基于小尺度构造约束的网格层析方法及其在火山岩发育区速度建模中的应用

Grid tomography method based on small scale construction constraints and its application in velocity modeling of volcanic rock zone

速度场精度是影响偏移成像质量最为关键的因素,因此,速度模型的建立成为解决复杂地质体成像的核心工作.但在火山岩发育区,由于火山岩岩性、岩相复杂,空间相互叠置、尺度小等原因,导致地震波场复杂,成像难度大.常规基于网格的层析成像技术完全是数据驱动,其要求地震数据具有较高信噪比.而火山岩发育区地震反射杂乱,该方法无法满足精细建模需求.为此本文提出一种基于小尺度构造约束的网格层析速度建模方法.该方法既可以通过偏移距共成像点道集的剩余曲率对全局速度进行更新,也可以利用层位约束进行小尺度速度的局部修饰,即,在基于数据驱动的网格层析基础上通过地质约束提高速度模型精度.通过在渤海M油田的实际应用表明该方法在保证计算效率的同时大幅提高小尺度特殊构造体的反演精度,为后续火山岩发育区地震精确成像奠定坚实的基础.

Velocity model accuracy is the most critical factor affecting the quality of seismic imaging. Therefore, the establishment of the velocity model has become the core work to solve the imaging of complex geological bodies. But in the volcanic rock development area, due to the lithology of the volcanic rocks and the complex rock facies, and the space overlaps each other and the scale is small, lead to complex seismic wave fields and difficult imaging. Conventional grid-based tomography is completely data driven method, and it requires seismic data with a high signal to noise ratio. But the seismic reflections in the volcanic rock area are disorderly. This method cannot meet the needs of fine modeling. To this end, this paper proposes a mesh tomography velocity modeling method based on small-scale construction constraints. The method can not only globally update the velocity modeling utilizing the residual curvature of the common image point gather, but also perform local modification of small scale velocity using the horizon constraint. And it is to say that this method can Improve velocity model accuracy through geological constraints based on data-driven mesh tomography. Through the practical application of the Bohai M oilfield, this method has high computational efficiency, meanwhile the inversion precision of small scale special structures is greatly improved, which lays a solid foundation for the subsequent volcanic rock characterization.