复杂断裂精细成像技术在南海东部惠州21洼的应用

Application of high precision complex fault imaging in Huizhou 21 sag,eastern South China Sea

珠江口盆地惠州21洼地下构造及断裂极为复杂,以前的地震采集方式和处理技术相对落后,地震资料存在断层成像不清、断点不落实、断层下降盘成像模糊等问题,极大地影响了对圈闭形态、构造高点及构造圈闭幅度的准确判断,导致构造圈闭难以识别和落实。为此,提出针对断裂发育区地震信号的深入挖潜处理技术,通过开展精细的信号处理,充分挖掘常规拖缆采集地震数据潜力,获得能够有效改善复杂断裂区成像的中、低频信号及大入射角范围内的有效地震反射,提高了断裂发育区地震资料信噪比。利用高保真的地震信号,开展基于数据与地质模式相约束的高精度叠前深度偏移速度建模,针对复杂断裂区,较好地利用大炮检距地震信息和中、低频有效信号,采取优势信号驱动下的高精度网格层析速度建模,极大地提高了速度拾取精度。同时,利用地质模式对速度模型进行有效约束,将成像效果与速度模型的相关性相结合,确定最终的成像速度模型,改善了惠州21洼复杂断裂区的构造成像效果。该项技术在惠州21洼勘探研究中得到较好应用,极大地降低了断层不落实对构造圈闭评价带来的影响,提高了构造圈闭解释的准确性,有效推动了该区勘探进程。

The Huizhou 21 sag of the Pearl River Mouth Basin is known for its complex underground structures and faults.Due to outdated seismic acquisition and processing techniques,there are issues with unclear fault imaging,unconfirmed faulting points,and blurry imaging of the fault s downthrown side.These issues greatly impact the accurate determination of trap morphology,structural highs,and amplitude of structural traps.To address these issues,deep processing techniques for seismic signals in the fractured zones are investigated.Seismic signals are processed finely to maximize the potential of seismic data collected by conventional towed acquisition technique.In this way,the low-to medium-frequency signals and effective seismic reflections within a large incidence angle range that can effectively improve the imaging results for complex fault zones are obtained to improve the signal-to-noise ratio of seismic data in the fractured zones.Meanwhile,high-fidelity seismic signals are utilized for high-precision prestack depth migration velocity modeling constrained by data and geological models.For complex fault zones,large-shot seismic data and low-to medium-frequency effective signals are efficiently utilized,and high-precision grid tomography velocity modeling driven by dominant signals is conducted to greatly improve the velocity picking accuracy.Moreover,the velocity model is effectively constrained with geological models,and coupling with the correlation between imaging effects and velocity models,the final imaging velocity model is determined.This imaging approach significantly improves the structural imaging effect of the complex fault zone in the Huizhou 21 sag.It has been successfully applied in exploration research in the Huizhou 21 sag by reducing the impact of unconfirmed faults on the evaluation of structural traps and improving the accuracy of structural trap identification,thereby driving the exploration research in this area.