Theoretical Modeling of Gas Exsolution and Liberation during Foamy-Oil Flow in Porous Media
过去，许多岩心驱替实验室测试已被用于研究一次开采稠油过程中的泡沫油流动以及基于溶剂的提高采收率工艺（如循环溶剂注入）。然而，由于复杂的非平衡相态行为，这些实验测试只能获得有限的重要技术数据。通常，数学或数值建模被用于历史拟合实验数据并理解不同实验条件下的泡沫油流动趋势。历史拟合过程中需要调整和确定许多重要参数，这可能耗时且可能产生较大误差。
本文提出了一种新颖且有效的理论模型，用于量化多孔介质中泡沫油流动过程中的气体析出和释放。实验方面，我们在二维砂体模型中进行了两次实验室测试，使用差分流体生产（DFP）方法研究重油-甲烷（CH₄）系统的一次采油过程，采用两种不同的压力衰竭步长。理论方面，我们开发了一个基于物质平衡的罐式模型来描述这两次测试中的泡沫油生产。在该模型中，溶解气和析出气的量通过物质平衡方程利用实测生产数据直接确定。随后的气体释放过程通过具有两个可调参数的压力相关关系进行建模，这两个参数利用砂体测试中测得的游离气-油比（GOR）确定。该模型进一步用于生成两次测试中泡沫油和游离气的相对渗透率。随后，针对不同衰竭情景进行的CMG-STARS模拟进行了数值验证，显示出相似的生产趋势。这一比较表明，所提出的理论模型捕捉了泡沫油流动的本质特征，并表明其作为冷采稠油（CHOP）油藏筛选的实用高效替代方法的潜力。
CMG软件应用情况
| 应用领域 | 具体功能 | 技术细节 |
|---|---|---|
| 数值验证 | CMG-STARS | 作为验证理论模型的基准数值模拟器 |
| 衰竭情景模拟 | 不同压力衰竭方案 | 与理论模型预测进行对比 |
| 生产趋势对比 | 历史拟合验证 | 验证理论模型捕捉泡沫油流动特征的能力 |
CMG应用特点：
- 验证作用：CMG-STARS用于数值验证理论模型，而非直接作为建模工具
- 对比分析：通过不同衰竭情景的模拟，验证理论模型预测的准确性
- 效率优势：理论模型相比数值模拟更实用高效，适合快速筛选冷采稠油油藏
研究结论
- 模型有效性：提出的理论模型能够有效量化泡沫油流动过程中的气体析出和释放过程
- 实验验证：通过二维砂体模型中的两次DFP实验（不同压力衰竭步长）验证了模型的适用性
- 数值验证：CMG-STARS模拟结果与理论模型预测显示出相似的生产趋势，证实了模型捕捉泡沫油流动本质特征的能力
- 工程应用价值：该理论模型可作为冷采稠油（CHOP）油藏筛选的实用高效替代方法，避免了复杂耗时的数值历史拟合过程
- 关键参数：通过两个可调参数的压力相关关系描述气体释放过程，参数利用实测游离气-油比（GOR）确定
研究亮点
| 方面 | 内容 |
|---|---|
| 创新点 | 基于物质平衡的罐式模型直接确定溶解气和析出气，无需复杂调参 |
| 实验方法 | 差分流体生产（DFP）方法，二维砂体模型 |
| 体系 | 重油-甲烷（CH₄）系统 |
| 关键输出 | 泡沫油相对渗透率和游离气相对渗透率 |
| 优势 | 相比传统数值历史拟合更快速、更实用 |
Summary
In the past, many coreflooding laboratory tests have been conducted to study foamy-oil flow in primary heavy oil production and solvent-based enhanced oil recovery processes (e.g., cyclic solvent injection). However, limited important technical data can be obtained from these experimental tests due to the complex nonequilibrium phase behaviors. In general, mathematical or numerical modeling is often performed to history match the experimental data and understand foamy-oil flow trends under different experimental conditions. Many important parameters need to be tuned and determined in the history matching processes, which could be time-consuming and possibly cause large errors.
In this paper, we propose a novel and effective theoretical model to quantify the gas exsolution and liberation during foamy-oil flow in porous media. Experimentally, we conducted two laboratory tests in a 2D sandpack model to study the primary production of a heavy oil–methane (CH4) system by using a differential fluid production (DFP) method with two different pressure depletion step sizes. Theoretically, we developed a material-balance-based tank model to describe the foamy-oil productions in these two tests. In this model, the amounts of dissolved and evolved gases were determined directly from material-balance equations by using the measured production data. The subsequent gas-liberation process was modeled through a pressure-dependent relation with two adjustable parameters, which were determined using the measured free-gas–oil ratio (GOR) from the sandpack tests. The model was further used to generate the foamy-oil and free-gas relative permeabilities for the tests. Subsequently, numerical validation was performed against CMG-STARS simulations conducted under different depletion scenarios, which showed similar production trends. This comparison shows that the proposed theoretical model captures the essential features of foamy-oil flow and indicates its potential as a practical and efficient alternative for screening cold heavy oil production (CHOP) reservoirs.
