Open Access

ARTICLE

Research of Chemical Additive-Assisted CO₂ Huff-n-Puff for Enhanced Heavy Oil Recovery

Sijin Zhu^1,2, Jian Guan^1,2, Songyan Li^1,2,*
1 National Key Laboratory of Deep Oil and Gas, China University of Petroleum (East China), Qingdao, China
2 School of Petroleum Engineering, China University of Petroleum (East China), Qingdao, China
* Corresponding Author: Songyan Li. Email:
(This article belongs to the Special Issue: Unconventional Energy Resources as Sources of Critical Minerals: Coal, Oil, Gas, and Produced Waters)

Energy Engineering https://doi.org/10.32604/ee.2026.081442

Received 02 March 2026; Accepted 02 April 2026; Published online 23 April 2026

Abstract

Carbon Capture, Utilization and Storage (CCUS) is a critical decarbonization technology, and CO₂-enhanced oil recovery (CO₂-EOR) effectively combines CO₂ geological storage with crude oil production, especially for high-difficulty heavy oil reservoirs. To overcome viscous fingering and early gas channeling in conventional CO₂ huff-n-puff, this study focused on chemical additive-assisted CO₂ huff-n-puff for cold heavy oil production in the Gudong reservoir. Through screening and optimization, 0.5% HY-2 foaming agent and 0.5% SR-1 viscosity reducer were identified as optimal, showing stable performance and strong synergy with CO₂. High-temperature high-pressure experiments indicated the suitable CO₂ injection volume is 0.15–0.2 PV, the optimal injection sequence is chemical solution followed by CO₂, and the technology is applicable for crude oil viscosity below 3000 mPa·s. The 0.5% HY-2 + 0.5% SR-1 system enhanced oil recovery to 45.07%, 14.4% higher than pure CO₂ huff-n-puff, while the 0.5% SR-1 single-agent scheme achieved 42.13% recovery with better economics. The main mechanisms include emulsification and viscosity reduction, gas mobility control, and expanded sweep efficiency, supplemented by CO₂ dissolution, oil swelling, and elastic drive. Field tests in four wells showed an average daily oil increase of 2.7 t per well and a total incremental oil of 1748.6 t, with a CO₂ storage rate of 80.4% and an input-output ratio of 8.02:1. This study verifies the technical and economic feasibility of chemical-assisted CO₂ huff-n-puff, providing support for its field application and a practical route for heavy oil EOR and carbon reduction coordination.

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Keywords

Heavy oil reservoirs; CO₂ huff-n-puff; chemical-assisted; oil production enhancement mechanism; field application

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