Background: After the oilfield development coming into the middle and later periods, many oil wells only had liquid production less than 5m3 per day, therefore the present sucker-rod pumps didn’t satisfy the need for oilfield production. We revised all patents relating to small displacement pump and didn’t found any suitable pump for low production well. A new type of pump with small diameter was needed to design for solving the unbalance between the production and feed in lower production wells.
Objective: To resolve the problems of supply and production imbalance of the low producing well, low pump efficiency and low system efficiency, a low displacement pump with non-coaxial delivery valve had been designed.
Methods: This type pump adopted a solid plunger and its delivery valve was not coaxial with the pump axial that would enhance its structural strength and been useful to reduce the partial flow loss of oil flowing through the static pump valve. At the down dead point of pump plunger, the delivery valve was located at the top of the pump chamber that was to the benefit of discharge of the gas and the oil from the pump chamber. The uneven distribution of the delivery hole was suitable for the wellhead diameter of the traditional oil wells.
Results: The delivery valve was non-coaxial with the plunger that would decrease the flow loss through the passage and increase the pump efficiency. At the down-dead point, the plunger entered the extension nipple and the delivery valve was located up the end of the solid plunger that promoted the remnant gas flowing out of the pump cylinder and decreased the effect of gas on the pump efficiency.
Conclusion: As to this low displacement pump, we suggested: The suitable stroke was 2-3m; the stroke frequency was less than 3min-1. A reasonable range of submersible depth for low production well was 200-300m. It was used in the gas content well lower than 20%, else used the gas anchor firstly. The low displacement pump with non-coaxial delivery valve and solid plunger (NLDP) can improve the pump efficiency and reduce the polish rod load. At the same, this NLDP provides a new equipment for production of the low oil well and improves the artificial lift design theory.