Dispersion Stability of Graphene Oxide in Extreme Environments and Its Applications in Shale Exploitation

Graphene oxide (GO) is one of the most potential nanoplugging additives in shale gas and oil exploitation. However, poor colloidal stabilization of GO nanosheets in extreme downhole environments (with high salinity, elevated temperature, and weakly alkaline) seriously restricted its application. Herein, GO nanosheets were successfully modified to improve their colloidal stability in harsh environments by grafting high-density anionic polymer poly (3-sulfopropyl methacrylate potassium) (pSPMA) on the GO surface via the surface-initiated atom-transfer radical polymerization (SI-ATRP) method. The results showed that the modified GO-g-SPMA exhibited excellent colloidal stability, which could be fully dispersed in American Petroleum Institute (API) brine and saturated brines at least for 10 days. Meanwhile, the GO-g-SPMA particles were ultrastable at a high temperature of 170 degrees C as well as in a weakly base environment. Furthermore, the molecular dynamics (MD) simulation demonstrated that the strong hydration capacity of GO-g-SPMA can provide enough steric stabilization for GO nanosheet dispersion in concentrated electrolytes. After modifications, the GO-g-SPMA exhibited the effective plugging performance for a low permeate reservoir even with adding 0.3 wt % GO-g-SPMA. Herein, the dispersion stability of the modified GO had been greatly improved under extreme conditions of high salinity and elevated temperature, and the small size of well-dispersed modified GO matched with the nanopores of shale formation, which could effectively prevent water from penetrating low-permeability shale formation and improve the shale stability.