Open Access

ARTICLE

Experimental Investigation of CO₂–Gel–Nanowater Multi-Media Flooding for Enhanced Oil Recovery in Tight Reservoir

Yongquan Sun¹, Wenxin Yan^2,3,*, Guangzhong Lv⁴, Chuixian Kong⁵, Zhonghui Wu⁶, Yongmao Hao^2,3
1 Dongsheng Jinggong Petroleum Development Group Co., Ltd., Shengli Oilfield Company, SINOPEC, Dongying, China
2 Key Laboratory of Unconventional Oil & Gas Development (China University of Petroleum (East China)), Ministry of Education, Qingdao, China
3 School of Petroleum Engineering, China University of Petroleum (East China), Qingdao, China
4 Shengli Oilfield Company, Sinopec, Dongying, China
5 Research Institute of Exploration and Development, Xinjiang Oilfield Company, Karamay, China
6 Changqing Oilfield Company, PetroChina, Xi’an, China
* Corresponding Author: Wenxin Yan. Email:
(This article belongs to the Special Issue: Geomechanical Issures in the Development of Reservoirs and New Energy)

Energy Engineering https://doi.org/10.32604/ee.2026.077987

Received 21 December 2025; Accepted 03 April 2026; Published online 20 July 2026

Abstract

Tight oil reservoirs are prone to severe gas channeling during CO₂ flooding, resulting in low sweep efficiency and significantly limiting oil recovery. In this study, a multi-medium composite flooding system involving CO₂-nanowater-gel-water was proposed and its enhanced oil recovery potential was systematically investigated through series and parallel long-core flooding experiments. The experimental results indicate that the recovery factor of CO₂ flooding in homogeneous cores can reach 62.54%, primarily driven by the extraction of light and intermediate hydrocarbon components, as well as the effects of crude oil swelling and viscosity reduction. In fractured cores, by adopting the optimal injection sequence of gel + water + nanowater, the final recovery factor reached 67.66%. The high-strength steric hindrance and plugging effect of the gel effectively suppress gas channeling in fractures and high-permeability layers, forcing CO₂ to divert into unswept zones. Simultaneously, the nanowater further enhances microscopic displacement efficiency by reducing oil-water interfacial tension and improving wettability, achieving a synergistic effect of deep profile control and efficient displacement. In multi-layer parallel experiments, the recovery factors of cores with different permeabilities were all improved, with the gel + water + nanowater system yielding a recovery increment of 46.60%. This study provides critical technical support and a strategic reference for the efficient development of tight oil reservoirs.

---

Keywords

Multi-media combination; CO₂ flooding; gel; long core

---