中国陆相湖盆沉积岩中方沸石的产状、成分和成因

天然方沸石是沉积岩中的常见矿物,与油气储层关系密切.在总结前人研究成果的基础上,对天然方沸石的产状、成分特点、成因类型以及方沸石对储层的影响进行了归纳.结果表明:方沸石是含有结晶水的架状结构硅酸盐矿物,平面上硅氧四面体构成封闭环,三维空间中具有笼状结构,结构内部的孔道有利于溶解作用的发生.陆相湖盆中的天然方沸石有5种典...

Occurrence,composition and origin of analcime in terrestrial lacustrine sedimentary rocks in China

Natural analcime closely related to oil and gas reservoirs, is quite common in sedimentary rocks.We summarize the occurrence, composition, genesis of natural analcime and discuss its impact on reservoirs based on previous researches.The results show that analcime, a kind of silicate mineral containing crystalline water and of framework structure, is characterized by a silica-oxygen tetrahedron on map view to form a closed ring, and a cage structure in 3-D visualization space, the pore pathways in which are conducive to dissolution.There are five typical types of natural analcime in terrestrial lacustrine basins, among which the analcime with intergranular cements and fracture fillings is euhedral, and the exhalative analcime comes in two kinds of occurrence, namely, porhyritic texture and discontinuous coarse-grained laminae.The compositional differences of analcime concentrate on the content of Na and K ions: the K ion content tends to be higher, and the Si/Al ratio in analcime mainly ranges from 2.0 to 2.69, when it comes to alkaline volcanic rock as the host-rock.Among the four categories of natural analcime in terms of genesis, that in terrestrial lacustrine basins is mainly derived from diagenesis and hydrothermal exhalation.In all, sedimentary facies is key in the formation and dissolution of analcime; the analcime with intergranular cements is widely spread in the fan delta front developed from volcanic materials, while the analcime out of hydrothermal exhalation is common in the deep-semi-deep lacustrine subfacies; and dissolution of analcime by acidic fluid in the later stage is different in different sedimentary facies.