New Method Based on CO2-Switchable Wormlike Micelles for Controlling CO2 Breakthrough in a Tight Fractured Oil Reservoir

CO 2 is widely used for enhanced oil recovery (EOR) as a result of its high ability of washing oil and favorable injectivity, especially for a tight oil reservoir. During the EOR process, the oil recovery is significantly affected by gas channeling and the sweep efficiency of CO 2 is limited. Herein, we report CO 2 -switchable smart wormlike micelles (WLMs) based on sodium dodecyl sulfate (SDS) and diethylenetriamine (DETA) to prevent gas channeling of CO 2 in a tight fractured oil reservoir. The proof to the microstructure, formation mechanism, and plugging performance of CO 2 -switchable WLMs was studied by cryo-transmission electron microscopy, dynamic light scattering, nuclear magnetic resonance, rheology, and plugging property measurement. The results indicated that the system can be reversibly circulated between spherical micelles and wormlike micelles by repeatedly bubbling and removing CO 2 . When CO 2 is introduced to the solution, part of DETA molecules is protonated and two SDS molecules are “bridged” to form a pseudo-gemini surfactant by non-covalent electrostatic attraction, behaving as a high-viscosity fluid. Upon removal of CO 2, the protonated DETA molecules return to the original state, causing the pseudo-gemini structure to be destroyed and the viscosity of the fluid to be recovered. Moreover, on the basis of the results of the plugging property measurement, the solution presents conspicuous injection and plugging performance. This WLM viscoelastic fluid might have potential application in the enhancement of CO 2 flooding in a tight fracture reservoir.