被盖层分隔储层油源断裂输导油气有效时期厘定方法及其应用

Determination method and its application of effective period for transporting oil and gas by the oil source fault of reservoir separated by caprock

为了准确研究含油气盆地被盖层分隔储层油源断裂在油气成藏中的作用,在被盖层分隔储层油源断裂输导油气机理及有效时期研究的基础上,通过断裂停止活动时期、断裂开始破坏泥岩盖层封闭能力时期和断裂填充物开始封闭时期确定出油源断裂输导油气时期,利用源岩地化特征确定出源岩排烃时期,将二者叠合建立了一套被盖层分隔储层油源断裂输导油气有效时期的厘定方法.应用结果表明:在测线L2处F1油源断裂向东一段储层输导油气有效时期相对较长,为5.3 Ma,较有利于油气在东一段储层中运聚成藏(目前构造高部位尚未钻探);在测线L8处F1油源断裂向东一段储层输导油气有效时期相对较短,为2.4 Ma,且主要为断裂填充物输导油气,不利于油气在东一段储层中大规模运聚成藏,和F1油源断裂在测线L8附近东一段虽已发现油气,但规模有限一致.该方法可有效用于厘定被盖层分隔储层油源断裂输导油气有效时期.

In the combination of source rock and reservoir separated by the caprock of a petroliferous basin,the scale of oil and gas accumulation is controlled by the relative length of the effective period of oil and gas transported by the oil source fault.The accurate determination of the effective period of oil and gas transported by the oil source fault in the combination of source rock and reservoir separated by caprock plays an essential role in identifying the oil and gas distributions and guiding oil and gas exploration.Based on a study of the oil–gas transport mechanism and the effective period by the oil source fault of reservoir separated by caprock,a set of determination methods of the effective period for transporting oil and gas by the oil source fault of the reservoir separated by caprock was established herein by coupling the period for transporting oil and gas by the oil source fault and that when the source rocks expelled hydrocarbon.The period for transporting oil and gas by the oil source fault was determined by determining the period when the faults started to destroy the sealing capacity of the mudstone caprock,the period when the faults stopped their activity,and the period when the fault fillers began sealing.The geochemical characteristics of the source rock were used to determine the period when the source rocks expelled hydrocarbon.The application results show that at line L2,the effective period for transporting oil and gas from the F1 oil source fault to the reservoir of the 1;member of Dongying Formation(E;d;)is relatively long(i.e.,time:5.3 Ma).This is conducive to transporting the oil and gas generated by the source rocks of the 1;member of Shahejie Formation(E;s;)to the 3;member of Dongying Formation(E;d;)through the mudstone caprock of the 2;member of Dongying Formation(E3d2)to accumulate in the reservoir of E;d;(the upper part of the structure has not been drilled yet).At line L8,the effective period for transporting oil and gas from the F1 oil source fault to the reservoir of E;d;is relatively short(i.e.,time:2.4 Ma).Oil and gas are mainly transported by fault fillers,which is not conducive to transporting the oil and gas generated by the source rocks of E;s;to the E;d;through the mudstone caprock of E;d;to accumulate in the reservoir of E;d;.The results are coincident with the fact that small-scale oil and gas have been found near line L8 of the F1 oil source fault in E;d;of the Nanpu 5;structure,suggesting that the method is feasible for application in the determination of the effective period for transporting oil and gas by the oil source fault of a reservoir separated by caprock.