Comparison of AVO indicators: A modeling study
Comparison of AVO indicators: A modeling study
复制标题
DOI：
10.1190/1.1443572
复制
发表时间：
1994-12
期刊：
影响因子：
3.3
通讯作者：
J. Castagna;Steven W. Smith
中科院分区：
文献类型：
--
作者：
J. Castagna;Steven W. Smith
利用全波形声波、偶极声波和常规测井设备和/或在实验室中采集了来自邻近页岩、盐水砂和气砂的25组速度和密度测量值。这些数据提供了理论上的盐砂上的页岩和气砂上的页岩的P波和S波垂直入射反射系数（Rp和Rs）、AVO截距（A）、AVO梯度（B）、AVO指标Rp-Rs（反射系数差）和A * B（AVO产品）。在碎屑岩地层中，反射系数差比AVO产品更具有普遍性。对于盐砂上的页岩反射，平均Rp-Rs趋于零，且随深度相对不变。不管气砂阻抗如何，对于储层质量气砂反射，页岩的Rp-Rs总是负值，并且比相应的盐水砂反射的Rp-Rs更负。相比之下，对于含气砂岩，AVO产品可能为正、接近零或为负，这取决于与上覆页岩的阻抗对比。这些测量也证实了R p - R s可以很好地近似为A和B的简单线性组合。
A worldwide collection of 25 sets of velocity and density measurements from adjacent shales, brine sands, and gas sands was acquired with full-waveform sonic, dipole sonic, and conventional well logging devices and/or in the laboratory. These data provide theoretical shale over brine-sand and shale over gas sand P-wave and S-wave normal-incidence reflection coefficients (R p and R s ), AVO intercepts (A), AVO gradients (B), the AVO indicators R p - R s (reflection coefficient difference), and A * B (AVO product). The reflection coefficient difference is found to be a more universal indicator than the AVO product in clastic stratigraphic intervals. For shale over brine-sand re flections, the average R p - R s tends to be near zero and relatively invariant with depth. Irrespective of gas-sand impedance, R p - R s is always negative for shale over reservoir quality gas-sand reflections and more negative than for the corresponding brine-sand reflections. In comparison, the AVO product may be positive, near zero, or negative for gas-sands depend ing on the impedance contrast with the overlying shale. These measurements also verify that R p - R s is well approximated by a simple linear combination of A and B.