Open Access

ARTICLE

Performance Evaluation of Gas-Soluble Surfactants for CO₂ Injection Development in Tight Oil Reservoirs

Bo Jing^1,2, Yuejun Zhu^1,2, Wensen Zhao^1,2, Bo Huang^1,2, Engao Tang^1,2, Anfeng Xiao^3,*, Mingda Dong³
1 State Key Lab of Offshore Oil & Gas Exploitation, Beijing, China
2 CNOOC Research Institute Ltd., Beijing, China
3 College of Oil and Gas Engineering, Chongqing University of Science and Technology, Chongqing, China
* Corresponding Author: Anfeng Xiao. Email:
(This article belongs to the Special Issue: Progress and Prospects of Hydraulic Fracture Network Morphology Characterization, Flow Simulation and Optimization Technology for Unconventional Oil and Gas Reservoirs)

Energy Engineering https://doi.org/10.32604/ee.2026.079022

Received 13 January 2026; Accepted 19 March 2026; Published online 21 April 2026

Abstract

To investigate the applicability of different gas-soluble surfactants in CO₂ miscible flooding for tight oil reservoirs and clarify the underlying mechanism of their enhanced oil displacement, this study first employed the cloud point pressure method to determine the solubility of surfactants in supercritical CO₂ under reservoir temperature, thereby identifying the pressure threshold for their stable dispersion. Subsequently, a falling-ball viscometer and an interfacial tension meter were utilized to analyze the viscosity reduction effect of surfactants on crude oil and the regulation law of CO₂-crude oil interfacial tension under high-temperature and high-pressure conditions. Next, slim-tube displacement experiments were conducted to quantify the capacity of different surfactants to reduce the minimum miscibility pressure (MMP) of the CO₂-crude oil system. Finally, core displacement experiments were performed to systematically evaluate the impacts of surfactants on key development performance parameters of CO₂ flooding, including oil recovery factor, oil production rate, and gas-oil ratio (GOR). The results demonstrate that surfactants with a higher number of CO₂-philic functional groups and a higher degree of alkyl chain branching exhibit superior solubility in CO₂, along with more significant effects on crude oil viscosity reduction and interfacial tension reduction, as well as stronger ability to lower MMP. Among the tested surfactants, AT-1, benefiting from the synergistic effect of its diester groups and isobutyl branches, can reduce the MMP to 39.4 MPa. Core displacement experiments indicate that compared with pure CO₂ flooding, AT-1-enhanced CO₂ flooding increases the oil recovery factor by more than 5 percentage points, while effectively delaying gas channeling and optimizing displacement dynamics. This study provides certain guidance for the further application of CO₂ flooding technology in tight oil reservoirs.

---

Keywords

Tight oil reservoirs; gas-soluble surfactants; CO₂ flooding; interfacial tension; oil recovery factor

---