Abstract:

The characteristics of low-permeability reservoir of Youshashan Formation and its origin in Youquanzi Oilfield of Qaidam Basin were studied synthetically using data of core observation and description,scanning electron microscope and core analysis in laboratory.The analysis results showed that the reservoir mainly developed remaining inter-granular pores and emposieu with micro-bore to fine porous throats.The low-permeability reservoir was affected by some sediment factors,including fine grade,high content of carbonate and shale,and undeveloped primary pores,so it could be easily compacted,which made the acid fluid difficultly penetrate into the reservoir where the dissolution was slow and weak.Diagenesis was the key factor for genesis of the low-permeability reservoir.The compaction and cementation could reduce the primary pore and pore-throat,make the porosity and permeability of reservoir lower and make sandstone tighter.The denudation and undeveloped micro-fractures could not improve the porosity and permeability of the reservoir obviously,which resulted in the low-permeability reservoir in this area.

Key words: Qaidam Basin, low-permeability reservoir, reservoir evaluation, sedimentary micro-facies, diagenesis

摘要：

根据岩心观察描述、铸体薄片、扫描电镜、岩心分析化验等资料,对柴达木盆地油泉子油田油砂山组储层特征及低渗透成因进行的研究结果表明,储层物性总体较差,储集空间以剩余原生粒间孔隙和溶蚀孔隙组合为主,孔隙结构类型属小孔-微细喉道型。沉积因素对低渗透储层的形成起决定性作用,储层粒度细,碳酸盐和泥质含量高,原生孔隙不发育,储层极易被压实,地下酸性流体难以进入,影响了溶蚀作用的进程。成岩作用是储层低渗透成因的最主要的影响因素,压实和胶结作用使原生孔隙空间不断缩小,储层孔隙渗透性降低,岩石致密。溶蚀作用和微裂缝发育不充分,对储层没有明显的改造作用,也是低渗透储层形成的一个重要原因。

关键词: 柴达木盆地, 低渗透储层, 储层评价, 沉积微相, 成岩作用