Application of high density velocity analysis to low relief structure in the southwest part of Tahe Oilfield
密点速度分析技术在塔河油田西南部低幅构造中的应用

As the ever-increasing accuracy requirement for seismic survey, conventional velocity analysis methods have been shown failure in providing adequate accuracy of velocity for fine structural analysis, reservoir characterization, and anisotropic study. We adopted high density prestack velocity analysis technology to automatically pick the traveltime, amplitude, and coherency of the regular waves, as well as the ray parameters at shot and receiver to calculate the velocity of reflection at peaks for traces of different offset. To further improve the accuracy of velocity, measures such as spatially time-variant velocity filtering, frequency filtering, and dip filtering were used according to the geology. The method has been applied to calculate the detailed velocity on prestack 3-D data set from an area covering 1200 km2 in TFT, Tahe Oilfield. From which, low relief structures of main targets and its geometry and features are determined. Furthermore, the reservoir intervals are delineated by differential interformation velocity analysis, envelope difference of AVO energy, and velocity variability study in the Devonian sandstone of Donghe Formamation.