The Migration Characteristics of Strong Earthquakes on the North-South Seismic Belt and Its Relation with the South Asia Seismic Belt

Migration of strong earthquakes （M≥ 7.0） along the North-South Seismic Belt of China since 1500 AD shows three patterns： Approximately equal time and distance interval migration from N to S, varied patterns of migration from S to N and grouped strong earthquake activity in a certain period over the entire seismic belt. Analysis of strong earthquakes in the past hundred years shows that the seismicity on the North-South Seismic Belt is also associated with strong earthquake activities on the South Asia Seismic Belt which extends from Myanmar to Sumatra, Indonesia. Strong earthquakes on the former belt often lag several months or years behind the quakes occurring on the later belt. So, after the occurrence of the December 26, 2004 Ms8.7 great earthquake off the western coast of Sumatra, Indonesia, the possibility of occurrence of strong earthquakes on the North-South Seismic Belt of China cannot be ignored. The abovementioned migration characteristics of strong earthquakes are related to the northeastward collision and subduction of the India Plate as well as the interaction between the Qinghai-Xizang （Tibet） Plateau and the stable and hard Ordos and Alashan Massifs at its northeastern margin.     

应用地震干涉法定位四川九寨沟7.0级地震震源位置

利用地震干涉法对2017年8月8日九寨沟M7.0主震及部分余震进行定位.地震干涉法在可控源地震勘探领域有着广泛应用,但由于震源机制和震源辐射花样的复杂性,在天然地震研究中,地震干涉震源成像应用较少.本研究将地震干涉震源成像技术应用到了天然地震定位中,通过计算原始地震波形记录的特征函数,消除了由于震源辐射花样不同而引起的初动方向不一致性.通过对干涉波形进行偏移叠加,选择互相关型和卷积型两种偏移核函数,分别对震源水平位置和深度进行偏移成像,确定了九寨沟M7.0主震及11次M > 3.5余震的震源位置参数.结果显示,这次地震发生在一个之前未被关注的无名断裂（现已命名为树正断裂）上,研究分析推测,树正断裂与虎牙断裂存在连接的可能性.     

基于激发振幅成像条件的探地雷达逆时偏移成像

针对基于互相关成像条件的探地雷达（GPR）逆时偏移计算效率低、存储量大及易产生低频假象的不足,本文将激发振幅成像条件应用于GPR逆时偏移成像中.通过在源点电磁波场正向传播过程计算每个网格点的能量密度,并保存最大能量密度的时刻和相应的电磁波场值;在接收点电磁波场逆向传播过程提取每个网格点最大能量密度时刻及对应的电磁波场值,并利用保存的最大能量源点电磁波场及走时做归一化,从而获得了依赖反射系数成像剖面,避免了源点正向传播电磁波场的存储和重建.此外,为了提高电磁波场的模拟精度,采用了基于三角形剖分的时间域有限单元法（FETD）计算电磁波正向和逆向传播过程.最后通过模型试算表明：激发振幅成像条件相比于归一化互相关成像条件,成像结果低频噪声更弱,空间分辨率更高,计算效率提高了近2倍.     

多分量地震数据的成像技术

从水平叠加成像、叠前时间偏移以及叠前深度偏移三个方面总结了多分量地震成像技术的发展现状.在水平叠加成像方面,分析了转换波与纵波在道集抽取方面的差异,总结了常用的转换点计算公式,着重对比了由炮检坐标映射地下的转换点以及由地表的网格节点映射地下的反射点两种共转换点道集抽取方式各自的优缺点以及应用化程度.概述了各向同性与各向异性叠前时间偏移技术的基本原理,总结了多分量偏移技术发展以及配套软件的工业应用现状,并对最近发展的层匹配多分量偏移技术进行了介绍.最后,从射线理论以及波场延拓理论的角度总结了多分量叠前深度偏移的发展现状与存在的问题,介绍了标量偏移与矢量偏移的差异,并提出了深度域速度建模存在的问题.     

波动方程偏移成像阴影的照明补偿

受地下复杂构造和地震数据采集系统的影响,使地震波对地下目标的照明出现不均匀性,地震采集系统难以有效地获取地下某些目标的反射信息,进而使数据偏移成像在这些目标体上出现成像阴影. 根据波场和Green函数的窗口Fourier框架展开,利用角度域波动方程偏移成像和波动方程照明分析,并结合波动方程反演理论,提出一种角度域波动方程偏移成像阴影照明补偿方法. 这种补偿方法能同时考虑地震数据采集系统和波场传播路径对偏移成像的影响,消除复杂构造区的偏移成像阴影,改进波动方程叠前深度偏移成像在复杂构造区的成像效果.     

