The objective of most seismic time-lapse studies is to detect rock-property changes in a subsurface formation caused by fluid withdrawal or injection, often by comparing seismic reflection images of the subsurface before and after the operation. Because rock-property changes can affect the amplitudes of seismic reflection events associated with the boundaries of the formation, amplitude anomalies are the usual target of time-lapse experiments. Sometimes, however, particularly in harder, less porous rocks, a seismic amplitude anomaly can be relatively small and difficult to detect. There is a secondary time-lapse effect, however, which may be detectable even in the absence of a significant reflectivity anomaly: the time delay of reflections from layers beneath a formation whose wave propagation velocity has been altered by the pore-fluid change. We have developed a near-surface correction technique for land data, which we call joint raypath interferometry, to specifically enhance and detect small time delays between corresponding events on two or more comparable time-lapse seismic images. We demonstrate the technique first on a numerical model, and then on an actual time-lapse field survey in which a reflection amplitude anomaly is difficult to detect.

中文翻译：

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使用射线路径干涉仪进行延时检测

大多数地震时移研究的目的通常是通过比较手术前后地下的地震反射图像，来检测由流体抽出或注入引起的地下地层的岩石属性变化。由于岩石属性的变化会影响与地层边界相关的地震反射事件的幅度，因此幅度异常是延时实验的常见目标。但是，有时，特别是在较硬，多孔性较小的岩石中，地震振幅异常可能相对较小且难以检测。但是，存在次要的时移效应，即使没有明显的反射率异常也可以检测到：地层下方各层的反射的时间延迟，该层的波传播速度已因孔隙流体的变化而改变。我们已经开发了一种用于陆地数据的近地表校正技术，我们将其称为联合射线路径干涉测量法，以专门增强和检测两个或多个可比较的时移地震图像上相应事件之间的小时间延迟。我们首先在数值模型上演示该技术，然后在难以检测反射振幅异常的实际延时田野调查中进行演示。