Drilling fluid with chemical reverse osmosis function

The invention relates to a drilling fluid with a chemical reverse osmosis function and belongs to the technical field of water-based drilling fluids for petroleum drilling. The drilling fluid is prepared from raw materials such as a nano-microemulsion blocking agent, a nano blocking agent and a reverse osmosis agent. The drilling fluid can be formed into a semipermeable membrane with high membrane efficiency on the wall of a shale well under the action of the nano-microemulsion blocking agent and the nano blocking agent; the reverse osmosis agent is used for keeping the water activity of the drilling fluid less than or equal to the water activity of stratum shale, so that reverse chemosmosis differential pressure can be generated between the drilling fluid and the wall of the shale well; consequently, water in the drilling fluid is prevented from penetrating and migrating into the shale stratum and the purpose of stabilizing the wall of the well is achieved. Besides, the drilling fluid provided by the invention is used for solving the problems that in the prior art, only the blocking capacity is paid attention to and the chemosmosis driving force of water migration of the drilling fluid and the shale is neglected, and as a physical blocking method is adopted, the semipermeable membrane has seepage phenomenon so that a solvent medium is incapable of completely preventing water from penetrating through the membrane, and as a result, collapse accidents caused by unstable rock on the wall of the well still occur.