A fractal model for quantitative evaluating the effects of spontaneous imbibition and displacement on the recovery of tight reservoirs

In the petroleum industry, there is a consensus that the spontaneous imbibition (SI) is important for improving the recovery of tight reservoirs. However, how great is the effect of SI on the recovery of tight reservoirs when comparing with displacement? In the paper, a model for quantitative evaluating the effects of SI and displacement on tight reservoir development is built by fractal theory and verified by comparing with published experimental data. Two evaluation parameters (EP and EPR), which can be determined by the proposed model, are introduced to discuss the problem that how great the effect of SI on the recovery of tight reservoirs when comparing with displacement is. The influences of related parameters on EP and EPR are conducted. The results show that reservoir properties have a great effect on the imbibition time. And the effects of reservoir properties on the flow rate of SI is similar to that of displacement. The effect of SI becomes significant comparing with displacement when the water viscosity decreases. However, with the decrease of contact angle or the increase of interfacial tension force (ITF), the effect of SI becomes significant. The decrease of displacement pressure difference indicates the effect of SI becoming relatively significant. When the ITF and displacement pressure difference are 35.5 mN/m and 1 x 10(4) Pa, respectively, the maximum oil flow rate of SI is 1.85 times of displacement. This work has a crucial role in promoting the development of tight reservoirs.