1/C3 of oil-cracked gases are less than that of kerogen-cracked gases, under the condition that the ratios of C2/C3 are similar in value, so are the value of dryness indexes. There exists wide diffidence between this view and the former discrimination method in theory. The analysis of the spot sample indicates that we can apply the above basic view to dealing efficiently with the problem of the discrimination between oil-cracked gas and kerogen-cracked gas.

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2.
Fifteen submarine glasses from the East Pacific Rise (CYAMEX), the Kyushu-Palau Ridge (DSDP Leg 59) and the Nauru Basin (DSDP Leg 61) were analysed for noble gas contents and isotopic ratios. Both the East Pacific Rise and Kyushu-Palau Ridge samples showed Ne excess relative to Ar and a monotonic decrease from Xe to Ar when compared with air noble gas abundance. This characteristic noble gas abundance pattern (type 2, classified by Ozima and Alexander) is interpreted to be due to a two-stage degassing from a noble gas reservoir with originally atmospheric abundance. In the Kyushu-Palau Ridge sample, noble gases are nearly ten times more abundant than in the East Pacific Rise samples. This may be attributed to an oceanic crust contamination in the former mantle source.There is no correlation between the He content and that of the other noble gas in the CYAMEX samples. This suggests that He was derived from a larger region, independent from the other noble gases.Except where radiogenic isotopes are involved, all other noble gas isotopic ratios were indistinguishable from air noble gas isotopic ratios. The3He/4He in the East Pacific Rise shows a remarkably uniform ratio of (1.21±0.07)×10?5, while the40Ar/36Ar ranges from 700 to 5600.  相似文献   

3.
Sulfur isotope ratios were measured in eight lava incrustations and three volcanic gas samples and their corresponding lava flows. The lava incrustations of sulfate composition are from five recent eruptions and occur as thenardite or as aphtitalite-thenardite mixtures, with abundant trace elements. The incrustations show small sulfur isotope fractionation of 1–2‰ compared with corresponding lavas and the volcanic gas samples. The sulfate incrustations are formed through oxidation of SO2 from the emitted volcanic gas and subsequent reaction with metal halides. The volcanic gas samples show a distribution of decreasing δ34S through time from +3.4 to −1.8‰; sulfate was preferentially degassed compared to sulfide. The data indicate that sulfate incrustations serve as a late-stage volcanic gas sample with respect to sulfur isotopes.  相似文献   

4.
Low-mature gases and typical low-mature gas fields in China   总被引：2，自引：0，他引：2  
No natural gas pool of industrial importance could be formed at the low-evolution stage of organic matter. In the 1980s, on the basis of the development in exploration practice, the hypotheses of bio-thermo-catalytic transitional zone gases and early thermogenic gases were proposed. The lower-limit Ro values for the formation and accumulation of natural gases of industrial importance have been expanded to 0.3%―0.4%. In the light of the two-stage model established on the basis of carbon isotope fractionation in coal-type natural gases, the upper-limit Ro values have been set at 0.8%―1.0%. In terms of the geological practice in the low-mature gas zones and China's main coal-type gas fields, it is feasible and proper to set the upper-limit Ro value of low-mature gases at 0.8%. Supper-large gas fields such as the Urengoy gas field in western Siberian Basin should belong to low-mature gas fields, of which the natural gas reserves account for more than 20% of the global proven reserves, providing strong evidence for the significance of such a type of resources. The proven natural gas reserves in the Turpan-Hami Basin of China have almost reached 1000 × 108 m3. The main source rocks in this area are the Jurassic Xishanyao Formation, which occurs as a suite of coal series strata. The corresponding thermal evolution indices (Ro ) are mainly within the range of about 0.4%―0.8%, the δ 13C1 values of methane vary between-44‰ and-39‰ (correspondingly Ro =0.6%―0.8%), and those of ethane are within the range of-29‰―-26‰, indicating that natural gases in the Turpan-Hami Basin should be designated to coal-type low-mature gases. The light hydrocarbon evolution indices of natural gases also fall within the area of low evolution while the precursor type of light hydrocarbons also shows the characteristics of the coal-type. The geological background, carbon isotopic composition and light hydrocarbon index all provide strong evidence suggesting that the proven natural gases in the Turpan-Hami Basin are low-mature gases. In China a gas field with the gas reserves reaching 300 ×108 m3 can be defined as a large gas field, and thus the proven low-mature gases in the Turpan-Hami Basin are equivalent to the reserves of three large gas fields. Its existence is of great significance in research on and exploration of low-mature gases in China.  相似文献   

