四川盆地东部下三叠统飞仙关组白云岩化作用及其与储集层发育的关系

摘要

四川盆地东部下三叠统飞仙关组鲕滩相储集层多为白云岩,主要分布于环开江—梁平盆地的台地边缘相带.岩石学和地球化学特征表明,飞仙关组鲕滩相储集层经历了多期白云岩化作用,其中最重要的一期发生于成岩早期近地表环境,由蒸发海水回流引起,形成的粉晶交代白云石构成了现今白云岩的主体.飞仙关组早期白云岩经历了不同程度的埋藏重结晶作用,形成了不同的岩石结构类型.飞仙关组白云岩的孔隙多为原岩中继承而来,白云岩化作用对储集层发育的意义并非创造孔隙,而是保存已有的孔隙.由于白云岩化作用发生的时间早以及白云岩的抗压溶性质,原生(鲕)粒间孔以及早期大气淡水溶蚀作用形成的鲕模孔/粒内溶孔可以在很大程度上保存下来,构成了现今鲕滩相储集层的主要储集空间.%Gas reservoirs of the Lower Triassic Feixianguan Formation in eastern Sichuan Basin are mostly dolostones, which are distributed in the platform margin around Kaijiang-Liangping Basin. Petro-graphic and geochemical evidences indicate multiple dolomitization events, and the most significant one of which was triggered penecontemporaneously by reflux of evaporative seawater. Dolostones formed in early periods had undergone various degree of recrystallization during burial, which resulted in the complex rock textures. Pore of the Feixianguan Formation dolostones is predominantly intergranular and/or oomoldic (or intragranular) , which is inherited from the precursor limestones rather than creating during dolomitization. These kinds of pore are well preserved in dolostones, owing to early dolomitization and the resistance of dolomites to compaction.