共查询到20条相似文献，搜索用时 31 毫秒
1.
LUO XiaoRong YU Jian ZHANG LiuPing YANG Yang CHEN RuiYin CHEN ZhanKun ZHOU Bo 《中国科学D辑(英文版)》2007,50(Z2):91-102
Mathematic modeling, established on the basis of physical experiments, is becoming an increasingly important tool in oil and gas migration studies. This technique is based on the observation that hydrocarbon migration tends to take relative narrow pathways. A mathematical model of hydrocarbon migration and accumulation is constructed using the percolation theory. It is then calibrated using physical experimental results, and is tested under a variety of conditions, to understand the applicability of the model in different migration cases. Through modeling, dynamic conditions of large-scale migration pathways within homogeneous formations can be evaluated. Basin-scale hydrocarbon migration pathways and their characteristics are analyzed during the model application to the Chang-8 Member of the Triassic Yanchang Formation in Longdong area of Ordos Basin. In heterogeneous formations, spatial changes in fluid potential determine the direction of secondary migration, and heterogeneity controls the characteristics and geometry of secondary migration pathways. 相似文献
2.
3.
2003年9月27日俄蒙中边界7.9级地震的中期预测及其重要意义 总被引：3，自引：0，他引：3
2003年9月27日在俄罗斯(靠近蒙古、中国边界)发生了7．9级地震。作者在两年前对俄蒙中边界7．9级地震作过中期预测，预测意见和这一巨震的比较表明：这一预测是成功的，预测的依据是清楚和明了的。这显示了12个8级左右巨震的空间有序图象。6对对应地震的迁移速度(v)的平均值为14．50km/a，6个v值的变化范围在10—22km/a之内。从而提出：在地壳深处(甚至上地幔上部)可能存在一种巨型结构，它在控制着这些巨震的有序和重复迁移。 相似文献
4.
常速叠加是根据给定的速度将炮检距空间的地震数据映射到叠加速度空间，在实际叠加速度位置形成叠加能量；速度变换是将叠加速度空间的能量数据映射到均方根速度空间，消除地层倾角对速度的影响，这实际上是一种ＤＭＯ方法；常速偏移是在每个均方根速度剖面上独立地进行波场归位，消除反射点位置对速度的影响．经过这三步处理获得最终叠前偏移结果． 相似文献
5.
High-frequency rupture process of the Oct 23, 2011 Van-Merkez earthquake is imaged by back-projection method using high-quality teleseismic P wave data from the US Array, and prestack Kirchhoff migration using P wave data from a subarray of global seismic networks. The rupture model with two asperities is confirmed by previous two methods. In low-frequency imaging, a large asperity derived from the migration method corresponds to the second one from the high-frequency P waves. The consistency of the locations of asperities from datasets with different frequency bands indicates that there is possible insignificance of the frequency-dependent feature for the earthquake. The resultant images illustrate the spatial and temporal evolution of the rupture, which mainly propagated WSW over a length of 33 km during the first 18 s, accompanying with bursts of two asperities at 3 and 11–13 s. The rupture direction is confirmed by the S wave corner frequency variations of strong ground accelerations. The rupture fronts are mainly located at the updip of the causative fault. Based on polarities of the P waveforms and focal mechanisms of the mainshock and aftershocks, the failure of these two asperities is determined to have occurred on a reverse fault with a dip angle of 47°. Hence, the rupture pattern of the 2011 Van-Merkez earthquake was dominated by a unilateral rupture toward the west-southwest direction. 相似文献
6.
Geological interpretation based on gravity gradiometry data constitutes a very challenging problem. Rigorous 3D inversion is the main technique used in quantitative interpretation of the gravity gradiometry data. An alternative approach to the quantitative analysis of the gravity gradiometry data is based on 3D smooth potential field migration. This rapid imaging approach, however, has the shortcomings of providing smooth images since it is based on direct integral transformation of the observed gravity tensor data. Another limitation of migration transformation is related to the fact that, in a general case, the gravity data generated by the migration image do not fit the observed data well. In this paper, we describe a new approach to rapid imaging that allows us to produce the density distribution which adequately describes the observed data and, at the same time, images the structures with anomalous densities having sharp boundaries. This approach is based on the basic theory of potential field migration with a focusing stabilizer in the framework of regularized scheme, which iteratively transfers the observed gravity tensor field into an image of the density distribution in the subsurface formations. The results of gravity migration can also be considered as an a priori model for conventional inversion subsequently. We demonstrate the practical application of migration imaging using both synthetic and real gravity gradiometry data sets acquired for the Nordkapp Basin in the Barents Sea. 相似文献
7.
