CO2-responsive agent for restraining gas channeling during CO2 flooding in low permeability reservoirs
CO2-responsive agent for restraining gas channeling during CO2 flooding in low permeability reservoirs
复制标题
低渗透油藏 CO2 驱气窜抑制剂 CO2 响应剂
DOI：
10.1016/j.fuel.2021.120306
复制
发表时间：
2021-02-15
期刊：
影响因子：
7.4
通讯作者：
Dong, Zhaoxia
中科院分区：
文献类型：
--
作者：
Shen, Hao;Yang, Zihao;Dong, Zhaoxia
水力压裂和CO2驱是低渗透油藏提高采收率的重要手段。但由于地层非均质性严重，CO2容易过早突破油层，导致波及体积减小。常规堵剂存在注入困难、稳定性差、封堵强度弱等缺点。因此，研制一种适用于低渗透裂缝性油藏的新型封窜剂具有重要意义。本研究从10种含叔氨基的化合物中筛选出最有效的CO2响应剂，即N，N-二甲基芥酸酰胺叔胺（DMETA）。随后，通过流变实验、CO2响应实验和低温透射电镜，系统研究了优选出的调剖剂的流变性能、响应性能和微观结构。结果表明，通过自组装成蠕虫状胶束（WLM），DMETA溶液的粘度可以增加到近605，700 mPa.s。通过交替引入和去除CO2，它可以在低粘度和高粘度之间可逆地循环，这赋予了它在充满CO2的环境下修复其粘弹性的能力。提出了一种基于光学微观流变学的研究无外力作用下WLM粘弹特性的新方法。实验证明，这种网络结构在形成后并不稳定，而是作为一种“活性聚合物”，在不断的分离和重构过程中保持着。“此外，使用压裂致密岩心评价了封堵性能和提高采收率能力。实验结果表明，优选出的防气窜剂能有效地抑制气窜，提高采收率21.7%。我们希望我们的工作可以为CO2响应WLM的合成提供见解，并指导在低渗透油藏CO2驱期间减缓气窜。
Hydraulic fracturing and CO2 flooding are extensively used in low-permeability reservoirs to enhance oil recovery (EOR). However, due to the serious heterogeneity of the formation, CO2 is prone to break through the oil-bearing zone prematurely, which leads to the decrease of the swept volume. Conventional blocking agents have some defects such as difficult injection, poor stability and weak sealing strength. Therefore, it is critical to developing a new type of channeling blocking agent for low-permeability fractured reservoirs. In this study, ten kinds of chemicals with tertiary amino groups are filtered for the most effective CO2-responsive agent, which turns out to be N, N-Dimethyl erucamide tertiary amine (DMETA). Subsequently, rheological properties, response performance, and microstructure of the optimum agent are researched systematically through rheological experiments, CO2-response processes and Cryo-TEM. The results show that the viscosity of the DMETA solution can increase to nearly 605,700 mPa.s by self-assembly into wormlike micelles (WLMs). And it can be reversibly circulated between low viscosity and high viscosity by alternately introducing and removing CO2, which endows it with the ability to healing its viscoelasticity under an environment full of CO2. A new method based on optical microrheology is proposed to study the viscoelastic properties of WLMs under no external force. The experiments prove that the network structure is not stable after formation, but remains in a continuous process of separation and reconstruction as "a living polymer." Furthermore, the plugging performance and EOR capacity are evaluated using fractured tight cores. The experiments demonstrate that the optimum agent can effectively restrain gas channeling and enhance recovery factor by 21.7%. We expect our work can provide insights for the synthesis of CO2-responsive WLMs and guidance for retarding gas channeling during CO2 flooding in low permeability reservoirs.