咸化湖盆过渡相组沉积控储作用浅析

咸化湖盆过渡相组（三角洲前缘与浅湖亚相）沉积特征与淡水湖盆存在显著差异，尤其在骨架砂体微相类型、分布等方面。研究其沉积控储机制，既是对湖盆沉积学理论的重要发展，也对中国陆相盆地碎屑岩油气勘探开发具有实际指导意义。应用大量岩芯、测录井及铸体薄片资料，分析了柴达木盆地英东地区下油砂山组（N₂¹）与上油砂山组（N₂²）三角洲前缘浅湖沉积特征及优质储层形成主控因素。研究表明，咸化湖盆三角洲前缘浅湖主要发育水下分流河道与滩坝两种储集砂体沉积微相类型。两者在沉积构造、粒度分布、微观组构及测井曲线叠加样式等方面存在显著差异。沉积微相是优质储层形成的物质基础，与湖盆水体咸化程度共同控制了优质储层的分布。咸化湖盆碎屑岩储层整体成分成熟度偏低，以原生孔隙为主，溶蚀作用较弱，次生孔隙相对欠发育。强烈的早成岩期碳酸盐胶结作用增加了岩石的抗压能力。储层物性主要受控于岩石粒度与胶结物含量。

Preliminary Analysis on the Controls on Hydrocarbon Reserves by Transitional Facies Sedimentationin Saline Lacustrine Basins

The sedimentary characteristics of transitional facies in saline lacustrine basins (delta fronts and shallow lake subfacies) differ significantly from those of freshwater lacustrine basins, especially with regard to the distribution of skeletal sand body microfacies. Research into the control mechanisms of sedimentation over hydrocarbon reserves leads to important developments of sedimentological theories regarding lacustrine basins and practical guidance for oil and gas exploration and exploitation in terrestrial basin clastic rocks in China. Core, logging and cast thin section data are used to analyze the major controlling factors of sedimentation in the delta front-shallow lake and high-quality reservoir formation of the Lower (N₂¹) and Upper (N₂²) Youshashan Formations in the Yingdong region of the Qaidam Basin. The results show that, there are primarily two types of reservoir microfacies for the delta front-shallow lake regions in the saline lacustrine basins, namely underwater distributary channels and beach sandbars. They are considerably different in terms of their sedimentary structures, particle size distributions, microscopic structures, and superposition of logging curves. Sedimentary microfacies provide the primary material for high-quality reservoir formation. Meanwhile, microfacies and salinization of water bodies in lacustrine basins jointly control the distribution of high-quality reservoirs. In general, saline lacustrine basin clastic rock reservoirs are relatively immature. Primary pores and relatively weak corrosion were observed, while secondary pores were less developed. Intensive carbonate cementation in the early diagenetic stages enhances the compression resistance of rocks. The reservoir properties are primarily determined by the particle sizes and cement content of rocks.