常速叠加是根据给定的速度将炮检距空间的地震数据映射到叠加速度空间，在实际叠加速度位置形成叠加能量；速度变换是将叠加速度空间的能量数据映射到均方根速度空间，消除地层倾角对速度的影响，这实际上是一种ＤＭＯ方法；常速偏移是在每个均方根速度剖面上独立地进行波场归位，消除反射点位置对速度的影响．经过这三步处理获得最终叠前偏移结果． 相似文献
8.
Sun, climate, hunger, and mass migration 总被引：9，自引：1，他引：8
Kenneth J. Hsu 《中国科学D辑(英文版)》1998,41(5):449-472
Paleoclimatic studies indicate four epochs of global cooling during the last 4 000 years, i. e. during the few centuries before
and after 2000 BC, 800 BC, 400 AD, and 1 600 AD; the quasiperiodicity corresponds to cyclic variation of solar activity. Global
temperature changes influenced regional precipitation patterns: Northern Europe was wetter while the middle- and low-latitude
lands were more arid during colder epochs. Both sets of cold climatical conditions were unfavorable for agricultural production.
Historical records show that large demographic movements in history took place because of crop failures and mass starvation,
rather than escaping from war zones. The “wandering” of the Germanic tribes during the first two or three centuries of the
Christian Era is one example. Whereas the accelerated release of carbon dioxide from the burning of fossil fuels is ultimately
to cause global warming, historical evidence indicates, however, that global warming has been on the whole a blessing to mankind.
Global cooling, on the other hand, has curtailed agricultural production and has led to famines and mass migrations of people.
Perhaps the most important task at the present is not so much computer-modelling of greenhouse effect on global climate, but
water-management and agricultural researches to insure food-supply for an everincreasing world population. 相似文献
9.
虚拟偏移距偏移(POM)是一种新的转换波叠前时间偏移方法,是对等效偏移距偏移(EOM) 的一种改进,它与EOM方法映射方式上虽然不同, 但本质都是相同的,都是将原始输入道集映射成为共转换散射点道集。本文主要介绍了两种偏移方法的原理,通过理论模型来验证两种方法对模型参数的敏感性。在远偏移距情况下,为了能在速度分析中得到更精确的偏移速度,分别用小排列拟合的双曲线公式、三阶近似式、双平方根旅行时公式对映射后的POM道集做动校正,从而验证了三个公式的精度。最后用POM方法对复杂构造进行了叠前时间偏移。 相似文献
10.
Zhang Liyan Liu Yang 《应用地球物理》2006,3(1):18-26
Pseudo-offset migration （POM） is a new method for prestack time migration of converted waves that improves on equivalent-offset migration （EOM）. The mapping of POM is different than EOM but the purpose of the two methods is to map the input samples to the common conversion scatter point （CCSP） gathers. This paper introduces the principles of the two migration methods and model parameter sensitivity tests for both POM and EOM. At large offset-to-depth ratios the hyperbolic approximation, the three-term approximation and the double square root （DSR） equation are used to NMO-correct the mapped POM gathers to obtain more accurate migration velocities. These equations were derived and calculated by small pseudo offset. POM is then used to image complex structure and prestack time migration. 相似文献
11.
High-frequency rupture process of the Oct 23, 2011 Van-Merkez earthquake is imaged by back-projection method using high-quality teleseismic P wave data from the US Array, and prestack Kirchhoff migration using P wave data from a subarray of global seismic networks. The rupture model with two asperities is confirmed by previous two methods. In low-frequency imaging, a large asperity derived from the migration method corresponds to the second one from the high-frequency P waves. The con- sistency of the locations of asperities from datasets with different frequency bands indicates that there is possible insignificance of the frequency-dependent feature for the earthquake. The resultant images illustrate the spatial and temporal evolution of the rupture, which mainly propa- gated WSW over a length of 33 km during the first 18 s, accompanying with bursts of two asperities at 3 and 11-13 s. The rupture direction is confirmed by the S wave comer frequency variations of strong ground accelerations. The rupture fronts are mainly located at the updip of the causative fault. Based on polarities of the P waveforms and focal mechanisms of the mainshock and aftershocks, the failure of these two asperities is determined to have occurred on a reverse fault with a dip angle of 47°. Hence, the rupture pattern of the 2011 Van-Merkez earthquakewas dominated by a unilateral rupture toward the west- southwest direction. 相似文献
12.
