鄂尔多斯盆地姬塬地区长_8储层成岩作用与有利成岩相研究

Diagenesis and favorable diagenetic facies of Chang8 reservoir in Jiyuan area of Ordos Basin

利用铸体薄片、扫描电镜等测试技术和储层综合评价方法对姬塬地区长8砂岩成岩作用及有利成岩相带进行了系统分析,结果表明,长8砂岩处于晚成岩阶段A期,压实作用造成砂岩中原生孔隙丧失;受酸性成岩环境影响,长石类不稳定矿物发生溶蚀,产生的溶蚀孔隙有效地改善了孔隙的连通性和渗透性,成岩早期形成的绿泥石粘土膜保留了大量原生粒间孔,保持了较好的储层物性。结合成岩作用和沉积特征,研究区可划分出4种主要成岩相带。长石溶蚀成岩相和绿泥石膜—粒间孔成岩相是最为有利的成岩相带,分布在刘卯塬—堡子湾一带的三角洲前缘水下分流河道砂体发育区,以及小涧子一带三角洲分流河道交汇处的砂体发育区。

The diagenesis and favorable diagenetic facies of Chang8 reservoir in Jiyuan area of the Ordos Basin were studied by means of cast thin section, SEM and reservoir comprehensive evaluation. The Chang8 sandstones were during the subphase A of late diagenesis. Compaction effect caused the disappearance of primary pores. Influenced by acidic diagenetic environment, feldspars were corroded, improving pore connectivity and permeabili- ty. In the well-developed chlorite film which generated during early stage, a large quantity of primary pores was preserved, showing good reservoir physical property. According to diagenetic and sedimentary features, 4 diagenetic facies belts were classified. The diagenetic facies belts of feldspar corrosion and chlorite film-intergranular pore were most favorable, mainly distributing in sandbody zones in subaqueous distributary channel of delta front in Liumaoyuan and Baoziwan areas, and in distributary channel of delta in Xiaojianzi area.