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81.
Boris Gurevich 《Geophysical Prospecting》2015,63(1):141-150
Naturally fractured reservoirs are becoming increasingly important for oil and gas exploration in many areas of the world. Because fractures may control the permeability of a reservoir, it is important to be able to find and characterize fractured zones. In fractured reservoirs, the wave‐induced fluid flow between pores and fractures can cause significant dispersion and attenuation of seismic waves. For waves propagating normal to the fractures, this effect has been quantified in earlier studies. Here we extend normal incidence results to oblique incidence using known expressions for the stiffness tensors in the low‐ and high‐frequency limits. This allows us to quantify frequency‐dependent anisotropy due to the wave‐induced flow between pores and fractures and gives a simple recipe for computing phase velocities and attenuation factors of quasi‐P and SV waves as functions of frequency and angle. These frequency and angle dependencies are concisely expressed through dimensionless velocity anisotropy and attenuation anisotropy parameters. It is found that, although at low frequencies, the medium is close to elliptical (which is to be expected as a dry medium containing a distribution of penny‐shaped cracks is known to be close to elliptical); at high frequencies, the coupling between P‐wave and SV‐wave results in anisotropy due to the non‐vanishing excess tangential compliance. 相似文献
82.
Faisal Alonaizi Roman Pevzner Andrej Bóna Mohammad Alshamry Eva Caspari Boris Gurevich 《Geophysical Prospecting》2014,62(2):197-209
Time‐lapse seismic analysis is utilized in CO2 geosequestration to verify the CO2 containment within a reservoir. A major risk associated with geosequestration is a possible leakage of CO2 from the storage formation into overlaying formations. To mitigate this risk, the deployment of carbon capture and storage projects requires fast and reliable detection of relatively small volumes of CO2 outside the storage formation. To do this, it is necessary to predict typical seepage scenarios and improve subsurface seepage detection methods. In this work we present a technique for CO2 monitoring based on the detection of diffracted waves in time‐lapse seismic data. In the case of CO2 seepage, the migrating plume might form small secondary accumulations that would produce diffracted, rather than reflected waves. From time‐lapse data analysis, we are able to separate the diffracted waves from the predominant reflections in order to image the small CO2 plumes. To explore possibilities to detect relatively small amounts of CO2, we performed synthetic time‐lapse seismic modelling based on the Cooperative Research Centre for Greenhouse Gas Technologies (CO2CRC) Otway project data. The detection method is based on defining the CO2 location by measuring the coherency of the signal along diffraction offset‐traveltime curves. The technique is applied to a time‐lapse stacked section using a stacking velocity to construct offset‐traveltime curves. Given the amount of noise found in the surface seismic data, the predicted minimum detectable amount of CO2 is 1000–2000 tonnes. This method was also applied to real data obtained from a time‐lapse seismic physical model. The use of diffractions rather than reflections for monitoring small amounts of CO2 can enhance the capability of subsurface monitoring in CO2 geosequestration projects. 相似文献
83.
Yu. P. Tsvetkov O. M. Brekhov T. N. Bondar S. V. Filippov V. G. Petrov N. M. Tsvetkova A. Kh. Frunze 《Geomagnetism and Aeronomy》2014,54(2):263-268
Two global analytical models of the main magnetic field of the Earth (MFE) have been used to determine their potential in deriving an anomalous MFE from balloon magnetic surveys conducted at altitudes of ~30 km. The daily mean spherical harmonic model (DMSHM) constructed from satellite data on the day of balloon magnetic surveys was analyzed. This model for the day of magnetic surveys was shown to be almost free of errors associated with secular variations and can be recommended for deriving an anomalous MFE. The error of the enhanced magnetic model (EMM) was estimated depending on the number of harmonics used in the model. The model limited by the first 13 harmonics was shown to be able to lead to errors in the main MFE of around 15 nT. The EMM developed to n = m = 720 and constructed on the basis of satellite and ground-based magnetic data fails to adequately simulate the anomalous MFE at altitudes of 30 km. To construct a representative model developed to m = n = 720, ground-based magnetic data should be replaced by data of balloon magnetic surveys for altitudes of ~30 km. The results of investigations were confirmed by a balloon experiment conducted by Pushkov Institute of Terrestrial Magnetism, Ionosphere, and Radio Wave Propagation of the Russian Academy of Sciences and the Moscow Aviation Institute. 相似文献
84.
Condensation of water vapor and carbon dioxide in the jet exhausts of rocket engines during last stages of Proton, Molniya, and Start launchers operating in the upper atmospheric with different types of fuels is considered. Particle heating is taken into account with emission of latent heat of condensation and energy loss due to radiation and heat exchange with combustion products. Using the solution of the heat balance and condensed particle mass equations, the temporal change in the temperature and thickness of the condensate layer is obtained. Practically, no condensation of water vapor and carbon dioxide in the jet exhaust of a Start launcher occurs. In plumes of Proton and Molniya launchers, the condensation of water vapor and carbon dioxide can start at distances of 120–170 m and 450–650 m from the engine nozzle, respectively. In the course of condensation, the thickness of the “water” layer on particles can exceed 100 Å, and the thickness of carbon dioxide can exceed 60 Å. 相似文献
85.
