松辽盆地营城组火山岩储层裂缝特征

Fracture characteristics of volcanic reservoir in Yingcheng Formation,Songliao Basin

松辽盆地营城组火山岩储层裂缝普遍发育,但不同相带内裂缝的发育规模存在较大差异。通过对外围露头火山岩储层裂缝的实测数据及微观特征观察并结合钻井岩芯研究,认为松辽盆地营城组火山岩储层裂缝可分为原生裂缝、次生裂缝和人为诱导裂缝3种成因类型。其中次生裂缝中的构造裂缝对油气运移及聚集起决定性作用;喷溢相、侵出相和火山通道相是构造裂缝最发育的相带,线密度分别为22条/m、18条/m和14条/m;爆发相不发育,线密度为4条/m。构造裂缝的形成期分为早白垩世营城组早期、营城组末期和晚白垩世嫩江组早期等3期,裂缝主要形成于前两个时期;裂缝走向以北东向最为发育,占总量的50%以上,其次为北西向、南北向和近东西向;裂缝的整体充填程度低,开启情况及有效性较好。研究成果与徐家围子断陷内裂缝的发育规律具有一定的可对比性。

The fractures in volcanic reservoirs are widely developed in Yingcheng Formation of Songliao Basin, but there are much different in fracture scale in various facies. Based on the study of measured data and microscopic characteristic observation of fractures in volcanic reservoirs of peripheral outcrop and combined with drilling core research, the author considers that the fractures in volcanic reservoirs can be divided into 3 genetic types, including primary fractures, secondary fractures and human-induced fractures, and the structural fractures from the secondary fractures play a decisive role to hydrocarbon migration and accumulation. Effusive facies, extrusive facies and volcanic conduit facies are most developed in the structural fractures, the linear densities are 22/m, 18/m and 14/m respectively, while the explosive facies are not developed, with only 4/m in line density. The period for the structural fractures forming are the early and late stages of Yingcheng Formation in Early Cretaceous, and of the Nenjiang Formation in Late Cretaceous, in which the two formers are main stages. The fracture strikes most developed in northeast trending, accounted for 50%; while the north -west, south-north and approximate east-west trendings take the second place. Generally, the fractures is low in filling degree, but the opening situation and effectiveness are relative good. The research results can compared with the developing regularity of the fractures in the Xuiiaweizi depression.