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1.

The Lucaogou Formation carbonate-rich oil shale source rock is exposed at the southern margin of the Junggar Basin, Xinjiang, NW China. We have sampled it in detail and conducted microstructural, mineralogical and geochemical studies, including thin section petrography, UV fluorescence petrography, X-ray diffraction, vitrinite reflectance, bitumen reflectance, fluid inclusion analysis and Raman spectroscopy. Organic matter is disseminated through the carbonate-bearing siltstone source rocks and concentrated in numerous bedding parallel stylolites and in two sets of carbonate veins, one along bedding parallel fractures and the other cross-cutting stylolites and bedding. The research about maturity of organic matter finds vitrinite reflectance values increase from the dispersed kerogen (0.64%) to the stylolites (the one of oriented vitrinite is 0.72% and the one of migrated bitumen is 2.38%); Homogenization temperatures of fluid inclusions in veins containing hydrocarbon fluid inclusions show an increase from 178.5°C in the bedding parallel veins to 222°C in the cross-cutting veins, confirmed by Raman spectroscopy. These results support a model of progressive heating accompanied by fluid loss during later stages of thermal maturation of source rock and the onset of primary migration. Obviously, the occurrence of organic matter is the trace of hydrocarbon primary migration, and the bedding lamination surfaces and cross-cutting fissures are the principal pathways of hydrocarbon-bearing fluids migration. Bedding lamination surfaces evolved into stylolites along the earliest primary migration pathways, followed by bedding parallel and cross-cutting fissures.

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2.
The Lucaogou Formation carbonate-rich oil shale source rock is exposed at the southern margin of the Junggar Basin, Xinjiang, NW China. We have sampled it in detail and conducted microstructural, mineralogical and geochemical studies, including thin section petrography, UV fluorescence petrography, X-ray diffraction, vitrinite reflectance, bitumen reflectance, fluid inclusion analysis and Raman spectroscopy. Organic matter is disseminated through the carbonate-bearing siltstone source rocks and concentrated in numerous bedding parallel stylolites and in two sets of carbonate veins, one along bedding parallel fractures and the other cross-cutting stylolites and bedding. The research about maturity of organic matter finds vitrinite reflectance values increase from the dispersed kerogen (0.64%) to the stylolites (the one of oriented vitrinite is 0.72% and the one of migrated bitumen is 2.38%); Homogenization temperatures of fluid inclusions in veins containing hydrocarbon fluid inclusions show an increase from 178.5°C in the bedding parallel veins to 222°C in the cross-cutting veins, confirmed by Raman spectroscopy. These results support a model of progressive heating accompanied by fluid loss during later stages of thermal maturation of source rock and the onset of primary migration. Obviously, the occurrence of organic matter is the trace of hydrocarbon primary migration, and the bedding lamination surfaces and cross-cutting fissures are the principal pathways of hydrocarbon-bearing fluids migration. Bedding lamination surfaces evolved into stylolites along the earliest primary migration pathways, followed by bedding parallel and cross-cutting fissures.  相似文献   

3.
The kinetic parameters of generation have been obtained for different hydrocarbon classes, including methane, C2-C5 gas hydrocarbons, C6-C13 light hydrocarbons and C13+ heavy hydrocarbons, and vitrinite reflectance (R°) by the kinetic simulating experiment of kerogen cracking. Then, combined with the detailed geology of Sichuan Basin, the effective gas-generating intensity of the Lower Cambrian source rock is approximately estimated by applying these parameters.  相似文献   

