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1.
Determination of geomechanical parameters of petroleum reservoir and surrounding rock is important for coupled reservoir–geomechanical modeling, borehole stability analysis and hydraulic fracturing design. A displacement back analysis technique based on artificial neural network (ANN) and genetic algorithm (GA) combination is investigated in this paper to identify reservoir geomechanical parameters based on ground surface displacements. An ANN is used to map the nonlinear relationship between Young’s modulus, E, Poisson’s ratio, v, internal friction angle, Φ, cohesion, c and ground surface displacements. The necessary training and testing samples for ANN are created by using numerical analysis. GA is used to search the set of unknown reservoir geomechanical parameters. Results of the numerical experiment show that the displacement back analysis technique based on ANN–GA combination can effectively identify reservoir geomechanical parameters based on ground surface movements as a result of oil and gas production.  相似文献   

2.

Data assimilation in reservoir modeling often involves model variables that are multimodal, such as porosity and permeability. Well established data assimilation methods such as ensemble Kalman filter and ensemble smoother approaches, are based on Gaussian assumptions that are not applicable to multimodal random variables. The selection ensemble smoother is introduced as an alternative to traditional ensemble methods. In the proposed method, the prior distribution of the model variables, for example the porosity field, is a selection-Gaussian distribution, which allows modeling of the multimodal behavior of the posterior ensemble. The proposed approach is applied for validation on a two-dimensional synthetic channelized reservoir. In the application, an unknown reservoir model of porosity and permeability is estimated from the measured data. Seismic and production data are assumed to be repeatedly measured in time and the reservoir model is updated every time new data are assimilated. The example shows that the selection ensemble Kalman model improves the characterisation of the bimodality of the model parameters compared to the results of the ensemble smoother.

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3.
Ore microscopic investigation of the Fe?CTi oxide minerals was carried out on samples from three Oligo-Miocene basaltic occurrences from Sinai, Egypt. These occurrences are Gebel Maghara (north Sinai), Rageibet Naama (central Sinai), and Wadi Matulla (west Sinai). The results and correlations of magnetic parameters such as NRM intensity and susceptibility, coercive force H c, and the ratio M r/M s, H c and Q value, the ratio M r/M s, saturation magnetization M s, and K are discussed in light of opaque mineralogical studies. It has been found that the variations in the magnetic properties of the basaltic occurrences are strongly dependent on the crystallite size and nature and style of exsolution textures and fabrics. The latter are controlled by the cooling conditions, being most sensitive to the partial pressure of oxygen in the melt.  相似文献   

4.
The satellite radiointerferometry data revealed deformations of the coastal part of Sakhalin Island caused by the earthquake with M w = 6.2 that occurred in the Tatar Strait near Nevelsk. Based on the joint analysis of the satellite and seismological data, dislocation models were contrived for the main shock and its strong aftershocks with the western dip of the fault planes. This made it possible to determine the source mechanisms and the geometrical parameters of the seismic ruptures and to calculate the coseismic vertical and horizontal displacements. In contrast to the one-dimensional model of the insular land displacements determined from the satellite radiointerferometry measurements, this provided a three-dimensional model of the surface deformations for the epicentral zone.  相似文献   

5.
There have been instances of premonitory variations in tilts, displacements, strains, telluric current, seismomagnetic effects, seismic velocities ( Vp, Vs) and their ratio (Vp/Vs), b-values, radon emission, etc. preceding large and moderate earthquakes, especially in areas near epicentres and along faults and other weak zones. Intensity and duration (T) of these premonitory quantities are very much dependent on magnitude (M) of the seismic event. Hence, these quantities may be utilised for prediction of an incoming seismic event well in advance of the actual earthquake. In the recent past, tilts, strain in deep underground rock and crustal displacements have been observed in the Koyna earthquake region over a decade covering pre- and postearthquake periods; and these observations confirm their reliability for qualitative as well as quantitative premonitory indices. Tilt began to change significantly one to two years before the Koyna earthquake of December 10, 1967, of magnitude 7.0. Sudden changes in ground tilt measured in a watertube tiltmeter accompanied an earthquake of magnitude 5.2 on October 17, 1973 and in other smaller earthquakes in the Koyna region, though premonitory changes in tilt preceding smaller earthquakes were not so much in evidence. However, changes in strains in deep underground rock were observed in smaller earthquakes of magnitude 4.0 and above. Furthermore, as a very large number of earthquakes (M = 1–7.0) were recorded in the extensive seismic net in the Koyna earthquake region during 1963–1975, precise b-value variations as computed from the above data, could reveal indirectly the state of crustal (tectonic) strain variations in the earthquake focal region and consequently act as a powerful premonitory index, especially for the significant Koyna earthquakes of December 10, 1967 (M = 7.0) and October 17, 1973 (M = 5.2). The widespread geodetic and magnetic levelling observations covering the pre- and postearthquake periods indicate significant vertical and horizontal crustal displacements, possibly accompanied by large-scale migration of underground magma during the large seismic event of December 10, 1967 in the Koyna region (M = 7.0). Duration (T) of premonitory changes in tilt, strains, etc., is generally governed by the equation of the type logT = A + BM (A and B are statistically determined coefficients). Similar other instances of premonitory evidences are also observed in micro-earthquakes (M = − 1 to 2) due to activation of a fault caused by nearby reservoir water-level fluctuations.  相似文献   

