沧东凹陷孔二段致密砂岩储集层微观孔喉结构特征

Characteristics of Micro-Pore Throat Structures in Tight Sandstone Reservoir of the Second Member of Kongdian Formation in Cangdong Sag

应用薄片观察、场发射扫描电镜、物性分析、压汞分析和激光共聚焦显微镜观察等手段，对渤海湾盆地黄骅坳陷沧东凹陷孔店组二段致密砂岩储集层岩石学特征、储集空间类型、储集层物性及孔喉分布特征进行了研究。结果表明，孔二段储集层主要为岩屑石英砂岩和岩屑砂岩，储集空间以次生溶蚀孔隙和晶间微孔隙为主，含少量残余原生孔隙和裂缝，平均孔隙度为7.71%，平均渗透率为0.59 mD，属于特低孔超低渗储集层。储集层的孔喉结构较差，孔喉多呈孤立状分布，连通性较差。储集层的孔隙半径相差不大，多数为100~200 μm；喉道半径相差较大，多属于微米—纳米级别。储集层的渗流能力主要受喉道半径、频数及分布形态的控制。对孔二段致密砂岩储集层的开发应采取保护喉道的改造工艺，才能取得更好的开发效果。

Based on thin section observation, analysis on SEM, physical property and mercury injection and laser scanning confocal microscope observation, the petrological characteristics, reservoir space type, physical property and pore throat distribution are studied for the tight sandstone reservoir in the second member of Kongdian formation in Cangdong sag of Huanghua depression, Baohai Bay basin. The result shows that the reservoir in the second member of Kongdian formation is dominated by lithic quartz sandstone and lithic sandstone, and the reservoir space is mainly composed of secondary dissolved pores and intercrystalline micro-pores, containing a few residual primary pores and fissures. The porosity and permeability of the reservoir average 7.71% and 0.59 mD, respectively, indicating that the reservoir belongs to super-low porosity and extra-low permeability reservoirs. The reservoir pore throats have relatively poor structures and are mostly distributed separately, so the pore connectivity is poor. The reservoir pore radiuses are similar with the most ranging from 100 to 200 μm. Pore throat radiuses vary largely with the most in micron-nano scale. The filtration capacity of the reservoir is mainly controlled by radius, frequency and distribution pattern of pore throats. Some treatment technologies should be adopted to protect the pore throats in the tight sandstone reservoirs in the second member of Kongdian formation and better development effects can be gained .