Development of Thermotransformable Controlled Hydrogel for Enhancing Oil Recovery

A novel thermotransformable controlled polymer system (tPPG) is developed that can be injected into fractures or fracturelike features as a millimeter-sized particle gel (100 mu m to a few millimeters) and acts as a plugging agent, then dissolves into linear polymer at a designated period (e.g., 6 months), because of the reservoir's temperature. The dissolved polymer seeps into the depth of the formation and performs as a mobility control agent with high viscosity. Working together with permanent cross-linking the polymer, polyethylene glycol diacrylate 200 (PEG-200) entails the role of controlling dissolution time which has been added into the tPPG as a labile cross-linker. The polymer's viscosity will not be influenced by the shearing stress during pumping or salinity in the reservoir. The time tPPG requires for transformation is dependent primarily upon the reservoir temperature and labile cross-linker concentration. This strategy offers a facile and economic approach to fabricating a promising dual-functional polymer system. In order to evaluate our proposed approach, main properties of the tPPG polymer are probed, including the swelling ratio, mechanical strength, and thermostability before transformation, viscosity, moving ability, and mobility control ability after transformation.