6.
We present a parallel framework for history matching and uncertainty characterization based on the Kalman filter update equation for the application of reservoir simulation. The main advantages of ensemble-based data assimilation methods are that they can handle large-scale numerical models with a high degree of nonlinearity and large amount of data, making them perfectly suited for coupling with a reservoir simulator. However, the sequential implementation is computationally expensive as the methods require relatively high number of reservoir simulation runs. Therefore, the main focus of this work is to develop a parallel data assimilation framework with minimum changes into the reservoir simulator source code. In this framework, multiple concurrent realizations are computed on several partitions of a parallel machine. These realizations are further subdivided among different processors, and communication is performed at data assimilation times. Although this parallel framework is general and can be used for different ensemble techniques, we discuss the methodology and compare results of two algorithms, the ensemble Kalman filter (EnKF) and the ensemble smoother (ES). Computational results show that the absolute runtime is greatly reduced using a parallel implementation versus a serial one. In particular, a parallel efficiency of about 35 % is obtained for the EnKF, and an efficiency of more than 50 % is obtained for the ES.  相似文献   

7.
Abdo  Hazem Ghassan 《Natural Hazards》2020,104(1):681-703

Floods are one of the most severe hydrological hazards that cause an excessive threat to landscape stability, population welfare, infrastructure and spatial development in the Syrian coastal region. Al-Hussain river basin, like other Syrian coastal basins, is prone to a hazardous, frequent-flooding threat. However, investigating the probable areas of flooding risk is a difficult challenge that results from the almost complete absence of spatially distributed geo-hydrological measurements in Al-Hussain river basin. In this regard, geohydromorphometric parameters (Stream number Nu, Stream length Lu, Bifurcation ratio Rb, Form factor F, Elongation ratio Eb, Drainage density Dd, Stream frequency Fs, Drainage texture Td, Lemniscate ratio K, Compactness index C, Circulatory ratio Rc, Ruggedness number Rn, Basin relief Hr, and Relief ratio Rr) derived from remote sensing data in the GIS environment can provide a comprehensive and objective approach that can be utilized to map the spatial distribution of flood hazards at the level of delineated sub-basins. This being the case, the present research focuses on exploring the spatial distribution of flood risk in ten sub-basins belonging to Al-Hussain river basin by using spatial techniques tools in order to overall determine the hydro-prioritization of conservation. The geo-visualization map of generated flash flood susceptibility evaluates five degrees of the flood risk: very low, low, moderate, high, and very high. The flood risk map indicates that Qalea, and Talaa sub-basins have massive hydrodynamic risk, which, in turn, indicates the urgent need of soil and water maintaining measures. This hydrological dynamic in these sub-basins is explained by high values of Dd, F, Rr, Rn, Rc, and K, respectively. Overall, the spatial outcomes of the current work successfully proved the efficiency of extracted geohydromorphometric layers from RS data in the context of the spatial assessment of flash flood hazard; they also ensure ecological sustainability and productivity of the study basin.

