杏北西斜坡区扶余油层成藏模式及主控因素

摘要

斜坡是油气区域运移的主要指向和主要成藏地带，具有较大的勘探潜力。为了探究杏北西斜坡区扶余油层油藏特征及勘探重点，综合利用地震、测井、录井、油田实际生产等资料开展了研究。研究表明，该区主要是发育受断层和岩性控制的断层遮挡、断块、断鼻、断背斜、岩性上倾尖灭和断层-岩性等油藏。油水分布整体呈现“上油下水”的规律，没有统一的油水界面。对油成藏模式的研究表明，该区具有“源内倒灌运移”、“源外侧向运移”聚集成藏两种模式：即油源区内青山口组源岩生成并排出的油在青山口组古超压的动力作用下，以沟通油源和下部扶余油层砂体以及圈闭的源断裂为路径，向下“倒灌”进入了圈闭成藏；第二种模式是西侧齐家-古龙凹陷青山口组源岩生成的油先“倒灌”到扶余油层后，沿着连通齐家-古龙凹陷和杏北地区的砂体和断层等通道，向东进入杏北地区。该区油藏的分布主要受油源、断层和砂体的有机匹配及反向正断层的控制。首先青山口组的超压是倒灌运移的关键，充足的油源是成藏基础，断层和砂体的有机匹配提供了倒灌运移的通道。最后指出了断砂匹配较好的反向正断层的上升盘是本区勘探的重点，下降盘对油聚集起到诱导作用。%A slope zone is an important region for hydrocarbon migration and accumulation ,thus has relatively high explo-ration potential.Through integration of seismic ,well logging and oilfield production data ,this paper studied the oil reser-voir characteristics and important exploration targets in the Fuyu oil layer in the western slope zone of the northern Xing -shugang oilfield ,Songliao Basin .The results show that oil reservoirs in this area are developed under the joint control of fault and lithology,and the major oil reservoir types include fault-screened,fault block,fault-nose,fault anticline,updip lithologic pinch-out,and fault-lithologic reservoirs .These oil reservoirs are characterized by ‘upper oil and lower water without unified oil-water contact ’ .Two hydrocarbon accumulation patterns are identified in the Fuyu oil layer , namely downward migration and accumulation within the source kitchen and lateral migration and accumulation beyond the source kitchen .The former refers to that ,driven by the paleo-overpressure of the Qingshankou Formation ,the oil sourced from the 1 st Member of Qingshankou Formation ( K2 qn1 ) ,migrated downward along the faults connecting the K 2 qn1 source rock and the underlying sand bodies and traps of the Fuyu oil layer ,forming oil reservoirs.The latter means that the oil sourced from the K 2 qn1 source rock in the Qijia-Gulong depression first migrated downward to the Fuyu oil layer ,and then migrated laterally into the northern Xingshugang region along pathways such as sand bodies and faults connecting the Qi -jia-Gulong depression and the northern Xingshugang region , forming oil reservoirs .The distribution of oil reservoirs are mainly controlled by available oil sources ,match of faults and sand-bodies ,and antithetic normal faults .The overpressure of the Qingshankou Formation is the key to ‘downward migration ’ of oil,while abundant oil sources form the material ba-sis and match of faults and sand-bodies provides pathways for ‘downward migration ’ of oil.At last,it is suggested that the hanging walls of antithetic normal faults in good match with sandbodies are important targets for oil exploration .