北塘凹陷新港探区新生代岩浆活动的石油地质意义

Formation style of oil accumulations in interior basins

黄骅坳陷北塘凹陷近东西走向高密度岩浆岩体导致的布格重力异常高曾被解释为下古生界潜山。新港地区渐新世晚期—中新世早期强烈的岩浆活动与沿海岸带北北东向断裂的大规模走滑伸展有关 ,岩浆活动形成火成岩刺穿圈闭 ,深源热流体萃取分散有机质和对有机质起加氢、催化作用 ,促进了烃源岩中的有机质向油气转化 ,作为岩浆上涌通道的断裂也是油气向上运移通道 ,因此油气纵向分布层位多。因火成岩的屏蔽作用 ,新港地区深部地震资料品质差 ,构造畸变严重 ,应采用变速成图。图 4表 2参 2

Interior rift basins are one of the very important petroliferous basins. Based on the analyses of origins, structural style and sedimentary systems of rift basins and the differences of oil accumulation formation between the active and passive rift-type petroleum systems, active rift-basins are characterized by the gentle boundary fault, high sedimentation rate, more volcanic activities, and high thermal gradient. The multi-phase thermal perturbation caused several secondary cycles within the first-order course-fine-course sedimentary cycle, forming excellent source-reservoir-seal combination. Rollover-anticlines, drape-anticlines and buried-hill traps are the main types of oil accumulations. Oil and gas reserves are mainly located in the syn-rift sequence. Passive rift-basins are featured by the steep boundary fault, low extension rate and sedimentation rate, few volcanic activities, and low thermal gradient. Braided-river sandstones in the post-rift sequence are the main reservoir rocks, and the littoral-shallow lake shale within the newly developed syn-rift sequences act as the regional seal, thus forming an excellent source-reservoir-seal combination. Antithetic fault-block is the main type of oil accumulations where the oil and gas are mainly enriched in post-rift sequence.