CO2注入对储层多孔介质及赋存流体性质影响实验研究

明确CO2注入对储层多孔介质及赋存流体性质的影响规律是分析油藏条件下CO2驱油机理和确定提高采收率潜力的基础。开展了不同压力条件下CO2与岩心静态接触实验和岩心驱替实验,测试了CO2注入前后岩心物性及微观孔喉结构和地层流体主要离子含量、采出原油组分、黏度及其沥青质含量等特征参数。实验结果表明:CO2注入压力由5 MPa升至20 MPa过程中,储层多孔介质平均孔隙度增大19.16%,平均渗透率降低11.23%,直径为100~150μm的孔隙空间增加9.73%,直径小于1.5μm的喉道空间增加15.83%,岩心亲水性显著增强;随着CO2在不同压力下的逐渐注入,地层水中Ca^2+和HCO-3含量增大,采出原油中C 5~C 33组分含量呈现先增大后基本不变的规律,采出原油黏度及其沥青质含量呈现先迅速降低,后保持不变的规律。

Experimental research of the effect of CO2 injection on porous media and fluid property in reservoir

The base of analyzing CO2 flooding mechanism and potential to improve oil recovery is clearing the effect on porous media and fluid property under the reservoir condition during CO2 injection.Therefore,static contact experiment and displacement experiment between CO2 and core is carried out under different pressure.At the meantime,characteristic parameters such as core physical property,microcosmic pore structure,main ion concentration of formation fluid,composition content of produced oil,viscosity and asphaltene content are tested before and after CO2 injection.The experimental results show that the average porosity of the porous medium increases by 19.16%and the average permeability decreases by 11.23%in the process of CO2 injection pressure rising from 5 MPa to 20 MPa.Besides,pore space with the diameter of 100-150μm increases by 9.73%and throat space with the diameter less than 1.5μm increases by 15.83%,and the hydrophilicity of core significantly enhanced.Meanwhile,the concentration of Ca^2+and HCO-3 in formation water increase with the injection pressure rising.The component content of C 5-C 33 in produced crude oil increases first and then remains stable,while its viscosity and asphaltene content decrease rapidly first and then remain unchanged.