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8.
We evaluated the efficiency of various models in describing the time decay of aftershock rate of 47 simple sequences occurred in California (37) from 1933 to 2004 and in Italy (10) from 1976 to 2004. We compared the models by the corrected Akaike Information Criterion (AICc) and the Bayesian Information Criterion (BIC), both based on the log-likelihood function and also including a penalty term that takes into account the number of independent observations and of free parameters of each model. These criteria follow two different approaches (probabilistic and Bayesian respectively) well covering the wide spectra of current views on model comparison. To evaluate the role of catalog incompleteness in the first times after the main shock, we compared the performance of different models by varying the starting time Ts and the minimum magnitude threshold Mmin for each sequence. We found that Omori-type models including parameter c are preferable to those not including it, only for short Ts and low Mmin while the latters generally perform better than the formers for Ts longer than a few hours and Mmin larger than the main shock magnitude Mm minus 3 units. For Ts > 1 day or Mmin > Mm − 2.5, only about 15% of the sequences still give a preference to models including c. This clearly indicates that a value of parameter c different from zero does not represent a general property of aftershock sequences in California and Italy but it is very likely induced in most cases by catalog incompleteness in the first times after the main shock. We also considered other models of aftershock decay proposed in the literature: the Stretched Exponential Law in two forms (including and not including a time shift) and the band Limited Power Law (LPL). We found that such models perform worse than the Modified Omori Model (MOM) and other Omori-type models for the large majority of sequences, although for LPL, the relatively short duration of the analyzed sequences (one year) might also contribute to its poor performance. Our analysis demonstrates that the MOM with c kept fixed to 0 represent the better choice for the modeling (and the forecasting) of simple sequence behavior in California and Italy.  相似文献   

9.
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10.
In order to identify the parameters that best characterize the chemical and structural evolution of organic matter during coalification, the relationships between optical, chemical and micro-structural parameters in high-rank coals and natural graphite were studied. The samples include anthracites from Peñarroya–Belmez–Espiel Basin (Spain), Douro Basin (Portugal), and Alto Chicama Basin (Peru); and natural graphite from Canada, Mozambique, and Austria.Correlations between the following optical parameters were assessed: vitrinite random reflectance (Rr), Reflectance Indicating Surfaces (RIS) axis (RMAX, RINT and RMIN), and RIS parameters (Ram, Rev and Rst), as well as Bw and AI anisotropy parameters. Furthermore, the chemical parameters used were chosen according to their significant variation in coals, namely volatile matter, carbon, and hydrogen contents calculated in dry ash free basis (VMdaf, Cdaf, Hdaf), as well as the H/C atomic ratio. Structural organization was characterized by micro-Raman spectroscopy and XRD. Raman parameters used were the full width at half maximum (FWHM) and position of G and D1 bands on the first-order Raman spectrum, and the ID1/IG intensity area ratio. The selected XRD parameters were interlayer spacing d002, and crystallite sizes La and Lc.Results show that: (i) RMAX RIS axis seems to correlate best with chemical and micro-structural parameters; (ii) for the majority of studied samples, Hdaf and H/C atomic ratio are the only chemical parameters with significant correlations with RMAX; (iii) the FWHM of the G band of Raman spectrum shows good linear correlation with the XRD parameter d002; and, (iv) structural organization of carbon materials, as measured by trends in their optical and crystalline parameters, is influenced by their hydrogen content (daf basis) and therefore by the H/C atomic ratio.  相似文献   

11.
In this study, magnetic techniques were used to characterize the surface soil from different geomorphologies (i.e., sand desert, oasis, Gobi, and dry lake) in Central Asia. Results demonstrate that the main magnetic minerals in the surface soil are magnetite, maghaemite and haematite with some paramagnetic materials. Cross plots of M rs/M s versus B cr/B c and χfd% versus χarm/saturation isothermal remanent magnetization (SIRM) indicate that the main magnetic grain sizes in surface soil are pseudo single domain (PSD) and multidomain (MD). The samples from West China (i.e., Tarim basin and Junggar basin) are dominated by magnetic minerals with larger grain size, while those from North China (i.e., Alxa plateau, Erdos plateau, and Mongolia plateau) are dominated by fine magnetic minerals. The similarity in magnetic mineral constitutions between the Chinese loess and the surface soils from Central Asia implies that the loess originated from a vast area of arid, semi-arid regions of Central Asia. The low value of concentration-dependent magnetic parameters indicates that the low concentration of magnetic minerals in the surface soils from Central Asia and the magnetic enhancement from the pedogenic take place in both the loess and the paleosols, although the progress is stronger in the latter. Translated from Quaternary Sciences, 2006, 26(6): 937–946 [译自: 第四纪研究]  相似文献   

12.
North-east India is seismically very active and has experienced many widelydistributed shallow, large earthquakes. Earthquake generation model for the region was studied using seismicity data [(1906–1984) prepared by National Geophysical Data Centre (NGDC), Boulder Colorado, USA]. For establishing statistical relations surface wave magnitudes (M s≥5·5) have been considered. In the region four seismogenic sources have been identified which show the occurrences of atleast three earthquakes of magnitude 5·5≤M s≤7·5 giving two repeat times. It is observed that the time interval between the two consecutive main shock depends on the preceding main shock magnitude (M p) and not on the following main shock magnitude (M f) revealing the validity of time predictable model for the region. Linear relation between logarithm of repeat time (T) and preceding main shock magnitude (M p) is established in the form of logT=cM p+a. The values ofc anda are estimated to be 0–36 and 1–23, respectively. The relation may be used for seismic hazard evaluation in the region.  相似文献   

