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
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

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.