Effect of viscosity on oil recovery by spontaneous imbibition from partially water-covered matrix blocks

Qi Zhang,Qingbang Meng,Xinyue Wu,Yingfu He

doi:10.1177/0144598720984207

Abstract

Spontaneous imbibition is an important mechanism of oil recovery from fractured reservoirs and unconventional reservoirs. Oil is produced by combining co- and counter-current imbibition when the matrix blocks was partially covered by water. In this paper, we focused on the effect of viscosity ratios on oil production by spontaneous imbibition and established the numerical model for one-dimensional linear imbibition with TEO-OW boundary conditions, which was validated by the experimental data. The effect of viscosity ratio on co- and counter-current imbibition is investigated and scaling result of the imbibition recovery curve for wide range of viscosity ratio using the conventional scaling equation was tested, which indicates that the close correlation was achieved only when oil-water viscosity ratios are higher. Then, a modified scaling equation was developed based on the piston-like assumption for one-dimensional co-current imbibition and close correlation of imbibition recovery curves was achieved when viscosity ratios are lower. Finally, correlation of imbibition recovery curves was improved for wide range of viscosity ratios by combining conventional and modified scaling equation. Results show that since the shape of imbibition recovery curves is not similar for different viscosity ratios, it is difficult to obtain the perfect correlation using the constant viscosity term.

Highlights

Spontaneous imbibition plays an important role in oil recovery from fractured reservoirs (Morrow and Mason, 2001; Rangel-German and Kovscek, 2006) and unconventional reservoirs (Cheng et al, 2018; Jia et al, 2019; Roshan et al, 2016)
We focused on spontaneous imbibition with TEO-OW boundary conditions
We focused on one-dimensional spontaneous imbibition under strongly waterwet conditions with TEO-OW boundary conditions

Summary

Introduction

Spontaneous imbibition plays an important role in oil recovery from fractured reservoirs (Morrow and Mason, 2001; Rangel-German and Kovscek, 2006) and unconventional reservoirs (Cheng et al, 2018; Jia et al, 2019; Roshan et al, 2016). Understanding the mechanism of oil recovery by spontaneous imbibition with partially water-covered boundary conditions can make a contribution to predicting production performance in fractured (Chen and Mohanty, 2013; Cui et al, 2020; Zhong et al, 2020) and unconventional reservoirs (He et al, 2020; Jia et al, 2020; Wang et al, 2018). The pattern of flow fluid is very complex for spontaneous imbibition with partially watercovered boundary conditions because oil can be by produced by combining co-and countercurrent imbibition (Meng et al, 2019). The viscosity term was proposed from the imbibition with fully covered by water Whether it is applicable for spontaneous imbibition with partially water-covered needs to be investigated. The relative permeability to oil and water can be expressed by modified Corey-functions (Meng et al, 2019; Pooladi-Darvish and Firoozabadi, 2000)

À Sor 1 À Sor

Á S2 wf

Conclusions