渤海湾盆地东濮凹陷南部地区古水动力演化与油气运聚

Evolution of paleo-hydrodynamics and hydrocarbon migration and accumulation in southern Dongpu Sag,Bohai Bay Basin

油气的运移、聚集与地下水动力场密切相关。从古水动力场演化角度分析东濮凹陷南部油气运聚机理,流体流动与断裂开启性之间的匹配关系,并利用流体包裹体均一温度数据,结合研究区热演化史和生烃史特征分析了油气藏形成时间,恢复其油气充注过程。结果表明:研究区可划分为3个水动力单元:东、西次凹带发育泥岩压实水离心流;兰聊断裂带发育大气水下渗向心流;中央隆起带位于东西两侧离心流汇合越流泄水区,是油气聚集成藏的有利区域。东营组沉积期是石油最主要的运移、聚集期,该阶段油气主要聚集在中央隆起带断层下盘的底部;东营运动抬升剥蚀期是石油的主要调整运移期。早期形成的深层油气藏向构造高部位的顶部运移调整,重新聚集形成浅层次生油藏;馆陶组-明化镇组沉积期为天然气主成藏期,断层封闭性增强,天然气聚集在构造翼部的深部地层,形成"上油下气、顶油边气"的分布格局。

Hydrocarbon migration and accumulation are closed related with hydrodynamic field. In this paper,the hydrocarbon migration and accumulation mechanism of southern Dongpu Sag was analyzed in respect of the paleo-hydrodynamic evolution. Forming time of hydrocarbon reservoir was determined by analyzing the homogenization temperature of fluid inclusions,and then hydrocarbon charging process was restored. The results show that there are three hydrodynamic units in southern Dongpu Sag： centrifugal flow of mudstone compaction-released water developed in the east and west sub-sags,centripetal flow of meteoric water occurred in the Lanliao fault belt,and cross-formational flow and discharge area in the central uplifted belt. The later is the most favorable place for hydrocarbon accumulation. The sedimentary period of Dongying Formation（ Ed） was the primary stage for hydrocarbon migrating to and accumulating in the bottom of downthrown blocks of faults. The stage of Dongying tectonic uplifting was the main period of hydrocarbon adjustment. Hydrocarbons from the deep reservoirs formed in early stage remigrated to and accumulated in the shallow layers on structural high,forming the secondary oil reservoirs. The Guantao and Minghuazhen were the main periods for gas accumulation.Natural gas mainly accumulated in the deep strata of structural limbs,owing to the increasing sealing ability of faults,resulting in the ＂upper oil lower gas,top oil marginal gas＂hydrocarbon distribution pattern.