中国东北油气区晚侏罗世—早白垩世断陷油气成藏特征

晚侏罗世—早白垩世,中国东北部进入环太平洋构造域大陆边缘构造演化阶段,发育一系列呈雁行排列的走滑拉分裂陷盆地,具有以下油气成藏特征:①继承性深断陷及多期叠加型断陷烃源岩厚度大、品质优、热演化充分,油气保存条件好,油气资源丰度较高;②走滑拉分断陷的一个突出特点是烃源条件由深断槽向两侧迅速变差,因此,高生烃丰度的深断槽控制油气富集;③发育控凹走滑断裂带、深洼槽周边、斜坡区坡折带、断陷周边隆起带等四类复式油气聚集带;④由于构造分割性强,沉积体系规模小,油气资源丰度中等—较低,使其发育数量众多的中小型油气田;⑤由于热演化程度差异大,母岩类型多样,加之多期多次成藏,油藏、油气藏、气藏常共存;⑥由于晚侏罗世—早白垩世断陷后,又经历了多次构造运动,从而发生了多期多次成藏,由于各区块油气成藏条件的差异,使各区块原生、次生油气藏比例存在明显差异。据此认为,今后只要根据该区走滑拉分裂陷盆地的油气成藏特征,开展区块和目的层优选和针对性勘探,还将有较大的储量增长。

Oil and Gas Migration and Accumulation Characteristics of Late Jurassic-Early Cretaceous Rifts in Northeast China Oil and Gas Area

From Late Jurassic to Early Cretaceous, the northeast part of China entered the continental peripheral structural development stage of the Pacific-rim structural region. There developed a series of strike-slip pull-apart rift basins in the swallow-shaped array. They have the following oil and gas migration and accumulation characteristics. The hydrocarbon source rock of successive deep rift and multi- stage overlapped rift is large in thickness, good in quality and high in thermal development. The oil and gas storage conditions are desirable with high abundance of oil and gas resources. One of the prominent characteristics for the strike-slip pull-apart rift is that the hydrocarbon source conditions are rapidly becoming poorer towards the two sides from the deep fault groove. Therefore, the high-abundance deep fault groove controls the oil and gas abundance. There develops four compound oil and gas accumulation zones: sag-controlled strike-slip fault belt, deep groove periphery, slop fold belt of slop zone and uplift on the periphery of rift. The oil and gas abundance is of the middle to relatively low degree owing to the strong structural separation and the small scale of the sedimentary system, thus developing a large number of the medium-size and small oil and gas fields. There is a great difference in thermal development degree with a variety of mother rock types. The oil and gas migrated and accumulated in multiple stages with co-existence of oil reservoirs, gas reservoirs and oil-gas reservoirs. The region has experienced multi-stage multi-stage structural movements following the Late Jurassic-Early Cretaceous rifts, leading to multi-stage oil and gas migration and accumulation. The difference is apparent in the ratio of the original and secondary oil and gas reservoirs in each block owing to the difference in the oil and gas migration and accumulation conditions in each block. Therefore, if the blocks and target layers are optimized and selected according to the oil and gas reservoir characteristics in the strike-slip pull-apart rift basins in this region, the reserves will be raised significantly in the future.