南黄海盆地北部坳陷海底油气渗漏的声学探测

Acoustic detection of seabed hydrocarbon seepage in the north depression of South Yellow Sea Basin

为查明南黄海盆地北部坳陷调查区内与海底油气渗漏有关的海底浅表层声学特征,分析天然气渗漏与构造的关系,为下一步地球化学取样站位的选择和油气勘探提供参考,采用全覆盖侧扫声纳和高分辨率地震方法首次对调查区的海底油气渗漏现象进行了调查。在镶嵌处理后的侧扫声纳图像上,呈条带状散布的强反射斑块为麻坑和海底圆丘地貌。在地震剖面上可见由于气体聚集产生的振幅增强、柱状扰动、气窗及空白反射等特征。分析结果表明,广泛发育的接近或直达海底的断层为油气渗漏提供了通道和气源,海底浅表层气体的聚集和渗漏是深部地层中孔隙流体向上运移的结果,且调查区海底目前仍处于微渗漏阶段。

The full-covered Side-Scan Sonar and high resolution seismic survey method is initially adopted to research on the seabed hydrocarbon seepage in the survey area, for the purpose of the following： clarifying the shallow acoustic features related to seabed hydrocarbon seepage in the north depression area of South Yellow Sea Basin, analyzing the relations between the seepage and the structure, and providing evidence for selection of geochemistry sampling station and petroleum exploration. On the mosaic image of Side-Scan Sonar, the strong reflecting spots in strip-like distribution present the physiognomy of pockmark and dome. On the seismic profile, we can see the characteristics such as enhanced amplitude, columnar disturbance, gas chimney, and blank reflection, which result from gas accumulation. The analysis results indicate that the widely developed faults which approach or connect to seabed provide the channel and source of hydrocarbon seepage. The accumulation and seepage of subsea shallow-layer gas results from the upward migration of fluids from deep-layer pores, and the sub-sea survey area is still at tiny seepage stage.