基于叠前地震数据的流度属性计算方法

A mobility attribute calculation method based on pre-stack seismic data

虽然从叠后地震资料的低频信息中提取流体流度属性进行储层预测和流体识别已经有了较好的应用效果,但是叠前地震资料相对叠后地震资料包含有更多关于储层和流体的信息,为了利用叠前地震资料中更多关于储层和流体的信息,将频散AVO分析与流体流度计算方法相结合,建立了流体流度与地震波入射角的关系,进一步推导了基于同步挤压广义S变换(SGST)的叠前流体流度预测方法,从而提取叠前地震资料中流体流度信息,并将其定义为叠前流体流度属性。建立AVO理论模型,计算了碳酸盐岩储层分别含水与含油时的叠前流体流度,证实了利用角道集振幅变化信息得到的叠前流度值变化更加明显;同时,对比不同时频分析方法对于流度计算精度存在的差异,验证了本文方法的理论有效性。将该方法应用于塔里木盆地某实际地震资料,并对比了叠前流度方法与叠后流度方法的应用结果,发现:叠后流度方法得到的流度属性虽然能够得到相对的流度值大小,但是很大程度上需要通过已钻井资料进行流度值门槛值标定,从而达到区分流体性质的目的;而叠前流度方法可通过流度变化正负值来直接确定流体性质。因此,叠前流度方法相对而言可以更好地预测流体性质。

The extraction of fluid mobility(FM)attributes from low-frequency information contained in post-stack seismic data has yielded promising results for reservoir prediction and fluid identification.Pre-stack seismic data contain more information about reservoirs and fluids than post-stack data.To extract FM information from pre-stack data,a pre-stack FM prediction method based on the synchro-squeezed generalized S-transform is proposed herein to improve the prediction accuracy.In this method,the relationship between FM and incident angle was established by combining the dispersion amplitude-versus-offset(AVO)analysis with the FM calculation method.In this step,FM information in pre-stack seismic data was extracted and expressed in terms of FM variation with offset.By establishing an AVO theoretical model,the FM of carbonate reservoirs with water and oil was calculated based on pre-stack data.Clear variations could be evaluated in the pre-stack-based mobility value obtained from the variation of amplitude in corner gathers.The time-frequency analysis method offers a different accuracy for mobility calculation,thereby verifying the theoretical effectiveness of the proposed method.An application of the method to actual seismic data in the Tarim Basin was conducted to compare the performance of the pre-and post-stack mobility methods.Although the relative mobility value can be successfully obtained from post-stack mobility attributes,calibration of the threshold value of the mobility value through drilled wells is necessary to quantify the fluid properties.Moreover,these properties can be directly determined by analyzing the positive and negative values of the changes in the mobility value.Therefore,it can be concluded that the pre-stack method offers a superior capability in predicting fluid properties compared with that by the post-stack method.