永川新店子“双复杂”区近地表因素变化大,构造复杂,资料信噪比低,导致准确成像难度大。页岩气勘探开发过程中,面临新店子背斜构造内幕不清、局部小断层成像不准、水平井设计轨迹与实钻不符等问题。常规网格层析反演方法在低信噪比区速度建模中适用性较差,既难以求准浅层速度,消除复杂近地表对成像的影响,又难以在中深层实现有效数据驱动,准确更新中深层速度。针对“双复杂”地区深度域建模问题,采用全偏移距初至层析反演求取近地表速度,选取合适界面,将浅层与中深层模型进行融合。在网格层析迭代过程中,应用构造模型对速度进行约束,实现了速度低频量与构造分布相契合及高频收敛。应用结果表明,浅中深融合建模与构造约束网格层析技术的联合应用弥补了通常方法的不足,形成的最终速度场精度更高,“双复杂”地区成像得到较明显改善,更有力地支撑了该区勘探开发。

In the “dual complex” area of Xindianzi, Yongchuan, all the reasons that the near surface factors vary greatly, the structure is complex, and the signal-to-noise ratio of data is low make the accurate imaging difficult. During the shale gas exploration and development, there are some problems of Xindianzi such as unclear anticline structure, inaccurate imaging of local small faults, and inconsistency of horizontal well design trajectory with actual drilling. The conventional grid tomography inversion method has poor applicability in velocity modeling of low signal-to-noise ratio area. It is difficult not only to obtain the quasi shallow velocity and eliminate the influence of complex near surface on imaging, but also to realize effective data driving in the middle and deep layers and update the velocity accurately in the middle and deep layers. In order to solve the problem of depth domain modeling in “dual complex” area, full offset first break tomography inversion is used to obtain near surface velocity, then the appropriate interface is selected to fuse the models of shallow and medium depth. In the iterative process of grid tomography, the constraints on velocity by the construction model can realize the corresponding between low-frequency velocity and structural distribution, and get high-frequency convergence. The application results show that the joint application of shallow, medium and deep fusion modeling and structural constraint grid tomography technology make up for the shortcomings of the conventional methods, the resulting final velocity field is more accurate, and the imaging of the “dual complex” area is obviously improved. The results strongly support the exploration and development of this area.