Packer

The invention discloses a packer. The packer comprises a central pipe, a rubber sleeve, a setting cylinder and a shear pin, wherein the rubber sleeve sleeves the central pipe; the setting cylinder sleeves the central pipe; the shear pin is arranged between the setting cylinder and the central pipe. The packer is characterized in that a driving chamber is formed between the setting cylinder and the central pipe; the driving chamber is internally provided with reactants which can be subjected to a chemical reaction under a pre-set temperature to generate a gas. According to the packer disclosed by the invention, the driving chamber is internally provided with the reactants which can be subjected to the chemical reaction under the pre-set temperature to generate the gas, so that the packer can be subjected to setting under the condition that the temperature is relatively low, and furthermore, an applicable range of the packer is expanded, and steam injection cost and setting difficulty are reduced when the packe