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本文基于目的层P波反射时差的方位角变化提出了一个确定裂缝方位的算法。特定目的层底面的正交测线间的微分时差揭示:在偏移距固定时,cos2φ随测线以裂缝走向为测量标准的方位角φ而变。四条相交测线的组合可用于确定裂缝走向。这四条测线组成两个正交对,通过分析两个对应对微分时差的交会图可以确定裂缝走向。为使确定的时差之差可靠,通常要求偏移距-深度比等于1.0或更大(可高达1.5)。方法的敏感性会由于目的层顶面处的低/高阻抗差而进一步提高,但却又会由于高/低阻抗差大大地降低。该方法可能对不同时期在同一地区反复测量的海上勘探特别有用,在这些地区往往无法获得连续的方位角覆盖。一个北海的数据集被用于说明该方法。
In this paper, we propose an algorithm to determine the fracture orientation based on the azimuthal variation of P-wave reflection time-lapse in the target layer. The differential time difference between the orthogonal test lines at the bottom of a particular target layer reveals that cos2φ varies with the strike of the test line at azimuth φ of the measurement standard at offset offset. The combination of four intersecting lines can be used to determine the fracture direction. The four lines form two orthogonal pairs and the fracture direction can be determined by analyzing two cross plots corresponding to the differential time difference. To make sure the difference between the determined time differences is reliable, it is often required that the offset-depth ratio be equal to 1.0 or greater (up to 1.5). The sensitivity of the method is further increased by the low / high impedance difference at the top of the target layer, but again greatly reduced due to the high / low impedance differences. This method may be particularly useful for offshore surveys that repeatedly measure in the same area over different periods of time, where continuous azimuthal coverage is often not available. A North Sea dataset is used to illustrate this approach.