柴达木盆地油砂山油田下油砂山组砂岩成岩作用和孔隙结构

对青海柴达木盆地油砂山油田下油砂山组砂、泥岩样品的分析测试表明，下油砂山组湖相三角洲砂岩的成分成熟度和结构成熟度均较低，成岩作用已达到中成岩阶段的成熟Ａ期或Ｂ期；早成岩阶段的主要成岩作用是碳酸盐胶结作用以及压实作用引起的颗粒重排；中成岩阶段未成熟期则以机械实作用为主，半成熟期以方解石和方沸石胶结作用为主，成熟Ａ期或Ｂ期的主要成岩事件是烃类大量成熟引起的晚期溶蚀。该三角洲体系中河道砂体、河口坝砂体和

Diagenesis and Pore Structure of Lower Youshashan Sandstone in Youshashan Oilfield, Chaidamu Basin

The lithologic analysis for sandstone an4 mudstone samples shows that the composition and texture maturity of lacustrine deltaic sandstones in Lower Youshashan Formation in westerm Chaidamu Basin are lower'The diagenesis of Lower Youshashan Formation has reached the A or B matured period of mesodiagenesis. Main diagenesis of the syndiagenesis is carbonate cementation in the shallow lake sheet sands and rearrangement caused by compaction.Main mechanical compaction takes place in the unmatured period of mesodiagenesis.During the semi-matured period of mesodiagenesis,the cementation of calcite and analcite is active.Main diagenesis events in the A and B matured period of mesodiagenesis are late dissolution and restraint of inorganic diagenesis due to abundant hydrocarbon generation.In this deltaic system,channel sandbodies,river mouth bar sandbodies and thick delta front sheet sands have higher porosity and permeability.The shallow lake sheet sands have almost no reservoir significance because of early carbonate cementation.The difference of the depositional environment,component and texture of sandbodies give rise to the difference of diagenesis history and reservoir quality.The sandstones have mainly interparticle primary porosity.Throats are developed.