Sensitivity of the elastic anisotropy and seismic reflection amplitude of the Eagle Ford Shale to the presence of kerogen          下载免费PDF全文

Colin M. Sayers  Shiguang Guo  Josimar Silva 《Geophysical Prospecting》2015,63(1):151-165

The Eagle Ford Shale of Central and South Texas is currently of great interest for oil and gas exploration and production. Laboratory studies show that the Eagle Ford Shale is anisotropic, with a correlation between anisotropy and total organic carbon. Organic materials are usually more compliant than other minerals present in organic‐rich shales, and their shapes and distribution are usually anisotropic. This makes organic materials an important source of anisotropy in organic‐rich shales. Neglecting shale anisotropy may lead to incorrect estimates of rock and fluid properties derived from inversion of amplitude versus offset seismic data. Organic materials have a significant effect on the PP and PS reflection amplitudes from the Austin Chalk/Upper Eagle Ford interface, the Upper Eagle Ford/Lower Eagle Ford interface, and the Lower Eagle Ford/Buda Limestone interface. The higher kerogen content of the Lower Eagle Ford compared with that of the Upper Eagle Ford leads to a negative PP reflection amplitude that dims with offset, whereas the PS reflection coefficient increases in magnitude with increasing offset. The PP and PS reflection coefficients at the Austin Chalk/Upper Eagle Ford interface, the Upper Eagle Ford/Lower Eagle Ford interface, and the Lower Eagle Ford/Buda Limestone interface all increase in magnitude with increasing volume fraction of kerogen.  相似文献   

Retrieval of super‐virtual refraction by cross‐correlation          下载免费PDF全文

Baoping Qiao  Ping Guo  Pu Wang  Tianyue Hu 《Geophysical Prospecting》2015,63(3):552-566

Topography and severe variations of near‐surface layers lead to travel‐time perturbations for the events in seismic exploration. Usually, these perturbations could be estimated and eliminated by refraction technology. The virtual refraction method is a relatively new technique for retrieval of refraction information from seismic records contaminated by noise. Based on the virtual refraction, this paper proposes super‐virtual refraction interferometry by cross‐correlation to retrieve refraction wavefields by summing the cross‐correlation of raw refraction wavefields and virtual refraction wavefields over all receivers located outside the retrieved source and receiver pair. This method can enhance refraction signal gradually as the source–receiver offset decreases. For further enhancement of refracted waves, a scheme of hybrid virtual refraction wavefields is applied by stacking of correlation‐type and convolution‐type super‐virtual refractions. Our new method does not need any information about the near‐surface velocity model, which can solve the problem of directly unmeasured virtual refraction energy from the virtual source at the surface, and extend the acquisition aperture to its maximum extent in raw seismic records. It can also reduce random noise influence in raw seismic records effectively and improve refracted waves’ signal‐to‐noise ratio by a factor proportional to the square root of the number of receivers positioned at stationary‐phase points, based on the improvement of virtual refraction's signal‐to‐noise ratio. Using results from synthetic and field data, we show that our new method is effective to retrieve refraction information from raw seismic records and improve the accuracy of first‐arrival picks.  相似文献   

Point‐spread functions for interferometric imaging          下载免费PDF全文

Kees Wapenaar 《Geophysical Prospecting》2015,63(5):1033-1049

Interferometric redatuming is a data‐driven method to transform seismic responses with sources at one level and receivers at a deeper level into virtual reflection data with both sources and receivers at the deeper level. Although this method has traditionally been applied by cross‐correlation, accurate redatuming through a heterogeneous overburden requires solving a multidimensional deconvolution problem. Input data can be obtained either by direct observation (for instance in a horizontal borehole), by modelling or by a novel iterative scheme that is currently being developed. The output of interferometric redatuming can be used for imaging below the redatuming level, resulting in a so‐called interferometric image. Internal multiples from above the redatuming level are eliminated during this process. In the past, we introduced point‐spread functions for interferometric redatuming by cross‐correlation. These point‐spread functions quantify distortions in the redatumed data, caused by internal multiple reflections in the overburden. In this paper, we define point‐spread functions for interferometric imaging to quantify these distortions in the image domain. These point‐spread functions are similar to conventional resolution functions for seismic migration but they contain additional information on the internal multiples in the overburden and they are partly data‐driven. We show how these point‐spread functions can be visualized to diagnose image defocusing and artefacts. Finally, we illustrate how point‐spread functions can also be defined for interferometric imaging with passive noise sources in the subsurface or with simultaneous‐source acquisition at the surface.  相似文献   

