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弹性波阻抗及相关技术是以二项AVO方程和三项AVO方程为基础的,它的有效性在世界范围内的许多沉积盆地都得到了验证。在过去的几年中,大偏移距的数据采集使得入射角普遍大于30°,因此必须用三项AVO方程来解决储层流体和岩性识别问题。在入射角小于30°时,所有的线性弹性波阻抗方程都能给出可靠的结果,当入射角大于这一角度时,某些非线性弹性波阻抗方程也能给出理想的结果。然而,由非线性弹性波阻抗获得弹性参数并非易事,因为这需要进行一些复杂的数学变换。到目前为止,只有扩展弹性波阻抗能够适用于所有的入射角度,而在sin2θ域还没有一种能够用于大角度的线性弹性波阻抗。本文提出了另外一种线性弹性波阻抗——大角度弹性波阻抗(FEI)。理论模型和实际数据都证明FEI是大角度寻找油气的有力属性。
Elastic wave impedance and related techniques are based on the Binomial AVO equation and the three AVO equations and their validity has been validated in many sedimentary basins around the world. Over the last few years, data acquisition at large offsets has generally been done with incidence angles greater than 30 °, so three AVO equations must be used to solve reservoir fluid and lithology identification problems. When the incident angle is less than 30 °, all the linear elastic wave impedance equations can give reliable results. When the incident angle is larger than this angle, some nonlinear elastic wave impedance equations can also give ideal results. However, obtaining elastic parameters from nonlinear elastic wave impedance is not an easy task as it requires some complex mathematical transformation. So far, only the extended elastic wave impedance can be applied to all angles of incidence, but there is no linear elastic wave impedance that can be used for large angles in the sin2θ domain. In this paper, another kind of linear elastic wave impedance - high angle elastic wave impedance (FEI) is proposed. Both the theoretical model and the actual data prove that FEI is a powerful attribute for finding oil and gas in large angles.