利用快速匹配追踪子波分解技术识别强反射下砂岩储层

Application of Fast Matching Pursuit Wavelet Decomposition Technique in Identifying Sandstone Reservoirs under Strong Reflection

大庆油田长垣P区扶余油层T2界面上、下泥岩存在较大的波阻抗差,出现连续强反射低频同相轴;同时,由于强界面下部薄砂岩的相互叠置,造成反射轴波形进一步变宽,主频降低,完全淹没了界面下FⅠ1-1(扶余油层Ⅰ油组1-1小层)目的层的砂岩信息,阻碍了薄砂岩储层的有效预测。为去除强反射,利用基于雷克子波的快速匹配追踪(MP)分解来进行分离、削弱T2界面产生的强反射背景,突显覆盖在其中的砂岩储层信息。快速MP子波分解技术利用频率和尺度两参数动态扫描提高检索效率,并对连续2次残差能量差设阈值提高迭代效率,实现对原子库中的时频原子快速匹配。结合目标区实际地质情况,设计强反射背景下单层砂及薄互层砂岩的二维地质模型进行正演,再应用快速MP子波分解技术进行子波分解后重构以突出砂岩特征。该技术在大庆油田长垣P区勘探过程中取得了较好的效果。

In the Changyuan Fuyu Reservoir of Daqing Oilfield,there existed higher wave impedancedifference between the upper and lower mudstone on theτ2interface,which was the low frequency event with continuous strong reflection.Also due to thin sandstone overlapped each other below the strong interface,it resulted in the event waveform wider and the main frequency decrease,the sandstone information underneath FⅠ1-1target zone was completely flooded,which hindered the prediction of thin sandstone reservoir.For the removal of strong reflection,the fast matching pursuit(MP)decomposition based on Ricker wavelet was used to separate and weaken the strong reflection background induced onτ2to display the sandstone reservoir information.The frequency and scale dynamic scanning in the fast MP decomposition was used to improve the retrieval efficiency,and set threshold for the two consecutive residual energy difference to improve the efficiency of the iteration,the fast matching of atomic Library of time and frequency pursuit was achieved.In combination with the actual geological conditions of the target area,a 2Dgeological model including single sand layer and thin sandstone under strong background is designed for forward modeling.The MP decomposition method is applied to reconstruct the wavelet decomposition,which highlights the characteristics of sandstone.In practical application,good results are obtained in the P Area of Changyuan in Daqing Oilfield.