张韩地区长8_2特低渗透储层微观孔隙结构研究

运用岩心薄片、铸体薄片、常规压汞等资料,结合恒速压汞实验,对鄂尔多斯盆地张韩地区长8_2特低渗透砂岩储层微观孔隙结构进行了综合分析研究。结果表明,长8_2储层储集空间多样,以原生粒间孔为主,孔隙结构可划分为三种类型:低排驱压力-中喉型、中排驱压力-细喉型、高排驱压力-微细喉型;储层孔隙结构复杂多样,压汞排驱压力和中值压力偏高,孔喉连通性较差,依孔隙结构特征将储层划分为Ⅰ类储层、Ⅱ类储层、Ⅲ类储层。综合分析表明,长8_2储层由于流动孔喉半径偏小,渗流能力较差,油藏启动压力较高,通常对储层进行压裂改造后才可获得较高产能。在张韩地区8_2低渗透油层开发过程中要注重对储层喉道的保护,以便取得更好的开发效果。

Microscopic pore structure in ultra-low permeability reservoir of Chang 8_2 reservoir in Zhanghan area

The study of reservoir microscopic pore structure is an important part in comprehensive reservoir evaluation.Based on slice observation,casting thin section and conventional constant-pressure mercury injection,combined with constant-speed mercury injection,the comprehensive analysis of ultra-low permeability sandstone reservoir from Chang8_2 reservoir in Zhanghan area of Ordos Basin was carried out.The results indicated Chang 8_2 reservoir was of multiple storage space,the main type was of primary intergranular pore and the pore structure could be divided into three categories:low displacement pressure-medium throat,medium displacement pressure-fine throat,high displacement pressure-micro-fine throat.The reservoir pore structure was complex and various,the expulsion pressure and median pressure were on the high side,while the pore connectivity was poor.According to reservoir pore structure characteristics,the reservoirs were divided into typeⅠ,typeⅡ and typeⅢ.Comprehensive analysis indicated due to small flow pore radius,poor flow capacity and high reservoir starting pressure,high productivity could be only obtained through fracturing.In development process of low permeability reservoir of Chang 8_2 reservoir,the protection of throat reservoir should be paid attention to so as to achieve better development effect.