4.
人为干扰和气候变化会改变湖泊水位状态,明确不同水位条件下湖泊沉积物有机碳矿化特征及其影响因素,对了解内陆水生态系统碳循环具有重要意义.为探究干旱区典型盐湖沉积物有机碳矿化速率对水位变化的响应,以巴里坤湖干涸湖底原状沉积物为研究对象,初步探究了0（T1）、-9（T2）、-23（T3）、-34（T4）和-45 cm（T5）水位处理对沉积物有机碳矿化速率的影响.结果表明,T1、T2和T3处理有机碳矿化速率在试验初期较高（0~10 d）,10 d后缓慢下降,T4和T5处理有机碳矿化速率呈先增加后降低趋势;T1（1.718 μmol/（m2·s））与T3（1.784 μmol/（m2·s））处理有机碳矿化速率不存在显著差异,T1处理有机碳矿化速率是T2、T4和T5处理的1.09、3.31和3.57倍,不同处理有机碳累积矿化量表现为T3 > T1 > T2 > T4 > T5.有机碳累积矿化量（Ct）占沉积物有机碳（C0）的比例（Ct/C0）介于0.012~0.044之间,沉积物有机碳潜在排放量（Ci）占C0的比例（Ci/C0）介于0.018~0.045之间;水位降低,沉积物有机碳矿化常数（k值）减小,T1处理k值最大（0.137 d）,T4处理最小（0.032 d）.线性方程Cr=0.008x+0.488能较好地模拟有机碳矿化速率（Cr）与水位（x）的关系;不同水位处理有机碳矿化速率与模拟柱中沉积物5 cm温度呈显著的指数函数关系,T4、T5处理有机碳矿化温度敏感系数（Q10）显著高于T1、T2和T3处理,即水位降低增加了巴里坤湖干涸湖底沉积物Q10.因此,就巴里坤湖干涸湖底沉积物而言,水位从0 cm降至-45 cm时有机碳矿化速率降低,Q10增加;反之水位上升则会促进有机碳矿化分解,Q10降低.水位持续下降抑制有机碳矿化可能是维持干旱区盐湖沉积物碳库稳定的机制之一.  相似文献   

5.

Devonian strata in the Guizhong region, Guangxi, China consist mainly of marine deposition carbonates (limestones and dolomites) as well as restricted clastic rocks. The strata thickness is measured as 2041m and classified into 14 formations. An integrated field geological, petrographic, sedimentological, palaeobiological, and geochemical study of these strata reveals that the depositional paleoenvironments were carbonate tidal flat, restricted platform, open platform, shelf, platform margin slop, and algal herm. The total organic carbon (TOC) of sedimentary organic matter ranges between 0.07% and 1.96% with average of 0.21%. The organic matter types are Type I and Type III. The vitrinite reflectance (R 0) of kerogen ranges between 0.99% and 2.03%, indicating the maturated and highly maturated stages. The analytical results of the representative samples collected from shelf and subtidal facies show that the differences of organic matter type and biological diagnostic compounds are related to the types of source rocks deposited in different paleoenvironments.

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6.
There are mainly 3 kinds of existing states of oil generating from source rocks, that is, dispersive liquid hydrocarbon inside of source rock, dispersive liquid hydrocarbon outside of source rock and concentrated liquid hydrocarbon outside of source rock. Because of the differences in thermal history and medium conditions around, and the interaction of organic and inorganic matter, the liquid hydrocarbon with 3 kinds of existing state has different cracking conditions. The gas generation dynamics experiments of crude oil matching different mediums indicate that the distribution of activation energy of methane changes a lot according to medium difference. The carbonate has a main influence on oil cracking conditions and can largely reduce its activation energy, which reflects the lower cracking temperature of crude oil. The mudstone takes a second place and the sandstone is the smallest. The catalytic cracking function to the oil of the carbonate, of the mudstone and of the sandstone changes weaken in turn. The corresponding R o values of main gas generation period in different mediums are as follows: 1.5%–3.8% with pure crude oil, 1.2%–3.2% with dispersive crude oil in carbonate, 1.3%～3.4% with dispersive crude oil in mudstone and 1.4%–3.6% with dispersive crude oil in sandstone. The influence of pressure to crude oil cracking is relatively complicated. In the low heating speed condition, pressure restrains the oil cracking and gas generation, but in the high heating speed condition, pressure has an indistinctive influence to the oil cracking and gas generation. Pressure also makes a different effort in different evolvement stage. Taking the middle and lower Cambrian source rocks in the Tarim Basin as an example, primary oil generating quantity is 2232.24×108t, residual oil and oil cracking gas quantity is 806.21×108t and 106.95×1012m3 respectively.  相似文献   

7.
In this paper, by using concentration and carbon stable isotope the CO2 sources of soil profiles developed on limestone, dolostone and claystone basements in Central Guizhou, China are comparatively studied. The results show that CO2 concentration of soil profiles developed on different basements is different, having the following sequence: limestone ; dolostone;claystone. Below the soil depth of 20 cm from the surface the δ13 value of CO2 in soil profile developed on limestone ranges from -12.811%. - -13.492%.(PDB), that in soil profile developed on dolostone varys from -13.212%. - -14.271%.(PDB) and that in soil profile developed on claystone is about-20.234%. - -21.485%.(PDB). Taking the carbon isotope of soil organic matter and carbonate rock as two isotopic endmembers, the proportion of soil CO2 generated by dissolution of carbonate rock is calculated, about 21%–25% for soil profile developed on limestone basement, 19%–21% for soil profile developed on dolostone basement. There is almost no influx of CO2 generated by the dissolution of carbonate rock in soil profile developed on claystone basement.  相似文献   

