Cement setting accelerator, preparation method and application thereof, and set cement

The invention provides a cement setting accelerator, and a preparation method and application thereof, and belongs to the field of well cementation in thickened oil exploitation. The cement setting accelerator provided by the invention comprises the following components in percentage by mass: 5-10% of polyaluminium chloride, 20-25% of calcium chloride, 15-20% of sodium oxalate, 5-10% of calcium aluminate, 5-10% of calcium formate, 10-15% of sodium sulfate, 5-10% of a dispersing agent and 10-15% of nano silicon. The cement accelerator provided by the invention is prepared by adopting specific components and content, so that setting is fast at low temperature, early strength is high, and the early strength is not reduced at high temperature. The result of the embodiment shows that when the adding amount of the cement accelerator provided by the invention is 2%, the thickening time of cement paste is 56-137 minutes in a temperature range of 32-52 DEG C; the early strength of set cement after 8 hours is 8.1 MPa a