Optimum design and application of non‐traditional tuned mass damper toward seismic response control with experimental test verification          下载免费PDF全文

Ping Xiang  Akira Nishitani 《地震工程与结构动力学》2015,44(13):2199-2220

A variant type of tuned mass damper (TMD) termed as ‘non‐traditional TMD (NTTMD)’ is recently proposed. Mainly focusing on the employment of TMD for seismic response control, especially for base‐isolated or high‐rise structures, this paper aims to derive design formulae of NTTMDs based on two methodologies with different targets. One is the fixed points theory with the performance index set as the maximum magnitude of the frequency response function of the relative displacement of the primary structure with respect to the ground acceleration, and the other is the stability maximization criterion (SMC) to make the free vibration of the primary structure decay in the minimum duration. Such optimally designed NTTMDs are compared with traditional TMDs by conducting both numerical simulations and experiments. The optimum‐designed NTTMDs are demonstrated to be more effective than the optimum‐designed traditional TMDs, with smaller stroke length required. In particular, the effectiveness of the TMDs combined with a base‐isolated structure is investigated by small‐scale model experimental tests subjected to a time scaled long period impulsive excitation, and it is demonstrated that the SMC‐based NTTMD can suppress structural free vibration responses in the minimum duration and requires much smaller accommodation space. Additionally, a small‐scale shaking table experiment on a high‐rise bending model attached with a SMC‐based NTTMD is conducted. This study indicates that NTTMD has a high potential to apply to seismic response control or retrofit of structures such as base‐isolated or central column‐integrated high‐rise structures even if only a limited space is available for accommodating TMDs. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

2014年于田M_S7.3地震序列的频谱特征分析及其前震识别     

郑建常  王鹏  许崇涛  徐芳芳 《中国地震》2015,31(2):253-261

利用新疆区域数字地震台网的波形资料,对2014年2月12日于田MS7.3地震前震和余震序列的频谱特征进行了分析。基于Brune模型,对观测记录进行仪器响应、传播路径和场地响应的校正,使用遗传算法对于田地震序列103次ML≥3.0地震的震源谱进行了反演计算。结果表明:1前震序列的拐角频率相对偏低,扣除地震矩影响后,余震的拐角频率有明显增高的趋势;2距离震中最近的YUT台资料分析显示,于田地震几次前震活动的台站观测谱相对较为独立,与主震以及彼此之间的相关系数均不高;3序列事件和主震的台站观测谱相关系数的变化反映了序列发展的动态破裂过程,相关系数较低的事件基本上偏离了主震破裂区而发生在分支断裂上;4前震的震源谱中存在异常的高频成份。  相似文献   

海南东北部地区地壳地震各向异性特征初步研究     

张慧 《中国地震》2015,31(2):362-371

基于海南省地震台网2000~2013年的区域地震波形数据,用剪切波分裂系统分析方法(SAM)获得了海南琼东北部地区"九五"数字台网中2个台站的剪切波分裂参数。结果表明,快剪切波偏振优势方向代表了原地最大主压应力方向。七星岭台NE方向的快剪切波偏振优势方向与区域水平主压应力场方向不一致,与NE走向的断裂一致,体现了局部构造和局部应力场的复杂性;青山岭NNE向的快剪切波偏振优势方向揭示了NNE走向断裂的构造意义。同时,本研究证实,位于活动断裂上或几条活动断裂交汇部位的台站的快剪切波偏振优势方向与对所选用的小地震起控制作用的活动断裂走向一致,而快剪切波偏振优势方向较为离散则反映了该区域复杂的断裂构造和应力分布特征。  相似文献   

牵引式滑坡推力计算方法研究     

谭福林  胡新丽  张玉明  徐聪  李蕊 《岩土力学》2015,36(Z2):532-538

三峡工程运行期间引发大量库区滑坡地质灾害,由于库区水位及降雨等联合影响,使得牵引式滑坡在库区滑坡中占有相当的比例。通过对库区牵引式滑坡形成机制研究,根据变形破坏模式,把牵引式滑坡分为牵引区（初始滑动区）和被牵引区,分析牵引式滑坡在演化过程中牵引区滑体与被牵引区滑体之间的相互依存关系,针对其相互作用力学特征建立合理的物理和数学力学计算模型,初步推导牵引式滑坡推力计算公式,为抗滑桩设计提供合理的设计推力。以三峡库区朱家店牵引式滑坡为例,在确定被牵引区滑体对牵引区滑体存在推力作用情况下,通过推力计算表明,推导出的公式计算得到牵引区滑体的设计推力比单独计算牵引区滑体设计推力更大,相比将牵引区滑体和被牵引区滑体视为整体计算设计推力更小,说明此方法计算的推力用于抗滑结构设计可以达到既安全又经济的效果,为牵引式滑坡治理设计提供新的思路。  相似文献   

