Small-flow constant-flow blanking plug for low-permeability oil field

The invention relates to a small-flow constant-flow blanking plug for a low-permeability oil field. The problems that the actual water injection rate of an existing blanking plug changes along with pressure fluctuation, the testing time is long, and a small-flow injection allocation layer cannot be accurately controlled are mainly solved. Comprising an upper main body (4) and a lower main body (8) which are in threaded connection, a plunger main body (11) is arranged in the lower main body (8), a centralizing rod (9) is arranged on the upper portion of the plunger main body (11), and a plunger spring (7) is arranged between the top of the centralizing rod (9) and the upper main body (4); a plunger main body water outlet hole (18) is formed in the side wall of the plunger main body (11); and a lower main body water outlet hole (19) is formed in the side wall of the lower main body (8). The small-flow constant-flow blanking plug for the low-permeability oil field is low in starting pressure, the water injection