储层砂岩中自生绿泥石对孔隙结构的影响--来自鄂尔多斯盆地上三叠统延长组的研究结果

Influences of authigenic chlorite on pore structure in sandstone reservoir: A case study from Upper Triassic Yanchang Formation in Ordos basin,China

通过对鄂尔多斯盆地陇东地区延长组10个砂岩样品的薄片分析、X射线衍射分析、扫描电子显微镜分析、物性分析和压汞分析,研究了这些砂岩中自生绿泥石含量与各种孔隙结构参数之间的关系。研究结果表明:①在孔隙度变化不大的情况下,随着自生绿泥石含量的增加,砂岩的渗透率降低,排驱压力和中值压力增加,与之对应的喉道半径显著减小,同时喉道均值和各种类型喉道的百分数也都显著降低。②自生绿泥石含量的增加可以改善喉道的分选性和非均质性,但这是牺牲了大喉道的数量来实现的。③砂岩中自生绿泥石含量的增加还会显著降低退出效率。因此,在孔隙度类似的前提下,以孔隙衬里方式产出的自生绿泥石含量的增加,会降低砂岩储层的质量并影响烃类开发的效果。

We studied the relationship between authigenic chlorite content in sandstone and the parameters of pore structure by thin section analysis,XRD,SEM,physical property analysis and mercury intrusion analysis on 10 samples in Longdong area of Ordos basin.The result indicates that,when sandstone porosity changes little,with increasing authigenic chlorite content,the permeability of the sandstone decreases while drainage pressure and median pressure increase,and the corresponding throat radius decreases obviously;meanwhile,throat mean value and the number of throats in different types also decrease significantly.Our research results also indicate that although the increasing of authigenic chlorite content would ameliorate the sorting and heterogeneity of throats,the number of large throats would reduce correspondingly;furthermore,the increasing of authigenic chlorite content would remarkably reduce ejection efficiency.Therefore,increasing pore-lining authigenic chlorite would reduce the quality of sandstone reservoirs and affect hydrocarbon exploitation under the prerequisite of similar porosity.