CO2非混相驱微观孔喉波及特征研究

Study on Microscopic Pore Throat Sweep Characteristics of CO2 Immiscible Flooding

为明确CO2非混相驱波及特征与其影响因素,采用实验与数值模拟相结合的方式,对低渗岩心取样并进行CT扫描构建其二维微观孔喉模型。在此基础上,借助Comsol流体软件进行有限元计算,从微观角度对比了CO2驱和水驱的波及特征与区别,并对不同岩石润湿性下的CO2驱进行研究。结果表明:微观孔喉内水驱形成单一流通通道,油水界面分明并以活塞式驱油的方式流动,而CO2驱则形成多个流通通道,油气界面存在明显过渡段并以顶替原油的方式流动;不同的孔喉壁面润湿性会对油相流动效果产生显著影响,岩石由亲油向中间润湿性转变后油相流动效果变好,亲油岩石向疏油性转变后油相流动效果变差。

In order to clarify the sweep characteristics and influencing factors of CO2 immiscible flooding,a two-dimensional microscopic pore-throat model was constructed by sampling the low-permeability core and performing CT scanning through experiments and numerical simulation.On this basis,the finite element calculation was carried out with Comsol fluid software.The sweep characteristics and differences of CO2 flooding and water flooding were compared from the microscopic point of view,and the CO2 flooding under different rock wettability was studied.The results showed that the water flooding in the micro-hole throat formed a single circulation channel,the oil-water interface was distinct and flowed in the form of piston-type oil displacement,while the CO2 flooding formed multiple circulation channels,and there was a significant transition section at the oil-gas interface and flowed in the form of displacement of crude oil.Different wettability of the pore throat wall had significant influence on the oil phase flow effect.The oil phase flow effect was better after the transition from oleophilic wettability to intermediate wettability,and the oil phase flow effect was worse after the transition from the lipophilicity to oleophobicity.