叠前三维地震近地表吸收补偿技术在大庆油田的应用研究(英文)

与深层致密岩石相比,相对疏松的近地表地层严重吸收了地震波的高频成分,降低了地震数据的分辨率和高频成分的信噪比。本文利用井中雷管激发、地面检波器接收的微测井直达波资料,通过分析近地表地层不同传播距离的地震直达波频谱信息差异,采用维纳滤波方法,进行近地表吸收补偿反滤波器的求取,将不同微测井测量点对应的近地表吸收补偿反滤波器应用于相应的叠前共检波点道集地震数据,完成了叠前地震数据的空变吸收衰减补偿,克服了叠后地震数据无法实现空变补偿的难题。叠前三维地震近地表吸收补偿后的数据,较补偿前地震数据的优势信噪比频带宽度明显拓宽,低频成分基本保持,反射信息量有较大程度增加,而且与合成记录吻合更好,能更好的满足地质解释的需要,提高解释精度。     

表层火成岩覆盖地区的表层结构调查

在地震勘探中,近地表的不均匀性给激发、接收和静校正等带来很大的困难.WX地区浅表层分布有多期火成岩,对地震勘探造成很大的影响,本文实际工作从发分析了各种地震表层结构调查方法,并对小折射、井中激发地表接收微测井和地表激发井中接收的微测井等常用方法,进行了同点对比试验.选择了最合适的表层结构调查方法,辅以钻井岩性描述,建立了工区的详细准确的表层岩性变化模型,指导地震野外采集方法设计,并求取模型静校正量.取得了较好的地震资料.     

地震波衰减规律及其恢复方法

针对地面地震分辨率低,不能有效识别薄层储层、薄层地层等问题,本文通过地震波衰减规律的分析,提出了一种恢复地震波高频衰减获得宽频带地震剖面的方法,从而大幅度地提高了地震分辨率.应用双井微地震测井资料对松辽盆地地震波动力学特征研究表明,地震波衰减规律是在近地表低速层和近地表低速层的近震源区地震波高频衰减巨大,而在高速层地震波高频衰减很小.药量大近震源区地震波高频衰减大,药量小近震源区地震波高频衰减小.那么,近震源区和近地表低速层对地震波的衰减是地面地震资料频带窄、分辨率低的主要原因.据此提出了如下确定性反褶积方法,用双井微地震测井资料求取近震源区、近地表低速层和虚反射等滤波因子,用其对地面地震资料作确定性反褶积处理,从而恢复近震源区、近地表低速层等几种因素的地震波衰减,将大药量激发地表接收的地面地震延拓成小药量激发高速层接收的宽频带地震.应用该方法对松辽盆地优势频带宽5~90 Hz,视主频50 Hz的地面地震资料处理后,地震剖面优势频带宽达5~360 Hz,视主频达180 Hz,使常规地震剖面分辨率提高2倍.具体的说松辽盆地中部含油组合的地面地震分辨能力由9~15 m提高到3~5 m.宽频带地震剖面与160 Hz的人工合成地震记录对比符合的很好,表明其处理结果是正确.该成果在油气勘探开发中的油气储层预测、构造学研究、沉积学研究等方面有重要的意义.     

复杂山区高分辨率地震采集分析与应用——以四川盆地及周缘地区为例

震源药柱激发因素选择是影响地震资料品质的一个重要环节,在南方复杂山区高分辨率地震采集中合理选择激发岩性、井深、药量等激发因素尤为重要.本文根据复杂山区地震地质条件多样性、复杂性等特点,从理论上分析了地震激发机理、井深、药量、虚反射效应、岩性与药柱长度等对激发子波的影响,开展了基于适应近地表结构特征的动态井深设计、双微测井和综合表层结构调查（微测井和高密度电法联合）等,结合四川盆地及周缘等地区不同地震地质条件下进行了采集试验研究,获得了高品质单炮记录.     

