苏北盆地金湖凹陷腰滩地区古近系阜宁组储层物性特征及其影响因素

Quality of Reservoir Sandstones of Funing Formation in Yaotan Area from Jinhu Depression,Subei Basin,and Its Influencing Factors

苏北盆地金湖凹陷腰滩地区古近系阜宁组储层岩石类型以岩屑长石砂岩和长石砂岩为主,其成分成熟度中等,结构成熟度中等到好。腰滩地区储层成岩作用主要包括压实、胶结、溶蚀和交代四种类型,目前处于晚成岩阶段A期。研究区储层的储集物性受成岩作用和构造运动的共同影响,主要表现为对孔隙度和渗透率的影响,其中压实和胶结作用使储层原生孔隙迅速减少、渗透率降低、储集物性变差,而溶解作用则是导致次生孔隙发育及改善砂岩储集性能的主要因素。压实作用主要表现为刚性颗粒发生脆性破裂、塑性颗粒挤压变形或刚性颗粒嵌入塑性颗粒中、颗粒之间呈线接触和凹凸接触、碎屑颗粒呈明显的定向排列等;溶蚀作用表现为碳酸盐矿物的溶解;胶结物主要为自生黏土矿物、碳酸盐和自生石英。交代作用主要为碳酸盐胶结物交代石英、长石及岩屑颗粒及碳酸盐胶结物之间的相互交代等。构造运动使局部的储层物性得到改善。

Reservoir sandstones of the Paleogene Funing Formation in Yaotan Area of Jinhu Depression mainly consist of lithic arkose and arkose,with medium compositional maturity and median-high textural maturity.The Funing Formation reservoir sandstones in Yaotan area are in the A stage of epigenesis,the main diagenesis of which includes compaction,cementation,dissolution,and replacement.Diagenesis and tectonic movement influence the reservoir physical properties together,especially affect the porosity and permeability of the reservoir in the study area.Compaction and cementation rapidly decrease the porosity and permeability of the reservoir as well as the whole reservoir quality,while dissolution can improve the reservoir quality and cause the development of secondary pores.Compaction in the reservoir of the study area mostly show as brittle fractures of rigid particles,compressional deformation of plastic particles,rigid particles embedding into plastic particles,linear and concave- convex contacts between particles,and the obvious directional alignment of detrital grains.Dissolution mainly present as the dissolution of carbonate minerals,with the sements between detrital grains mostly being authigenic caly minerals,carbonate minerals and authigenic quartz.The replacement in the study area mainly show as the replacement between the carbonate cements and quartz,the feldspars and lithic debris,or inside the carbonate cements.The tectonic movement can partly improve reservoir physical properties in the study area.