弹性阻抗方程中的K值选取问题探讨

Discussion on the selection of K in Elastic impedance equation

(1.中国石油化工股份有限公司中原油田博士后工作站,河南濮阳457001;2.中国石油化工股份有限公司中原油田分公司物探研究院,河南濮阳457001;3.中国石油勘探开发研究院,北京100083;4.中国石油化工股份有限公司中原油田分公司信息中心,河南濮阳457001;5.中国石油大港油田测试公司,天津大港300280)

Su Yun, Postdoctoral Workstation of Zhongyuan Oilfield Company,SINOPEC,PuYang 457001,China

叠前弹性阻抗反演需要计算弹性阻抗曲线,而常规计算均是基于K值为常数这一假设条件,与实际的K值不符,因而导致弹性阻抗曲线计算以及后续岩性参数提取时存在偏差。提出了利用K值扫描法来优化K值选取的方法,其原理是:选用不同的K值分别计算弹性阻抗,然后将其转化为反射系数,最后求取转化得到的反射系数与精确的Zoeppritz方程计算的反射系数之间的差,两者差值最小时的K值即为最佳。理论模型及实际测井曲线应用结果证明该方法能够确定最优K值。

Pre-stack elastic impedance inversion involves the calculation of elastic impedance curve,while the conventional calculations are based on the assumption that K is a constant,but the assumption does not match with the actual situation,which results in the deviation in calculating elastic impedance curve and extracting the lithology parameters.Therefore,we introduced K scan method to optimize the selection of K.The method includes three steps.Firstly,different K was selected to compute elastic impedance.Then,the elastic impedance was transformed into reflectivity.Finally,the difference of the reflectivity obtained from the second step and accurate Zeoppritz equation was calculated,and the minimum difference was the optimal K.application on theoretical model and actual logging curve show that the method can be used to select best K and has good applicability.

10.3969/j.issn.1000-1441.2011.04.006