绕射波叠前共虚震源道集分离方法

绕射波携带了地下小尺度非均质体的高分辨率信息，对岩溶体储层等的识别具有重要意义。能量较弱的绕射波易被反射波场掩盖，导致偏移成像不清、小尺度异常体精细识别与刻画难度大等。传统的绕射波分离方法存在深层绕射波能量损失严重、绕射波与反射波场相交或相切时难以分离的问题。为此，提出一种叠前绕射波分离方法：首先通过共虚震源变换将共炮点道集转换成共虚震源道集，然后在共虚震源道集中进行偏移—反射波去除—反偏移，最后通过共虚震源反变换得到共炮点道集绕射波场。数值模型和实测资料的应用表明，该方法能有效地压制反射波，同时较完整地保留绕射波能量，提升成像剖面上小尺度地质体的识别精度。

Diffraction separation method in the prestack common virtual source gather

Diffractions carry high-resolution information on underground small-scale heterogeneous geolo-gical bodies, which are of great significance to the recognition of karst reservoirs. The diffractions with weak energy can be easily masked by the reflected wave field,which results in many problems such as unclear migration imaging as well as poor fine-grained recognition and difficult characterization of small-scale anomalies. The traditional diffraction separation method confronts serious energy loss of deep diffractions and difficult separation when diffractions intersect with or are tangential to the reflected wave field. To solve the above problems,we propose a prestack diffraction separation method. Specifically,by the common virtual source transformation,the common shot gather is converted into a common virtual source gather,on which the migration,reflected wave removal,and demigration are performed. Then,the diffraction field of the common shot gather is obtained by inverse transformation of the common virtual source. The application of the numerical model and field data reveals that the method can effectively suppress the reflected waves, keep the energy of diffractions,and improve the recognition accuracy of the small-scale geological bodies on the imaging section.