探讨海底浅层生物礁及海沟对目标层构造的影响

To explore the influence of submarine shallow and trench on the target layer structure

H-1N位于珠江口盆地东沙隆起之上,是该区为数不多的大型构造之一。受浅层生物礁及海沟的影响,下覆某层灰岩顶面构造形态难以落实。这里利用地震正演技术,根据已钻井资料,建立初始阻抗模型,通过正演获得合成地震记录。将正演得到的合成记录与实际地震剖面对比,以振幅比例关系一致为判断准则,通过不断迭代修改海沟物性参数,生成合成地震记录与实际剖面对比。当合成记录振幅比例关系与实际地震剖面振幅比例关系一致时,即得到较为准确的海沟速度、密度信息。再结合浅层生物礁、海沟及已钻井信息,用层剥离时深转换方法获得了下覆某层灰岩顶面构造形态。创新点在于探索出一套根据已知振幅信息推算未知层平均速度的方法。

H-1Nis located in the Dongsha uplift,the Pearl River basin,and it is one of the largest structures.Due to the shallow reef and trench,it is difficult to implement the limestone top structure morphology of the overlying layer.According to drilling data,this paper mainly uses the seismic forward modeling technology to establish the initial impedance models and gain synthetic seismic records.Comparing the synthetic seismogram gained from the forward model and the actual seismic section,it is to determine with the principle that is whether the amplitude proportional relationship is consistent,the trench physical parameters are modified iteratively and then generate synthetic seismic records to compare with actual profile.When the amplitude proportional rations of the synthetic seismogram and the actual seismic profile are the consistent,the accurate information of the velocity and density is obtained.Combined with the shallow reef,trench and drilling data,by using the layer stripping time depth conversion method,the limestone top structure morphology of the overlying layer can be obtained.The innovation point is to explore a set of method according to that the known amplitude information to calculate the average speed of unknown layer.