鄂尔多斯盆地中部长4+5低渗透储层微观孔喉特征及物性响应

Micro Pore and Throat Characteristics and Physical Response of Permeability Reservoir of Chang4+5 in the Middle Ordos Basin

论文对鄂尔多斯中部长4+5储层20组样品进行薄片鉴定、扫描电镜以及压汞实验,系统地研究了储层的微观孔喉结构特征。研究区砂岩储层主要为长石砂岩,粒间孔发育,次生溶孔主要为长石溶孔。主要喉道类型为片状喉道和弯片状喉道,偶尔可见缩颈型喉道。储层平均孔隙度为12%,平均渗透率为1.01×10^(-3)μm^(2),属于低渗透砂岩储层。中值孔喉半径、平均孔喉半径以及最大连通半径均与渗透率有较好的正相关性,与孔隙度相关性较差,说明渗透率主要受到孔喉半径的影响。喉道个数与渗透率呈良好的正相关性,说明喉道对渗透率的贡献较大。退汞效率与渗透率呈较好的正相关性,与孔隙度相关性较差,其原因在于低渗透储层非均质性较强,会在一定程度上影响储层的渗流能力。

In this paper,thin section identification,scanning electron microscopy and mercury injection experiments were carried out on 20 groups of samples from Chang4+5 reservoir in Ordos,and the micropore throat structure characteristics of the reservoir were systematically studied.The sandstone reservoir in the study area is mainly arkose sandstone with more inter-grain pore.The secondary dissolution pores are mainly feldspar dissolution pores.The main laryngeal types are lamellar and curved lamellar,with occasional necked throat.The reservoir,with an average porosity of 12%and an average permeability of 1.01×10^(-3)μm^(2),belongs to a low-permeability sandstone reservoir.Median pore throat radius,average pore throat radius and maximum connecting radius are positively correlated with permeability,but weakly correlated with porosity,indicating that permeability is mainly affected by pore throat radius.The number of larynx is positively correlated with permeability,indicating that the contribution of larynx to permeability is greater.Mercury removal efficiency has a positive correlation with permeability,but a poor correlation with porosity,which is due to the strong heterogeneity of low-permeability reservoirs,which will affect the seepage capacity of reservoirs to a certain extent.