零井源距VSP初至旅行时反演

Inversion of first arrival time of zero-offset VSP data

本文在Byun反演各向异性参数方法的基础上,将最小平方反演技术用于零井源距VSP初至旅行时反演,以求取层速度和地层深度。文中给出了求解地层参数的准确计算公式。该方法的特点是在迭代反演之后进行相似性分析,将迭代反演的结果作为相似性分析的初值,然后根据最小均方误差求出地层参数的准确值。对理论模型和实际资料的计算表明,该方法是有效的。相似性分析可以部分地克服上层参数计算带来的累积误差,提高反演的精度。

Having referred to Byun's method for the inversion of anisotrop- ic-medium parameter, I apply least-square inversion technique to the inversion of first arrival time of zero-offset VSP data so as to solve for interval velocity and formation depth. Formula for correctly cal- culating formation parameter is given. This method is characterized by (1) making similarity analysis after iterative inversion, (2) using iterative inversion result as the initial value of the similarity analysis and (3) solving for correct formation parameters with the use of least mean square error. Theoretical and practical results prove this method effective. The similarity analysis can partly remove the accumulative error caused in calculating the parameters of overlying formations, thus improving inversion accuracy.