8.
Gas formation mechanism of marine carbonate source rocks in China   总被引：5，自引：1，他引：4  
It has been proven in exploration practice that thecarbonates in China not only can generate hydrocar-bons, but also form commercial reservoirs. The car-bonates are different from clastic rocks in view of theirdeposition environment as well as their sedimentaryand diagenetic processes. Therefore, the evaluationcriteria and hydrocarbon generation mechanism forcarbonates can not be the same as that for clasticrocks, and it is important to establish a special hydro-carbon generation mechanism and…  相似文献   

9.
The geopotential scale factor R o = GM/W o (the GM geocentric gravitational constant adopted) and/or geoidal potential Wo have been determined on the basis of the first year's (Oct 92 – Dec 93) ERS-1/TOPEX/POSEIDON altimeter data and of the POCM 4B sea surface topography model: R o °=(6 363 672.58°±0.05) m, W o °=(62 636 855.8°±0.05)m 2 s –2 . The 2°–°3 cm uncertainty in the altimeter calibration limits the actual accuracy of the solution. Monitoring dW o /dt has been projected.  相似文献   

10.
The hourly averaged Polar Cap (PC) index was used as the input parameter for the ring current index Dst variation forecasting. The PC index is known to describe well the principal features of the interplanetary magnetic field as well as the total energy input to the magnetosphere. This allowed us to design a neural network that was able to forecast the Dst variations 1 h ahead. 1995 PC and Dst data sets were used for training and testing and 1997 data sets were used for validation. From 15 moderate and strong geomagnetic storms observed during 1997, 10 were successfully forecasted. In 3 cases the observed minimum Dst value was less than the predicted value, and only in 3 cases the neural network was not able to reproduce the features of the geomagnetic storm.  相似文献   

11.
As a relatively stable craton block in the earth system, the petroliferous basin is influenced by the evolution of the earth system from the early development environment of source rocks, hydrocarbon formation, and reservoir dissolution to hydrocarbon accumulation or destruction. As a link between the internal and external factors of the basin, deep fluids run through the whole process of hydrocarbon formation and accumulation through organic-inorganic interaction. The nutrients carried by deep fluids promote the bloom of hydrocarbon-generating organisms and extra addition of carbon and hydrogen source, which are beneficial to the development of high-quality source rock and enhancement of the hydrocarbon generation potential. The energy carried by the deep fluid promotes the early maturation of the source rock and facilitates the hydrocarbon generation by activation and hydrogenation in high-mature hydrocarbon sources. The dissolution alteration of carbonate rocks and clastic reservoirs by CO_2-rich deep fluids improves the deep reservoir space, thus extending the oil and gas reservoir space into greater depth. The extraction of deeply retained crude oil by deep supercritical CO_2 and the displacement of CH_4 in shale have both improved the hydrocarbon fluidity in deep and tight reservoirs. Simultaneously, the energy and material carried by deep fluids(C, H, and catalytic substances) not only induce inorganic CH_4 formation by Fischer-Tropsch(F-T) synthesis and "hydrothermal petroleum" generation from organic matter by thermal activity but also cause the hydrothermal alteration of crude oil from organic sources. Therefore, from the perspective of the interaction of the earth's sphere, deep fluids not only input a significant amount of exogenous C and H into sedimentary basins but also improve the reservoir space for oil and gas, as well as their enrichment and accumulation efficiencies.  相似文献   

12.
Mineralogical and textural characteristics and organic carbon composition of the carbonate concretions from the upper Doushantuo Formation (ca. 551 Ma) in the eastern Yangtze Gorge area reveal their early diagenetic (shallow) growth in organic-rich shale. High organic carbon content (up to 10%) and abundance of framboidal pyrites in the hosting shale suggest an anoxic or euxinic depositional environment. Well-preserved cardhouse clay fabrics in the concretions suggest their formation at 0-3 m burial depth, likely associated with microbial decomposition of organic matter and anaerobic oxidation of methane. Gases through decomposition of organic matter and/or from methanogenesis created bubbles and cavities, and anaerobic methane oxidation at the sulfate reduction zone resulted in carbonate precipitation, filling in bubbles and cavities to form spherical structures of the concretions. Rock pyrolysis analyses show that the carbonate concretions have lower total organic carbon (TOC) content but higher effective carbon than those in the host rocks. This may be caused by enclosed organic matter in pores of the concretions so that organic matter was protected from further modification during deep burial and maintained high hydrocarbon generating potential even in over-matured source rock. As a microbialite sensu latu, concretions have special growth conditions and may provide important information on the microbial activities in depositional and early burial environments.  相似文献   