兵库县南部地震引起的尾波Q值的变化

通过微小地震尾波Ｑ值的变化,可以推测出发生在丹波山周围因兵库县南部地震引起的地壳介质非均匀性变化。１９８７￣１９９６年,统计上可置信的尾波Ｑ值变化是,兵库县南部地震前后患前后,只出现在３．０Ｈｚ和４．０Ｈｚ两个中心频段的频率上。通过尾波Ｑ值变化和地震活动变化,推测出非均匀区域的尺度为百米至千米,这表明了这个地区介质非均匀性的特征尺度。     

井下、地表地震计记录波形对比——以松原地震台为例

分析了相邻井下、地表地震计记录的背景噪声及近震、远震波形特征,以及相关的振幅谱及近震、远震接收函数波形特征。结果表明,井下地震计记录的背景噪声比地表地震计小1个数量级,其近震、远震波形记录较清晰、简洁;井下、地表地震计记录的远震振幅谱和径向接收函数具有较好的一致性,但背景噪声、近震振幅谱、近震接收函数、远震切向接收函数波形存在一定差异;由地表地震计得到的近震震级比井下地震计的大0.12,地表地震计到井下地震计之间的P波速度约为2 km/s。     

准南缘山前带精细近地表建模技术研究

准南缘米泉区块位于乌鲁木齐市东北部,博格达山西北缘,海拔高程在500～3500 m之间,地形高差较大.工区北部覆盖有较厚的黄土砾石,地震波吸收衰减严重,工区南部地层倾角大,并有灰岩出露.前期二维地震调查所获的成像剖面信噪比低,一个很重要的原因是小折射、微测井等常规近地表调查方法难以建立准确的山前带近地表模型,进而造成激发井深设计不准,并影响了后续的近地表静校正效果.为了建立山前带精细近地表模型,对工区进行了详细踏勘,利用地表露头信息明确了地表岩性分布规律;开展了试井及岩性录井工作,了解了近地表层岩性及厚度变化;利用微测井及超深微测井调查,得到了测点位置处黄土与砾石层的速度与厚度;实施了浅层二维层析,查清了沿线的近地表结构,并以浅层层析反演结果为依据,对老的二维地震测线开展了不同偏移距资料层析反演.综合利用这些资料,建立了全区精细的近地表模型.分不同近地表结构开展点试验,发现了激发井深与激发岩性及激发速度的关系,逐点确定了最佳激发井深,同时为后续近地表校正处理奠定了基础.     

井下、地表地震计记录波形对比——以松原地震台为例

分析了相邻井下、地表地震计记录的背景噪声及近震、远震波形特征,以及相关的振幅谱及近震、远震接收函数波形特征.结果表明,井下地震计记录的背景噪声比地表地震计小1个数量级,其近震、远震波形记录较清晰、简洁;井下、地表地震计记录的远震振幅谱和径向接收函数具有较好的一致性,但背景噪声、近震振幅谱、近震接收函数、远震切向接收函数...     

汶川地震震害与活动断层“避让带”宽度的分析研究

正2008年5月12日中国汶川发生里氏8.0级特大地震,沿地表可见活动断层无坚不摧的地震地表破裂与强烈的地震动使得地表破裂带沿线及其两侧近断层的建筑物遭受了毁灭性的破坏,同时,地震引发的大量山体滑坡、岩石崩塌、泥石流等次生地质灾害,加重了建筑物破     

1976年松潘7.2级地震前几种异常波形的记录特征及其在大震短临预报中的意义

本文研究了１９７６年松潘７．２级地震前，几个台站记录到的异常地震波形的形态特征及时空分布特征。异常波形可分为４种形态；震中距小于８０ｋｍ的台站都不同程度地记录到了异常波形；临近地震时，记录中出现的波形数量增多，振幅增大；临震前１０天波形密集，呈现明显的突跳变化。根据异常波形的特征，本文还对异常波形的物理机制进行了初步的研究，认为异常波形的出现是地震前孕震区岩石产生微破裂的结果。     

