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为了研究地震速度,在钻孔中使用垂直地震检波器排列已有好多年了。垂直地震剖面(VSP)的技术发展证明了,利用反射波就有可能减少常规地震数据解释和在井中实际观测之间的差距。垂直排列(如VSP中那样)所记录的反射波一般有较高的信噪比和较大的带宽,这就容易与多次波分开。新的连续垂直排列(CVA)技术可将几个井中的垂直排列与地面附近排成震源点线结合在一起。其结果就可获得类似于常规地震测量的那种多次复盖地震测线,但它能保持着垂直排列观测的特点。本文借助于理论上的一些依据、模型研究以及深400米间距为500米的九个钻孔获得的野外实例,讨论了这种新技术的可能性。新的资料采集和处理技术(主要是迭前偏移)已得到发展。连续垂直排列法仍还处于发展阶段,但它已为困难地区的详细勘测提供了新的可能.
For seismic velocities, vertical geophones have been used in boreholes for many years. The technical development of vertical seismic profiles (VSPs) proves that the use of reflected waves makes it possible to reduce the discrepancy between the interpretation of conventional seismic data and the actual observation in the well. Reflected waves recorded vertically (as in VSPs) typically have a higher signal-to-noise ratio and a larger bandwidth, which is easier to separate from multiple waves. The new continuous vertical alignment (CVA) technique combines the vertical alignment of several wells with line-of-origin lines near the ground. The result is a multi-cover seismic survey similar to conventional seismic surveys, but it maintains the characteristics of vertical alignment observations. This article discusses the possibilities of this new technique with some theoretical bases, model studies, and field examples from nine boreholes located 400m deep and 400m apart. New data acquisition and processing techniques (mainly pre-stack migration) have been developed. The continuous vertical arrangement is still in its development phase, but it has provided new possibilities for detailed surveys in difficult areas.