前前陆盆地层系砂岩成岩环境特征及其孔隙演化——以鄂尔多斯盆地西缘二叠系为例

The diagenetic environment of sandstone and porosity evolution of pre-foreland basin strata: a case study of Permian strata on the western Ordos foreland basin

鄂尔多斯西缘二叠系为前前陆盆地层系 ,砂岩成岩作用仍受前陆盆地构造的影响 ,不同构造分区砂岩储层的成岩环境存在一定的差别。研究发现 ,西缘逆冲带砂体经历了浅埋藏弱压实和溶蚀作用 ,储集物性最优 ;斜坡带砂岩储层不仅残留少量粒间孔隙 ,而且溶蚀作用形成的次生孔隙对储集空间的改善十分明显 ;压实压溶作用和胶结充填作用严重损害前渊带砂岩原生孔隙 ,但后期的凝灰质溶蚀蚀变作用对储层性能有一定的改善 。

The Permian strata on the western margin of Ordos belong to strata of the pre-foreland basin. On the whole, the tectonic belts of foreland basin regionally control the diagenesis of sandstone, with different belts characterized by different diagenetic dynamical environments. The Permian high quality reservoir was formed in the western thrust belt and underwent weak compaction with shallow burial and dissolution. The sandstone pores of Permian strata on the slope belt are mainly composed of secondary pores resulting from strong dissolution, with a certain quantity of relict original pores. Great losses of sandstone original pores in the geotectogene resulted from the compaction and cementation with deep burial, whereas the reservoir quality was improved by dissolution and the sandstones served as the effective gas reservoir.