喇嘛甸油田高含水后期储集层孔隙结构特征

Pore structure features of reservoirs at late high water-cut stage,Lamadian Oilfield,Daqing

针对大庆喇嘛甸油田高含水后期低效、无效循环注水开发状况,利用恒速压汞和恒压压汞法研究了喇嘛甸油田储集层岩样水驱前后的孔隙结构特征。恒速压汞分析表明,岩样经过长期水驱后流体主要渗流通道喉道半径增大,对渗流的贡献率增加,水驱前后孔隙半径分布没有明显的变化,说明喇嘛甸油田储集层控制渗流特征的主要是喉道特征,而不是孔隙特征。恒压压汞分析表明,经过长期水驱后,喇嘛甸油田储集层砂岩孔喉尺寸明显变化,孔喉半径中值增大,最大孔喉半径增大,渗透能力增强;水驱后大孔喉数量增加,对应的分布频率、孔喉渗透率贡献率增加。两种方法均表明,岩样在长期水驱后孔喉增大,大孔喉是流体渗流的主要通道。

Lamadian Oilfield has entered a high water cut stage after long-term water-flooding, and injected water circulates in high permeability channels. Constant-rate and constant-pressure mercury injections were used to study the change of reservoir physical properties during development by water-flooding and the features of the reservoir pore structure before and after long term water flush. The constant-rate mercury injection analysis shows that the throat radii of main infiltration paths are enlarged and the pore radius distribution remains after long-term water-flooding, suggesting the infiltrating features are controlled mainly by throats instead of pores. The constant-pressure mercury injection analysis shows that water-flooding enlarges the pore throat radius median and maximum radius, increases large thorats and the corresponding pore throat distribution frequency and permeability. Both methods reveal that pore throats are enlarged after long-term water-flooding and large pore throats are the main path of fluid infiltration.