黄骅坳陷孔西斜坡区奥陶系原生油气藏成藏过程及模式

Accumulation Process and Model of the Primary Ordovician Oil and Gas Reservoirs in Kongxi Slope Area,Huanghua Depression

黄骅坳陷孔西斜坡区经历了多期构造运动,上古生界煤系烃源岩多次生排烃,奥陶系储层发生两期油气充注。该斜坡区具有较大的油气资源潜力。针对该地区成藏过程与成藏模式认识不清的问题,通过三维地震解释、测录井资料分析、岩心观察、薄片鉴定、流体包裹体测温、气相色谱分析等方法,结合埋藏史-生烃史模拟,以孔西斜坡区构造演化过程为基础,开展了下古生界奥陶系碳酸盐岩油气藏储层特征、成藏过程及模式的综合研究。结果表明:储集空间分为孔隙型和裂缝型两类,其中多期次半充填裂缝是最主要的储集空间类型。加里东运动导致华北地区大规模抬升,奥陶系长期差异性剥蚀形成岩溶储层,早、中三叠世三叠世孔西斜坡区广覆式生烃,油气向下进入奥陶系的岩溶储层,古油藏形成;早中侏罗世晚期孔西斜坡区在构造应力作用下形成西高东低的逆冲带,古油气藏向构造高部位调整,原油被水洗、氧化等破坏;古近纪早期孔西地区普遍接受沉积,至始新世地势发生反转,逆冲带深埋,深洼区煤系烃源岩二次生烃,油气通过逆断层及裂缝进入奥陶系储层;逆冲带奥陶系油气藏顶部和侧部地层以泥岩为主,具有良好的封堵条件,使油气聚集成藏,盖层及侧向封堵层不利的斜坡区高部位和凸起区,油气难以保存,形成了低部位产油产气、高部位产水的局面。

The Kongxi slope area in the Huanghua depression has experienced multi-stage tectonic movements,the Upper Paleozoic coal measure source rocks have generated and discharged hydrocarbons several times,and the Ordovician reservoir has been charged with oil and gas for two stages,which has great potential of oil and gas resources.Aiming at the problem of unclear understanding of accumulation process and model in this area through three-dimensional seismic interpretation,logging data analysis,core observation,thin section identification,fluid inclusion thermometry,gas chromatography analysis and other methods,combined with the burial history-hydrocarbon generation history simulation,based on the tectonic evolution process in Kongxi slope area,the reservoir characteristics,accumulation process and model of the Ordovician carbonate reservoir in Lower Paleozoic are studied comprehensively.The results show that:The reservoir space is divided into porosity type and fracture type,of which multi-stage semi-filled fractures are the main type of reservoir space.The Caledonian movement led to the large-scale uplift of North China,and the Ordovician karst reservoirs were formed by long-term differential denudation.Hydrocarbon generation was widespread in Kongxi slope area in the Early-Middle Triassic,and the oil and gas entered the Ordovician karst reservoirs downward,and the ancient oil and gas reservoirs were formed.The thrusting belt with high west and low east was formed under the action of tectonic stress in the Late Early-Middle Jurassic.The ancient oil reservoirs were adjusted to the higher part of structure,and the crude oil was destroyed by water washing and oxidation,etc.In the Early Paleogene,Kongxi area generally received sediment,and the terrain reversed in the Eocene.The thrust belt was deeply buried,and the coal measure source rock in the deep depression area generated secondary hydrocarbon,and oil and gas entered the Ordovician reservoirs through thrust faults and fractures.The top and side strata of the Ordovician reservoir in the thrust belt are mainly mudstone,which has good sealing conditions for oil and gas to gather into the reservoir.In the high part and raised areas of the slope area where the cap layer and the lateral sealing layer are unfavorable,oil and gas are difficult to be preserved,resulting in oil and gas gathering in the lower part and water gathering in the higher part.