潮汕坳陷中生代沉积层纵横波速度结构

Joint P-wave and S-wave velocity structure of the Mesozoic sediments in the Chaoshan Depression

潮汕坳陷残留有巨厚的中生代沉积层,是南海油气勘探的重要区域。已经开展了大量的多道地震反射工作,同时也有折射地震和海底地震仪研究,但尚未开展纵横波联合研究。纵横波联合探测,可以获得更多的地下结构信息,对油气勘探有重要的意义。在OBS2006-3剖面潮汕坳陷中生代沉积层纵波速度结构的基础上,对转换横波震相进行了射线追踪和走时模拟。结果表明,潮汕坳陷中生代沉积层厚度较大,最大厚度达到8km,纵波速度从顶部的4.4km.s–1增加到底部的5.3km.s–1,相应的横波速度由2.6km.s–1增大到3.0km.s–1,泊松比为0.24—0.26,波速比为1.74—1.80,其成分可能包含有砂岩、泥岩和火山岩。同时根据该区的地球物理特征,结合前人的研究,分析了油气勘探潜力。

As a thick residual deposition depression of the Mesozoic strata,the Chaoshan Depression is an important area for oil and gas exploration in the South China Sea（SCS）.A lot of multiple-channel seismic（MCS） reflection studies have been conducted in this area,as well as refraction and ocean bottom seismometer（OBS） surveys,but joint P-wave and S-wave studies have not yet been done.Applying the joint exploration of P-wave and S-wave,the complex subsurface crustal structure can be obtained,which is helpful for oil and gas exploration.Based on the P-wave velocity structure of the Mesozoic sediments in the Chaoshan Depression of the profile OBS2006-3,we carried ray tracing and travel-time simulation of converted S-wave.The results reveal that the Mesozoic sediment in the Chaoshan Depression is remarkably thick with the maximum of 8 km,and the P-wave velocity increases downward from 4.4 km·s –1 at the top to 5.3 km·s –1 at the bottom. Accordingly,the S-wave velocity and Poisson＇s ratio are 2.6 3.0km·s –1 and 0.24 0.26,respectively,which may imply the composition of Mesozoic strata are sandstone,mudstone and volcanic rocks.According to the geophysical characteristics and previous research in the Chaoshan Depression,this paper analyzes the exploration potential in the Chaoshan Depression.