中东鲁卜哈利盆地古生界致密砂岩储层特征及评价

摘要

中东鲁卜哈利盆地古生界Unayzah组和Sarah组发育致密砂岩储层。薄片鉴定结果表明，其岩石类型以石英砂岩为主，少量的岩屑砂岩、岩屑长石砂岩、岩屑石英砂岩和长石石英砂岩，孔隙类型主要为残余粒间孔。胶结类型及发育程度与沉积环境密切相关。利用压汞法及电镜扫描结果测定了储层的孔隙结构。结果表明，岩石孔喉分布范围较大，小孔隙、细喉道的样品比例较高。根据毛细管压力曲线特征，大多数样品属于储集岩的范围。分别对每一组致密砂岩储层的岩石样品进行了孔隙度和渗透率的测试，结果表明Unayzah组和Sarah组储集性能较好。确定储层参数下限，提出了储层分类评价的标准，对储层进行综合评价。结果显示， Unayzah组纵向上Ⅰ类储层及Ⅱ类储层较为普遍发育，储集性能较好，属于中-好储层；Sarah组总体储集性能较Unayzah组差，以Ⅱ类和Ⅲ类储层居多，属于中-差储层。%Tight sandstone reservoirs occur in the Palaeozoic Unayzah and Sarah Formations in Rub Al Khali Basin in the Middle East.Thin section analysis reveals that quartz sandstone is the main rock type ,with some lithic sandstone ,lithic arkose ,lithic quartz sandstone and feldspathic quartz sandstone .The main pore type is residual intergranular pore .The ce-ment types and their development degree are closely related with the depositional environment .Measurement of reservoir pore structure through mercury intrusion and SEM indicates that pore throat size distribution is large and the proportion of samples with small pores and narrow throats is large .The capillary pressure cures show that most samples have the po-roperm characteristics of reservoir rocks .The testing data indicates that the Unayzah and Sarah formations have good re-servoir quality.On this basis,we determined the lower limits of the reservoir parameters and proposed the evaluation crite-ria for reservoir classification .The comprehensive evaluation indicates that the Unayzah Formation is moderate-good reser-voir,with typeⅠand typeⅡreservoirs widely developed vertically ,whereas the Sarah Formation is moderate-poor reser-voir,with typeⅡand type Ⅲreservoirs being predominate .