子长油田上三叠统长2油层组储层成岩作用及物性的影响因素

通过对子长油田20余口取心井的岩心观察和大量样品的铸体薄片、扫描电镜分析,对子长油田长2油层组储层取得以下认识:(1)本区长2油层组储层岩性主要为长石细砂岩,含少量的岩屑长石细砂岩,具成分成熟度低、结构成熟度高的特点;(2)长2砂岩已达晚成岩A期,经历了早成岩阶段早期的机械压实和黏土膜析出,早成岩阶段晚期的石英、长石压溶及次生加大,晚成岩阶段早期的自生矿物析出和随后发生的溶蚀形成次生孔隙等成岩作用过程;(3)砂岩中发育粒间孔、粒内溶孔、微孔隙、裂隙孔等几种孔隙类型,以粒间溶孔为主,占总孔隙的80%以上;(4)储层物性主要受沉积微相及成岩后生作用的影响,具体表现为砂岩的成分(碎屑云母、方解石胶结物)和结构(粒度)对物性影响较大.

Diagenesis of Chang2 reservoir of Upper Triassic Series in Zichang oilfield and the factors of influencing the physical property of the reservoir

Based on the core observation from over 20 wells and the study of cast thin section and scanning electron microscope analysis results from a great deal of samples, it is held that, (1) Chang2 sandstone reservoir in Zichang oilfield is mainly composed of fine feldspathic sandstone, and there is also a little fine lithic arkose in it, which is characterized by lower composition maturity but higher texture maturity; (2) Chang2 sandstone has reached "A" period of late diagenesis phase which underwent compaction and clay membrane separating out in early period of early diagenesis phase, pressure solution of quartz and feldspar and secondary adding in late period of early diagenesis phase, authigene cementation and dissolution which results in the forming of secondary pore in early period of late diagenesis phase; (3) in Chang2 sandstone, there are intergranular pore (including relic primary intergranular pore, intergranular dissolution pore), intragranular dissolution pore, micro pore and fracture pore. The main type of pore is intergranular dissolution pore, which amounts to more than 80% of total pore; (4) the physical property of Chang2 reservoir is mainly influenced by sedimentary microfacies and diagenesis, which is shown by the greater effects of the composition (detrical mica, calcite cement) and the texture (grainsize) of Chang2 sandstone on the physical property.