吴定地区侏罗系延9段储层特征及影响因素

Characteristics and influencing factors of Jurassic Yan 9 reservoir in Wuding area

吴定地区是鄂尔多斯盆地开采规模较大的油田之一,延9段储层作为主要开采层位,其储层特征及影响因素研究较少,明确研究区储层特征及沉积、成岩作用对其影响是后续勘探开发工作急需解决的问题。采用岩心观察、扫描电镜、铸体薄片等方法对吴定地区延9段储层特征及影响因素进行研究,结果表明:延9段储层以岩屑长石砂岩和长石岩屑砂岩为主,砂岩碎屑分选为中等-好,磨圆较差,成熟度较低;储层孔隙度的平均值是15.08%,渗透率的平均值是59.02 mD。储层特征主要受沉积与成岩作用两个因素影响,水下分流河道砂体是有利沉积相带;延9段储层主要受压实、胶结及溶蚀作用的影响,压实、伊利石胶结及碳酸盐胶结作用破坏了原有孔隙结构,使储层物性变差;高岭石在储层物性的影响上表现出双面性;溶蚀作用产生较多的次生孔隙,是提高孔渗能力改善储层物性的关键;研究区延9段储层成岩演化已进入中成岩阶段B期。该研究为储层综合评价及有利区优选提供了地质依据。

Wuding area is one of the larger oilfields in the Ordos Basin,and Yan 9 reservoir,as the main exploitation layer,is less studied in terms of reservoir characteristics and influencing factors,so clarifying the reservoir characteristics of the study area and the influence of sedimentation and diagenesis on it is an urgent problem to be solved in the subsequent exploration and development work.The characteristics and influencing factors of the Yan 9 reservoir in the Wuding area were explored using core observation,scanning electron microscopy,cast thin section.The results show that the Yan 9 reservoir is dominated by rock⁃chip feldspathic sandstone and feldspathic clastic sandstone,with sandstone clasts sorted to medium⁃good,poorly rounded,and low maturity;the average value of reservoir porosity is 15.08%,and the average value of permeability is 59.02 mD.The characteristics of the reservoirs are mainly influenced by both sedimentation and diagenesis,of which,the sand body of the submerged diversion channel is a favourable depositional phase zone;the Yan 9 reservoirs are mainly affected by compaction,ilmenite cementation and carbonate cementation destroy the original pore structure and deteriorate the physical properties of the reservoir;kaolinite has a dual influence on the physical properties of the reservoir;dissolution produces more secondary pore space,which is the key to increase the pore permeability to improve the physical properties of reservoirs;the evolution of the Yan 9 reservoir mafic rocks in the study area has entered the meso⁃mafic stage B.The study provides geological basis for the comprehensive evaluation of the reservoir and the selection of favourable areas.