绕射波成像在潜山裂缝储层预测中的应用——以渤中A气田为例

渤中A凝析气田太古界潜山埋藏深且构造运动复杂,岩性以变质岩为主。潜山内幕裂缝储层非均质性强,地震资料反射波成像质量较差,储层精细表征难度大。绕射波是地下介质不连续性和非均质性的指示标志,可利用地震波场中的绕射信息预测潜山裂缝储层。基于共偏移距道集,利用叠前绕射波分离成像方法,分两步实现绕射波分离。首先,利用局部倾角滤波提取出大倾角绕射波。然后,利用核主成分分析方法提取出小倾角绕射波,二者联合实现绕射波分离。该方法降低了绕射波的能量损失,提高了绕射波分离的精度,进而改善了绕射波成像的保幅性。最后,利用绕射波的能量和曲率等属性实现裂缝密度和裂缝方向的综合预测。实际资料应用结果表明,叠前绕射波分离成像有效改善了潜山内幕的成像效果,提高了潜山裂缝储层预测精度,指导了该区探井的井位部署,对变质岩潜山裂缝储层研究具有重要意义。

The Archean buried hill in the BZ-A condensate gas field is deeply buried.It experienced complex tectonic movement and the lithology is mainly metamorphic rock.The fracture reservoir inside the buried hill is highly heterogeneous.The reflected wave imaging quality of seismic data is poor,and it is difficult to accurately characterize the reservoir.However,diffraction waves can indicate the discontinuity and heterogeneity of underground media,and the diffraction information in seismic wave fields can be used to predict buried hill fractured reservoirs.In this study,the pre-stack diffraction wave separation imaging method is used.Diffraction wave separation is realized in two steps.First,the large angle diffraction wave is extracted by local dip filtering.Then,small angle diffraction waves are extracted by the kernel principal component analysis method.The conventional diffraction wave separation method based on common offset gathers is improved herein,which reduces the energy loss of diffraction waves,improves the accuracy of diffraction wave separation,and further improves the amplitude preservation of diffraction wave imaging.Finally,the comprehensive prediction of fracture density and fracture direction is realized by using the energy,curvature,and other attributes of diffracted waves.The application of practical data indicates that pre-stack diffracted wave separation imaging effectively improves the imaging of the interior of buried hills,improves the prediction accuracy of buried hill fractured reservoirs,can guide the well deployment of exploration wells in this area,and is of great significance for studying metamorphic buried hill fractured reservoirs.