华庆地区东部长6_3储层特征及成岩作用研究

Reservoir Characteristics and Diagenesis of Chang 6_3 Member, Eastern Huaqing Area

根据铸体薄片、扫描电镜、储层物性、孔隙结构与岩心分析和化验资料,对鄂尔多斯盆地华庆地区东部长63砂岩储层特征进行研究的结果表明:该区储层储集空间以粒间孔为主,储层物性差,微裂缝对改善孔隙渗透能力贡献不大;排驱压力和饱和度中值压力较高,孔喉半径小且分选性较差,溶蚀作用对物性影响较弱。由于高长石、低石英的矿物组成特点,并且黏土矿物和碳酸盐胶结物广泛分布,压实作用和胶结作用对储层产生破坏性作用,而溶蚀作用对孔隙形成相对有利。根据长63储层致密化的影响因素,研究区划分出两大类五小类成岩相,即较弱压实、较弱胶结、长石溶蚀成岩相和较强压实或较强胶结成岩相,较弱压实、较弱胶结、长石溶蚀成岩相分布范围广,易形成高渗区,较强压实或较强胶结成岩相主要分布在北部砂体边部、南部砂体边部和其他零星地区,不利于储层发育。

Based on casting thin-section identification,SEM observation,and some petrophysical property and porous structure data from core analysis,the reservoir characteristics of Chang 6_3 sandstone,eastern Huaqing area,Ordos Basin,were summed up.Results show that(1)this reservoir is characterized by poor petrophysical property,its space is dominated by intergranular pore,and microfractures contribute little to improving the penetration ability of pores;and(2)it is also featured by higher displacement pressure and median saturation pressure,small radius of pore and throat,poor sorting,and weaker effect of dissolution on petrophysical property.Both compaction and cementation are destructive to generating a reservoir whereas dissolution is conducive to forming pores due to high content of feldspar,low content of quartz,and wide distribution of both clay mineral and carbonate cement.Based on some factors affecting the densification of Chang 6_3 Member,this study area can be divided into two types(including five subtypes)of diagenetic facies,containing weaker compaction,weaker cementation,feldspar dissolution,strong compaction,and strong cementation.Large extension of the weaker compaction,weaker cementation,and feldspar dissolution diagenetic facies easily forms many high-permeability belts.And the strong compaction and strong cementation diagenetic facies,mainly distributed at the edge of both north and south sandbodies and other part areas,are not good for reservoir development.