冀北坳陷郭杖子单斜带中上元古界成藏条件分析

Analysis of hydrocarbon accumulation condition of Middle-Upper Proterozoic in Guozhangzi monoclinal zone,Jibei Depression

冀北坳陷发育巨厚的中上元古界地层。地表油苗丰富，发现多个古油藏，说明该区已有油气成藏过程，郭杖子单斜带发育洪水庄组灰黑色页岩和铁岭组黑色灰岩2套好的有效烃源岩，有机质质量分数0．5％-4．58％，镜质体反射率1．07％～1．10％。铁岭组中下部的高角度裂缝白云岩和雾迷山组上部晶白云岩和叠层石白云岩是该区主要储层，储集空间主要是裂缝和溶洞．并发育与这2套储层有关的2套生储组合：洪水庄组生-雾迷山组储、洪水庄组生-铁岭组储。主生烃期、构造格局定型期、构造裂缝和溶孔溶洞的形成期都在白垩纪中后期。高角度裂缝遮挡油气是该区油气能成藏的最重要的条件。

Middle-Upper Proterozoic formations with huge thickness were developed in Jibei Depression. Abundant oil seepages have been discovered on the surface and many paleo-reservoirs have also been found, which indicates that the process of hydrocarbon accumulation has occurred in this area. Two sets of active source rocks were developed in Guozhangzi monoclinal zone, consisting of grey black shale in Hongshuizhuang Formation and dark limestone in Tieling Formation. Content of organic matter was 0.5%-4.58% and vitrinite reflectance is 1.07%-1.10%. The high-angle fractured dolomite in the middle-lower part of Tieling Formation and the crystal dolomite and stromatolithie dolomite in the upper part of Wumishan Formation were the principal reservoirs in the area. The reservoir space was mainly the fractures and caverns. Two sets of source-reservoir association related to these two sets of reservoirs were developed, with Hongshuizhuang Formation as source rocks and Wumishan Formation as reservoirs and with Hongshuizhuang Formation as source rocks and Tieling Formation as reservoirs. Primary hydrocarbon generation, tectonic framework completion, formation of structural fractures, dissolved pore and caverns all happened in the middle-later periods of Cretaceous. High angle fracture barrier was the most important condition for hydrocarbon accumulation in this area.