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研究横波分裂可以提供有关裂隙走向、裂隙密度以及裂隙其他参数的信息,也可以提供原地岩体内成行排列的包体的信息。这些信息在储层特性及其他油气开采的应用上是重要的。裂隙密度通常用两种分裂横波间的时间延迟测量出横波各向异性百分比来推断。储层也许太薄,以致于不能形成可辨别的时间延迟,因此在反射测量或垂直地震剖面的常规波至时分析中,储层的时间延迟也许是不可分辨的。我们研究横波振幅与炮检距的关系(AVO),目的是看一看他们能否提供确定薄储层各向导性参数的更为可行的方法。反射横波振幅随入射角变化的特性是在简单的两层模型中研究的。针对第二层(代表的某一储层)含水裂隙及干裂隙的某一横波各向异性百分比的范围,计算横波AVO的变化,用以研究关于储层性质的特征信息能否从横波AVO特征中提取出来。就薄裂隙而言,横波AVO曲线对各向异性及裂隙含量的变化敏感。有关裂隙含量的大部分信息包含于大炮检距的反射资料之中,它说明在井间监视提高石油采收率方面的可应用性。横波AVO的变化也许由于采集系统而畸变。有关百分各向异性的大部分信息,包含在近垂直入射的反射横波的振幅中。回顾了垂直入射反射振幅法,提出了一种确定其在不同储层环境下可行性的简单图解法。
Studying shear-wave splitting can provide information on fracture strike, fracture density, and other parameters of fractures, as well as information on inclusions arranged in rows within the in situ rock mass. This information is important for reservoir characterization and other oil and gas exploration applications. Fracture density is usually inferred by measuring the percentage of shear wave anisotropy with the time delay between two types of split-wave. The reservoirs may be too thin to form a discernable time delay, so reservoir time delays may be indistinguishable in conventional wave-to-time analysis of reflectance measurements or vertical seismic profiles. We study the relationship between shear amplitude and offset (AVO) to see if they provide a more viable method of determining the anisotropy of thin reservoirs. The characteristics of the amplitude of the reflected transverse waves with respect to the angle of incidence are studied in a simple two-layer model. For a range of shear wave anisotropy percentage of the water-bearing fractures and dry fractures of the second layer (representing a certain reservoir), the variation of the shear wave AVO is calculated to investigate whether the characteristic information about reservoir properties can be derived from the shear wave AVO features In the extracted. For thin fractures, shear wave AVO curves are sensitive to changes in anisotropy and fracture content. Much of the information on fissure content is contained in offset information at offsets, which illustrates the applicability of crosswell monitoring for enhanced oil recovery. The change in shear wave AVO may be distorted by the acquisition system. Much of the information on percent anisotropy is contained in the amplitude of a reflection wave that is incident nearly vertically. The vertical incident reflection amplitude method is reviewed and a simple graphical method to determine its feasibility in different reservoir environments is proposed.