A small-displacement rod type
oil well pump with an annular
plunger comprises an outer pump
barrel, an inner pump
barrel and the annular
plunger. The upper end of the outer pump
barrel is connected with a supporting leather cup
assembly through a lengthening
coupling, and the lower end of the outer pump barrel is connected with a valve housing of an oil
inlet valve through a pump barrel
coupling. The upper end of the inner pump barrel is connected with a sealing segment joint, and the lower end of the inner pump barrel is connected with the pump barrel
coupling through a valve housing of an oil outlet valve. An annular work cavity is formed between the inner pump barrel and the outer pump barrel, the annular
plunger is in small clearance fit with the inner pump barrel and the outer pump barrel, the annular plunger is connected with a valve rod through a valve rod lower joint, and the lower end of the valve housing of the oil
inlet valve is connected with a
tail pipe joint in a threaded mode through the lower joint. The annular plunger moves upwards along with the
oil pump, an oil outlet valve ball is closed, an oil
inlet valve ball is opened, well fluid is sucked in, fluid with a receding size of the plunger is discharged out of a well mouth, the oil inlet valve is closed, and well fluid stops from entering. In the downstroke, fluid in a pump cavity is extruded downward, and liquid is discharged into an oil
pipe through a liquid outlet of a valve rod guiding sleeve after passing through the oil outlet valve
assembly. The small-displacement rod type
oil well pump with the annular plunger has the advantages of being high in efficiency and free of pump seizure and blocking.