渤中凹陷西部北缘生烃期边界断层活动对油气富集的影响

Effect of Boundary Fault Activities on Oil and Gas Accumulation in the Northern Margin of the West of Bozhong Sag in Hydrocarbon Generation Period

通过对渤中凹陷西部北缘边界断层活动、烃源岩热演化及成藏史等综合分析,定量探讨了生烃期边界断层活动与油气差异富集的关系。结果表明,研究区生烃期主要为馆陶组至现今,断层活动以“弱—弱—强”为主。馆陶组与明化镇组下段时期,断层活动弱（活动速率小于10 m/Ma）,在明化镇组中期（约7.5Ma）,烃源岩由生烃进入主要生烃阶段,油气向古近系圈闭中运移并成藏,断层以封堵作用为主。在明化镇组上段（大约5.3 Ma）开始,烃源岩进入高熟阶段,断层活动增强,油气开始差异成藏,当断层活动速率小于10 m/Ma时,油气主要在古近系成藏;当断层活动速率在10~25 m/Ma时,断层具有一定的输导作用,且对古近系油气藏造成一定的破坏,油气主要在古近系和馆陶组分布;当断层活动速率大于25 m/Ma时,断层主要起到输导作用,且古近系油气藏被破坏,油气向浅层运移并在新近系成藏。

The relationship between boundary fault activities and hydrocarbon accumulation in hydrocarbon generation period is quantitatively studied through the comprehensive analysis of the boundary fault activities, the thermal evolution of hydrocarbon source rocks and hydrocarbon accumulation history in the northern margin of the west of Bozhong Sag. The results show that, the major hydrocarbon period in the study area is from Guantao Formation period （Ng） to the present, and the fault activity is ＂ weak - weak - strong＂. The fault activity is weak （the activity rate is less than 10 m/Ma） from Guantao Formation period to the lower member period of Minghua- zhen Formation. In the middle period of Minghuazhen Formation （ about 7.5 Ma）, hydrocarbon source rocks enter the main hydrocarbon generating stage, hydrocarbon migrated to Paleogene traps and accumulated there, and the fault mainly plays the role of plugging hydrocarbon. Starting from the upper member （about 5.3 Ma） of Minghuazhen Formation, the hydrocarbon source rock entered into the high mature stage, and the fault activity became strong, and the hydrocarbon began to accumulate. When the fault activity rate is less than 10 m/Ma, hydrocarbon mainly accumulated in Paleogene formation;when the fault activity rate in 10-25 m/ Ma, the faults play the role of hydrocarbon migration channel to a certain extent,it has a certain damage effect on Paleogene hydrocarbon reservoirs, and hydrocarbon mainly distributed in Paleogene and Guantao Formation;when the fault activity rate is greater than 25 m/Ma, the faults mainly play the role of hydrocarbon migration channel, the Paleogene hydrocarbon reservoirs were destroyed, the hydrocarbon migrated to shallow formation and accumulated in Neogene reservoirs.