5.
The migration mechanisms of endogenous gases in the geosphere are defined in relation to the fluid-rock conditions and analyzed by basic transport equations. Upon examining the geological factors that influence the physical parameters in the equations in porous and fracture media, and considering the widespread high-permeability of deep subsurface rocks, in terms of fracture aperture, (orders of 10−2 to 101 mm at depths of thousands meters, as suggested by recent crustal surveys) advection of carrier gases, in its several forms (gas-phase flow, water displacement by gas, gas slugs and bubbles) seems to represent a major migration process. Accordingly, in contrast with early views, the role of gas diffusion and water advection in the transport of endogenous gas to the Earth surface should be strongly minimized in many contexts. In a wide range of geological settings, carrier gases (CO2, CH4) may assume a dominant role in controlling transport and redistribution toward the Earth’s surface of trace gases (Rn, He). Bubble movement in fissured rocks seems to be an effective way of rapid (gas velocities in the order of 100 to 103 m per day) and long-distance gas migration. The evolution from bubble regimes to continuous phase flow and vice versa, as gas pressure and fracture width change, is the most suitable mechanism towards determining the surface geochemical processes of seismo-tectonic, environmental and geo-exploration relevance. The transport effectiveness of trace gases by a carrier gas has yet to be studied in quantitative terms. It is already clear, however, that further studies on the distribution and behavior of trace gases approaching the Earth’s surface may not be meaningful unless accompanied by carrier gas dynamics analyses.  相似文献   

6.
Rapidly cooled portions of eleven samples of mid-ocean ridge tholeiitic basalt pillows have noble gas abundance patterns which resemble the solar rare gas pattern rather than the noble gas pattern of the terrestrial atmosphere. We conclude that these samples contain primordial noble gases. In contrast, holocrystalline samples and a sample from the interior of a basalt pillow have noble gas abundance patterns which resemble the sea water pattern. Whereas the quenched glossy margins of basalt pillows record a non-atmospheric gas reservoir, these slowly cooled samples apparently have undergone exchange of their noble gases with those dissolved in sea water.  相似文献   

7.
Eruptive gases, as sampled at temperatures ca. 1000°C, show strong and swift variations, both in space and time. High gradients and short periods characterize their chemical and physical parameters. On the other hand when collected in conditions preventing strong groundwater or air contamination, water is usually less abundant than carbon dioxide, and several times even absent. Carbon dioxide appears as the major component of the eruptive gas phase during high velocity high pressure (explosive) release phenomena. This tentatively suggests that this prevalence of the dense CO2 (1.5 heavier than air, 3 times heavier than steam) would account for the somewhat puzzling characteristics of nuées ardents and ignimbritic ash-flows, viz., their strong horizontal propagation component and their long heat-content preservation, that allow welding of pyroclasts at scores of kilometers from their emission vent.  相似文献   

8.
Kinetic experiments of gas generation for typical samples of marine gas precursors including low-maturity kerogen, residual kerogen and oil as well as dispersed liquid hydrocarbon (DLH) in source rocks were performed by closed system, and the evolution trends of molecular and isotopic compositions of natural gases from different precursors against the maturity (R 0%) at laboratory conditions were analyzed. Several diagrams of gas origin were calibrated by using the experimental data. A diagram based on the ratio of normal and isomerous butane and pentane (i/nC4 ? i/nC5) was proposed and used to identify the origins of the typical marine natural gases in the Sichuan Basin and the Tarim Basin, China. And the maturities of natural gases were estimated by using the statistical relationships between the gaseous molecular carbon isotopic data and maturities (δ13C-R 0%) with different origins. The results indicate that the molecular and isotopic compositions of simulated gases from different precursors are different from each other. For example, the dryness index of the oil-cracking gas is the lowest; the dryness indices of gases from DLH and kerogen in closed system are almost the same; and the dryness index of gases from residual kerogen is extremely high, indicating that the kerogen gases are very dry; the contents of non-hydrocarbon gases in kerogen-cracking gases are far higher than those in oil-cracking and DLH-cracking gases. The molecular carbon isotopes of oil-cracking gases are the lightest, those of kerogen in closed system and GLH-cracking gases are the second lightest, and those of cracking gases from residual kerogen are the heaviest. The calibration results indicate that the diagrams of In(C1/C2)-In(C2/C3) and δ4 3C2-δ4 3C3-In(C2/C3) can discriminate primary and secondary cracking gases, but cannot be used to identify gas origin sources, while the diagram of i/nC4 ? i/nC5 can differentiate the gases from different precursors. The application results of these diagrams show that gas mixtures extensively exist in China, which involved the gases from multiple precursors and those from different maturity stages. For example, marine gases in the Sichuan Basin involve the mixture of oil-cracking gases and high-over-maturated kerogen gases, while those in the Tarim Basin involve not only the mixture of gases from multiple precursors, but also those from different maturity gases and post-reservoir alternations such as oxidized degradation and gas intrusion processes.  相似文献   

