浅析影响砂岩渗透性的主要因素

研究表明,砂岩层内的早期成岩作用(压实、压溶、胶结和交代作用)使孔隙度和渗透性降低。自生高岭石胶结可保留粒间微孔隙,对渗透性影响较小,甚至可增强渗透性。中后期成岩作用下,有机质成熟直至生烃以及产生的酸性水发生溶蚀形成了次生孔隙,可使砂岩渗透性大大增强,是砂岩型铀矿床形成的有利前提条件。后生改造期层间氧化蚀变和油气还原低温热液蚀变也生成了次生孔隙,最终决定了砂岩型铀矿床形成后的渗透性,它是地浸利用的重要条件。

Elementary analysis on the main factors affecting the permeability of sandstones

Researches show that in the early stage of sandstone diagenesis,compaction,pressure solution,cementation and replacement reduce both the porosity and the permeability. The cementation of authigenic kaolinite may preserve the tiny intergranular pore-space,and slightly influence the porosity,and even increase the permeability. During the middle to late stage of diagenesis,the organic matter becomes matured,hydrocarbon and acidic water are produced,which forms secondary porosity by the dissolution and the corrosion,and greatly increases the permeability of sandstones and provides a favorable prerequisite for the formation of sandstone-type uranium deposits. The interlayered oxidation alteration,oil-gas reduction and low-temperature hydrothermal alteration also produce secondary porosity in epigenetic reforming stage,which finally decides the permeability after the formation of sandstone-type uranium deposits. This is an important condition for in-situ leaching of sandstone-type uranium deposit.