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调谐是薄层顶、底反射之间的干涉对转换反射波振幅的影响。对于油柱覆盖在盐水之上的均质砂岩油藏,其顶部反射与油水界面反射之间的干涉是油柱高的函数。如果油水界面上下的砂岩特征不改变,那么油水界面的SS、PS和SP反射系数比PP反射系数小。这就可以推导出油藏的PP和PS有效反射系数的解析表达式,包括油柱内所有P波多次波。对于给定的炮检距,由于PPPS反射的射线路径不对称,油柱内PPPP反射垂直界面的波矢量分量比PPPS反射垂直界面的波矢量分量要大。因此,对于确定油柱高度,PPPS反射比PPPP反射更有用,尤其在炮检距范围较宽时更好。 Rutherford和Williams方案是对上覆泥岩的含烃砂岩油藏的AVO响应进行常规分类。第1类砂岩的法线入射声阻抗高于上覆泥岩的声阻抗;第2类砂岩具有与上覆泥岩几乎相同的声阻抗;第3类砂岩的声阻抗低于上覆泥岩的声阻抗。对这三类砂岩计算的合成炮道集是油柱高度的函数,表明将PPPP振幅与PPPS振幅结合绘制成调谐轨迹图,可用于确定油柱高度。该方法对于属于第1类、第2类AVO的油藏最灵敏,因此在第1类、第2类油藏的AVO分析中有用,而对传统的AVO指示(已发展为第3类油藏)并不起多大作用。这些结果表明海洋环境下炮检距范围较宽时记录的横波是有用的。
Tuning is the effect of the interference between the top and bottom reflections on the amplitude of the converted reflected wave. For homogeneous sandstone reservoirs with oil columns overlying brine, the interference between the top reflection and the oil-water interface reflection is a function of the height of the oil column. If the sandstone features above and below the oil-water interface do not change, then the SS, PS and SP reflectance coefficients at the oil-water interface are smaller than the PP reflection coefficients. This leads to an analytical expression for the effective reflection coefficient of PP and PS in the reservoir, including all P-wave multiples in the oil column. For a given offset, due to the asymmetric ray path reflected by the PPPS, the wave vector component at the PPPP reflection vertical interface within the column is larger than the wave vector component at the PPPS reflection vertical interface. Therefore, PPPS reflections are more useful than PPPP reflections to determine column height, especially when the offset range is wide. The Rutherford and Williams schemes routinely classify the AVO response of hydrocarbon-bearing sandstone reservoirs with overlying mudstone. The acoustic input impedance of the first type sandstone is higher than the acoustic impedance of the overlying mudstone. The second type sandstone has almost the same acoustic impedance as the overlying mudstone. The acoustic impedance of the third type sandstone is lower than the acoustic impedance of the overlying mudstone. The synthetic shot set calculated for these three types of sandstone is a function of the height of the oil column, indicating that combining the PPPP amplitude with the PPPS amplitude is plotted as a tuned trajectory that can be used to determine the height of the oil column. This method is most sensitive to reservoirs belonging to Type 1 and Type 2 AVO and is therefore useful in AVO analysis of Type 1 and Type 2 reservoirs and to conventional AVO indications (developed as Type 3 reservoirs ) Does not contribute much. These results show that shear waves recorded in the wide range of offsets in the marine environment are useful.