小尺度体反射系数近似公式研究

Approximate formula of reflection coefficient for small-scale body

AVO技术经过几十年的发展已成为石油勘探中的一种重要技术,针对非均质性油气藏的储层预测,AVO方法具有其他方法不可替代的作用。应用波动方程差分数值解方法,研究了横向变速小尺度体的AVO特征,讨论了横向小尺度体的宽度和速度变化对反射系数的影响,然后应用最小二乘法原理拟合出了反射系数变化量与小尺度体宽度和速度的数学表达式,并结合测试数据进行了误差分析。结果表明:拟合公式与测试数据之间的误差小于0.5%,较好地反映了小尺度体宽度及岩石弹性参数对反射系数的影响。该公式可为利用AVO异常来预测小尺度体的宽度和岩石弹性参数奠定基础,同时也为下一步横向小尺度变速情况下反射系数精确表达式的验证提供保障。

AVO technology has become an important means for petroleum exploration after decades of development. In the aspect of finding heterogeneous reservoir, AVO technique plays an irreplaceable role compared with other methods. This paper analyzed the AVO characteristics of the lateral variable small-scale body through wave equation finite difference numerical solution method, and discussed the influences of size variation and speed change of lateral small- scale body on the reflection coefficients. The least square method was used to fit the relations of the reflection coefficient difference with scale body width and scale velocity. The result of error analysis combined with test data shows that the error between fitted formula and the experiment data is less than 0.5%, which indicates the influence of small-scale body width and elastic parameters on the reflection coefficient. The formula can be used to predict the size of small-scale body and rock elastic parameters through AVO abnormalities, and provide protection for the validation of the exact expression of reflection coefficient with velocity change of transverse small-scale body.