志丹探区西南部长_(4+5)段成岩作用及其对储层的影响

Diagenesis of Chang_(4+5) formation sandstones and its impact on reservoir property in southwest Zhidan region in Ordos basin

为了认清鄂尔多斯盆地志丹探区西南部三叠系延长组长4+5段有利储层的分布规律,通过大量岩石薄片和铸体薄片的镜下鉴定,并结合扫描电镜、阴极发光和X-衍射等测试结果,研究了该区长4+5段主要成岩作用及其对储层物性的影响。研究结果显示,长4+5段主要成岩作用类型有压实作用、胶结作用和溶蚀作用;强烈的压实作用及胶结作用导致其原生孔隙丧失殆尽,成为形成特低孔渗储层的主要原因,而晚期较弱的溶蚀作用,对储层的改善发挥了较大作用,从而使鄂尔多斯盆地延长组发育部分有利储层,形成较好的储集-成岩相带。

The paper is aimed at making clear the distribution of the favorable reservoirs in chang4＋5 of Zhidan regions. Based on core description, cast section, scanning election microscope, x-ray diffraction etc, it was believed that the main diagenesis types were pressure solution, cementation and dissolution. Intensive compaction and cementation resulted in complete loss of primary porosity. It was the main reason which formed the low porosity and the lowest permeability; however, the later weak dissolution had great effect on improvement of reservoir permeability, hence, there are some efficient reservoir and become advantaged reservoir-diagenetic facial belt in Yang- chang formation in Ordos basin.