13.
Empirical mb, Ms and Mo data are used to develop an average spectral scaling relation for plate-margin earthquakes. Using equations based upon a rectangular, bilateral dislocation model with uniform rupture velocity, the spectra give values of fault rupture length and width, static stress drop and average fault displacement as a function of mb, Ms and Mo. Compared to mid-plate earthquakes of the same seismic moment, the large average plate-margin earthquake has a bigger rupture length, rupture area and average fault displacement and a smaller rupture width and static stress drop.  相似文献   

14.
Tokutaro Hatori 《GeoJournal》1996,38(3):313-319
The regional characteristics of tsunami magnitudes in the SE Asia region are discussed in relation to earthquake magnitudes during the period from 1960 to 1994. Tsunami magnitudes on the Imamura-Iida scale are investigated by the author's method (Hatori 1979, 1986) using the data of inundation heights near the source area and tide-gauge records observed in Japan. The magnitude values of the Taiwan tsunamis showed relatively to be small. On the contrary, the magnitudes of tsunamis in the vicinities of the Philippines and Indonesia exceed more than 1–2 grade (tsunami heights: 2–5 times) compared to earthquakes with similar size on the circum-Pacific zone. The relation between tsunami magnitude, m, and earthquake magnitude, M s, is expressed as m = 2.66 M s– 17.5 for these regions. For example, the magnitudes for the 1976 Mindanao tsunami (M s= 7.8, 3702 deaths) and the 1992 Flores tsunami (M s= 7.5, 1713 deaths) were determined to be m = 3 and m = 2.5, respectively. The focal depth of tsunamigenic earthquakes is shallower thand< 36 km, and the detectively of tsunamis is small for deep earthquakes being d > 40 km. For future tsunamis, it is indispensable to take precautions against shallow earthquakes having the magnitudes M s> 6.5.  相似文献   

15.
A homogenous earthquake catalog is a basic input for seismic hazard estimation, and other seismicity studies. The preparation of a homogenous earthquake catalog for a seismic region needs regressed relations for conversion of different magnitudes types, e.g. m b , M s , to the unified moment magnitude M w. In case of small data sets for any seismic region, it is not possible to have reliable region specific conversion relations and alternatively appropriate global regression relations for the required magnitude ranges and focal depths can be utilized. In this study, we collected global events magnitude data from ISC, NEIC and GCMT databases for the period 1976 to May, 2007. Data for mb magnitudes for 3,48,423 events for ISC and 2,38,525 events for NEIC, M s magnitudes for 81,974 events from ISC and 16,019 events for NEIC along with 27,229 M w events data from GCMT has been considered. An epicentral plot for M w events considered in this study is also shown. M s determinations by ISC and NEIC, have been verified to be equivalent. Orthogonal Standard Regression (OSR) relations have been obtained between M s and M w for focal depths (h < 70 km) in the magnitude ranges 3.0 ≤ M s  ≤ 6.1 and 6.2 ≤ M s  ≤ 8.4, and for focal depths 70 km ≤ h ≤ 643 km in the magnitude range 3.3 ≤ M s  ≤ 7.2. Standard and Inverted Standard Regression plots are also shown along with OSR to ascertain the validation of orthogonal regression for M s magnitudes. The OSR relations have smaller uncertainty compared to SR and ISR relations for M s conversions. ISR relations between m b and M w have been obtained for magnitude ranges 2.9 ≤ m b  ≤ 6.5, for ISC events and 3.8 ≤ m b  ≤ 6.5 for NEIC events. The regression relations derived in this study based on global data are useful empirical relations to develop homogenous earthquake catalogs in the absence of regional regression relations, as the events catalog for most seismic regions are heterogeneous in magnitude types.  相似文献   

