Open Access

ARTICLE

A Study on the Performances and Parameter-Dependence of Water-Alternating-Gas Flooding for Conglomerate Reservoirs

Haishui Han¹, Jian Tan¹, Junshi Li¹, Changhong Zhao², Ruoyu Liu¹, Qun Zhang^3,4, Zemin Ji^3,4, Hao Kang^5,6,*

1 CNPC Advisory Center, CNPC, Beijing, 100724, China
2 Fengcheng Oilfield Operation Area of PetroChina, Xinjiang Oilfield Company, PetroChina, Karamay, 834000, China
3 State Key Laboratory of Enhanced Oil Recovery, PetroChina, Beijing, 100083, China
4 Research Institute of Petroleum Exploration and Development, PetroChina, Beijing, 100083, China
5 Polytechnic Institute, Hebei Normal University, Shijiazhuang, 050000, China
6 Hebei Provincial Key Laboratory of Information Fusion and Intelligent Control, Shijiazhuang, 050000, China

* Corresponding Author: Hao Kang. Email:

(This article belongs to the Special Issue: Fluid and Thermal Dynamics in the Development of Unconventional Resources II)

Fluid Dynamics & Materials Processing 2025, 21(2), 293-308. https://doi.org/10.32604/fdmp.2025.058989

Received 25 September 2024; Accepted 16 December 2024; Issue published 06 March 2025

Abstract

To address the water sensitivity of conglomerate reservoirs, a series of core sensitivity tests were conducted to evaluate the effects of varying ionic content. These findings serve as a foundation for improving reservoir fluid dynamics and optimizing the concentration of anti-swelling agents in water flooding operations. The experiments revealed a marked disparity in response between cores with differing permeabilities. In Core No. 5, characterized by low permeability, a 0.5% anti-swelling agent achieved only a modest 7.47% reduction in water sensitivity. Conversely, in the higher-permeability Core No. 8, a 5% anti-swelling agent significantly reduced the water sensitivity index by 44.84% while enhancing permeability. Further, two displacement strategies—gas flooding following water flooding and water flooding after gas injection—were tested to assess the potential of CO₂ water-alternating-gas (WAG) displacement. CO₂ injection after water flooding in Core No. 5 increased oil recovery by 9.24%, though gas channeling, evidenced by a sharp rise in the gas-liquid ratio, emerged as a critical concern. In Core No. 8, water flooding following gas injection failed to improve recovery, likely due to pronounced water sensitivity, reduced permeability, and the formation of dominant flow channels under high displacement pressure, which limited sweep efficiency.

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Keywords

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