准南安集海地区近地表逐级约束层析反演研究与应用

Research and Application of Step-by-Step Constrained Tomographic Inversion of Near-Surface in the Anjihai Area of Southern Junggar Basin

准噶尔盆地南缘勘探的最大瓶颈,是如何克服复杂近地表和地下高陡地质构造对地震剖面成像造成的影响。以准南安集海地区地震资料处理为研究目标,探索出一种有效解决近地表问题的可行方案。首先应用先验信息获取低降速带各层间的相关曲线,建立初始模型。在此基础上,从上至下进行逐层约束逐级反演,改变了常规层析反演一次成型的过程。该方法建立的近地表速度场有效降低了速度模型的等效性,并向实际真实速度结构逼近。计算的静校正精度进一步提高,将近地表速度融入深层偏移速度场,改善了叠前深度偏移成像效果,归位准确,井震误差大幅减小。实际应用效果证明了该方法的有效性,在准噶尔盆地南缘类似地震资料处理中具有应用参考价值。

A great breakthrough has been made in oil and gas exploration of lower combination in the south margin of Junggar basin,and the focus of exploration has shifted to the south margin.At present,the biggest bottleneck of exploration in this area is how to overcome the impact of complex near-surface and underground high and steep geological structures on seismic profile imaging.Taking the seismic data processing in the Anjihai area of southern Junggar Basin as a research goal,this paper develops a feasible solution to effectively solve the near-surface problem.Firstly,the correlation curves between different layers in the low deceleration zone are obtained by using the prior information,then the initial model is established,and finally,layer-by-layer constrained step-by-step inversion is carried out from top to bottom on this basis,which changes conventional tomographic inversion of one-time forming.The near-surface velocity field established by this method effectively reduces the equivalence of the velocity model and approaches to the actual true velocity structure.On this basis,the accuracy of static correction is further improved,and the imaging effect is significantly improved.The near-surface velocity is integrated into the deep migration velocity field,so that the imaging accuracy of prestack depth migration is obviously improved,and the well seismic error of depth migration is greatly reduced.The method has been proved to be reliable and effective in the practical application,and has reference value in the processing of seismic data similar to the southern margin of Junggar Basin.