基于频谱分解的测井曲线标准化方法

摘要

Well log normalization can effectively reduce systematic errors during logging data interpretation, therefore has been used to improve the accuracy of formation parameter calculation and reservoir prediction.However,lack of a stable marker bed makes the marker-based normalization method too rigid to be adapted to continental sedimentary sequences with rapid variation of lithology.This paper analyzes the geological meaning of spectral decomposition, determines the contributions of different cycles to sedimentary formations, and then regards the superimposed formation of low-frequency cycles which represents the background values of formation as a macro marker bed with stable lateral distribution.The extreme value of low-frequency component was selected as characteristic value and the marker bed values were determined through trend surface analysis.Then translation correction and scale correction were carried out on the low-frequency and high-frequency components of the curves.Finally, log normalization can be achieved.This method had been applied to the normalization of logs of the Putaohua Formation in Daqing central uplift in Songliao Basin, and the correlation coefficient of core porosity and normalized curves was significantly higher than that of core porosity and original curves.This demonstrates that the log normalization method based on spectrum decomposition can be effectively applied to the continental sequences without stable marker beds.%测井曲线标准化可有效消除测井资料的系统误差,是提高储层参数计算和预测精度的关键性基础工作.由于缺乏稳定标准层,基于标准层的曲线标准化方法难以适用于岩性变化频繁的陆相沉积地层.文章从频谱分解的地质含义入手,分析不同周期旋回对沉积地层的贡献,将反映沉积地层“背景值”的低频旋回叠加地层视为一套横向稳定分布的“宏观标准层”.优选曲线低频分量的极值作为特征值,结合空间趋势面分析技术确定标准值,对曲线低频分量、高频分量分别进行平移校正和比例校正,进而实现曲线的标准化.应用该方法对松辽盆地大庆长垣南部葡萄花油层测井曲线进行实际处理,岩心孔隙度与标准化后曲线的相关系数明显高于标准化前曲线,从而证明基于频谱分解的曲线标准化方法能够有效地应用于标准层缺乏的陆相沉积地层.