Pore-Scale Simulations of CO2/Oil Flow Behavior in Heterogeneous Porous Media under Various Conditions

Qingsong Ma,Jingjing Bi,Qilin Wang,Zhanpeng Zheng,Jiarui Fan,Mengxin Li,Pei Hu,Wei Wei,Jingdong Jia,Dayong Wang

doi:10.3390/en14030533

Abstract

Miscible and near-miscible flooding are used to improve the performance of carbon-dioxide-enhanced oil recovery in heterogeneous porous media. However, knowledge of the effects of heterogeneous pore structure on CO2/oil flow behavior under these two flooding conditions is insufficient. In this study, we construct pore-scale CO2/oil flooding models for various flooding methods and comparatively analyze CO2/oil flow behavior and oil recovery efficiency in heterogeneous porous media. The simulation results indicate that compared to immiscible flooding, near-miscible flooding can increase the CO2 sweep area to some extent, but it is still inefficient to displace oil in small pore throats. For miscible flooding, although CO2 still preferentially displaces oil through big throats, it may subsequently invade small pore throats. In order to substantially increase oil recovery efficiency, miscible flooding is the priority choice; however, the increase of CO2 diffusivity has little effect on oil recovery enhancement. For immiscible and near-miscible flooding, CO2 injection velocity needs to be optimized. High CO2 injection velocity can speed up the oil recovery process while maintaining equivalent oil recovery efficiency for immiscible flooding, and low CO2 injection velocity may be beneficial to further enhancing oil recovery efficiency under near-miscible conditions.

Highlights

Oil production plays a significant role in global economies and is the prime focus of climate change policies [1]
Understanding CO2 /oil flow behavior in porous media is critical to evaluating the performance of CO2 -EOR technology [6] and optimizing CO2 injection schedules [2]
Immis2 field miscible flooding was adopted in the Liaohe oil field in China and the Heidelberg oil flooding was adopted in the Liaohewas oil field and theUnit

Summary

Introduction

Oil production plays a significant role in global economies and is the prime focus of climate change policies [1]. Most of the studies about CO2 /oil flow behavior were concentrated at the core scale [7,8,9]. These studies have played important roles in analyzing the multiphase seepage characteristics of oil and CO2 in reservoir rocks (e.g., oil-effective permeability reduction) [7,8] and disclosing the phase behavior of the mixture of CO2 and oil [9]. The core-scale studies have measured fluid and rock properties, such as relative permeability curves of oil and CO2 [10], the minimum miscibility pressure, and the interfacial tension between oil and CO2 [11,12], which provide important parameters for core-scale numerical modeling of CO2 /oil flow behavior [13].

Methods

Results

Conclusion