Diagenesis of Chang 6 and Chang 7 turbidite reservoirs of the Upper Triassic Yanchang Formation in Fuxian and Huangling areas, Ordos Basin

Based on the data analysis of thin-section, casting lamella, scan electronmicroscope and intrusive mercury etc, the characteristics of lithology and diagenesis are researched on the Upper Triassic Chang 6 and Chang 7 turbidite reservoirs and analyzed their influence on the reservoirs quality of Fuxian and Huangling areas in Ordos Basin. It is shown that the sandstones are granule arkose, which were formed by four types diagenesis that were compaction, cementation, metasomatism and dissolution. It is suggested that the compaction and cementation resulted in lossing primary porosity of the turbidites, and the porosity loss caused by compaction and cementation are 23.1% and 6.5%, respectively. But due to thin film of chlorite occurred around clastic granules, a part of primary intergranular pore were preserved, and a large of secondary pore were formed with dissolution and metasomatism, which improved the reservoir quality for the turbidites.