Vertical distribution of the dominant planktonic crustaceans in a mesotrophic reservoir, Xujiahe reservoir (central China) 总被引：1，自引：0，他引：1
The day and night vertical distributions of the dominant planktonic crustaceans in Xujiahe Reservoir were investigated on July 7, 1998. Sampling was carried out at Station D in the upstream region, Doupuohe, and Stations LI and LII in the downstream region, Lujiaodao. At Station D and Station LI, Leptodora kindti showed diel vertical migrations. In Daphnia galeata and Diaphanosoma dubia a limited reverse diel vertical migration was found at Station D, and large individuals tended to stay in lower layers during the day. Neutrodiaptomus incongruens seemed to avoid the water column of 0–6 m by day, but a detectable proportion of the population moved upwards at night. Mesocyclops thermocyclopoides showed a clearly defined diel vertical migration behavior at all three stations. The vertical distribution of Thermocyclops crassus was similar at different stations: in daylight hours it was found almost exclusively in the water column below 6 m and during the night a significant proportion of the population shifted upwards. 相似文献
13.
The formation of the complex linear dunes in the central Taklimakan Sand Sea is discussed based on analyses of wind regimes, sand grain size distributions on the topography of the dunes, and a combination of geomorphic and geophysical investigations into the morphology of the dunes. Complex linear dune formation is shown to have ?ve stages. Analysis clearly shows that under the control of wind regime, sand supply and other factors, the simple linear dunes move sideways while they evolve. This is the main cause for the formation of complex linear dunes in the central Taklimakan Sand Sea. We have not collected enough evidence to show whether the complexity of the complex linear dunes is left over from previous wind regimes or whether the previous wind regimes had different dominant wind directions compared to those of modern winds. The evolutionary processes of complex linear dunes in the region partly support the theory of ‘barchan evolution’ but do not support the ‘roll‐vortex’ and ‘bimodal wind regime’ hypotheses. After the complex linear dunes were developed, the local wind regime and the other controls such as sand supply suggest it is possible for them to maintain their linear shape. The evolutionary process discussed is limited to the region indicated in this paper, and may not be applicable to the whole Taklimakan Sand Sea. There are different evolutionary processes in different dune?elds because of variations in the factors that control complex linear dune formation. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
14.
文中讨论了在浅层地震勘探中地质结构和构造的复杂性以及对浅层地震勘探成果要求精度较高的特殊性,指出了在浅层地震勘探中发展叠前深度偏移的重要性,并对相移法叠前深度偏移的基本原理和实现方法进行了详细论述,编制了相应的软件。通过使用该方法对 2种理论试验模型进行试算,获得的深度偏移剖面层位清晰,构造明显,较准确地体现了理论模型地质结构和构造的特征,效果良好。然后又使用实际浅层地震反射资料进行了叠前偏移计算,所得结果与已知地质结构和构造相吻合,也取得了较好的结果,证实了该方法及软件的可靠性和实用性,可用于实际浅层地震反射勘探资料的叠前深度偏移处理 相似文献
15.
李献智 《地震地磁观测与研究》1994,15(6):25-30
本文研究了青藏地震区地震的迁移，发现Ｍｓ≥６．７地震有自西向东的定向迁移规律，该现象有助于研究中国大陆西部地区所受作用力的方向和预测地震的可能发生地区。 相似文献
16.
Origin and accumulation of the oils from Bamianhe Oilfield, Bohai Bay Basin, Eastern China 总被引：2，自引：0，他引：2
Utilizing basic principles and methodologies of geology and organic geochemistry, kinetics of hydrocarbons generation and accumulation, quantitative assessment of crude oils sourced from different source rocks, and hydrocarbons migration pathways for the oils from the Bamianhe Oilfield, the Bohai Bay Basin, Eastern China are discussed. Results of oil-rock correlation showed that the oils were mainly derived from Es4 member (with buried depth >2700 m) of Niuzhuang and Guangli Sags within normal oil window though there is a little amount of mixed immature oils. Quantification of mixed oils with different sources indicated that mature oils account for about 80% of the total oils discovered and immature oils for only 20%. Migration of the oils sourced from the sags is controlled by predominant hydrocarbons migration passages determined by faults, unformalities and favored sandstone reservoir. Results of the origin and migration models for the oils have been recently further testified by considerable quantity of oils discovered in the Bamianhe area, which is obviously playing an important role in guiding further oil exploration. 相似文献
17.