16.
A simple method is developed to determine seismic moments of earthquakes. The method is qualified through criteria such as simplicity of calculations, coverage of wide magnitude range, and insensitivity to detailed instrumental response. The method is applied to 163 major earthquakes which occurred underneath Japan and the Japan Sea in the time from 1926 to 1977. Magnitudes of these earthquakes, which have been determined by the Japan Meteorological Agency, (MJMA) cover the range from 4.3 to 7.5. At first, source spectra are analyzed through a very simple way introducing two new parameters: characteristic period Tc and seismic-moment factor Mc. The former is defined as an average value of apparent periods of seismic waves with the maximum trace amplitude at many stations. The latter is an average of products of maximum trace amplitude and its apparent period multiplied by epicentral distance. It is shown that Tc corresponds to the period of the corner frequency of an earthquake and Mc to the seismic-moment density at the period of Tc. A scaling model of earthquake source spectra is presented which satisfies the empirical relations between the surface-wave magnitude Ms and MJMA, and MJMA and the body-wave magnitude mb. Those relations are independent of the Gutenberg and Richter relation between Ms and mb, because MJMA is determined from maximum amplitudes of seismic waves with a period of about 4 sec. The static seismic moment of each earthquake can be estimated from calculated Mc using the source spectra of the scaling model. Seismic moments of 18 earthquakes determined by conventional analyses from near- and/or far-field observations are consistent with static seismic moments thus estimated over the range from 2 × 1023 to 3 × 1027 dyne cm. This shows the potential in practice of the present method, especially in the routine processing of seismic data.  相似文献   

17.
岩土力学参数空间变异性的集合卡尔曼滤波估值   总被引：3，自引：1，他引：2  
赵红亮  冯夏庭  张东晓  周辉 《岩土力学》2007,28(10):2219-2223
岩土参数具有结构性和随机性的空间变异特征,该特征导致岩土参数具有不确定性。以地质统计学作为岩土参数空间变异性分析的理论基础,将分布于研究区的岩土参数视为区域化变量,变异函数既描述了岩土参数整体的空间结构性变化,又描述了其局部的随机性变化,用变异函数理论模型作为描述岩土参数空间变异规律的数学模型。引入集合卡尔曼滤波（EnKF）分析方法,利用时空分布的观测数据,对岩土参数空间变异性进行估值。数值算例表明,EnKF能够有效地融合观测数据,较好地提供岩土参数空间变异性的估值。  相似文献   

18.
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19.
There are various types of the windblown sediment traps developed for wind tunnel and field studies. One of the main supports expected from these traps is in measuring surface dust concentrations to appropriately derive flux equations. The measurement performance and accuracy of a trap is very important and depends strictly upon the physical characteristics and the behaviors of dust grains with air flows. This paper presents the measurement results of static pressure distribution (SPD) of wind flow around Vaseline-coated slide (VCS) catchers with an aim of finding out whether or not particle trapping efficiency (η) of the VCS is related to the SPD. The SPD was evaluated by a wind reduction coefficient (R c) in a series of wind tunnel experiments with different VCS settings which have different attachment configurations on a pole. Three VCS configurations were considered: a configuration on a circular plastic pole (CPP) and two configurations on wooden square poles (WSP1 and WSP2, respectively). Thus, the primary contribution of this work was to experimentally analyze the effect of the different attachment configurations on the SPD, and the secondary objective was to determine the effect of the SPD on the η. It was shown that spatial correlation and spatial pattern of the R c were different in the surrounding area of each configuration, and ANOVA and DUNCAN tests indicated that η(s) of WSP1, WSP2, and CPP were different at the significant level of P ≤ 0.05 with the mean of 0.94 ± 0.09, 0.63 ± 0.14, and 1.13 ± 0.07, respectively. Additionally, the amount of PM20, PM40, PM60, PM80, and PM100 trapped by the configurations of WSP1, WSP2, and CPP considerably varied depending upon the particular aerodynamic circumstances associated with every configuration.  相似文献   

20.
The surface-wavemagnitudes Ms are determined for 30 great shallow earthquakes that occurred during the period from 1953 to 1977. The determination is based on the amplitude and period data from all available station bulletins, and the same procedure as that employed in Gutenberg and Richter's “Seismicity of the Earth” is used. During this period, the Chilean earthquake of 1960 has the largest Ms, 8.5. The surface-wave magnitudes listed in “Earthquake Data Reports” are found to be higher than Ms on the average. By using the same method as that used by Gutenberg, the broad-band body-wave magnitudes mB are determined for great shallow shocks for the period from 1953 to 1974. mB is based on the amplitudes of P, PP and S waves which are measured on broadband instruments at periods of about 4–20 s. The 1-s body-wave magnitudes listed in “Bulletin of International Seismological Center” and “Earthquake Data Reports” are found to be much smaller than mB on the average. Through the examination of Gutenberg and Richter's original worksheets, the relation between mB and Msis revised to mB = 0.65 Ms+ 2.5 which well satisfies the mg and Msdata for Msbetween 5.2 and  相似文献   

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