Effect of spool posture on control valve performance considering outlet shape and large fit clearance

Abstract

The control valve serves as a crucial component of the downhole integrated water distributor in water injection oilfields, enabling waterflooding into oil reservoirs. However, the control valve opening cannot be adjusted in the practical environment, resulting in ineffective injection, which means that the spool is stuck. Furthermore, it is difficult to observe the details of the spool sticking and reproduce this phenomenon during testing. To reveal the mechanism of sticking, this paper establishes a CFD model, which considers the spool posture, large fit clearance and outlet shape, to study the spool performance. Additionally, the proposed model is demonstrated experimentally and theoretically. It is found that larger fit clearances result in significant distortion of the flow characteristic curve, with a flow regulation rate of only 90.87% observed when the fit clearance is 0.25 mm. Furthermore, the lateral outlet causes a reduction of 77.27% and 69.15% in radial forces for eccentricity or inclination angles changed from 0° to 180°, respectively. Sticking is strongly correlated with radial forces, the axial force is contingent upon the spool end face area. These findings provide crucial theoretical guidance for the design of control valves.