河流相和三角洲相储层成岩作用及其对储层的影响——以青化砭油田长2油层组和长6油层组砂岩为例

根据砂岩薄片、铸体薄片、扫描电镜、X-衍射等分析,研究了鄂尔多斯盆地青化砭油田长2油层组河流相及长6油层组三角洲相砂岩储层的成岩作用,分析了它们对储层物性的影响状况。研究结果表明,长2油层组河流相和长6油层组三角洲相砂岩储层目前分别处于晚成岩A期和B期。压实作用、胶结作用和溶解作用是控制二者物性演化的主要成岩作用,其中压实作用和胶结作用强烈破坏了它们的原生孔隙,溶解作用则有效地改善了它们的孔隙结构,从而提高了储层的孔渗条件。优质储层多出现在长2油层组河道及长6油层组三角洲平原分流河道砂体中。但在不同强度的成岩作用影响下,长2油层组河流相砂岩储层物性明显好于长6油层组三角洲相砂岩储层,因此优质储层的勘探应以长2油层组河流相河道砂体为重点,兼顾长6油层组三角洲相平原分流河道砂体。

Diagenesis and Its Influence on Reservoir Quality of Fluvial and Delta Sandstone: a Case Study of the Upper Triassic sandstones of Chang-2 and Chang-6 Formation in the Qinghuabian Oil Field

Based on such means as data analysis of thin-section,casting lamella,scan electronmicroscope and X-ray diffraction,the authors studied the diagenetic characteristics of Upper Triassic Chang 2 fluvial facies and Chang 6 delta facies sandstone reservoirs and analyzed their influence on the reservoir quality of the Qinghuabian Oilfield in Ordos Basin. It is shown that the diagenesis of Chang 2 fluvial facies and Chang 6 delta facies sandstone includes compaction,cementation and dissolution,belonging to the "A" and "B" late diagenesis,respectively. At the same time,the compaction and cementation destroyed their primary pore intensely,dissolution changed the pore structure effectively,and consequently the reservoir quality was improved. So favorable reservoirs mostly occurred in the sandbodies of fluvial channels and delta plain distributary channels. Influenced by different intensities of diagenesis,the reservoir quality of Chang 2 fluvial channels sandbodies is better than that of Chang 6. Therefore,the Chang 2 fluvial facies channel sandsbodies should be attached much importance while the Chang 6 delta facies distributary channel sandbodies should also be given attention in exploration.