Depressuriz od for downhole annulus drilling fluid

A depressurization device for downhole annulus drilling fluid, comprising a central shaft and a barrel body sheathed outside the central shaft, wherein the central shaft comprises a force transmission shaft and a liquid separation piston, which are connected successively;

• the barrel body comprises a spline barrel, an elastic element protection barrel, a connector and a depressurization barrel, which are all connected successively;
• the elastic element protection barrel and the connector are sheathed outside the force transmission shaft;
• an elastic element is provided between the elastic element protection barrel and the force transmission shaft;
• a cylinder liner is sheathed inside the depressurization barrel, and the cylinder liner is sheathed outside the liquid separation piston, a first liquid storage chamber is formed among the depressurization barrel, the connector and the liquid separation piston, and a second liquid storage chamber is formed between the depressurization barrel and the liquid separation piston;
• a downward first inlet passage and an upward first drain passage which both communicate the outside with the first liquid storage chamber are provided on the connector;
• a downward second inlet passage and an upward second drain passage which both communicate the outside with the second liquid storage chamber are provided on the depressurization barrel;
• at an end of the first inlet passage which communicated with the outside, a first suction valve is provided;
• at an end of the first drain passage which communicated with the outside, a first drain valve is provided;
• at an end of the second inlet passage which communicated with the outside, a second suction valve is provided;
• and, at an end of the second drain passage which communicated with the outside, a second drain valve is provided.