东海陆架盆地雁荡低凸起综合地球物理解释及其成因探讨   总被引：4，自引：0，他引：4       下载免费PDF全文

杨传胜  李刚  栾锡武  杨长清  龚建明  杨艳秋  索艳慧 《地球物理学报》2014,57(9):2981-2992

通过对东海陆架盆地西部地震和重磁资料的综合地球物理解释,对雁荡低凸起展布形态进行了细致刻画,凸起呈NE方向不连续展布于瓯江凹陷和闽江凹陷之间,长约170 km、宽约15~50 km.地震资料揭示雁荡低凸起上广泛发育了侏罗纪与白垩纪地层,厚度约为500~1500 m,展布面积约5000 km²,局部缺失中生界地层.凸起两侧中生代盆地结构差异明显,西侧瓯江凹陷为典型的断陷盆地,东断西超、断裂发育,半地堑、掀斜断块等中生界构造样式发育;东侧闽江凹陷为坳陷型盆地,断裂、火成岩不发育,挤压背斜、断背斜、反转构造等中生界构造样式发育.自由空间重力异常图与剩余重力异常图上,凸起表现为一系列NE向团块状重力高值区,而磁力异常ΔT图上则表现为深部磁场强度低的特征,火成岩影响部位可见磁力高值异常.综合凸起及邻域重磁震、莫霍面深度等地质地球物理资料,认为雁荡低凸起为一元古界组成的古隆起,区别于东部的台北低凸起.同时,结合区域构造演化及沉积特征,推测侏罗纪时期雁荡低凸起与浙闽隆起区可能连为一体,晚白垩世近东西向伸展作用下浙闽隆起发生裂陷进而形成了雁荡低凸起.  相似文献   

地震记录的时间域反褶积、仿真及在地震计方位角相对测量中的应用   总被引：6，自引：2，他引：4       下载免费PDF全文

谢剑波 《地球物理学报》2014,57(1):167-178

介绍了一种用冲击不变法从速度响应平坦地震计二阶传递函数设计得到的递归滤波方法,比用双线性变换得到的递归滤波系数少,因此使用更方便.作者用此方法作了反褶积与仿真的数值实验和实际地震记录的短周期仿真试验,仿真结果与实际仪器记录符合较好;并将此法应用于地震计方位角的相关分析法相对测量,结果与不仿真的相关分析测量相比更接近寻北仪的绝对测量结果.  相似文献   

流变边界层及其对华北克拉通热/地震岩石圈底界差异的意义   总被引：8，自引：5，他引：3       下载免费PDF全文

何丽娟 《地球物理学报》2014,57(1):53-61

二维热传导/对流数值模型显示,纯传导的固体岩石圈与纯对流的流体软流圈之间存在一过渡层,即流变边界层,其间传导与对流共同作用来传递热量.流变边界层厚度主要由软流圈黏性系数（η）控制,而受固体岩石圈厚度及热状态影响很小.随着η从1×10²¹Pa·s降低至1×10¹⁹ Pa·s,流变边界层也随之减薄,流变边界层的厚度与lg（η）成正比. 流变边界层的存在是造成热岩石圈与地震岩石圈厚度差异的重要因素. 全球典型克拉通岩石圈的对比结果表明,地震岩石圈厚度普遍大于热岩石圈厚度,二者的差异多数在70~90 km,很好地验证了流变边界层的存在. 研究发现二者的差异在华北克拉通自西向东逐渐减小：由西部鄂尔多斯的约80 km减少至渤海湾盆地的约20 km. 反映出华北克拉通岩石圈下部流变边界层厚度自西向东减薄,意味着软流圈黏性系数自西向东逐渐降低.这可能与中生代太平洋俯冲脱水形成的低黏大地幔楔有关,从一侧面印证了太平洋俯冲对华北克拉通破坏的影响.  相似文献