Unlocking shale oil: Synergistic mechanisms of CO2 extraction enhanced by fractures and surfactants

IF 6.4 1区工程技术 Q2 ENERGY & FUELS

Petroleum Science Pub Date : 2026-10-01 Epub Date: 2026-06-22 DOI:10.1016/j.petsci.2026.06.032

Huan Zhang, Ming-Wei Zhao, Hou-Jian Gong, Cai-Li Dai, Ming-Zhe Dong, Xin Li, Zhen-Feng Ma, Zhi-Hao Zhang, Zhong-Zheng Xu, Xin-Jie Xu

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引用次数: 0

Abstract

The development of unconventional oil and gas resources is currently the primary focus of the petroleum industry. Shale oil has attracted significant attention due to its vast reserves. However, shale oil reservoirs are characterized by low porosity and low permeability, combined with rich organic matter, resulting in low oil recovery. The extraction efficiency of CO₂ is one of the key mechanisms for enhancing oil recovery. In this study, a comprehensive analysis was conducted on the factors influencing the extraction efficiency of CO₂, including CO₂ development parameters, core properties, and fractures. Additionally, the effect of C₄EO₃PO₆ (a polyether surfactant) on enhancing extraction efficiency of CO₂ was evaluated. The results show that the developed micropore and nanopore structure in shale makes oil in micropores, as well as absorbed and adsorbed oil, particularly difficult to mobilize. Under comparable permeability and porosity conditions, the CO₂ extraction recovery for tight sandstone is 2.2 times higher than that for shale, and the mobilization efficiency of free oil is 3.87 times higher than that of absorbed and adsorbed oil. The presence of fractures facilitates the dissolution and diffusion of CO₂ within the rock matrix. After three CO₂ extraction cycles, the extraction recoveries reach 81.6% for the naturally fractured shale core (containing natural fractures) and nearly 100% for both shale block samples and tight sandstone block samples. C₄EO₃PO₆ effectively reduces the interfacial tension and minimum miscibility pressure between CO₂ and shale oil, significantly enhancing the extraction efficiency of CO₂. With the addition of C₄EO₃PO₆, the extraction recovery of the shale core increases by 29.43%, with improvements of 27.25% for oil in micropores and 27.31% for absorbed and adsorbed oil. This work aims to provide an innovative development strategy for enhancing shale oil recovery through CO₂ injection.

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解锁页岩油：裂缝和表面活性剂增强CO2提取的协同机制

非常规油气资源的开发是当前石油工业的首要重点。页岩油因储量巨大而备受关注。然而，页岩油储层具有低孔低渗的特点，且富含有机质，导致采收率低。提高CO2的萃取效率是提高采收率的关键机制之一。本研究综合分析了影响CO2提取效率的因素，包括CO2开发参数、岩心性质、裂缝等。考察了聚醚表面活性剂C4EO3PO6对提高CO2萃取效率的影响。结果表明，页岩发育的微孔和纳米孔结构使得微孔中的油以及被吸收和吸附的油特别难以调动。在相同的渗透率和孔隙度条件下，致密砂岩的CO2萃取采收率是页岩的2.2倍，游离油的动员效率是吸附油的3.87倍。裂缝的存在促进了CO2在岩石基质中的溶解和扩散。经过3次CO2萃取循环，天然裂缝页岩岩心（含天然裂缝）的萃取回收率达到81.6%，页岩块体样品和致密砂岩块体样品的萃取回收率均接近100%。C4EO3PO6有效降低了CO2与页岩油的界面张力和最小混相压力，显著提高了CO2的萃取效率。添加C4EO3PO6后，页岩岩心采收率提高29.43%，其中微孔油采收率提高27.25%，吸附油采收率提高27.31%。这项工作旨在为通过注入二氧化碳提高页岩油采收率提供一种创新的开发策略。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Petroleum Science 地学-地球化学与地球物理

CiteScore

7.70

自引率

16.10%

发文量

311

审稿时长

63 days

期刊介绍： Petroleum Science is the only English journal in China on petroleum science and technology that is intended for professionals engaged in petroleum science research and technical applications all over the world, as well as the managerial personnel of oil companies. It covers petroleum geology, petroleum geophysics, petroleum engineering, petrochemistry & chemical engineering, petroleum mechanics, and economic management. It aims to introduce the latest results in oil industry research in China, promote cooperation in petroleum science research between China and the rest of the world, and build a bridge for scientific communication between China and the world.