一种改进的DWD+SRME表面多次波组合法压制技术在南海西部浅水工区的应用

浅水区表面多次波的压制问题一直是业界难题,确定性水层多次波压制(DWD)+表面相关多次波压制(SRME)是近年来工业界应用较有效的方法之一,将该方法应用于南海西部某浅水工区表面多次波压制时发现存在两个问题:①由于一次水底反射与折射波混叠,DWD外推算子应用于数据时,一阶的强能量水底反射多次波难以有效预测;②DWD+SRME组合压制后道集中依然存在残留的多次波。为此,改进了噪声压制技术流程:在DWD环节引入正演的一次水底反射,利用波场外推算子模拟一阶水底全程多次波;然后将该模型与初始DWD模型进行能量匹配后相加,得到含有一阶水底多次反射波的DWD模型,与原始数据进行自适应匹配相减后,在SRME的自褶积环节,将改进的DWD处理后的数据与原始数据褶积,以提高振幅预测精度;最后将DWD多次波预测模型以及SRME预测出的多次波模型同时进行自适应相减进一步提高多次波压制效果。将改进的流程应用于南海西部浅水工区的地震资料处理,结果表明,叠加剖面中的一阶海底多次波得到了明显压制,多次波在炮域和共偏移距域道集上的相干相长现象也得到了明显缓解。

The suppression of shallow water surface multiples has always been a challenge in the industry.The combination of DWD+SRME technology for suppressing surface multiples has been an effective method used in industry in recent years.While applying this method to a shallow water area in the western South China Sea,two problems remain.The first is the interference of the primary underwater reflection and refraction waves.When the DWD extrapolation operator is applied to the data,the first-order underwater reflection multiples are difficult to predict effectively,leading to suppression failure.Second,residual multiple coherent phenomena still exist on the gather after the combined suppression of DWD+SRME.The improved process is aimed at solving the problem of first-order underwater multiples.In the DWD link,forward reflection of the underwater bottom was introduced.According to the water-layer model,the wavefield extrapolation operator was used to simulate the first-order underwater multiples,and the model was then combined with the initial DWD.The models were added after matching the energy to obtain the DWD model containing first-order underwater multiple reflections,and after adaptive matching and subtraction,the first-order underwater multiples could be effectively suppressed.Then,in the self-convolution of SRME,the convolution of the DWD processed data and the original data was performed to improve the accuracy of the amplitude prediction.Finally,the DWD and SRME multiple prediction models were simultaneously and adaptively subtracted to further improve the multiple suppression effect.A test of field data from the western shallow water area in the South China Sea showed that first-order seabed multiples were suppressed in the stacking profile,and the interference phenomenon of multiples on shot gathers and common-offset gathers was attenuated.