9.
Northern peatlands are a large source of atmospheric methane (CH4) and both a source and a sink of atmospheric carbon dioxide (CO2). The rate and temporal variability in gas exchanges with peat soils is directly related to the spatial distribution of these free‐phase gases within the peat column. In this paper, we present results from surface and borehole ground‐penetrating radar surveys – constrained with direct soil and gas sampling – that compare the spatial distribution of gas accumulations in two raised bogs: one in Wales (UK), the other in Maine (USA). Although the two peatlands have similar average thickness, physical properties of the peat matrix differ, particularly in terms of peat type and degree of humification. We hypothesize that these variations in physical properties are responsible for the differences in gas distribution between the two peatlands characterized by (1) gas content up to 10.8% associated with woody peat and presence of wood layers in Caribou Bog (Maine) and (2) a more homogenous distribution with gas content up to 5.7% at the surface (i.e. <0.5 m deep) in Cors Fochno (Wales). Our results highlight the variability in biogenic gas accumulation and distribution across peatlands and suggest that the nature of the peat matrix has a key role in defining how biogenic gas accumulates within and is released to the atmosphere from peat soils. © 2015 The Authors. Hydrological Processes published by John Wiley & Sons Ltd.  相似文献   

10.
The Rankine–Hugoniot (RH) jump relations for normal shock waves in van der Waals fluids have been studied in order to improve a theoretical understanding of those shock related phenomena as observed in a real atmosphere which cannot be accounted for by the ideal gas model. The RH jump relations for the pressure, density, particle velocity, temperature, speed of sound, adiabatic compressibility and change-in-entropy across the shock front have been analysed in terms of the non-idealness parameter of the gas, downstream Mach number and adiabatic index of the gas. Further, as the strength of shock waves may range from weak to strong, the convenient forms of RH jump relations for weak and strong shock waves have been discussed, simultaneously. Finally, the effects on the flow-field behind the shock front have been explored due to the non-idealness parameter of the gas, downstream Mach number and adiabatic index of the gas.  相似文献   

11.
All twenty-three stable rare gas isotopes have been measured in a mantle-derived amphibole, kaersutite. The elemental abundance pattern of the rare gases is similar to the “planetary” rare gas pattern as defined by carbonaceous chondrites. The3He/4He ratio, (4.9 ± 0.6) × 10?5, is suggestive of primordial He degassing from the mantle. Excess21Ne is present. The measured40Ar/36Ar ratio,400 ± 5, may represent a mantle40Ar/36Ar ratio <240 when corrected for radiogenic40Ar. The heavy isotopes of Kr and t0he Xe isotopes are within error of the atmosphere values.  相似文献   

12.
A diffusion mechanism is proposed which takes into account phenomena observed in ion-implanted solids, in particular the precipitation of rare gas in the form of bubbles and their migration. The composition of rare gases in the bubbles is inferred from the calculated distribution of solar wind rare gas ions as a function of depth in the grains. These calculations are made for the location and average composition of Apollo 11 samples. It is shown by analogy with experimental observations in ion-implanted solids that the bubbles would migrate towards the surface and that the diffusion constant for this migration would be strongly depth dependent. Relative abundances of rare gas nuclides remaining behind due to the resultant degassing are estimated for one Apollo 11 soil sample and are compared with observed relative abundances for this sample. A qualitative explanation of some of the experimental observations of Ducati et al. on individual lunar grains is also offered.  相似文献   

13.
The rate of escape of 40Ar from the moon is calculated from mass-spectrometer data obtained at the Apollo-17 landing site. It is shown that the rate of loss of Ar from the moon varies significantly over periods the order of one lunation and that the average loss rate is about 3 t/a, corresponding to about 6% of the present rate of Ar production by K decay within the moon. These features of the Ar loss-rate data are interpreted as evidence that this gas originates in the partially molten asthenosphere, which in turn requires that early differentiation only affected the outer 600–1,000 km of the moon, trapping significant amounts of radioactive materials in the present asthenosphere. The relationship of the venting of Ar and other radiogenic gases of the lunar atmosphere are discussed.  相似文献   

14.
气体受激增温的实验研究   总被引：1，自引：0，他引：1  
试验结果基本证明了热红外温度异常与太阳照射、大气电场、大气成分密切相关。非极性气体如CO2 、CH4 的含量越高, 增温越大。而极性气体, 如水蒸气则相反, 含量越高, 增温越小。CO2 、CH4 含量高的大气, 其增温远远超过单纯由温室效应引起的增温, 其幅度可达10℃,而水蒸气引起的增温还没有单纯由其温室效应引起的高。  相似文献   