Physical properties of the Earth's core

Calculations of the compression and temperature gradient of the core are facilitated by the use of the thermodynamic Grüneisen ratio, =3Ks/C _P . A pressure-dependent factor in is found to have the same numerical value for the core as for laboratory iron, justifying the use of a constant value for (1.6) in core calculations. The density of the outer core is satisfied by the assumption that it contains about 15% of light elements, particularly sulphur, whereas the inner core is probably ironnickel with very little lighter component. The presence of sulphur in the outer core reduces its liquidus at least 600° below pure iron, so that the adiabatic gradient does not intersect the liquidus, as Higgins and Kennedy have shown would occur in a pure iron core. The inner core is probably close to its melting point, 4700 K, and the adiabatic temperature gradient of the outer is calculated with this as a fixed point, giving 3380 K at the core-mantle boundary. The estimated electrical resistivity of the outer core, 3×10^–6 m, corresponds to a thermal conductivity of 28 W·m^–1·deg^–1, which, with the adiabatic core gradient gives a minimum of 3.9×10¹² W of heat conduction to the mantle. The only plausible source of this much heat is the radioactive decay of potassium in the core. As pointed out by Goles, Lewis, and Hall and Murthy, the presence of potassium becomes geochemically probable once sulphur is admitted as a core constituent. Thus it appears that the recognition of sulphur in the core resolves the two major difficulties which we have faced in attempting to understand the core.List of Symbols a equilibrium atomic spacing at zero pressure, also a constant - A surface area of core - b a constant - c a constant - C _V ,C _P specific heat at constant volume, constant pressure - D dimension of core (or core eddy) - E(r) atomic interaction energy - E energy due to atomic displacement from equilibrium - lattice energy of material - f ₁,f ₂ structure-dependent constants - F(P) pressure dependent factor in Grüneisen's ratio - g gravitational acceleration; also a constant (Equation (13)) - H latent heat of solidification - I integral (Equation (23)) - k Boltzmann's constant - K incompressibility (bulk modulus) - K _T ,K _S isothermal, adiabatic incompressibilities - N number of atoms in a volume of material - P pressure - dQ/dt core to mantle heat flux - r atomic spacing - r _e equilibrium value ofr under pressure - R _m magnetic Reynolds number - T temperature - T _c critical temperature - T _R reduced temperature (Equation (39)) - U specific internal energy of a material - v velocity of internal core motion - V volume - 3 volume expansion coefficient - compressibility - thermodynamic Grüneisen ratio (Equation(2)) - magnetic diffusivity - thermal conductivity - _e electronic contribution to - ₀ permeability of free space - density - _e electrical resistivity - R reduced conductivity,eM/e     

Geometric properties of the coronal neutral surface

The interrelation between the density inhomogeneity and the magnetic field configuration in the solar corona has been studied. The situation of consistency with the regular cellular magnetic field organization, established by the authors based on polarization data, and helmet-shaped coronal structures has been analyzed. Consistency was found when coronal helmets appeared as projections on the plane of the sky of dense layer folds. It turned out that a dense layer on a regularly deformed neutral surface on a scale of 60° generates coronal shapes typical of solar activity minimum epochs. Threby, a weighty argument for the Molodenskii hypothesis that a dense layer is formed on the neutral surface has been obtained and it has been determined that one can find the 3D geometry of the coronal neutral surface based on modeling the visible shape of coronal helmets. The study of this geometry based on the observed coronal structures in the epoch of minimum and low solar activity indicated that the neutral surface longitudinal deformation scale remains stable and the surface latitudinal amplitude at the corona base reaches 50°–70° latitudes and tends to increase with increasing solar activity. This amplitude decreases as a power function with a variable index close to ?1 with increasing distance from the Sun. In addition, a 10° small-scale deformation of the studied surface with a predominant latitudinal flexure direction has been revealed.     

