延长气田山西组致密砂岩储层及微观孔喉特征研究

Reservoir characteristics and sandstone microstructures of Shanxi Formation in the Yanchang gas areas

为探讨微观孔喉结构与致密砂岩物性的关系物性,进一步为延长气田致密气勘探部署方案调整提供依据。应用铸体薄片、扫描电镜、物性分析及压汞分析等技术手段,对鄂尔多斯盆地延长气田山西组砂岩储层及其微观孔喉结构特征进行了研究。结果表明,山西组以岩屑石英砂岩、石英砂岩、岩屑砂岩为主,颗粒以细-中粒为主,成分成熟度较高,孔喉类型多样,非均质性很强,属于致密砂岩储层。综合研究认为:山西组砂岩呈现出高粘土、高硅质、较高的火山灰充填胶结特点以及较差的孔喉组合类型是储层渗透性差的主要原因。致密砂岩储层孔、渗与平均孔喉半径、分选系数具正相关关系,而与排驱压力呈负相关关系。

Study the relationship between the mierostructure and the tight sandstone physical property, which provides the theoretical basis for the gas exploration deployment and development adjustment of the gas field. Reservoir characteristics and sandstone micro-structures of Shanxi formation compacted sandstone reservoir in the western gas areas of Yanchang are studied, based on the Casting Sheet Image, scanning electron microscopy（SEM） ,the Physicality Analysis and mercury intrusion method. The studies show that the reservoirs mainly belongs to tight sandstone, mainly consisting of lithic quartz sandstone, quartz sandstone and lithic sandstone, with the thin or middle particles, nipping silty sand or fine sand, and also with characteristics of the higher compositional maturity ,various types of pore throat and strong heterogeneity. The bad permeability can be attributed to the poor pore-throat combination patterns and cementation and filling with high silica, clay minerals, and volcanic ash. The porosity and permeability are positively related to the average diameter of the pore throat radius and the sorting coefficient and are negatively correlated with the displacement pressure.