3D hydrocarbon migration by percolation technique in an alternate sand–shale environment described by a seismic facies classified volume

Modelling hydrocarbon migration in complex depositional environments is a difficult task. This paper illustrates a workflow that has been developed in order to make use of information at seismic resolution for migration modelling purposes. After a regional identification of the main seismic sequence boundaries and systems tracts, the first step of the workflow consists in a semi-automatic classification of the sand and shale prone seismic facies that are interpretable in the seismic volume. A software based on supervised neural network techniques and textural seismic attributes supports volumetric classification. Each class represents a different facies with specific petrophysical properties (threshold pressure, porosity, irreducible water saturation, etc.), assigned according to concurrent sedimentological studies; the result is a 3D lithofacies model. Petroleum system modelling is performed on a 3D regional model up to the calculation of hydrocarbon quantities expelled from the source rock. Then migration modelling is performed on the smaller area covered by the 3D lithofacies model. Invasion percolation approach has been chosen because it allows to perform migration modelling at a scale that is small enough to maintain a sufficient detail of the channels' shape and of their connections. A probabilistic approach allows to estimate charge risk in new prospects and to check modelling consistency. This workflow has been applied in a deep water setting in West Africa, characterized by an interconnected channel system, where a number of prospects had to be evaluated. A well was drilled in the area prior to this study, resulting dry in spite of being located in a position where the source rock is present and is deemed to have expelled interesting amounts of hydrocarbons. This study has shown that hydrocarbons expelled from the source appear to be deviated laterally by the presence of a local seal and therefore do not reach the channel system in the well location.     

Calibrating fault seal using a hydrocarbon migration model of the Oseberg Syd area,Viking Graben

It is widely acknowledged that fault rock capillary properties are important in controlling the distribution of hydrocarbons in sedimentary basins, and methods exist for predicting the capillary seal capacity of prospect bounding faults. However, fault seal capacity is rarely incorporated into models of hydrocarbon migration. This paper presents the results of migration modelling of the Oseberg Syd area of the Viking Graben incorporating fault rock capillary properties. Seal capacity is calculated in the model as a function of Shale Gouge Ratio (SGR), i.e. the percentage shale in the sequence moved past a point on a fault. Over 3000 model realisations were run for different SGR to fault seal capacity relationships and the calculated hydrocarbon distributions were compared with known distributions. Realisations were ranked according to the closeness of fit between model and actual oil–water contacts for 7 traps. The best-fit to all 7 traps was provided by realisations with significant seal capacity at SGR values greater than ca. 0.2; a value which is in agreement with an independently derived fault-by-fault calibration between SGR and seal capacity. The level of fill calculated for an individual trap is extremely sensitive to minor changes in the seal capacity relationship because it is controlled not only by the seal capacities of the faults that bound the trap, but also by the pattern of fill–spill of upstream traps. This sensitivity to minor changes in seal capacity introduces large uncertainties when fault seal capacity relationships are used in a predictive mode and emphasises the requirement for migration modelling in fault seal prospect evaluation.     

康山“古油藏”讨论之三——康山“沥青脉”的成因

通过对康山固体可燃脉体产状、脉石矿物性质、构造发展史的综合分析,认为其成因很可能是下寒武统荷塘组中的软沥青和有机质,在加里东运动期间,由于区域应力体系的变化而爆炸运移形成的。康山脉石矿物是沥青和有机质,不是煤和无机物。沥青的源岩为下寒武统荷塘组富有机质的黑色泥岩、硅质泥岩、硅质岩。康山脉中的固体沥青和有机质,当初挤入时应呈塑性流动状态,康山沥青系由石油经热演化而成。     

基于偏微分方程的定向插值在偏移成像中的应用

对于射线类偏移成像来说,求解射线追踪系统中所涉及的属性值不在网格节点上的插值计算问题是一个非常重要的环节,它影响到求解走时、路径和振幅信息的计算效率和精度,进而影响到整个偏移成像的质量和效率.本研究根据速度模型的空间梯度特点,考虑被插值点处速度的梯度在横向和纵向的分布特征,构建基于速度梯度空间变化的偏微分方程算法,将近...     

地震勘探基于波场分离的逆时偏移去噪方法

基于双程波动方程的逆时偏移（RTM）具有原理简单、无倾角限制、可以适用于速度任意变化的模型,并具有对各类波正确成像等优点,是当今最好的偏移方法之一.本文阐述了逆时偏移存在的缺陷并分析了低频噪声的产生机制,重点探讨了使用波场分离的逆时偏移去噪方法,并通过模型的试算证明了该方法的有效性.