Geotechnical properties of the Cassino Beach mud

Knowledge of the marine soils properties, together with hydrodynamic and climatic data, plays an important role for a better understanding of the dynamic behavior of sandy and muddy coasts. This paper deals with reporting and basic interpretation of two campaigns of exploration and characterization of the mud of Cassino Beach, southern Brazil, carried out during the years of 2004 and 2005. Samples were obtained by means of cores collected at some locations offshore, and were submitted to various laboratory geotechnical tests, including determination of the physical index, grain size distribution, Atterberg limits, and shear resistance by both triaxial and shear vane tests. Results confirm the existence of a very soft soil deposit offshore Cassino Beach, highly plastic, compressible, and viscous, forming an important database for further studies.     

Dielectric properties of the first 100 meters of the Moon

Reviewing 92 measurements of lunar sample dielectric constant versus density at frequencies above 100 kHz, gives the relationK′ = (1.93 ± 0.17)^p by regression analysis, where K′ is the dielectric constant of a soil or solid at a density ofpg/cm³. This formula is the geometric mean between the dielectric constant of vacuum (1) and the zero porosity dielectric constant of lunar material. Similarly, the loss tangent (D) can be described byD = [(0.00053 ± 0.00056) + (0.00025 ± 0.00009)C]p whereD is the loss tangent at densitypg/cm³ withC percent of total FeO + TiO₂ (approximately proportional to ilmenite content). Using the density versus depth relations derived from lunar surface core tubes, and from laboratory studies of lunar soil compression gives a model of the dielectric properties as a function of depth in the lunar regolith. The dielectric constant increases smoothly with depth, as a function of the soil compaction only. The loss tangent, however, is more sensitive to the ilmenite content than it is to density. Neither dielectric constant nor loss tangent varies significantly with the temperature observed in a lunar day.     

On the magnetic and mineralogical properties of basalts

Summary Systematic and extensive investigations on the magnetic and mineralogical properties of samples from basaltic lavas and doleritic dykes have been made. The results obtained lead to several interesting conclusions. Rocks giving Curie temperatures of around 250°C exhibit a high degree of magnetic stability, yield largeQn values (>40) and often contain ore minerals possessing skeletal crystal structure. Also, such rocks can be saturated in low fields of the order of 1000 Oe, and give a value of around 0.5 for the ratioR of saturation remanence to the saturation intensity of magnetization. In contrast to this, rocks giving Curie temperatures of about 580°C are comparatively less stable, give smaller values ofQn, require higher fields for saturation and yield values ofR less than 0.2. Rocks with Curie temperatures ranging from 250°C to 550°C show general magnetic properties intermediate to those of the above two categories.     

Cycles in the scaling properties of length-of-day variations

Variations in the length-of-day (LOD) reflect the effects of several mechanisms in the Earth's rotation dynamics, including Earth–Sun and Earth–Moon line-up, geomagnetic effects and gravitational changes. Several studies showed that signatures of cycles occurring over a wide range of time scales are present in the LOD variations. The present work uses a fractal scaling study based on detrended fluctuation analysis (DFA) to study persistence of LOD variations and to provide insights in the different cycling mechanisms. The results showed that that the LOD variations are persistent over a wide range of time scales, meaning that an increment (resp., decrement) is more likely to be followed by an increment (resp., decrement). The temporal variation of the scaling exponent obtained from the DFA showed that several cycles already reported from the direct LOD variations analysis are inherited by the scaling properties. Inter-annual cycles, including 4.3 and 18.6 years cycles, are linked to the variations of the stochastic dynamics of LOD fluctuations. In this way, the 18.6 years cycle attains a period where variations are mostly affected by white noise effects, reducing the predictability of the LOD anomalies. The results are discussed in terms of the different lunar tidal and core–mantle mechanisms and related to recent results in the literature.