四川盆地川中地区上三叠统须家河组绿泥石胶结相储层特征

Characteristics of chlorite cemented face reservoirs in upper Triassic Xujiahe Formation in central region of Sichuan Basin

四川盆地川中地区须家河组储集砂岩中发育大量自生绿泥石,本文通过绿泥石胶结相砂岩样品的薄片观察、扫描电镜以及压汞等实验分析,发现绿泥石胶结相的砂岩储层中绿泥石与孔隙之间存在密切关系,随着绿泥石含量增加,孔隙度相应提高,绿泥石与面孔率呈明显正相关关系。绿泥石在岩石孔隙中以包膜或孔隙衬里的形态产出,绿泥石环边在成岩过程中抑制石英的次生加大,可提升储层岩石的机械强度和抗压能力,造成储层岩石的原生孔隙在复杂的地质作用中得以保存。然而,随着绿泥石含量增加,渗透率明显降低,表现出负相关关系,因此,绿泥石对须家河组致密储层影响表现为两方面,它虽能提高面孔率却降低了储层渗透率,在储层评价过程中应分别描述。

Chlorite is widely distributed in reservoir rocks in the Xujiahe formation of Central Sichuan Basin.We take the chlorite cemented sandstone samples as an example,through sheet observation,SEM and mercury instrusion experimental analysis.Finally we find a close relationship between chlorite and pores in chlorite cemented sandstone reservoirs:with the increasing chlorite content,porosity increases also.It is positive correlation between chlorite and plane porosity.Chlorite is produced in rock pores as coat or pore lining form,Secondary increase of quartz is inhibited during rock formation of chlorite ring,and It can improve the mechanical strength and pressure resistance ability of the reservoir rock,resulting in the primary pores of the reservoir rock to be preserved in the complex geological action.However,with the increasing chlorite content,the permeability decreased significantly,showing a negative correlation,We therefore found the effect of chlorite on Xujiahe formation to dense reservoir is manifested in the following two aspects:Chlorite can improve the plane porosity but reduce permeability,it should be described separately in the reservoir evaluation process.