Design and experiment of hydraulically guided cleaning tool for outer annulus of screen pipe

To address the technical challenges of low gravel cleaning efficiency in the outer annulus of the screen pipe during offshore workover operations and the risks of failure and sticking associated with mechanically sealed sand-washing tools, a novel non-contact hydraulically guided cleaning tool was designed and developed. The tool breaks away from conventional rubber sealing mechanisms and innovatively employs high-speed annular jets generated by the annular nozzles at both the upper and lower ends to effectively guide and force the washing fluid into the target screen-casing annular space by the hydraulic mechanism of guidance instead of sealing, enabling continuous cleaning. In this study, Computational Fluid Dynamics (CFD) simulations were carried out to analyze the flow field characteristics and optimize the annular nozzle structure, followed by systematic field testing in an experimental well for performance verification. With an optimized annular nozzle width of 0.5 mm, the results showed that the tool pressure drop is 8.8 MPa and the actual sand return rate reaches 94.41% at a sand washing displacement of 1 m³/min. Featuring as a simple structure and reliable operation, this tool fundamentally eliminates wear and sand-sticking risks caused by wall contact. It provides a promising technical solution for improving the success rate of workover and fishing in offshore oilfields.