A graphene plugging material for high-temperature and high-salt water-based drilling fluids

During the drilling process in deep oil reservoirs with high temperature and high salinity, the drilling fluid faces the risk of performance failure. Experiments have shown that the high-temperature and high-salinity environment weakens the negative charges on the surface of bentonite, causing the particles to aggregate, destroying the network structure and losing its rheological properties, as well as its ability to carry rock and filtrate. To solve this problem, this study improved the Hummers method to prepare rigid graphene oxide particles (GO-Y). In the experiment, 0.05 wt% graphene oxide was added to the drilling fluid containing 4% bentonite. Under the conditions of 10 wt% NaCl and 160 °C, graphene oxide adsorbed onto the surface of bentonite, increasing the particle spacing, and its spatial steric hindrance effect inhibited the aggregation of bentonite in the high-temperature and high-salinity environment, maintaining a smaller particle size distribution, and thus preserving the network structure of bentonite in the drilling fluid. The results showed that the rock-carrying capacity of the drilling fluid increased by 75.3%, and the filtrate volume decreased by 19.7%. Moreover, after adding 4% graphene-based leak stopper to the water-based drilling fluid, the permeability decreased to 1.89×10 -2 mD, and the leak stop rate reached 91.7%. The synthesized graphene-based leak stopper is suitable for high-temperature and high-salinity environments and can provide technical support for the drilling development of deep oil reservoirs.