全方位局部角度域偏移成像技术在顺北油气田的应用

顺北油气田二叠系地层火成岩广泛发育, 断控缝洞储集体横向非均质性强因而精确速度建模及目标地质体成像困难。在常规地震数据处理中, 传统的OVT分扇区处理技术无法获得地下真实角度信息, 不能准确反映引起的速度突变, 为进一步提高顺北复杂构造区的宽方位地震成像精度, 利用全方位局部角度域偏移成像技术实现了顺北油气田的分方位、分角度的精确成像。利用全方位网格层析速度建模技术分析全方位道集的剩余延迟, 建立层析成像矩阵, 实现各向异性场的精确速度建模。采用全方位地下局部角度域分解与成像技术, 对全方位共倾角道集进行分倾角叠加、散射增强和镜像增强处理, 提高深层小尺度地质体的可识别能力; 利用倾角道集的特点进行散射成像, 获得散射数据体, 突出了地下缝洞体的能量; 利用不同波场的传播特点进行镜像能量成像, 获得信噪比更高、细节更清晰的叠加数据, 清晰刻画断裂展布特征, 为顺北油气田缝洞储层及小尺度地质体的预测提供了基础数据该项技术。也可为其它地区的缝洞型地质异常体的预测提供技术参考。顺北油气田的应用结果表明, 火成岩建模及成像精度明显提升, 突出了缝洞储层的串珠反射能量, 提高了断裂识别的准确度。相较于常规克希霍夫偏移技术, 全方位局部角度域偏移成像技术保留了不同传播方向波场成像值的局部方位信息, 能更准确地反映地下成像点地质特征。

Permian igneous rocks are widely developed in the Shunbei oil and gas field, and the strong transverse heterogeneity of fracture-controlled fracture-cavity reservoirs makes accurate velocity modeling and imaging difficult.Wide-azimuth seismic acquisition results in consistent underground observation energy and all wave fields required for accurate imaging of underground targets, which facilitates anisotropy analysis and utilization.The CIP gathers generated by the traditional OVT seismic processing technology exhibit poor performance in lateral velocity mutations and cannot obtain true underground angle information.To ensure the efficient application of wide-azimuth seismic data, full-azimuth local angle domain migration imaging technology can achieve accurate azimuth and dip imaging in complex structural areas.The residual delay of the full-azimuth gathers was analyzed using the full-azimuth mesh tomography velocity modeling technology, and a tomographic imaging matrix was established to realize accurate velocity modeling of the anisotropic field.To improve the recognition of deep small-scale geological bodies, full-azimuth local angle decomposition and imaging technology were used, and the full-azimuth gathers were processed for inclination gather stacking, scattering, and image enhancement.Full-azimuth local angle domain decomposition imaging technology can perform ray-tracing and imaging decomposition of seismic data in the underground local angle domain, obtain inclination and reflection gathers simultaneously, and then perform weighted superposition imaging of the reflection and diffraction wave fields according to imaging requirements.Scatter data were obtained using the characteristics of the inclination gathers, and the energy of the underground fracture-cavity reservoir was obtained.By using the characteristics of the reflection wave fields to perform mirror-energy imaging, stack data with a higher signal-to-noise ratio and clearer details were obtained, and the fault distribution was clearly depicted.This provides basic data for the prediction of fracture-cavity reservoirs and small-scale geological bodies in the Shunbei oil and gas fields, and provides a technical reference for the prediction of fracture-cavity geological anomalies in other areas.Compared with the conventional Kirchhoff migration technology, the full-azimuth local angle domain migration technology retains the local orientation information of wave field imaging in different propagation directions and can reflect the information of underground imaging points more accurately.This technology has achieved a good application effect in the Shunbei area, where the imaging accuracy was improved, the energy reflected by the beads was highlighted, and the lateral resolution of the faults was increased.