大震源长缆深沉放地震采集技术在南黄海中古生代盆地的应用

南黄海海域中古生代盆地具有原型盆地类型多样、成盆背景复杂、后期构造改造强烈等特点,导致地震资料品质一直是制约其油气勘探的关键问题。针对南黄海中古生代盆地开展地震采集攻关,以研究区内地震地质条件与地震物性条件的分析为先导,剖析了该区地震勘探存在的关键问题:浅层强界面屏蔽、目的层内部阻抗界面弱、地震成像品质差,并有针对性地开展了相应的大震源长缆深沉放地震采集技术攻关实践,其震源能量超过6 180 cu.in3,电缆长度10 050 m,枪缆沉放深度分别为10和25 m。实践证明,该新技术手段可以有效增大向深部中古生界传播的低频地震分量,降低外源噪音干扰,增加目的层信噪比,使得地震剖面成像品质得到了明显提高。

A LARGE-SCALE SEISMIC SOURCE,DEEP GUN AND CABLE SINKING AND LONG CABLE PENGTH APPLICATION IN MESOZOIC-PALEOZOIC BASIN IN THE SOUTH HUANGHAI SEA

Because of diversified antetype basins, complicated background of basin formation and later intensive structural reconversion, the quality of seismic data has always been the key problem in hydrocarbon exploration of the Mesozoic-Palaeozoic basins in the South Yellow Sea. This paper aimed to solve this problem by seismic acquirement technology. By analyzing geophysic and geologic conditions, we researched the key problems existed in this area, such as hard shielding interface in shallow layer, weak impendence interface and poor seismic quality in target layer. So relevant target oriented acquiring methods is developed which is characterized by large-scale seismic source, deep gun and cable sinking, and long cable length. The abstract parameters are 6 180 cu.in3 source volume, 10-25 m gun-cable depth and 10 050 m cable length. This new acquiring practice testified that it can increase the low-frequency component of seismic energy that propagated to the Mesozoic-Palaeozoic basin, so the S/N in the target zone has been raised and the entire seismic section quality has been improved greatly.