The town of Zafferana Etnea, located on the southeastern slope of Mt. Etna volcano (Italy), has been repeatedly threatened
by lava flows in recent centuries. The last serious threat occurred during the 1991–1993 eruption, when the lava front came
to a halt only 1.7 km from the centre of town. Morphostructural data derived from light detection and ranging (LiDAR) surveys
carried out on Etna in 2005 have enabled us to evaluate the risk of lava invasion in a section (16 km2) of the Zafferana Etnea territory. Qualitative and quantitative results are obtained combining the information derived from
LiDAR analysis with geological, morphological and structural data using geographic information systems technology (GIS). The
study quantifies in unprecedented detail the areal extent and volume of forested and urban areas and its degree of exposure
to different levels of hazard from future lava invasion. Nearly 52% of the urban texture fall into areas of moderate to high
risk from lava invasion. Future land use planning should take these findings into account and promote new development preferentially
in areas of lower risk. 相似文献
86.
A. V. Maslov V. P. Shevchenko Yu. L. Ronkin O. P. Lepikhina A. N. Novigatsky A. S. Filippov N. V. Shevchenko 《Oceanology》2013,53(6):702-714
The study of the rare-earth element (REE) systematics in the modern bottom sediments of the White Sea and the lower reaches of the Severnaya Dvina River showed that they were derived by the simple mixing of the detrital material from two geochemically contrasting provenances: the Kola-Karelian geoblock almost completely consisting of Archean rocks and the northwestern Mezen syneclise made up of the Upper Vendian, Paleozoic, and Mesozoic rocks. This is best manifested by the changes in ?Nd(0). In terms of the GdN/YbN and Eu/Eu*, most of the studied samples are comparable with the Post-Archean craton complexes, some of which resemble the average composition of the Archean mudstone. Based on the ΣREE and LaN/YbN, the modern bottom sediments are subdivided into two groups: (1) those close to basalts and granites and (2) those approximating common sedimentary rocks. From the lower reaches of the Pinega River to the Tersky coast, the maximal average (La/Yb)RPSC, (Gd/Yb)RPSC, LaN/YbN, and GdN/YbN ratios were determined in the samples taken at the boundary of Dvina Bay with the Basin, i.e., in the sediments with the highest content of the pelitic component. In general, the geochemical composition of the modern bottom sediments of almost the entire White Sea area was defined by input of the eroded products of the mature continental crust with the Severnaya Dvina River, the main river of the region. Such a setting, when the formation of the sediments in a peri- or intracontinental marine basin is controlled by one large river system, presumably may be propagated to the sedimentation in the Laptev Sea, the eastern Kara Sea, the Bay of Bengal, and other basins. 相似文献
87.
V. I. Silaev G. A. Karpov L. P. Anikin V. N. Filippov V. A. Petrovsky A. E. Sukharev Yu. S. Simakova 《Doklady Earth Sciences》2017,476(1):1048-1053
The results of X-ray structural, electron-microscopic, and X-ray spectral microprobe studies of Al-based metal solid solutions that underwent nuclear disintegration and that were discovered in nature for the first time are presented. Based on the similarity to technical counterparts, it is suggested to recognize the previously unknown alloys as natural duralumin. 相似文献
88.
Hartmut H. Hellmer Monika Rhein Günther Heinemann Janna Abalichin Wafa Abouchami Oliver Baars Ulrich Cubasch Klaus Dethloff Lars Ebner Eberhard Fahrbach Martin Frank Gereon Gollan Richard J. Greatbatch Jens Grieger Vladimir M. Gryanik Micha Gryschka Judith Hauck Mario Hoppema Oliver Huhn Torsten Kanzow Boris P. Koch Gert König-Langlo Ulrike Langematz Gregor C. Leckebusch Christof Lüpkes Stephan Paul Annette Rinke Bjoern Rost Michiel Rutgers van der Loeff Michael Schröder Gunther Seckmeyer Torben Stichel Volker Strass Ralph Timmermann Scarlett Trimborn Uwe Ulbrich Celia Venchiarutti Ulrike Wacker Sascha Willmes Dieter Wolf-Gladrow 《Ocean Dynamics》2016,66(11):1379-1413
89.
90.
Pacific superplume-related oceanic basalts hosted by accretionary complexes of Central Asia, Russian Far East and Japan 总被引:5,自引:0,他引:5
I. Yu. Safonova A. Utsunomiya S. Kojima S. Nakae O. Tomurtogoo A.N. Filippov K. Koizumi 《Gondwana Research》2009,16(3-4):587-608
Plume-related oceanic magmatism form oceanic islands, seamounts and plateaus (hereafter “seamounts” or “paleoseamounts”), which are important features in geological history. The accretion of oceanic seamounts to active continental margins significantly contributed to the formation of the continental crust. This paper reviews occurrences of Late Neoproterozoic–Mesozoic seamounts of the Paleo-Asian and Paleo-Pacific oceans, which are hosted by accretionary complexes (ACs) of Russian Altai, East Kazakhstan, Mongolia, Russian Far East and Japan. The paleoseamounts commonly consist of Ti–LREE–Nb-enriched plume-related basalts (OIB-type or intraplate basalts) capped with massive limestone and associated with other units of oceanic plate stratigraphy (OPS): oceanic floor basalts (MORB), pelagic chert, epiclastic slope facies, etc. The paper presents available geochemical data on the plume-related basalts including the first geochemical data on the Middle Paleozoic OIB-type basalts of the Paleo-Asian Ocean hosted by the Ulaanbaatar AC of Mongolia. An emphasis is made for the structural setting of OPS units, specific geochemical features of intraplate basalts, problems of their identification, and distinguishing from magmatic units of a different origin such as MORB, island-arc and back-arc basalts. Finally, we propose a continuous, though periodical, evolution of the Pacific superplume-related magmatism, which can be more reliably proved by studying Middle Paleozoic OPS units hosted by ACs of Mongolia and Tien Shan, and discuss prospects of future studies. 相似文献