致密油层自发渗吸与动态渗吸驱油微观机理实验分析OA

In order to clarify the utilization characteristics of microscopic pores in spontaneous imbibition and dynamic imbibition of tight sandstone reservoirs with different permeability levels,the conversion coefficient between T2 and pore throat radius of CMP pore-throat distribution was calibrated based on the experimental data of constant mercury injection(CMP)and low-field nuclear magnetic resonance(NMR).The spontaneous imbibition and dynamic imbibition experiments of the tight sandstone cores with three permeability levels fromYanchang Formation of Ordos Basin were carried out to study the micro oil displacement mechanism of the cores with differ-ent permeability levels under two imbibition modes,and to quantitatively evaluate the recovery factor of pores with three sizes and their contributions to imbibition recovery factor.The experimental results show that the permeability of Chang 6 reservoir in the study area can be divided into three levels of 0.03×10-3 μm2,0.13×10-3 μm2 and 0.26×10-3 μm2,and the throat radius is the main parameter controlling hydrocarbon connectivity and percolation ability.In the process of spontaneous imbibition,the contribution rate of small pores(r<1.56 μm)to the recovery factor is more than 30%,and with the decrease of permeability,the contribution rate of small pores in-creases.The dynamic imbibition recovery factor(17.73%～33.66%)is always higher than the spontaneous imbibition recovery factor(8.64%～17.52%).The contribution rate of mesopores(1.56～15.60 μm)to the recovery factor is always 40%,and it is domi-nant.With the increase of permeability,the contribution rate of small pores decreases,and the contribution rate of large pores(r>15.60 μm)increases.The research results provide a reference for improving the water injection development effect of tight oil reser-voirs.