渤海海域庙西中南洼勘探潜力分析

Exploration Potentials of Miaoxizhongnan Sag in Bohai Sea

渤海海域庙西凹陷为渤海湾盆地众多边缘凹陷之一,其成凹、成烃、成藏研究相对富生烃凹陷较为薄弱,制约了勘探进程。通过对庙西凹陷中南洼构造、沉积、地化及成藏等综合研究,形成了一套边缘凹陷分析方法:以凹陷构造研究为切入点,综合考虑断裂、隆起作用,明确凹陷动力成因机制,进而厘定边缘凹陷构造演化和原型盆地,在此基础上进行资源潜力及圈闭演化研究,预测有利勘探方向。通过研究,总结了4种断裂-隆起协同演化模式,明确了研究区盆地边缘的演化特征,发现中南洼古近纪盆地面积为现今残留盆地的3倍以上;确认沙三段烃源岩是庙西凹陷中南洼的一套优质烃源岩,估算了其生烃量;并在断裂-隆起协同演化模式指导下,明确了圈闭成因模式及分布;结合区域成藏研究,预测了庙西中南洼有利勘探方向及区带,提出了下一步勘探建议。

Miaoxi Sag of Bohai Sea is one of several marginal sags in the Bohai Bay Basin. Compared with those ol rich hydrocarbon-generating sags, Miaoxi Sag of Bohai Sea has limited researches related to sag formation, hydro- carbon generation and reservoir fbrmation. Such conditions may have negative impacts on reservoir exploration in the Area. Through comprehensive studies over structures, sedimentary, geochemical and reservoir conditions in the cen- tral and southern parts of the Miaoxi Sag, a comprehensive package of analysis methods for marginal sag have been developed ： With studies related to structure of the sag as the starting point, faulting and uplifting activities shall be considered comprehensively to identify genetic mechanism of sags. Eventually, tectonic evolution and prototype ba- sin of the marginal sag can be identified. In addition, more researches can be performed for resource potentials and history of trap evolution to highlight favorable exploration targets. Through implementation of relevant researches, four faulting-uplifting co-evolution patterns have been highlighted to clarify evaluation features of basin margins in the study area. It was determined that total area of Paleogene Basin in central and southern parts are 3 times higher than the area of residual basin at present; It was also determined that hydrocarbon source rocks in the Sha-3 Inter- val of Miaoxi Sag can be seen as high-quality hydrocarbon source rocks in central and southern parts of the Area. Total volume of hydrocarbons generated in the area has been estimated ; Under guidelines of faulting-uplifting co- evolution patterns, genesis modes and distribution of traps have been determined ; With combination with regional reservoir formation researches, favorable exploration directions and potential zones in the Miaoxizhongnan Sag have been predicted. In addition, proposals related to further exploration operations have been proposed.