13.
Devonian strata in the Guizhong region, Guangxi, China consist mainly of marine deposition carbonates (limestones and dolomites) as well as restricted clastic rocks. The strata thickness is measured as 2041m and classified into 14 formations. An integrated field geological, petrographic, sedimentological, palaeobiological, and geochemical study of these strata reveals that the depositional paleoenvironments were carbonate tidal flat, restricted platform, open platform, shelf, platform margin slop, and algal herm. The total organic carbon (TOC) of sedimentary organic matter ranges between 0.07% and 1.96% with average of 0.21%. The organic matter types are Type I and Type III. The vitrinite reflectance (R 0) of kerogen ranges between 0.99% and 2.03%, indicating the maturated and highly maturated stages. The analytical results of the representative samples collected from shelf and subtidal facies show that the differences of organic matter type and biological diagnostic compounds are related to the types of source rocks deposited in different paleoenvironments.  相似文献   

14.
The self-diffusion of water and hexadecane in medium and coarse sands from glacial sand deposits in central Germany were investigated by pulsed field gradient nuclear magnetic resonance (PFG NMR). Due to the restriction of the diffusion path at the pore/grain interface, the measured apparent self-diffusion coefficients (D(Δ)) in the pore space depend on the observation time (Δ) in the PFG NMR experiment. Although the bulk self-diffusion coefficients of water and hexadecane differ by about one order of magnitude, the apparent self-diffusion coefficients in the pore space obey the same characteristic time-behaviour, which depends only on geometrical properties of the pore system. Using the “short-time diffusion” model, surface-to-volume (S/V) ratios and inherent self-diffusion coefficients (D0) of the pore fluids were extracted from these diffusion measurements. The S/V ratios obtained are independent of the pore fluid used and agree with known geometrical properties of the sand grains. Moreover, the D0 values are consistent with the corresponding bulk self-diffusion coefficients measured separately. In contrast to these results of PFG NMR, simultaneous investigations of longitudinal (T1) nuclear magnetic relaxation reveal that the relaxation time of the pore fluid is a less suitable parameter for a quantitative estimation of geometrical properties of the pore/grain interface in these unconsolidated sediments since it depends on chemical properties of the fluid/grain interface.  相似文献   

15.
In the light of the single scattering model of coda originating from local earthquakes, and based on the aftershock coda registered respectively at the 4 short period stations installed near the foci shortly after theM7.6 Lancang andM7.2 Gengma earthquakes, this paper has tentatively calculated the rate of amplitude attenuation and theQ c-value of the coda in the Lancang and Gengma areas using a newly-founded synthetic determination method. Result of the study shows the rate of coda amplitude attenuation demonstrates remarkable regional differences respectively in the southern and northern areas. The southern area presents a faster attenuation (Q c=114), whereas the northern area shows a slower attenuation (Q c=231). The paper also discusses the reasons causing such differences. Result of the study also suggests a fairly good linear relation between the coda source factorA o(f) and the seismic moment and the magnitude. Using the earthquake scaling law, the following formulas can be derived: lgM 0=lgA 0(f)+17.6,M D=0.67lgA 0(f)+1.21 and logM 0=1.5M D+15.79. In addition, the rates of amplitude attenuationβ s andβ m are respectively calculated using the single scattering and multiple scattering models, and the ratioβ s/βm=1.20−1.50 is found for the results respectively from the two models. Finally, the mean free pathL of the S-wave scattering in the southern and northern areas are determined to be 54 km and 122 km respectively by the relations which can distinguish between the inherentQ i and scatteringQ s, testify to this areas having lowQ-values correspond to stronger scatterings. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,14, 71–82, 1992. This study is partly supported by the Seismological Science Foundation of the State Seismological Bureau of China, and the present English version of the paper is translated from its Chinese original by Wenyi Xia, Seismological Bureau of Yunnan Province.  相似文献   

