断盖配置渗漏油气时期确定方法及其应用

Determination method and application of leakage period for oil and gas of fault-caprock configuration

为了客观把握含油气系统中断裂处的油气纵向分布规律,在断盖配置渗漏油气机制及其渗漏油气时期构成研究的基础上,通过厘定断裂开始破坏泥岩盖层封闭时刻、断层岩开始封闭时刻和断裂活动停止时刻,确定断盖配置渗漏时期,并结合源岩排烃史,建立了一套确定断盖配置渗漏油气时期的方法,并将其应用于渤海湾盆地南堡凹陷南堡5号油田,研究F3断裂对东二段泥岩盖层的破坏历史,确定油气渗漏时期。研究结果表明,南堡5号油田F3断裂对东二段泥岩盖层的破坏作用是有限的,仅在P2和P8处使得断盖配置失效,发生油气渗漏。而且通过研究确定P2和P8处油气渗漏时期分别为距今约16~7.4 Ma和13.6~4.8 Ma。比较而言,P8处与P2处断盖配置渗漏油气时期相差不大,但P8处比P2处裂缝渗漏时期明显要短,导致P8处F3断裂对东二段泥岩盖层的破坏作用要相对弱一点,这与目前东二段泥岩盖层之下P8处发现油气、P2处未发现油气的勘探现状相吻合,表明该方法用于确定断盖配置油气渗漏时期是可行的。

Objectives:In order to understand the objective distribution regularities of hydrocarbon near the faults in a petroliferous basin.Methods:The determining method of the hydrocarbon leakage period has been constructed based on the mechanisms and time units of leakage in fault—caprock configuration,which was established by determining the time when a fault starts to destroy the sealing of mudstone cap and seal hydrocarbon by forming some fault rocks and ceasing activity.Then by analyzing the F3 in the Oilfield-5 in the Nanpu Depression,Bohai Bay Basin,this method was applied to the determination of oil—gas leakage period of mudstone caprock configuration(Ed~2).Results:The results show that the destructive effect to the mudstone cap of Ed~2 is limited by F3 of the Oilfield-5 in the Nanpu Depression,only the fault—caprock configuration fails and oil—gas leakage occurs at the Point P2 and P8.The oil and gas leakage periods of P2 and P8 are about 16~7.4 Ma and 13.6~4.8 Ma respectively.Conclusions:There is few difference with the oil—gas leakage period of the fault—caprock configuration between P8 and P2.However,the oil—gas leakage period by fracturing at P8 was obviously shorter than P2,which is favorable for hydrocarbon accumulation under the mudstone caprock of Ed~2at P8.This analyzing is consistent with the current situation of petroleum exploration near F3,the situation shows that hydrocarbon was founded at P8instead of P2 under the mudstone cap of Ed~2,which means that this method is feasible for determining the period of oil and gas leakage.