松辽盆地深层火山岩岩性分类方案

Classification of deep volcanic rocks in Songliao Basin

在分析国内外火山岩分类研究的历史和现状基础上,依据对近15年来大庆深层127口钻遇火山岩探井和盆缘剖面的研究资料,提出松辽盆地深层火山岩及沉积岩、变质岩的分类方案。将火山岩类划分为火山熔岩、火山碎屑熔岩、火山碎屑岩和沉火山碎屑岩四类。前两者是冷凝固结成岩,其孔渗等物性特征与埋深无关;后两者为压实固结成岩,其物性随埋深增加而变差。珍珠岩、黑耀岩和松脂岩等玻璃质熔岩以酸性为主,中基性者也常见。隐爆角砾岩和具熔结结构的岩石均属于火山碎屑熔岩类。

History and situation about classification of volcanic rocks have been summarized. Based on core sections from 127 wells cutting through J3-K1 volcanic rocks and outcrops around the basin, a lithologic classification has been proposed for the deep basin volcanic rocks as well as sedimentary and metamorphic rocks of the northern Songliao Basin. Volcanic lavas, breccia -bearing lavas, pyroclastic rocks, and tuffites are classified and described in detail. The former two rocks are consolidated by cooling and the latter two ones by compaction. The two different ways of lithification, cooling or compaction, are crucial in determining reservoir features of volcanic rocks. Porosity and permeability of the volcanic rocks lithified by cooling will not affected by their buried depth, while those by compaction will loss their porosity and permeability with increasing buried depth. Perlite, obsidian and pitchstone are volcanic glass having the same compositions commonly with rhyolite as well as andesite and basalt. Blind explosive breccias and welded volcanics belong to breccia-bearing lavas in the classification.