松辽盆地火山岩相与火山岩储层的关系

根据钻井岩芯/岩屑和剖面地质研究结果,火山岩相可分为4类12型。松辽盆地徐家围子断陷火山岩储层具有孔隙和缝隙相互组合的所谓“双孔介质”。火山岩储层的储集空间类型受岩相控制,不同岩相带发育的火山岩储层其孔-缝及其组合关系差异很大。喷溢相主要发育气孔、流纹理层间缝隙和节理缝;爆发相的主要空隙类型为粒间孔隙;侵出相以角砾间孔和原生裂缝为主;火山通道相主要发育节理缝和各种原生裂隙。爆发相中每个冷却单元的底部经常发育有“松散层”,它们是未熔结的碎屑砂流层或原基岩的风化壳被快速披盖保存而形成的。侵出相内带亚相经常会出现大规模的“岩穹内松散体”,它们是大的珍珠岩球体的堆积体。在中酸性火山岩储层发育区应特别注意寻找这两类储集体。松辽盆地主要的构造裂隙是一组共轭的、高角度的(断层面倾角50°～90°)、走向NNE和NNW向的、剪性或压剪性的断层缝。这组高角度构造裂缝是松辽盆地油气运移的主要通道。

RELATIONSHIP BETWEEN VOLCANIC FACIES AND VOLCANIC RESERVOIRS IN SONGLIAO BASIN

Based on the study of cores, well cuttings, and outcrop sections, the facies of volcanic rocks can be divided into 4 types and 12 sub-facies. Pores and fissures are the two major types of reservoir spaces in volcanic rocks in Xujiaweizi fault-depression. The types of reservoir space in volcanic reservoirs have been found to be controlled by the facies. The volcanic reservoirs found in various facies belts have quite different pores and fissures and their assemblages. Gas cavities, fissures in rhyolitic lamination, and joint fissures have been identified mainly in eruption-overflow facies. The main pore-type identified in explosive facies is intergranular pore; and inter-breccia pore and primary fracture are dominant in extrusive facies.Joint fissures and various primary fractures are mainly developed in volcanic conduit facies.It is found that “unconsolidated formation” often distributes at the base of each cooling unit in explosive explosive facies,which might be resulted from fast covering and conservation of the weathered crusts of the original basement rocks or unclinkered drifting clasts. A large “unconsolidated bodies in rock-dome” can often be found in the inner belt sub-facies of extrusive facies, which are actually of large accumulation bodies of perlite balls. Special attention should be paid to looking for these two-type reservoirs in the intermediate-acidic volcanic rock area. The major tectoclase in this area is a set of conjugated, high-angle (fault plane with dip angle of 50°～60°), NNE and NNW strike, and shear or compressive-shear fractures, which constitute the main migration pathway of oil &; gas.