ABSTRACT The Dhidhessa River Basin (DRB), in the Abbay River Basin in Ethiopia, is undergoing large-scale dam construction for sugarcane irrigation. We focused on the dynamics of population migration, settlement, relocation and water resource development in the DRB using primary and secondary data. Two major migration waves were observed in the basin: the first in 1984–1986 during a severe drought and the second during 2005–2017. Most rural migrants were “pulled” by government initiative in the period 1984–2017, while a few migrated of their own accord due to famine. We found that the first migration wave from eastern Ethiopia (Harar) to DRB was due to scarcity of water, land and rainfall and the migration positively affected migrant livelihoods. In the second phase, dam construction displaced settled farmers and migrants, adversely affecting their livelihoods. Analysis is needed that considers the wellbeing of the displaced agrarian society and the migrant population in the dam-affected area. 相似文献
18.
青海及邻区强震迁移活动规律分析 总被引：3，自引：1，他引：2
通过分析,研究了青海及邻区Ms 6．8强震在不同地震带之间的迁移规律;6级地震在各个地震带内部不同地段的迁移特征及不同时段。强震集聚区在各个地震带的相互迁移规律和循环特征。研究结果表明,强震存在北东方向的迁移规律。同一个地震带内存在沿规模宏大的主活动断裂自西向东或者由东向西的迁移规律。利用马尔科夫过程讨论了其迁移概率。 相似文献
19.
The longitudinal dunes of the Simpson Desert, in the vicinity of Birdsville, have been reworked largely during the Holocene from dunes deposited up to 80000 years ago or earlier. The widespread asymmetry of these roughly northward-trending dunes, with steeper eastern faces and more gentle western faces, supports wind-rose data showing sand-transporting winds from the southwest obliquely intersecting the dunes. While this suggests a change in the wind pattern since the dune field was oriented, it does not indicate that the dunes are necessarily shifting leeward (eastward) as a consequence. It is hypothesized that the direction of migration is controlled by the extent to which the dunes are vegetated. Relatively well-vegetated dunes can accrete sand on their gentle stoss slopes and erode on their lee slopes causing them to shift westward and hence obliquely into the wind, a condition that probably prevails in wetter regions and during episodes of relatively humid climate. In contrast, in very dry areas or during arid phases, sand can move unimpeded up a sparsely vegetated stoss face and over the crest to form an avalanche or slip face on the lee side, thereby causing the dunes to shift eastward. Despite evidence that longitudinal dune crests can shift laterally to some extent, the dunes in the western part of the Simpson Desert have not migrated, either westward or eastward, more than 100m or so from their Pleistocene cores. Aeolian transport and partial or complete removal of iron cutans from around quartz grains results in dunes of widely varying colour yet of similar age. 相似文献
20.
Life history, habitat utilisation, and biomass of benthic and pelagic opossum shrimp (Mysis relicta) were studied in the oligotrophic Lake Jonsvatn, central Norway. Sampling in the pelagic zone was done by means of a closing zooplankton net; in the benthic zone by means of a benthic beam trawl.
M. relicta had a mixed one or two year life cycle. In the autumn, the proportion of mature females and males were larger in the pelagic than in the benthic habitat. Copulation took place in late autumn, and the first females with eggs occurred in November. In February, the first juvenile M. relicta were released in the benthic habitat. In May and July, however, juveniles were found in large numbers in all parts of the lake. The length distribution of M. relicta indicates that juveniles partly segregate between benthic and pelagic habitats.
Both juvenile and adult M. relicta performed vertical diel migrations in the pelagic habitat. In the benthic habitat, diel vertical migrations along the bottom were not as pronounced as vertical migrations in the pelagic habitat. In the benthic habitat, major migrations were performed only by adults in the autumn. Our results indicate that the light intensity in the green part of the spectrum gives the proximate cue for regulation of vertical distribution of M. relicta.
The mean total biomass varied between 288 and 1576 kg dry weight, corresponding to 23.2–127.1 mg dry weight m−2 surface area. M. relicta had smallest biomass during late spring/early summer and largest biomass during autumn and early winter. Estimated pelagic biomasses were largest in February, August, October and November, while benthic biomasses were largest in May and July. Estimated biomass of pelagic M. relicta during autumn was approximately 1/10 of the estimated biomass of zooplankton in this lake. 相似文献