塔河地区火成岩下成像精细速度建模方法应用

Application of Precision Velocity Modeling Method for Imaging under Igneous Rocks in Tahe Area

二叠系的火成岩在塔河地区分布广泛,其速度和厚度在横向上变化剧烈,导致下伏地层在构造特征上出现高频抖动,形成继承性假断裂,给奥陶系中缝洞的识别以及精细解释带来了困难。基于深度偏移算法,重点对研究区火成岩下伏地层成像开展速度建模的研究,通过变尺度的网格层析反演和多信息约束的目标反演构建高精度的速度模型,并用于偏移成像。成像剖面和综合属性的对比分析表明:该建模方法和传统网格层析建模相比,能更精细地刻画火成岩速度,最大限度消除火成岩下伏地层的继承性假构造和假断裂,恢复地下真实的构造特征,同时增强了奥陶系内部小缝洞成像的聚焦性。

The Permian igneous rocks are widely distributed in Tahe, Tarim Basin, where lateral variations in velocity and thickness are dramatic. This problem resulted in frequent shake in structural characteristics of underlying strata, inheritance pseudo-structure, and difficulties to the identification and interpretation of fractures and caves in the Ordovician underlain. Based on depth migration algorithm, velocity modeling was performed for the igneous rocks imaging in the study area. A high-precision velocity model was constructed by variable-scale grid tomography inversion and multi-information constrained target inversion, and then the velocity was used for migration. Compared with traditional grid tomography method, the velocity modeling could depict the igneous rock velocity more accurately, eliminate effectively the inheritance pseudo-structures and pseudo-faults in the underlying strata, reveal the true underground structural form, and enhance the precision of small fracture and cave imaging in the interior of the Ordovician strata.