SEISMIC FACIES ANALYSIS BASED ON 3D MULTI-ATTRIBUTE VOLUME CLASSIFICATION, DARIYAN FORMATION, SE PERSIAN GULF

Interpretation of recently acquired 3D seismic data from the adjacent Sirri C and D oilfields in the SE Persian Gulf indicates that a 3D interpretation of seismic facies is crucial to resolve the internal stratal geometries of the Aptian Dariyan Formation. This carbonate formation passes southward into the Shu'aiba Formation, a prolific reservoir rock of similar facies in the UAE. Lack of exposures and limited cored intervals have forced reliance on the seismic data for evidence of the depositional environment and the internal architecture of potential reservoir rocks. The progradational nature of the Dariyan Formation and the occurrence of carbonate build‐ups within it make this stratal geometry complex. The complex internal heterogeneity of the build‐ups and presence of seismic noise make mapping of the build‐ups in 3D space using conventional seismic interpretation tools difficult, despite the availability of high‐quality 3D seismic data covering the area. The high quality seismic and limited well data from this field is one of the few datasets of this kind presented in the literature. A procedure for the hierarchical multi‐attribute analysis of seismic facies using Paradigm's Seis Facies software is used in this study to provide a 3D interpretation of the stratal patterns. Principal component analysis reduces the noise and redundant data by representing the main data variances as a few vector components in a transformed coordinate system. Cluster analysis is performed using those components which have the greatest contribution to the maximum spread of the data variability. Six seismic attribute volumes are used in this study and the result is a single 3D classified volume. Important new information obtained from within the Dariyan Formation gives new insights into its stratigraphic distribution and internal variability. This method of processing seismic data is a step towards exploring for subtle stratigraphic traps in the study area, and may help to identify exploration targets.     

海底天然气渗漏地震探测方法的研究进展

海底天然气渗漏可以指示沉积层中的烃类聚集带，渗漏出的大量气体（主要是甲烷）还可能影响全球的气候变化。此外，与海底渗漏相关的浅层气改变了海底沉积物的土工性质，可能对海底工程构成威胁。因此对海底天然气渗漏进行研究意义重大。在海底渗漏探测方面，地震是一种有效的方法，它不仅能反映深部构造，为海底渗漏提供气体来源和运移通道信息；而且还可以直接用来寻找渗漏相关特征，为海底观测和取样提供依据。在地震剖面上，与海底天然气渗漏相关的浅层气表现为声混浊、声空白、亮点、多次波、速度下拉、气烟囱等特征，泥火山、泥底辟表现为隆起的地震透明带，而麻坑则表现为“V”字形截面和半透明状地震混浊。     

二维地震过障碍观测系统模式及其参数设计

在二维地震勘探中,为了避免因地表障碍物使地震反射剖面出现间断现象,需要改变观测系统设计,跨越障碍物(江河、城镇等),以保证反射同相轴能连续追踪对比。在以往地震勘探中,有时因过障碍观测系统设计不合理,不但增加勘探费用,而且影响采集质量。因此只有科学合理地设计过障碍观测系统模式和参数,才能保证地震测线顺利通过障碍物,得到较好的障碍物下方的地震资料并降低勘探成本。为此本文在调查和研究大量野外实际的过障碍观测系统的基础上,总结归纳成三大类过障碍观测系统模式,并分析其特点和应用范围。采用图解法,推导出主要模式的跨越宽度、最小炮检距及最大炮检距等参数公式。采用这套过障碍观测模式不仅可以得到和障碍区两侧等质量的地震资料,而且可以有效地降低勘探成本。     

基于模型正演的叠前深度偏移

川西龙门山前缘构造非常复杂，逆掩推覆构造带构造形变强烈，构造幅度大，地层倾角陡，断块发育，波场复杂，速度横向变化大，常规叠后时间偏移处理成像效果较差。文章将地震资料模型正演技术应用到叠前深度偏移，探讨了一种有助于川西龙门山前缘逆掩推覆构造地震资料精确成像技术。先利用已有地震资料解释成果，根据地质任务建立二维地质模型，在此基础上进行射线追踪、模拟出单炮地震记录和自激自收剖面，从而对观测系统的最大炮检距、道间距等参数进行论证的一些实用方法，这些方法对地震资料采集具有很好的指导作用；然后根据这些结果，再比较准确地进行叠前深度偏移的初始速度模型建立，从而达到了复杂地表下复杂构造精确成像的目的。     

频域吸收边界条件的构造理论

在频域中推导了适用于差分类数值方法的吸收边界条件的构造方法，并通过选取不同参数导出了几种现有的吸收边界条件。在计算了一般形式的吸收边界条件的反射系数之后，提出了一种简单实用的自适应吸收边界条件。     

浅谈天馈线电压驻波比对微波电路的影响

天馈线电压驻波比是微波电路运行的重要指标，通过典型事例来阐述天馈线电压驻波比的劣化对微波电路的影响，并根据多年实践经验提出天馈线维护需注意的事项。     

地震属性神经网络油气模式识别技术及其在东海的应用

神经网络油气模式识别技术是综合利用地震属性进行油气预测的技术之一 ,它首先通过计算获得多种地震属性 ,综合分析找出对储层油气比较敏感的地震属性组合 ;然后收集油气井与非油气井的井旁道地震属性 ,组成学习样本并进行神经网络学习 ;最后利用学习结果对储层进行油气预测。该技术在东海某工区的应用结果表明 ,振幅统计类和复数道统计类地震属性是对该地区储层油气最敏感的地震属性组合。神经网络油气模式识别技术可以作为东海地区储层油气预测的一种手段。     

爆破时差对地震效应的影响

通过对一次爆炸量为65t的硐室大爆破地震效应的实测,得出了一些有价值的结论。     

用有限带宽反射波波形分析法进行储层横向预测

以正演地震模拟为基础的有限带宽反射波渡形分析法是一种新的储层横向预测方法。首先利用波形分解确定地震反射层的地质属性,找出能反映岩性变化的反射波波形特征参数;然后,采用多元数据聚类分析和灰色系统理论完成储层横向的预测。文中以预测江苏 J 凹陷 F 构造上阜二段生物灰岩分布及厚度横向变化为例,简述了反射波波形分析的全过程。预测结果已为钻探证实。     

Optical analysis of crack tip stress fields: a comparative study

Four optical techniques for evaluating stress intensity factors in opaque specimens are described in outline, and compared for both an artificial crack and a fatigue crack. The results are compared to a standard solution for the geometry considered. All the techniques gave acceptable results over a range of stress levels and crack lengths. The methods of caustics and strain gauges were less good, whilst photoelasticity gave consistent results over a wide range of stress levels. Comments on the ease of application and the resource implications are also made in order to assist practitioners.