辽河盆地东部凹陷东营组火山岩特征及油气封盖作用

利用辽河盆地东部凹陷32口井11 431 m火山岩井段的岩芯、岩屑、测录井资料,通过火山地层-地震连井对比,研究了东营组火山岩的岩性、岩相、纵向序列及喷发期次;通过225口探井56923 m火山岩井段编制出东营组火山岩平面分布图;根据43口探井600余件实测孔隙度和渗透率数据分析东营组火山岩储集物性及其与沉积岩和下伏沙三段火山岩的相互关系。结果表明,东营组火山岩主要为玄武岩和粗安岩,归属为5个喷发期次,自下而上为基性-中性-基性火山喷发旋回;火山岩分布受边界断裂控制,在驾东断裂与其伴生断裂的交汇处火山岩厚度最大。火山岩和沉积岩的储集物性均随埋深变差,东营组埋深多2 500 m,其火山岩物性差于互层的砂岩,但好于埋深超过2 500 m的沙三段火山岩。揭示了东营组火山岩与油气成藏关系:1东营组火山岩孔渗(φ=15%,K=0.4×10-3μm2)相邻砂岩(φ=21%,K=29×10-3μm2),主要起封盖作用;2东营组火山岩储集物性通常好于沙三段火山岩(φ=10%,K=0.45×10-3μm2),但其不是储集层而是盖层,而沙三段火山岩多为有效储层,说明火山岩与互层沉积岩储层物性的相对高低是决定火山岩作为储层或者盖层的重要因素。

Characteristics of volcanic rocks from Dongying Formation and their sealing effects in eastern depression of Liaohe Basin

Based on drilling cores of volcanic rocks in 32 wells with a total length of 11 431 m and the cut- tings and well logging data，the volcano lithology，lithofacies，vertical sequence and eruption stage of Dongying Formation have been studied by volcano stratigraphical seismic- well correlation． The isopach map of volcanic rocks is sketched out based on the information of volcanic rocks in 225 wells with a total length of 56 923 m． More than 600 measured porosity and permeability data of 43 wells are compared in order to study the reservoirs physical prop- erty of Dongying Formation volcanic rocks，and its relationship with the sedimentary rocks and the volcanic rocks of underlying the third member of Shahejie Formation． The results show that the volcanic rocks are mainly composed of basalt and trachyandensite，and divided into 5 eruptive stages with the eruption cycles of mafic- intermediate- mafic volcanic ones upwards． The spatial distribution of volcanic rocks is controlled by the main boundary faults，and the thickest volcanic rocks are formed at the intersection of Jiadong fault and its associated faults． The porosity and per- meability descend with the increasing of burial depth for both volcanic rocks and sedimentary rocks． The regional burial depth is shallower than 2 500 m for the Dongying Formation，and the physical property of volcanic rocks are worse than interbedded sandstone but better than the volcanic rocks in 2 500 m for the third member of Shahejie Formation． The relationship between Dongying Formation volcanic rocks and reservoirs are is that: ①The averaged porosity and permeability (φ =15%，K =0. 4 ×10 -3 μm 2 ) for Dongying Formation volcanic rocks are worse than its interbedded sandstone (φ =21%，K =29 ×10 -3 μm 2 )． ② The reservoirs physical property of Dongying Forma- tion volcanic rocks are better than the volcanic rocks in the third member of Shahejie Formation (φ =10%，K = 0. 45 ×10 -3 μm 2 )． The volcanic rocks act as cap rocks in the Dongying Formation，and as reservoir rocks in the third member of Shahejie Formation． The controlling factor in determining volcanic rock as reservoir or cap is the relative level of porosity and permeability compared to the interbedded sedimentary rocks．