川西北地区飞仙关组滩体类型及储集性研究

川西北下三叠统飞仙关组滩体分为台地边缘鲕粒滩和台地内点滩2 种类型, 多数台地边缘鲕粒滩形成时水体相对较深, 未经大气淡水和混合水的成岩改造, 储集性能较差, 局部鲕粒滩形成时水体较浅, 在经过大气淡水和混合水的成岩作用改造后, 白云石化好, 可形成储集性能极好的储集体; 台地内点滩白云石化较好, 储集性能也较好, 但分布狭窄, 厚度较薄, 无规律可寻。由此可见, 滩相沉积体仅是储层发育的基本条件, 滩体最终能否形成有效的储集体, 还要取决于后期成岩作用的改造。当滩体暴露于水体之上时, 受到大气淡水和混合水的改造, 发生白云石化作用, 有利于后期埋藏溶蚀作用的发生, 可产生大量的储集空间, 并构成良好的储集体。

Beach body types and reservoir property of Feixianguan Formation in northwestern Sichuan

The beach body of Lower Triassic Feixianguan Formation in northwestern Sichuan can be divided into platform marginal oolitic beach and intraplatform point beach. The water is relatively deeper at the forming of most of platform marginal oolitic beach which is not transformed by the diagenesis of fresh water and mixed water and has poor reservoir properties. However, a part of oolitic beach formed under shallow water environment, and it is transformed by the diagenesis of fresh water and mixed water and well dolomitized, which can form excellent reservoir. The intraplatform point beach experienced good dolomitization and has good reservoir properties, with little development and thin thickness. Beach facies is only the basic condition for reservoir development. The forming of effective reservoir in the beach body depends on the later diagenesis. The beach body is dolomitized when it exposes above the water, which is favorable for the later buried denudation and forming of good reservoir.