15.
2017—2018年在依兰—伊通断裂黑龙江段开展断层氢气调查工作,沿断裂选取8个剖面进行跨目标断层观测及土壤氢气采样。结果表明：①断层氢气浓度常存在异常变化;②不同类型的断层,氢气浓度异常变化幅度没有明显差异;③走滑断层异常特征一般为断层两侧低、中间高,呈现“低—高—低”的特点;倾滑断层异常特征一般为断层的上盘略高、下盘略低;④断层氢气排放不仅受微观局部断层的影响,更受宏观的地震活动性大环境的影响。  相似文献   

16.
In this paper we report Ne, Ar, Kr and Xe analyses of josephinite, Josephine Peridotite, and serpentinized Josephine Peridotite. In all three samples the elemental abundance patterns resemble patterns associated with surface waters, the Ne data do not exhibit the large21Ne enrichments observed earlier, and the Kr and Xe compositions are indistinguishable from atmospheric composition at all isotopes, including129Xe. Our data thus offer no significant evidence for isotopic anomalies in the noble gases. We also argue that the previous claims for primordial atmospheric-like Ar, anomalous Kr and Xe, excess129Xe, and 4.6 × 109-year age are all questionable interpretations which cannot be defended against more prosaic alternatives. This leaves excess21Ne as the only noble gas argument for exotic origin; we suggest that this might be an experimental artifact. Until the21Ne question can be settled by more definitive experimentation, we feel that noble gas data cannot be used to support arguments that the origin of josephinite is more exotic than crustal serpentinization.  相似文献   

17.

The composition of fluid inclusions (FI) often represents the initial geochemical characteristics of palaeo-fluid in reservoir rock. Influence on composition and carbon isotopic composition of gas during primary migration, reservoir-forming and subsequent secondary alterations are discussed through comparing fluid inclusion gas with coal-formed gas and natural gas in present gas reservoirs in the Ordos Basin. The results show that primary migration of gas has significant effect on the molecular but not on the carbon isotopic composition of methane. Migration and diffusion fractionation took place during the secondary migration of gas in Upper Paleozoic gas reservoir according to carbon isotopic composition of methane in Fls. Composition and carbon isotopic composition of natural gas were nearly unchanged after the gas reservoir forming through comparing the FI gases with the natural gas in present gas reservoir.

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18.
Isotopic and elemental compositions of rare gases in various types of gas samples collected in the Japanese Islands were investigated. Excess3He was found in most samples. Many samples showed a regionally uniform high3He/4He ratio of about 7 times the atmospheric ratio. The He concentrations varied from 0.6 to 1800 ppm, and they were low in CO2-rich gases and high in N2-rich gases. Ne isotopic deviations from the atmospheric Ne were detected in most volcanic gases. The deviations and the elemental abundance patterns in volcanic gases can be explained by a mixing between two components, one is mass fractionated rare gases and the other is isotopically atmospheric and is enriched in heavy rare gas elements. Ar was a mixture of mass fractionated Ar, atmospheric Ar and radiogenic Ar, and the contribution of radiogenic40Ar was small in all samples. Except for He, elemental abundance patterns were progressively enriched in the heavier rare gases relative to the atmosphere. Several samples were highly enriched in Kr and Xe relative to the abundance pattern of dissolution equilibrium of atmospheric rare gases in water. The component which is highly enriched in heavy rare gases may be released from sedimentary materials in the crust.  相似文献   

19.
Rare gas trapping during crystallization from vapor phases of (1) CdTe, (2) Zn, (3) Mg and (4) Fe3O4 has been studied. Samples were deposited as very fine crystals (about several hundred angströms) in ambient Ar atmospheres of various pressures. It was found that the amount of Ar trapped in the samples was proportional to the ambient Ar pressure. Stepheating degassing of the crystals showed that Ar was rather loosely trapped and released at relatively low temperatures. However, on a simple mechanical compaction of the crystal powder the retentivity of Ar was considerably enhanced.  相似文献   

20.
Commercial accumulation of mantle-derived helium in the sedimentary shell is discussed. Generally speaking, a commercial helium pool is formed by accumulated4He that comes from uranium and thorium via α-decay; therefore, it has a very low3He/4He value in the magnitude of 10-8. The helium concentration in some gas wells of eastern China oil/gas provinces is about or over 0.05% —0. 1%, consequently forming commercial helium wells (pools), such as the Wangjinta Gas Pool in Songliao Basin, Huangqiao Gas Pool in North Jiangsu Basin and some gas wells in Sanshui Basin. Studies have proved that when the3He/4He value of a helium gas pool is about 3.7 × 10-6 -7.2×10-6 namely mantle-derived helium in its total helium concentration accounts for 33.5%—65.4%, it is a crust-mantle dual-source or dominantly mantle-derived helium gas pool, which is a novel helium resource and its formation is mainly related to the distribution of megafractures.  相似文献   

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