Effects of CO₂ Injection on Phase Behavior of Crude Oil

Abstract

CO₂ flooding is a win-win technology, sequestrating greenhouse CO₂ while producing a significant amount of crude oil to help defray the cost of CO₂ sequestrating and enhancing oil recovery. However, due to the difference of sedimentary environment and poor properties of formations, physical properties of the crude oil and the effect of CO₂ flooding are not always satisfactory in most oilfields of China. Therefore, in this article, to improve the understanding of the oil recovery mechanisms and feasibility of CO₂ flooding in China, based on the oil and gas of Mao-3 oilfields, phase behavior of the CO₂ and crude oil system was investigated. Parameters like saturated pressure, volume factor, gas oil ratio, and viscosity were measured and their relationships analyzed. Results show that crude oil of Mao-3 reservoir and CO₂ has good mutual dissolution under reservoir conditions, and CO₂ could expand the oil and reduce the oil viscosity greatly. As a result, formation energy could be enhanced and flow characteristics of the oil could be improved by CO₂ flooding.

Keywords:

• CO₂ and crude oil system
• gas oil ratio
• phase behavior
• viscosity reduction
• volume factor

Acknowledgments

This study was supported by National Basic Research Program of China (2011CB707304) and Natural Science Foundation of China (50874114). The authors would like to thank Mao-3 oilfield for its encouragement and assistance throughout the project and preparation of this article.