稠油油藏人工泡沫油强化混合气体吞吐方法及其机理研究

The principal problem of the gas huff-n-puff process is the high mobility of the gas phase, relative to the oil phase, during the production cycle. However, the problem mentioned above does not occur in the primary production process of some unconventional heavy oil reservoirs. In these reservoirs under solution gas drive, the solution gas is released from the oil to form dispersed gas bubbles inside the oil, due to the high viscosity, low diffusion rates, and higher pressure gradients of unconventional heavy oil. Thus, this application presents a new enhanced gas injection technique, called the foamy oil-assisted gas mixture huff-n-puff method, which is used to overcome this limitation of the gas huff-n-puff process. Firstly, in order to explain the reasons why the foamy oil can be formed in the unconventional heavy oil, the internal relations between group composition structures, polar functional groups and the interfacial activity are analyzed based on chemical research of the unconventional heavy oils. Then, a new experimental procedure is developed to prove that the selected foaming agent has an effective foaminess in conventional heavy oil with a specially designed experimental setup, and to investigate, quantitatively, the effects of various process parameters on foamy oil stability. Finally, a series of experiments are conducted to evaluate the performance of the new method and reveal its EOR mechanisms by PVT studies, interfacial tension measurements and pore-level investigation. The above knowledge will have significant importance for the development of heavy oil resources in China.

部分稠油油藏冷采过程中析出的溶解气可以分散在稠油中形成泡沫油，该现象使得气体产出速度减缓，稠油粘度降低，体积膨胀。受此启发，结合天然气和丙烷各自优点，提出一种人工泡沫油强化混合气体吞吐方法。该方法通过油溶性表面活性剂，在注气吞吐生产阶段形成人工泡沫油，解决传统吞吐过程中注入气快速产出，难以溶于稠油的问题。围绕上述思路，首先通过泡沫油生成的化学机制研究，明确稠油、族组分结构参数、极性官能团与油-气表面活性的内在关系，从分子水平解释特殊稠油形成泡沫油的原因。以此为基础，通过研制的可视化评价装置，优选油溶性表面活性剂，揭示气泡生成速度、分散程度、原油性质等对泡沫油有效性的影响规律。最后，通过变直径长岩心驱替装置，评价该方法的可行性，并从注混合气体后稠油相行为，表活剂对油-气表面张力的影响以及微观渗流过程三个方面，揭示其提高采收率机理。上述研究对于提高我国稠油油藏采收率具有重要的理论和工程意义。

针对传统注气吞吐过程中注入气快速产出，难以溶于稠油的问题，项目提出了一种人工泡沫油强化混合气体吞吐方法。该方法通过油溶性表面活性剂，在注气吞吐生产阶段形成人工泡沫油，从而解决了上述问题。项目围绕该方法及其机理开展研究，取得了以下创新成果：（1）多角度定量表征了多稠油及其族组分的油-气表面性质，确定特殊稠油中天然活性物种类及其活性排序，从官能团水平上揭示了特殊稠油形成泡沫油的原因。（2）优选出了能够形成人工泡沫油的油溶性表面活性剂，揭示了表面活性剂浓度、气泡生成速度、气泡大小等参数对泡沫油有效性的影响规律，基于最小二乘支持向量机模型，去除了实验数据中的异常值，并建立了泡沫油动态消泡模型。（3）系统评价了该方法的可行性，明确了天然气、丙烷、泡沫油机理各部分对采收率的贡献，揭示了混合气体组成、压降速度、蚯蚓洞和围压等对泡沫油形成过程以及采收率的影响规律。（4）从注气后稠油相行为，油溶性表活剂对油气表面张力的影响以及微观渗流过程三方面，全面揭示了该方法的提高采收率机理，并建立了稠油-混合气体体系泡点压力、膨胀系数和密度预测模型。相关成果在Fuel、Energy & Fuels、Journal of Petroleum Science and Engineering等期刊发表学术论文10篇（SCI论文9篇，EI论文1篇，其中SCI二区4篇，SCI三区4篇，ESI高被引论文1篇），申请国家发明专利7项，其中授权5项，授权实用新型专利和软件著作权各1项，出版学术专著1部，获国家出版基金、“十三五”国家重点出版物规划项目和中国石油大学（华东）学术著作出版基金资助。项目形成了多套特色科研仪器设备、实验方法和理论模型。上述研究为我国复杂稠油油藏开发提供一种有效的技术手段。此外，对于深入理解油基泡沫特征，扩展油溶性表面活性剂在油气田开发中的应用以及提高泡沫油油藏采收率等多个领域具有重要的理论和工程意义。