利用断层岩泥质含量判断断层垂向封闭性的方法及其应用

Method of Fault Vertical Sealing Ability Judged by the Mudstone Content of Fault-rock and Its Application

为了简便地判断断层垂向封闭性,在断层垂向封闭机理及影响因素研究的基础上,通过比较断层岩排替压力与下伏储层岩石排替压力的相对大小,建立了一套利用断层岩泥质含量判断断层垂向封闭性的方法,并将其应用于渤海湾盆地南堡凹陷南堡5号构造f_1、f_2、f_3、f_4、f_5等5条断裂在东二段泥岩盖层内的垂向封闭性研究中。结果表明:f_1、f_2、f_4等3条断裂断层岩泥质含量均大于其在东二段泥岩盖层内垂向封闭所需最小的泥质含量,断层表现为垂向封闭;但f_1断裂位于南堡凹陷沙三段和沙一段—东三段烃源岩分布范围之外,无油气供给,f2断裂受断层与盖层配置关系的影响,油气沿断裂向上运移,从而无油气聚集;f_3、f_5两条断裂断层岩泥质含量均小于其在东二段泥岩盖层内垂向封闭所需最小的泥质含量,断层表现为垂向开启,即使断裂沟通了烃源岩与储层,油气也将穿过盖层继续向上运移,不利于油气富集。这一评价结果与南堡凹陷南堡5号构造东二段下部已发现的油气分布有着较好的吻合关系,表明该方法用于简便地判断断层垂向封闭性是可行的。

In order to judge the fault vertical sealing ability simply,based on the mechanism and influence factors of fault vertical sealing,the displacement pressures of fault-rock and underlying reservoir rock were compared,and a set of convenient prediction method of fault vertical sealing ability by using the mudstone content of fault-rock was established,and then the method was applied to study the vertical sealing ability of faults f_1,f_2,f_3,f_4,f_5 in mudstone caprock of the second member of Dongying Formation of No.5structure of Nanpu depression,Bohai Bay Basin.The results show that the mudstone contents of fault-rock of faults f_1,f_2,f_4 are larger than the minimum of mudstone content required by vertical sealing of the three faults in mudstone caprock of the second member of Dongying Formation,so they are sealed in vertical;while the fault f_1 is located outside the distribution range of source rocks from the third member of Shahejie Formation and the first member of Shahejie Formation-the third member of Dongying Formation,and the fault f2 effected by the configuration of fault and caprock,petroleum migrates along the fault,so that there is no petroleum accumulation whether the faults are sealed or not;themudstone contents of fault-rock of faults f_3,f_5 are lower than the minimum of mudstone contents required by vertical sealing of the two faults in mudstone caprock of the second member of Dongying Formation,so they are open in vertical;though the faults f_3,f_5 connect the source rock and reservoir,petroleum would move upward through the caprock,and it is not favorable for petroleum accumulation.The evaluation has a good relation with currently discovered petroleum distribution underneath the second member of Dongying Formation of No.5structure of Nanpu Depression,so that the method is favorable to simply judge the fault vertical sealing ability.