Abstract: The asymmetric parallel screw pump oil production system can fundamentally solve the problems of limited diameter, too small bearing capacity and short service life of thrust ball bearings. However, there was only a conceptual model structure for the asymmetric counter-rotating parallel structure screw pump production system, and no one studied the parameter configuration method of the dual pump. Therefore, a new downhole asymmetric reverse rotation parallel structure motor-driven screw pump production system was proposed. Firstly, based on the concept of "equal life", the research on the parameter configuration method of twin-screw pump was carried out, the constraint conditions to be met for the matching of twinscrew pump were given, the stress analysis model of the parts prone to failure was established, the stress relationship between the parts was given according to the principle of force balance, the axial force and working torque of the single screw pump rotor were analyzed. Then, according to the principle of equal life (the fatigue service life of thrust ball bearing and universal coupling tends to be equal), the ratio between the axial pressure on the thrust ball bearing and the tension on the coupling was determined, and the ratio of the axial force between the upper and lower screw pumps was given. Finally, the parameter matching scheme of two pumps was determined under the condition that the stator rubber life was one year and the pump end pressure difference was 12 MPa, and the life and displacement of the selected scheme were compared and analyzed, and the influence of different pump end pressure difference on the limit displacement of the lower screw rod pump was studied. The research results show that the axial force ratio between the lower screw pump and the upper screw pump is 1.41∶1 for the specific thrust ball bearing and cross coupling. The stator rubber of the screw pump has a certain service life, and the displacement of the double pump is greatly improved compared with that of the single screw pump, with an average growth rate of about 50%.
Key words:  twinscrew pump oil recovery system; double pump matching constraint condition; equal life concept; axial force and working torque; pump end differential pressure; life and displacement analysis