The gas-assisted gravity drainage (GAGD) process has been suggested to improve oil recovery in both secondary and tertiary stages through immiscible and miscible injection modes. In contrast to continuous gas injection and water-alternating gas, the GAGD process takes advantage of the natural segregation of reservoir fluids to provide gravity-stable oil displacement and improve oil recovery. In the GAGD process, the gas is injected through vertical wells at the top of the reservoir to formulate a gas cap that allows oil and water to drain downward to the reservoir bottom, where horizontal producer(s) are placed. Extensive experimental works and limited reservoir-scale evaluation studies have been conducted to test the effectiveness of the GAGD process performance. In this paper, a comprehensive literature review is presented to summarize all of the references about concepts, principles, and field-scale evaluations of the GAGD process. Particularly, this paper presents an introduction to the mechanisms of CO₂–rock–fluid interactions, gas enhanced oil recovery injection approaches, the GAGD process physical model, the factors influencing the GAGD process, and a review of all of the previous field-scale evaluation studies. Furthermore, the validation of the GAGD process in reservoir-scale applications is fully discussed by focusing on its weaknesses with respect to the optimal implementation design for achieving maximum oil recovery.

中文翻译：

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从岩心驱替和大规模物理模型试验到现场规模的强化油采收率评估：天然气辅助重力排水过程的综合评述

有人建议采用气体辅助重力排水（GAGD）工艺，通过不混溶和可混溶的注入方式来提高第二级和第三级的采油率。与连续注气和水交替注气相比，GAGD工艺利用储层流体的自然隔离优势来提供重力稳定的驱油能力并提高采油率。在GAGD工艺中，通过储层顶部的垂直井注入天然气，以形成气顶，使油和水向下排到储层底部，水平的采油井位于该储层底部。已经进行了广泛的实验工作和有限的储层规模评估研究，以测试GAGD工艺性能的有效性。在本文中，进行了全面的文献综述，以总结有关GAGD流程的概念，原理和现场规模评估的所有参考资料。特别是，本文介绍了CO的机理。₂ –流体相互作用，天然气强化采油注入方法，GAGD过程物理模型，影响GAGD过程的因素，以及对所有以前的现场评估研究的回顾。此外，通过重点讨论GAGD工艺在实现最大采油量的最佳实施设计方面的弱点，来全面讨论GAGD工艺在油藏规模应用中的有效性。