16.
Through geological observation, simulation in laboratory and numerical modeling, the factors that control the changes in total organic content (TOC) of source rock have been studied. When the formula DTOC=(TOC0-TOC)/TOC0 (original organic carbon content in the rock) is used to measure the TOC (total organic carbon content) changes in the source rock through geological time, the degrees and directions of such changes are determined by losses and relative amounts both of organic and inorganic matter in the source rock. The DTOC equation, which is used to calculate the loss rate in the process of maturation for the source rock, is therefore obtained by analyzing the mass balance relations. For a certain type of source rock with a certain maturation history, the changes of its TOC respond only to the rates of hydrocarbon generation and expulsion. In actual cases of geological entities, DTOC generally ranges from -0.05 to 0.2, while the calculated reconversion coefficient (k) for organic carbon content remains between 0.90 and 1.25. Only in an ideal situation where there are extremely high rates of hydrocarbon generation and expulsion can the DTOC value experience significant changes, with k reaching up to 2.5. It is concluded, therefore, that the criterion for carbonates source rock assessment, based on reconverting the TOC to the value of its original state, may have overestimated the course of the "carbon-reduction", which is likely in many cases to make a poor source rock sound better.  相似文献   

17.
Characteristics of organic matter content, hydrocarbon generation and expulsion of carbonate rocks are discussed by analysis of organic carbon and pyrolysis. There is a strong inhomogeneity in distribution of organic matter in carbonate rocks. The organic matter abundance is higher in stylolites, carbonate varves or marls, while it is the lowest in matrixes (purer carbonate rocks around stylolites). Because of stable thickness and broad area, marls and carbonate varves may become good source rocks. At the same depth, stylolites, carbonate varves and matrixes generate and expel hydrocarbons almost at the same time. Expulsion efficiency of carbonate varve is the highest; that of rnatrixes is the lowest and that of stylolites is between marl’s or carbonate varve’s and matrix’s. Project supported by the Science and Technology Research of the 9th Five-Year Plan from China National Petroleum & Gas Company.  相似文献   

18.
Many evidences published in recent years reveal that the thickness,chemical composition and thermal state of lithosphere in eastern North China have ex-perienced dramatic transition during the Phanero-zoic.Comparative study[1—8]of early Paleozoic dia-mond-and xenoliths-bearing kimberlites to Cenozoic mantle peridotite xenoliths-bearing alkali basalts indi-cates that the early Phanerozoic lithosphere is thick and stable to depths within the diamond stability field(180–200km)with depleted ma…  相似文献   

19.
Due to hardware developments in the last decade, the high-frequency end of the frequency band of seismic waves analyzed for source mechanisms has been extended into the audio-frequency range (>20 Hz). In principle, the short wavelengths corresponding to these frequencies can provide information about the details of seismic sources, but in fact, much of the signal is the site response of the nearsurface. Several examples of waveform data recorded at hard rock sites, which are generally assumed to have a flat transfer function, are presented to demonstrate the severe signal distortions, includingf max, produced by near-surface structures. Analysis of the geology of a number of sites indicates that the overall attenuation of high-frequency (>1 Hz) seismic waves is controlled by the whole-path-Q between source and receiver but the presence of distinctf max site resonance peaks is controlled by the nature of the surface layer and the underlying near-surface structure. Models of vertical decoupling of the surface and nearsurface and horizontal decoupling of adjacent sites on hard rock outcrops are proposed and their behaviour is compared to the observations of hard rock site response. The upper bound to the frequency band of the seismic waves that contain significant source information which can be deconvolved from a site response or an array response is discussed in terms off max and the correlation of waveform distortion with the outcrop-scale geologic structure of hard rock sites. It is concluded that although the velocity structures of hard rock sites, unlike those of alluvium sites, allow some audio-frequency seismic energy to propagate to the surface, the resulting signals are a highly distorted, limited subset of the source spectra.  相似文献   

20.
China’s widespread marine carbonate rock series are mostly characterized by intensive thermal evolu- tion and low abundance of organic matter, especially the Lower Paleozoic carbonate rocks have experienced multi-episodes of tectonics and prolonged history of thermal evolution, thus making it more complicatedethe development and distribution of hydrocar- bon-source rocks reflected in the sedimentary, bio- logical and geochemical facies. Consequently, it seems much less powerful to assess the …  相似文献   

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